I. This study reports the rapid reaction under mild\r\nconditions of internal or terminal alkynes with methyl (acetyl-\r\nacetonato) (triphenylphosphine) nickel (1) in either aromatic or\r\nether solvents. In all cases vinylnickel products 2 are formed\r\nby insertion of the alkyne into the nickel-methyl bond. These\r\ncomplexes may be converted into a variety of organic products\r\n(e.g. alkenes, esters, vinyl halides) by treatment with\r\nappropriate reagents. Unsymmetrical alkynes give selectively the\r\none regioisomer with the sterically largest substituent next to\r\nthe nickel atom. In order to investigate the stereochemistry of\r\nthe initial insertion, ax-ray diffraction study of the reaction\r\nof 1 with diphenylacetylene was carried out. This showed that the\r\nvinylnickel complex formed by overall trans insertion was the\r\nproduct of the reaction. Furthermore, subsequent slow\r\nisomerization of this complex, to a mixture of it and the\r\ncorresponding cis isomer, demonstrated that this trans addition\r\nproduct is the kinetic product of the reaction. In studies with\r\nother alkynes, the product of trans addition was not always\r\nexclusively (or even predominantly) formed, but the ratio of the\r\nstereoisomers formed kinetically was substantially different from\r\nthe thermodynamic ratio. Isotope labeling, added phosphine, and\r\nother experiments have allowed us to conclude that the mechanism\r\nof this reaction does involve initial cis addition. However, a\r\ncoordinatively unsaturated vinylnickel complex is initially\r\nformed, which can undergo rapid, phosphine-catalyzed cis-trans\r\nisomerization in competition with its conversion to the isolable\r\nphosphine-substituted kinetic reaction products.
\r\n\r\nII. The reaction of CpMo(CO)3H (la) with CpMo(CO)3R (2, R =\r\nCH3, C2H5) at 5O\u00b0C in THF gives the aldehyde RCHO and the dimers\r\n[CpMo(CO)3]2 (3a) and [CpMo(CO)2]2 (4a). Labeling one of the\r\nreactants with a methylcyclopentadienyl ligand it was possible to\r\nshow that the mixed dimers MeCpMo (CO)3-CO)3MoCp (3b) and\r\nMeCpMo (CO)2\u2261(CO)2MoCp (4b) are the predominant kinetic products\r\nof the reaction. Additionally labeling the carbonyl ligands of la\r\nwith 13CO led to the conclusion that all three of the carbonyl\r\nligands in la end up in the tetracarbonyl dimers 4a if the\r\nreaction is carried out under a continuous purge of argon.\r\nTrapping studies failed to find any evidence for the intermediacy\r\nof either [CpMo(CO)3]- or [CpMo(CO)3]+ in this reaction. A\r\nmechanism is proposed that involves the initial migration of the\r\nalkyl ligand in 2 to CO forming an unsaturated acyl complex which\r\nreacts with la to give a binuclear complex containing a three\r\ncenter-two electron Mo-H-Mo bond. This complex then selectively\r\nlooses a carbonyl from the acyl molybdenum, migrates the hydride\r\nto that same metal, and forms a metal-metal bond. This binuclear\r\ncomplex with the hydride and acyl ligands on one metal\r\nreductively eliminates aldehyde, and migrates a carbonyl ligand,\r\nto give 4a directly. The other product 3a is formed by addition\r\nof two molecules of free CO to 4a.
", "doi": "10.7907/5pj3-sn83", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3018", "collection": "thesis", "collection_id": "3018", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08052009-075725", "primary_object_url": { "basename": "Frommer_je_1981.pdf", "content": "final", "filesize": 5065057, "license": "other", "mime_type": "application/pdf", "url": "/3018/1/Frommer_je_1981.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Syntheses and Reactions of Polymer-Bound Molybdenum Complexes and Hydrogenolyses of an Alkynyl Cobalt Carbonyl Cluster", "author": [ { "family_name": "Frommer", "given_name": "Jane Elizabeth", "clpid": "Frommer-Jane-Elizabeth" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nCo3(CO)9CCH2C(CH3)3 (1) was prepared and its hydrogen- mediated decomposition was studied. 1 reacted with hydrogen in aromatic solvents (60\u00b0C, 2-7 atm H2) to yield three products: 3,3-dimethylbutene (2), 2,2-dimethylbutane (3), and 4,4- dimethylpentanal (4). The final ratio of alkene to alkane to aldehyde was approximately 2.5 : 1.5 : 1.0. Kinetic data collected from both NMR- and vpc-monitored experiments indicated first order decomposition of starting material 1 and a hydrogen pressure dependence for the rate of appearance of total products. Nearly total inhibition of the hydrogenation was observed in the presence of carbon monoxide (CO:H2, 3.7:3.7 atm, 60\u00b0C). However, at elevated temperatures (85\u00b0), under the same CO/H2 atmosphere, aldehyde (4) production became the predominant reaction pathway at the expense of earlier-formed olefin 2. Incorporation of independently added olefins in the hydrogenation of 1 suggested the intermediacy of olefin in aldehyde and alkane production.\r\n\r\nA polystyrene-attached n[superscript 5}-cyclopentadienyl(tricarbony1)-hydridomolybdenum complex (P-6) was prepared and its reactions with several THF-soluble bases were investigated. Enolates of \u03b2-dicarbonyl compounds quantitatively deprotonated P-6, giving polymer-bound salts of the corresponding anion ([...]-Cp(CO)3Mo[...], P-7). Equilibration studies involving polymers P-6 and P-7 and their soluble monomeric analogues in THF demonstrated that little change in pKa was induced by binding the molybdenum hydride to the polymer. Even though the polymer-supported partners in these experiments were not soluble and therefore rendered the reactions heterogeneous, the systems adhered reasonably well to conventional equilibrium behavior, as exhibited by a simple equilibrium analysis which yielded effectively constant Keq values. A polymer-bound carboxylic acid (P-1) and its conjugate base (P-2) also displayed essentially conventional equilibrium dynamics.", "doi": "10.7907/MD7N-W189", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:17715", "collection": "thesis", "collection_id": "17715", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072025-210733150", "primary_object_url": { "basename": "Lockhart_TP_1981.pdf", "content": "final", "filesize": 42366128, "license": "other", "mime_type": "application/pdf", "url": "/17715/1/Lockhart_TP_1981.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Chemistry of 1,4-Dehydrobenzenes", "author": [ { "family_name": "Lockhart", "given_name": "Thomas Paul", "clpid": "Lockhart-Thomas-Paul" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Upon heating, alkyl substituted cis 1,2-diethynyl olefins\r\nundergo cyclization to yield reactive 1,4-dehydrobenzenes; the\r\nproducts isolated may be derived from either unimolecular or\r\nbimolecular reactions of the intermediate. Z-4,5-Diethynyl-4-\r\noctene (19) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-\r\ndehydrobenzene (33). Solution pyrolysis of 19 in inert aromatic\r\nsolvents produces three unimolecular products, (Z-dodeca-4,8-\r\ndiyn-6-ene (23), benzocyclooctene (25) and o-allyl-n-propylbenzene\r\n(26)) in high yield. When 1,4-cyclohexadiene is\r\nadded to the pyrolysis solution as a trapping agent, high yields\r\nof the reduced product o-di-n-propylbenzene (28) are obtained.\r\nThe kinetics of solution pyrolysis of 19 in the presence and\r\nabsence of trapping agent establish that 2,3-di-n-propyl-1,4-\r\ndehydrobenzene is a discrete intermediate on the pathway leading\r\nto products. When the reaction was run in the heated probe of an\r\nNMR spectrometer, CIDNP was observed in 26. This observation,\r\nalong with kinetic and chemical trapping evidence, indicates the\r\npresence of two additional intermediates, formed from 33 by\r\nsequential intramolecular [1,5] hydrogen transfer, on the pathway\r\nto products. The observation of CIDNP, coupled with the\r\nreactivity exhibited by 33 and the other two intermediates,\r\nimplicates a biradical description of these molecules.
\r\n\r\nTwo approaches have been used to determine the spin state(s)\r\nof 1,4-dehydrobenzenes produced in the solution reaction of\r\ndiethynyl olefins. The first method relies on the \"spin\r\ncorrelation effect\" which postulates a relationship between the\r\nspin state of a caged radical pair and the ratio of cage and\r\nescape reactions (C/E) which may occur in the pair. When the\r\n2,3-di-n-propyl-1,4-dehydrobenzene biradical abstracts hydrogen\r\nfrom 1,4-cyclohexadiene, a radical pair is generated. If a\r\nmixture of l,4-cyclohexadiene-do and -d4 is employed it is\r\npossible, by performing a VPC-MS analysis, to determine the ratio\r\nC/E leading from the radical pair to the reduced product, 28.\r\nApplying this method to the reaction of 19, C/E was found to be\r\n0.6, independent of the concentration of 1,4-cyclohexadiene\r\n(between 0.1 and 10 M) in the chlorobenzene reaction solution.\r\nThis result suggests the presence of the singlet state of 33 in\r\nthe reaction of 19. Independent support for this analysis came\r\nfrom the reaction of 3,4-dimethyl-1,5-diyn-3-ene (38) in\r\nhexachloroacetone sol vent in an NMR probe. The major product,\r\nl,4-dichloro-2,3-dimethylbenzene (39), obtained by chlorine\r\nabstraction from the sol vent, showed polarization (emission) in\r\nthe aromatic protons. The interpretation of this result is\r\nstraightforward and indicates solvent trapping of the singlet\r\nstate of the intermediate 2,3-dimethyl-1,4-dehydrobenzene. Both\r\nof these experiments indicate that only the singlet state of 1,4-\r\ndehydrobenzenes is generated upon thermal reaction of diethynyl\r\nolefins. The failure to observe evidence for the triplet state\r\nof the 1,4-dehydrobenzenes under the reaction conditions requires\r\nthat, if the triplet is the ground electronic state, the rate of\r\nintersystem crossing from the singlet must be <109 sec-1.
", "doi": "10.7907/35fh-q724", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:8475", "collection": "thesis", "collection_id": "8475", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032014-135236367", "primary_object_url": { "basename": "Brown 198.pdf", "content": "final", "filesize": 16459213, "license": "other", "mime_type": "application/pdf", "url": "/8475/1/Brown 198.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Synthesis and Matrix Isolated Photolysis of 2,3-Dimethylbicyclo[2.2.0]Hexa-2,5-Diene-1,4-Dicarboxylic Acid Anhydride: A Potential Precursor to 2,3 -Dimethyl-1,4-Dehydrobenzene", "author": [ { "family_name": "Brown", "given_name": "Duncan William", "clpid": "Brown-Duncan-William" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The synthesis of the first member of a new class of\r\nDewar benzenes has been achieved. The synthesis of 2,3-\r\ndimethylbicyclo[2.2.0]hexa-2,5-diene-1, 4-dicarboxylic acid\r\nand its anhydride are described. Dibromomaleic anhydride\r\nand dichloroethylene were found to add efficiently in a\r\nphotochemical [2+2] cycloaddition to produce 1,2-dibromo-\r\n3,4-dichlorocyclobutane-1,2-dicarboxylic acid. Removal\r\nof the bromines with tin/copper couple yielded dichloro-\r\ncyclobutenes which added to 2-butyne under photochemical\r\nconditions to yield 5,6-dichloro-2,3-dimethylbicyclo [2.2.0]\r\nhex-2-ene dicarboxylic acids. One of the three possible\r\nisomers yielded a stable anhydride which could be dechlorinated\r\nusing triphenyltin radicals generated by the photolysis\r\nof hexaphenylditin.
\r\n\r\nPhotolysis of argon matrix isolated 2,3-dimethylbicyclo\r\n[2.2.0]hexa-2, 5-diene-1,4-dicarboxylic acid anhydride produced\r\ntraces whose strongest bands in the infrared were at\r\n3350 and 600 cm^(-1). This suggested the formation of terminal\r\nacetylenes. The spectra of argon matrix isolated E- and Z-\r\n3,4-dimethylhexa-1,5-diyne-3-ene and cis-and trans-octa-\r\n2,6-diyne-4-ene were compared with the spectrum of the\r\nphotolysis products. Possibly all four diethynylethylenes\r\nwere present in the anhydride photolysis products. Gas chromatograph-mass spectral analysis of the volatiles from the anhydride photolysis again suggested, but did not\r\nconfirm, the presence of the diethynylethylenes.
\r\n", "doi": "10.7907/2spb-1x47", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:18500", "collection": "thesis", "collection_id": "18500", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04202026-165214989", "primary_object_url": { "basename": "Evitt_ER_1980.pdf", "content": "final", "filesize": 48449205, "license": "other", "mime_type": "application/pdf", "url": "/18500/1/Evitt_ER_1980.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Insertion and Thermal Decomposition Reactions of Cyclopentadienylcobalt (III) Dialkyl Complexes", "author": [ { "family_name": "Evitt", "given_name": "Eric Robert", "clpid": "Evitt-Eric-Robert" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "PMe3 replaces PPh3 in CpCo(PPh3) (Me)2 (1, Cp = \u019e5-\r\nC5H5) in a dissociative substitution reaction to give CpCo\r\n(PMe3) (Me)2; the first order rate constant for PPh3 loss\r\nfrom 1 is 4 x 10-4 sec-1 at 30\u00b0C in toluene-d8. Dialkyl\r\ncomplex 1 doubly alkylates CO in an intrarnolecular process\r\nto give acetone in high yield; this proceeds via CO substitution\r\nin 1 to give the spectroscopically observed intermediate\r\nCpCo(CO) (Me)2 (6), followed by migratory insertion,\r\nand reductive elimination from an acyl-alkyl complex.\r\nHeating and then carbonylating mixtures of 1-d0 and\r\n1-d6 (deuterated methyl groups) in benzene revealed the\r\npresence of an intermolecular methyl exchange process in 1.\r\nWe have reinvestigated the reaction of .2:_ with diphenylacetylene\r\nand, in addition to the organometallic products observed by\r\nprevious workers, isolated two new organic products 2,3-\r\ndiphenyl-1-butene (11) and Z-2,3-diphenyl-2-butene; these\r\nproducts account for >95% of the methyl groups in starting\r\n1 and were formed in the ratio 14:1 in the absence of added\r\nPPh3. Additional experiments designed to probe the mechanism\r\nof product formation led to the following conclusions: (1)\r\nhigh yield stereospecific double alkylation of diphenylacetylene\r\nis a feasible process; (2) reactions of 11 in this\r\nsystem involve two diastereomeric \u019e2-olefin complexes which\r\nare interconvertible only by dissociation of the olefinic\r\nligand from the metal; (3) hydrogen shifts involved in the\r\nCp(PPh3)Co-catalyzed isomerization of alkenes occur more\r\nrapidly than dissociation of the alkene from the metal center;\r\nand (4) interconversion of \u019e3-allyl complexes via rotation in\r\n\u019e1-allyl complexes is much slower than hydrogen transfer and\r\nproduct formation. Ethylene reacts with 1 to give methane,\r\npropene, and the new ethylene complex CpCo(PPh3) (C2H4) (14);\r\nthis was independently generated by thermal PPh3 or photochemical\r\nCO substitution in CpCo(PPh3)2 and CpCo(CO) (PPh3),\r\nrespectively. The production of propene from ethylene and\r\n1 is a model for the chain-growth step in the Ziegler-Natta\r\npolymerization of olefins. The products can be explained by\r\na classical mechanism involving insertion of ethylene into\r\na cobalt-carbon a-bond or an alternative one involving\r\nethylene addition to an intermediate metal-carbene complex\r\nformed by a-elimination. Labeling experiments in this system\r\nhave shown propene is formed by transfer of one intact methyl\r\ngroup to ethylene, in agreement with the classical view.\r\nThermal decomposition of 1 is competitive with the alkylation\r\nof ethylene and gives mostly methane, abstracting the fourth\r\nmethane hydrogen from the cyclopentadienyl ring. The decomposition\r\nhas been monitored by 1H NMR spectroscopy in the\r\npresence of added PPh3 and ethylene (conditions where no\r\npropene is generated) and CpCo(PPh3) (C2H4) (Cp' = \u019e5CH3C5H4)\r\nand Cp'Co(PPh3) (Me)2 have been observed spectroscopically\r\nand identified as the primary and secondary products of the\r\ndecomposition, respectively. Together, these reactions show\r\nreductive elimination in alkyl-acyl and alkyl-vinyl complexes\r\nis more favorable than alkyl-alkyl reductive elimination\r\nand this is attributed to the ability of the former systems\r\nto donate an additional pair of electrons to the metal center\r\nin the reductive elimination transition state.
\r\n\r\n\u019e5-cyclopentadieny(triphenylphosphine)cobaltacyclopentane\r\n(18) has been prepared by reaction of CpCo(PPh3)I2 with 1,4-\r\ndilithiobutane at low temperature. This metallacycle is\r\nthermally more sensitive than its dimethyl analog 1 and decomposes\r\nto give 1-butene which is subsequently isomerized\r\nby the organometallic products to a mixture of 2-butenes.\r\nIn this system, ethylene insertion cannot compete with thermal\r\ndecomposition, but CO and diphenylacetylene insertion can.\r\nCO reacts with 18 to give cyclopentanone via the CO substituted\r\nanalog of 18; this has been observed spectroscopically\r\nand builds up to a greater degree than the dimethyl analog\r\nobserved during the reaction of 1 with CO. Diphenylacetylene\r\nreacts with 18 to give the expected products of double alkylation,\r\n1,2-diphenylcyclohe.xene and 2,3-diphenylcyclohexene,\r\nand Z-1,2-diphenyl-1,5-hexadiene as well. The latter product\r\nis presumably derived from \u03b2-elimination in an intermediate\r\nmetallacycloheptene which also generates the cyclohexenes\r\nvia reductive elimination.
", "doi": "10.7907/sbv2-pc06", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:16867", "collection": "thesis", "collection_id": "16867", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11192024-221442048", "primary_object_url": { "basename": "White_MA_1980.pdf", "content": "final", "filesize": 51272101, "license": "other", "mime_type": "application/pdf", "url": "/16867/1/White_MA_1980.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Formation of Carbon-Carbon and Carbon-Nitrogen Bonds Mediated by Organometallic Cobalt Complexes", "author": [ { "family_name": "White", "given_name": "Mary Ann", "clpid": "White-Mary-Ann" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Binuclear cobalt complexes of the general formula\r\n[CpCo(CO)R]2 (Cp = \u019e5 C5H5) have been prepared and the reactivity of\r\nthese complexes has been investigated. Thermal decomposition of\r\n[CpCo(CO)(CH3)]2 in a variety of organic solvents leads to good yields\r\nof acetone (a process involving the formation of two new carbon-carbon\r\nbonds). The mechanism of this decomposition and that of analogous\r\ncomplexes where R = CH3CH2 and CF3CH2 has been elucidated. The\r\ncarbonylation reactions of these complexes have also been examined.
\r\n\r\nThe reaction of either CpCo(CO)2 or [CpCo(NO)]2 with NO and a\r\nvariety of olefins yields cobalt complexes containing 1, 2-dinitroso\r\nligands which are derived from the alkene substrate. Thus two new\r\ncarbon-nitrogen bonds are formed. The scope of this reaction is\r\nsurveyed and methods for removal of the 1, 2-dinitroso ligand, with the\r\nnewly formed carbon-nitrogen bonds intact, are investigated.
", "doi": "10.7907/mtgw-1g08", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:18494", "collection": "thesis", "collection_id": "18494", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04152026-230341334", "primary_object_url": { "basename": "Jones_WD_1979.pdf", "content": "final", "filesize": 46304822, "license": "other", "mime_type": "application/pdf", "url": "/18494/1/Jones_WD_1979.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Reactivity Patterns of Transition Metal Hydrides and Alkyls", "author": [ { "family_name": "Jones", "given_name": "William Davidson, II", "orcid": "0000-0003-1932-0963", "clpid": "Jones-William-Davidson-II" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The complex PPN+CpV(CO)3H- (Cp=n5-C5H5) has been\r\nprepared in 70% yield by sodium reduction of CpV(CO)4\r\nfollowed by protonation of the resulting dianion [CpV(CO)3]2-\r\nwith water and cation exchange with PPN+Cl-. The physical\r\nproperties and chemical reactions of PPN+CpV(CO)3H- have\r\nbeen investigated. The sodium salt of CpV(CO)3H- is contact\r\nion-paired in the solid state and in THF; dissociation\r\nof solvent-separated pairs occurs on conversion to the PPN+\r\nsalt or dissolution in polar solvents such as HMPA. \r\nPPN+CpV(CO)3H- reacts with a wide range of organic halides,\r\nresulting in substitution of the halogen atom by the hydrogen of CpV(CO)3H-.\r\nThe organometallic products of these\r\nreactions are the vanadium halides PPN+[CpV(CO)3X]-. In\r\nsome cases a second organometallic product is observed;\r\nthis material is the binuclear bridging hydride PPN+\r\n[CpV(CO)3]2 H-, and it is formed by reaction of the kinetic\r\nproduct CpV(CO)3X- with starting CpV(CO)3H- present in the\r\nreduction solutions. Irradiation of CpV(CO)4 in the\r\npresence of CpV(CO)3H- provides an alternate route to\r\nbridging hydride [CpV(CO)3]2 H-. Competition experiments\r\nagainst PPh3 have shown that CpV(CO)3H- reacts more rapidly\r\nthan the phosphine with transient, coordinatively unsaturated\r\nCpV(CO)3, but thermodynamically PPh3 is the better ligand.\r\nThe borohydride salt PPN+[CpV(CO)3BH4]- has also been\r\nprepared, by treating CpV(CO)4 with NaBH4 and by treating\r\nCpV(CO)3H- with BH3THF. The mechanism of the reaction\r\nbetween CpV(CO)3H- and organic halides has been investigated\r\nin detail, and compared in several cases with halide\r\nreductions carried out using tri-n-butyltin hydride.\r\nRelative reactivity, stereochemistry, cyclization and\r\ntrapping studies demonstrate that in almost all cases,\r\nthe reduction reaction proceeds via free radical intermediates.\r\nAs in the R3SnH case, these intermediates are\r\ngenerated in a chain process, and are trapped by hydrogen\r\ntransfer from CpV(CO)3H-. The absolute rate constant for\r\nthis transfer step can be estimated to be ca. 2 X 107 M-1\r\nsec-1, nearly an order of magnitude larger than the rate\r\nconstant for hydrogen transfer from tri-n-butyltin hydride.\r\nReduction of cyclopropylcarbinyl bromide appears to be\r\nexceptional, and probably proceeds by a two-electron mechanism,
\r\n\r\nSodium amalgam reduction of CpRh(CO)2 or a mixture of\r\nCpRh(CO)2 and CpCo(CO)2 affords two new anions, PPN+\r\n[Cp2Rh3(CO)4]- and PPN+[Cp2RhCo(CO)2]-. The latter compound appears to be physically and chemically similar to the known\r\nPPN+[Cp2Co2(CO2]-, whereas the former posesses the same\r\nsubstructure bridged by a Rh(Co)2 unit. Both anions\r\nreact with CH3I producing acetone via CpRh(CO)(CH3)2\r\nor CpCo(CO)(CH3)2. In addition, the compounds Cp2RhCo(CO2R2\r\n(R=CH3, CH2CF3) are formed upon alkylation of [Cp2RhCo(CO)]+\r\nand are observed to decompose to CpRh(CO)(CH2CF3)2 and\r\nCpCo(CO)(CH2CF3)2.
\r\n\r\nCpMo(CO)3H has been found to react with CpMo(CO)3R\r\n(R=CH3, C2H5, CH2C6H5; 2a, 2b, 2c) at 25-50\u00b0C to quantitatively\r\nproduce aldehyde RCHO and the dimers [CpMo(CO)3]2\r\nand [CpMo(CO)3]2. Evidence is presented indicating that\r\naldehyde formation occurs by insertion of CO into the Mo-R\r\nbond followed by hydride transfer by 1 forming an intermediate \r\nacyl hydride. The intermediate acyl CpMo(CO)2(COR)\r\nalso reacts with ethylene and CpMo(CO)3H producing ketones\r\nR-C-C2H5. A mechanism is proposed for these reactions and\r\na comparison with the cobalt analogues in the hydroformylation\r\nprocess discussed.
\r\n\r\nThe reactions of PPN+CpV(CO)3H- with some transition\r\nmetal carbonyls, alkyl and acyls are studied. In almost\r\nall cases substitution of hydride (H-) for CO is observed.\r\nThe chemistry of CpMo(CO)3H with similar compounds is also\r\nexamined and compared with that of CpV(CO)3H-. In general,\r\nCpV(CO)3H- appears to transfer a hydrogen atom to the\r\nmetal radical anion formed in an electron transfer process 5\r\nwhereas CpMo(CO)3H- transfers hydride in a 2-electron process\r\nto a vacant coordination site. The chemical consequences\r\nare that CpV(CO)3H- generally reacts with metal alkyls to\r\ngive alkanes via. intermediate alkyl hydride species whereas\r\nCpMo(CO)3H reacts with metal alkyls to produce aldehyde,\r\nvia an intermediate acyl hydride species.
", "doi": "10.7907/yj3c-pw50", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:17850", "collection": "thesis", "collection_id": "17850", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01302026-223031889", "primary_object_url": { "basename": "Johnson_GC_1979.pdf", "content": "final", "filesize": 23460174, "license": "other", "mime_type": "application/pdf", "url": "/17850/1/Johnson_GC_1979.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Approaches to the Elucidation of the Nature of 1,4-Dehyrobenzene", "author": [ { "family_name": "Johnson", "given_name": "Gilbert Collier", "clpid": "Johnson-Gilbert-Collier" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Two approaches to the generation of 1,4-dehydrobenzene are\r\ndescribed. The first, involving an attempted cycloreversion to\r\ngenerate initially the bicyclic form of the title compound,\r\n\"butalene,\" gave negative results. The second approach, pyrolysis\r\nof various substituted hexene-diynes to generate substituted\r\n1,4-dehydrobenzenes, gave evidence for the intermediacy\r\nof the 1,4-dehydrobenzene diradical in the formation of several\r\nisomerization products. A novel 1,2 silicon shift is proposed\r\nto give rise to other products through the intermediacy of\r\nsubstituted 1,3-dehydrobenzenes.", "doi": "10.7907/wpgh-0v33", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:17810", "collection": "thesis", "collection_id": "17810", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01092026-185831925", "primary_object_url": { "basename": "Kinney_RJ_1978.pdf", "content": "final", "filesize": 40085103, "license": "other", "mime_type": "application/pdf", "url": "/17810/1/Kinney_RJ_1978.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Synthesis and Characterization of the New Cyclopentadienyl Vanadium Tricarbonyl Hydride and Methyl Anions and their Reactions with Organic Substrates. II. Monomeric Organometallic Dianions", "author": [ { "family_name": "Kinney", "given_name": "Robert James", "orcid": "0000-0003-1963-5818", "clpid": "Kinney-Robert-James" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The new anionic cyclopentadienyl vanadium tricarbonyl complexes,\r\n(n5C5H5)V(CO)3R-, (R=H,CH3),have been isolated as the phosphineminium\r\nsalts. (n5C5H5)V(CO)3H- reacts with alkyl (primary, secondary, and tertiary),\r\nvinyl and aryl bromides at room temperature in THF to replace\r\nbromine with hydrogen. A gem-dibromocyclopropane was reduced to the\r\nmono-bromide, and acid chlorides were converted to aldehydes with\r\n(n5C5H5)V(CO)3H-. Primary alkyl iodides react more rapidly than the\r\nbromides and aklyl chlorides do not react at all. Alkyl tosylates react\r\nmuch slower than the corresponding bromides. Carbon radicals and\r\n(n5C5H5)V(CO)3Br- as the kinetic organometallic product imply a radical\r\nchain mechanism for these reactions.
\r\n\r\nThe reactions of (n5C5H5)V(CO)3CH-3 and alkylbromides and acyl\r\nchlorides do not produce new carbon-carbon bonds .
\r\n\r\nAttempts to prepare the dianious RM(CO)2-3, M = Cr, Mo; R = norbornadiene\r\nand M = Mo; R = cyclooctatetraene were not successful.
", "doi": "10.7907/pygb-k537", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:17866", "collection": "thesis", "collection_id": "17866", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02052026-185527488", "primary_object_url": { "basename": "McAlister_DR_1978.pdf", "content": "", "filesize": 22482316, "license": "other", "mime_type": "application/pdf", "url": "/17866/1/McAlister_DR_1978.pdf", "version": "v1.0.0" }, "type": "thesis", "title": "Organometallic Reaction Mechanisms: Catalytic Cyclotrimerization of Alkynes, Reduction of Carbon Monoxide and Reductive Elimination from an Alkylhydride Complex", "author": [ { "family_name": "McAlister", "given_name": "Donald Robert", "clpid": "McAlister-Donald-Robert" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Chapter I
\r\n\r\nThe cobaltacyclic compound, (n55-C5H5)Co(C(CH3)=C(CH3)c(CH3)=C(CH3))\r\n(PPh3) (3a), formed by reaction of (n55-C5H5)Co(PPh3)2 (1a) with 2-butyne\r\nis shown to be an efficient catalyst for cyclotrimerization of alkynes\r\nto provide arenes. An investigation of the substitution reactions of\r\nPMe3 and 2-butyne with 1a and with its PMe3 containing congeners (1b and 1c) is\r\nreported. A mechanism consistent with this data and in accord with\r\nthe observed dependence of the rate of formation 3a on PPh3 and 2-\r\nbutyne concentration is proposed.
\r\n\r\nThe kinetics of the cyclotrimerization of 2-butyne catalyzed by\r\n3a both in the presence and absence of excess PPh3 and the kinetics\r\nof substitution of PEt3 for PPh3 in 3a are reported. These results\r\nindicate a mechanism involving rate determining coordination of 2-butyne \r\nto cobalt. In contrast the reaction of C2(CO2Me)2 (dma)\r\nwith the PMe3 substituted analog of 3a,(3c), is shown to proceed without\r\nprior coordination of the alkyne.
\r\n\r\nChapter II
\r\n\r\nBis (pentamethyl cyclopentadienyl)-dihydrido zirconium (IV)\r\n(\u019e5-C5Me5)2ZrH2 (2) forms unstable adducts with PF3 and CO at -80\u00b0.\r\nThe carbonyl adduct (\u019e5-C5Me5)2ZrH2 (CO) yields {(\u019e5-C5Me5)2ZrH}2\r\n(\u03bc-OCH=CHO) and/or (\u019e5-C5Me5)2 ZrH(OCH3 upon warming depending on\r\nconditions. Carbonylation of (\u019e5-C5Me5)2 Zr(CH3)2 2 provides successively\r\n(\u019e5-C5Me5)2 Zr(CH3) (C(=O)CH3) and (\u019e5-C5Me5)2 Zr(OC(Me)=C(Me)O).\r\nReaction of the zirconocyclopentane (\u019e5-C5Me5)2 Zr(CH2(CH2)2CH2 \r\nwith CO affords (\u019e5-C5Me5)2Zr(H) (OCH=CH(CHMe2). Treatment of 2\r\nwith isobutylene gives (\u019e5-C5Me5)2Zr(H) (CH2) (13), which reacts\r\nwith CO to give (\u019e5-C5Me5)2Zr(H) (OCH=CH(CHMe2))(15). The results of\r\n13C and deuterium labeling studies indicate that (\u019e5-C5Me5)2 Zr(H)\r\n(C(=O)CH2CHMe2) is an intermediate in conversion of 13 to 15. The\r\nobserved reaction patterns of alkyl and hydride derivatives of\r\nzirconium with CO are attributed to carbenoid character of the carbonyl\r\ncarbon resulting from an unusual \"side-on\" coordination of acyl or\r\nformyl groups.
\r\n\r\nChapter III
\r\n\r\nThe alkyl hydride complex (\u019e5-C5Me5)2Zr(H)(CH2CHMe2) (5a),\r\nprepared by reaction of (\u019e5-C5Me5)2ZrH2 (4) with isobutylene, is\r\na monomeric, pseudotetrahedral compound. In direct contrast to\r\nother transition metal complexes bearing cis hydride and alkyl ligands\r\nit is reasonably thermally stable. However, isobutane is evolved from\r\nSa upon thermolysis at 75\u00b0. Reaction with H2 or ethylene also results\r\nin generation of isobutane.
\r\n\r\nThe isotopically labeled complexes (\u019e5-C5Me5)2Zr(D)(CH2CDMe2) (5b)\r\nand (\u019e5-C5(CD3)5)2Zr(D)(CH2CD(CH3)2)(5c) are prepared by reaction of\r\nisobutylene with (\u019e5-C5Me5)2ZrD2 and (\u019e5-C5(CD3)5)2ZrD2. respectively.\r\nThe deuterium distribution in isobutanes resulting from thermolysis\r\nof 5a, b and c and from their reactions with H2, D2, C2H4 and C2D4\r\nwere determined. The rates of thermolysis of those complexes are\r\nalso reported. Mechanisms consistent with these data are proposed.\r\nFor the cases of thermolysis and reaction with H2, the suggested\r\nmechanisms are similar to those proposed to account for exchange\r\nprocesses between 4 and a deuterium atmosphere.
", "doi": "10.7907/fat2-6j70", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:6970", "collection": "thesis", "collection_id": "6970", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04242012-160948000", "primary_object_url": { "basename": "Davis_jh_1977.pdf", "content": "final", "filesize": 23586493, "license": "other", "mime_type": "application/pdf", "url": "/6970/1/Davis_jh_1977.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Theoretical Studies of Organic Diradicals and the Thermal Rearrangement of Bicyclopropenyls", "author": [ { "family_name": "Davis", "given_name": "James Hubbard", "clpid": "Davis-James-Hubbard" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Part A. Generalized valence bond calculations on cyclopropene and vinylmethylene lead to the following conclusions: (1) the allyl-type \u03c0-system is strongly distorted by the presence of the unpaired sigma electron leading to a methylene-like triplet, ^3A^\", but a 1,3-diradical-like singlet state, ^1A^\"; (2) the lowest-lying singlet state of vinylmethylene has the form of a singlet methylene ^1A lying 12 kcal/mole above the triplet ground state, while the diradical singlet state lies at 14 kcal/mole.
\r\n\r\nPart B. Generalized valence bond calculations on trimethylenemethane indicate that the ground state is the planar triplet with the planar singlet state 26 kcal/mole higher. The rotational barrier for the triplet state is 18 kcal/mole, while one component of the planar singlet prefers the bisected geometry by 7 kcal/mole. Oscillator strengths for vertical transitions and ionization potentials are also reported.
\r\n\r\nPart C. Generalized valence bond calculations on vinylidene predict that the ground state is a singlet with a methylene-like triplet at 2 eV higher. With extensive CI calculations, we find CC bond energy of D_0(h_2C=C) = 150.1 kcal/mole and a heat of formation of 111.5 kcal/mole at 298\u00b0K. The dipole moment for the singlet is calculated to be 2.23D, while the dipole moment for the triplet is 0.55D.
\r\n\r\nPart D. Generalized valence bond calculations on aminonitrene indicate that the ground state is a singlet (^1A_1) with a low-lying triplet state (^3A_2) at 15 kcal/mole. We find the nitrogen-nitrogen bond dissociation energy for the singlet state is 70.4 kcal/mole. The dipole moment is found to be 4.036D for the ^1A_1 and 2.351D for the ^3A_2 state of aminonitrene. The ionization potential is calculated to be 9.4 eV.
\r\n\r\nPart E. The kinetic distribution of isomeric xylenes formed on the thermal aromatization of dl- and meso-1,1'-dimethyl-3,3'-bicylopropenyl and of 3,3'-dimethyl-3,3'-bicyclopropenyl has been determined by extrapolation of the time-dependent xylene percentages to zero percent conversion. The data is most consistent with a mechanism involving initial cleavage of one of the cyclopropene rings, followed by expansion of the other ring, closure to Dewar benzene and finally opening of the Dewar to form aromatic products.
", "doi": "10.7907/KZ6K-7P42", "publication_date": "1977", "thesis_type": "phd", "thesis_year": "1977" }, { "id": "thesis:10065", "collection": "thesis", "collection_id": "10065", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02242017-100127779", "primary_object_url": { "basename": "Wendling_LA_1976.pdf", "content": "final", "filesize": 46515183, "license": "other", "mime_type": "application/pdf", "url": "/10065/1/Wendling_LA_1976.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. The Synthesis, Absolute Configuration, and Stereochemistry of Thermal Decomposition of (+)-3R,5R- and (+)-3R,5S-3-Ethyl-5-Methyl-1-Pyrazoline. II. Mechanistic Investigations of the Thermal Decompositions of 2H-Azirines", "author": [ { "family_name": "Wendling", "given_name": "Larry Allan", "clpid": "Wendling-Larry-Allan" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "I. (+)-3R,5R- and (+)-3R,5S-3-ethyl-5-methyl-1-pyrazolines\r\n(34T and 34C, respectively) have been prepared in optically active\r\nform. Their stereochemistries have been determined by correlation\r\nwith (-)-R-3-hexanol and (-)-R-2-bromohexane. Pyrolysis of these\r\npyrazolines in the gas phase at 292\u00b0 allows a complete study of the\r\nstereochemistry of the 1-pyrazoline decomposition. 34T yields\r\ncis-1-ethyl-2-methylcyclopropane (48C) in nearly racemic form and\r\ntrans-1-ethyl-2-methylcyclopropane (48T) 22.5% optically active\r\nwith predominant inversion of the alkyl groups. 34C yields cis-\r\n1-ethyl-2-methylcyclopropane (48C) 36.5% optically active with\r\npredominant retention of stereochemistry and trans-1-ethyl-2-methycyclopropane\r\n(48T) 14.2% optically active with predominant single\r\ninversion of the ethyl group.
\r\n\r\n\r\nII. A series of phenyl-substituted 2H-azirines: 3,3-dimethyl-\r\n2-phenyl-2H-azirine (33c), 3-methyl-2-phenyl-2H-azirine (33a),\r\n3-ethyl-2-phenyl-2H-azirine (33b), and 2,3-dimethyl-3-phenyl-2H-azirine\r\n(33d) were synthesized and their thermal decompositions\r\nwere investigated. 2-aza-1,3-butadienes were formed as primary\r\npyrolysis products from 33a-c, which indicates that the thermal\r\nreaction proceeds via carbon-carbon bond cleavage leading to iminocarbene\r\nintermediates. 33d yields 2,3-dimethylindole as its only\r\npyrolysis product, which indicates initial carbon-nitrogen bond\r\ncleavage leading to vinyl nitrene: intermediates. Further thermal\r\nreactions of the azabutaaienes to yield olefins and nitriles, and\r\ndihydroisoquinolines were also studied.
", "doi": "10.7907/DFVF-ZS54", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:10060", "collection": "thesis", "collection_id": "10060", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02222017-142615284", "primary_object_url": { "basename": "Sukenik_CN_1976.pdf", "content": "final", "filesize": 35486167, "license": "other", "mime_type": "application/pdf", "url": "/10060/1/Sukenik_CN_1976.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Catalysis of Organic Reactions: Part I: Enhancement of a Solid State Reaction by Proper Orientation within a Crystal. Part II. Micellar Effects on the Stereochemistry and Rate of Aqueous Solvolysis Reactions", "author": [ { "family_name": "Sukenik", "given_name": "Chaim N.", "clpid": "Sukenik-Chaim-N" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Part I. The solid state rearrangement of methyl-p-dimethylaminobenzenesulfonate\r\nto the trimethylammoniumbenzenesulfonate zwitterion was studied\r\nby a combination of spectroscopic techniques. NMR, Field Desorption\r\nMass Spectrometry, and X-Ray Crystallography were employed to determine\r\nthe mechanism of this reaction. It was shown to be an intermolecular\r\nnucleophilic displacement whose rate is greatly enhanced by the\r\ncrystallinity of the starting material.
\r\n\r\nPart II. A study of the effects of micelles on the aqueous solvolysis\r\nof alkyl-p-trimethylammoniumbenzenesulfonates revealed that anionic\r\nmicelles could change the rate and stereochemistry of the solvolysis\r\nreaction. The mechanism for the observed rate retardation and induced\r\ndecrease in stereochemical integrity was probed and a unified mechanistic\r\nhypothesis is presented.
", "doi": "10.7907/QB90-WP98", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:1380", "collection": "thesis", "collection_id": "1380", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04142004-135323", "primary_object_url": { "basename": "Jones_rr_1976.pdf", "content": "final", "filesize": 19352019, "license": "other", "mime_type": "application/pdf", "url": "/1380/1/Jones_rr_1976.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Progress Toward the Synthesis and Characterization of 1,4-Dehydroaromatic Systems: I. 1,4-Dehydrobenzene (Para-Benzene or Butalene); II. 1,4-Dehydrotropyl Cation, Anion and the Bicyclo[3.2.0]heptatrien-3-one", "author": [ { "family_name": "Jones", "given_name": "Richard R.", "clpid": "Jones-Richard-R" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\t\t\t\t\t\r\nThis thesis concerns the attempted synthesis of two strained nonbenzenoid, conjugated bicyclic systems, 1,4-dehydrobenzene (butalene or para-benzyne, 28) and the 1,4-dehydrotropylium ion (30c). Both 28a and 30c contain a fused cyclobutadiene ring with [...] its accompanying antiaromaticity but overall possess 4n+2 [pi] electrons. The concept of nonbenzenoid aromaticity as it applies to compounds such as these is reviewed. The synthetic approach to 28 and 30 systems is based on the pyrolytic cyclization of a 1,5-hexadiyne moiety to form a dimethylenecyclobutene, thereby introducing the strain and unsaturation of the fused four-membered ring in one step.\r\n\r\nIn Part I, the synthesis and pyrolysis of cis-1,6-dideutero-1,5-hexadiyn-3-ene (cis-60a) is described. By a combination of nmr and ms techniques, it is demonstrated that cis-60a undergoes a degenerate rearrangement at 200?C in the gas phase at atmospheric pressure, interconverting cis-60a with its 3,4-dideuteroisomer cis-60b with an equilibration half-life of 30 sec. None of the single exchange isomer cis-60c or any trans-60 was formed in this pyrolysis. These data require a transition state or intermediate between cis-60a and cis-60b with [...] symmetry, i. e., [...] 1,4-dehydrobenzene. Similarly prepared trans-60a did not undergo isomerization or rearrangement at these temperatures.\r\n\r\nPyrolysis of cis- and trans-60 in solution provided a high yield of benzene in the presence of hydrogen donors at the expense of cis-60. In carbon tetrachloride, para-dichlorobenzene was the major product. In methanol, a 10% yield of benzyl alcohol but no anisole was formed. Since these are typical products of radical abstraction, it is suggested that the symmetrical species implicated in the deuterium scrambling is a true intermediate and of 1,4-benzenediyl structure 28d or e (instead of 28a). [...].\r\n\r\nWhile traces of benzene were seen in the atmospheric and vacuum pyrolysis of cis- and trans-60, no satisfactory gas phase trapping experiment has been performed. Neither have substantial levels of deuterium scrambling been demonstrated in liquid phase pyrolysis. These points together with some indication of the stereospecificity of the benzene forming reaction in solution remain to be answered. The added complication of a possible triplet ground state for the 1,4-benzenediyl (28d) must also be resolved before a truly consistent story can be told. A possible direct route to a triplet 28d, photosensitized irradiation of cis-60a, failed to produce scrambling in competition with a demonstrated approach to the photostationary state. No transfer of acetylenic label was observed also under direct (254 nm) irradiation of cis-60a.\r\n\r\nIn Part II, toward formation of the 1,4-dehydrotropylium ion (30c) as well as the 1,4-dehydrotropyl anion (30a) and the bicyclo [3.2.0]heptatrien-3-one (52), the synthesis of [...] bicyclo[3.2.0]hepta-1,4,6-trienes substituted in the 3-position is discussed. The required 3-substituted 1,2-diethynylcyclopropanes were approached via carbene addition to hexadiynenes, eneynes, and via y-elimination routes. Of these, only the addition of propargyl carbene to methoxybuten-3-yne (150) provided any cyclopropane product. The 3-methoxy-1,2-diethynylcyclopropane (61d) [...] prepared in < 1% isolated yield by this method readily isomerized to the air sensitive 3-methoxybicyclo[3.2.0]hepta-1,4,6-triene (62d) upon pyrolysis under atmospheric pressure flow conditions at 305?C (contact time 10 sec). Attempted formation of 30a by ether cleavage reduction of 62d with potassium led only to polymer without any evidence for formation of an anion. However, treatment of 62d with SbF5 containing a catalytic amount of HOSO2F in a soft matrix at -180?C gave evidence in the nmr of formation of 30c although at such low concentrations that a clear spectrum was not obtained. This interesting result is currently under reinvestigation.", "doi": "10.7907/QQ2T-5185", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:5644", "collection": "thesis", "collection_id": "5644", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03292010-092444069", "primary_object_url": { "basename": "Bogan_gw_1975.pdf", "content": "final", "filesize": 1228719, "license": "other", "mime_type": "application/pdf", "url": "/5644/1/Bogan_gw_1975.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Synthesis and Solvolytic Investigations of 2-Hexanone-5-(p-N-methylpyridinium) Ether and n-Hexyl-p-carboxybenzenesulfonate", "author": [ { "family_name": "Bogan", "given_name": "Gary Wayne", "clpid": "Bogan-Gary-Wayne" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The synthesis and purification of 2-hexanone-5-(p-N-methylpyridinium) ether was accomplished. The reaction of this compound with aqueous NaOH failed to produce the desired products, cis- and trans-2-methylcyclopropylmethyl ketone. It appears that the desired anionic ring closure of the starting material did not take place, but instead, a simple displacement reaction occurred to produce 5- \r\nhydroxyhexan-2-one.\r\n\r\nIn a second project, the synthesis of n-hexyl-p-carboxybenzene-sulfonate was attempted by two different routes. The first route involved esterification of p-carboxybenzenesulfonyl chloride and n-hexanol to form the desired sulfonate. This method proved unsuccessful, and\r\nwas abandoned. The second route involved oxidation of n-hexyl-p-toluenesulfonate to the carboxy compound. This method was successful, producing n-hexyl-p-carboxybenzenesulfonate in about 7% yield. This \r\nmolecule was found to have an approximate half-life of 14 hours when reacted with 1 N aqueous NaOD at room temperature.\r\n", "doi": "10.7907/SMH3-TM92", "publication_date": "1975", "thesis_type": "masters", "thesis_year": "1975" }, { "id": "thesis:16693", "collection": "thesis", "collection_id": "16693", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09042024-184628054", "type": "thesis", "title": "Organic Reactions in the Gas Phase. Part I: Decomposition of Isomeric Cis 6,7-dimethyl-2,3-diazabicyclo[3.2.0]hept-2-enes in the Gas Phase. Part II: The Wall-Less Reactor. Part III: Thermal Isomerization of Cyclopropenes", "author": [ { "family_name": "Keppel", "given_name": "Robert Andrew", "clpid": "Keppel-Robert-Andrew" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Part I: Decomposition of Isomeric Cis 6,7-dimethyl-2,3-diazabicyclo[3.2.0]hept-2-enes in the Gas Phase
\r\n\r\nThe thermal decomposition of the isomeric cis 6,7-dimethyl-2,3-diazabicyclo[3.2.0]hept-2enes was \r\nstudied. In order to account for the products observed,\r\ndual pathways for the decomposition are proposed. The formation of isomeric\r\ncis 2,3-dimethyl-bicyclo[2.1.0] pentanes is explained by a mechanism involving\r\na diradical intermediate. The formation of 2,3-dimethylpenta-1,4-dienes is best\r\nexplained by a stereospecific retro-1,3-dipolar cleavage to an acyclic\r\ndiazo compound which loses nitrogen to form a carbene. The absence of\r\na thermal \"Di-\u03c0-methane pathway is indicated from the products.
\r\n\r\nPart II: The Wall-less Reactor
\r\n\r\nA wall-less reactor was constructed based on one designed\r\npreviously at Kent State. The reactor was modified and used to study\r\nthe unimolecular decomposition of strained hydrocarbons. Cyclopropane\r\nwas found to isomerize to propylene with a rate law of log k =\r\n14.6 -65.1 kcal per mole/\u03b8 over the temperature range of 936 to\r\n1026\u00b0K. The wall-less reactor was also used to study the isomerization of\r\n3,3-dimethylcyclopropene (see abstract of Part III).
\r\n\r\nPart III: Thermal Isomerization of Cyclopropenes
\r\n\r\nThe thermal rearrangement of 3,3-dimethylcyclopropene (6)\r\nwas studied in the wall-less reactor over a temperature range of\r\n608 to 668\u00b0K. The rate law for the isomerization was found to be\r\nlog k = 12.6 -36.2 kcal per mole/\u03b8. 6 isomerized to 86.2% 3-methyl-1-butyne,\r\n12.9% 1-methyl-1,3-butadiene and 0.9% 3-methyl-1,2-butadiene.\r\nThe data were in accord with published results of the\r\nisomerization of 6 in a static thermal reactor.
\r\n\r\nThe thermal rearrangement of 1-methylcyclopropene (14) was\r\ninvestigated by entering the energy surface for the reaction by two\r\nroutes: thermal isomerization of the cyclopropene and pyrolysis of\r\na vinylcarbene precursor, 3-methyl-3-vinyldiazirine (12). The\r\nacyclic C4H6 products from both reactions are \r\nidentical, however the proportions vary greatly. Greater than 99% of the\r\nproduct from the diazirine is the cyclopropene, and the remainder of the\r\nproducts is 1,3-butadiene, 2-butyne and 1,2-butadiene in the\r\nratio of 1:0.6:0.2, respectively. The products from the isomerization of\r\n1-methyl-cyclopropene are the same but in the ratio of 5:93:2, respectively. From\r\nthe data it is concluded that two intermediates exist for the\r\nisomerization, a planar vinylcarbene and a 90\u00b0 rotamer, designated\r\na diradical.
", "doi": "10.7907/9ske-ad80", "publication_date": "1975", "thesis_type": "phd", "thesis_year": "1975" }, { "id": "thesis:4086", "collection": "thesis", "collection_id": "4086", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10142005-153023", "primary_object_url": { "basename": "Clarke_tc_1974.pdf", "content": "final", "filesize": 8267383, "license": "other", "mime_type": "application/pdf", "url": "/4086/1/Clarke_tc_1974.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Investigations on the Mechanism of Thermal Decomposition of l-Pyrazolines. II. The Stereochemistry of Solvolytic Displacement and Intramolecular Nucleophilic Substitution by a Double Bond at a Vinyl Center", "author": [ { "family_name": "Clarke", "given_name": "Thomas Carl", "clpid": "Clarke-Thomas-Carl" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "I. Two mechanisms have been proposed to account for the net single inversion of stereochemistry observed in the pyrolysis of 3,5-dialkyl-1-pyrazolines. The first, involving initial cleavage of both C-N bonds and formation of a [pi]-cyclopropane intermediate, predicts completely racemic singly inverted product on pyrolysis of an optically active pyrazoline. The sequential C-N bond cleavage proposed in the second mechanism predicts that, to the extent that the rates of initial cleavage of the two ON bonds are different, some optical activity should be observed in the singly inverted product. In order to resolve this problem, the pyrolysis of (+)-(3R,5R)-trans-3-ethyl-5-methyl-1-pyrazoline was undertaken. Flow pyrolysis of this pyrazoline at 292\u00b0 and atmospheric pressure led to 71% cis-1-ethyl-2-methylcyclopropane, 27% trans-1-ethyl-2-methylcyclopropane and minor amounts of olefin product. The cis cyclopropane was formed with 0.8% retention of optical purity while the trans product showed 23% retention of optically purity. Correlation of these results with the pyrolyses of this pyrazoline specifically deuterated at C3 and C5 will allow a distinction between the two mechanistic possibilities. This work is currently in progress.\r\n\r\nII. In order to determine the stereochemistry of solvolytic displacement and intramolecular nucleophilic substitution by a remote double bond at a vinyl center, the synthesis and solvolysis in trifluoroethanol of (Z)- and (E)-3-methyl-2,6-heptadien-2-yl trifluoro-methanesulfonate were undertaken. In addition to 3-methyl-1,2,6-heptatriene and the products of solvolytic displacement, four cyclized trifluoroethyl ether products were formed. These four products were also generated in the trifluoroethanolysis of 1,2-dimethyl-1-cyclohexen-4-yl tosylate. Net inversion of stereochemistry was observed in both the solvolytic displacement and cyclization processes in the vinyl triflates. Solvolysis of (Z)- and (E)-3-methyl-2-hepten-2-yl trifluoro-methanesulfonate also resulted in net single inversion in the vinyl trifluoroethyl ether products. These results are explained in terms of competitive attack on the initially formed ion pairs and on free vinyl cation intermediates.", "doi": "10.7907/CY15-8E04", "publication_date": "1974", "thesis_type": "phd", "thesis_year": "1974" }, { "id": "thesis:10661", "collection": "thesis", "collection_id": "10661", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01312018-114130193", "primary_object_url": { "basename": "Morton_TH_1973.pdf", "content": "final", "filesize": 78754198, "license": "other", "mime_type": "application/pdf", "url": "/10661/1/Morton_TH_1973.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Organic Reactions in the Gas Phase: Part I. The Thermal Rearrangement of 3,3-Dimethylcyclopropene. Part II. Interaction of Remote Functional Groups in the Ion Chemistry of Bifunctional Ethers", "author": [ { "family_name": "Morton", "given_name": "Thomas Hellman", "clpid": "Morton-Thomas-Hellman" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "PART I: The Thermal Rearrangement of 3, 3-Dimethylcyclopropene
\r\n\r\nThe thermal rearrangement of 3, 3-dimethylcyclopropene was\r\ninvestigated by entering the energy surface for the reaction by two \r\nroutes:\tthermal isomerization of the cyclopropene and pyrolysis \r\nof a diazo compound precursor, 3-methyl-1-diazo-2-butene. The\r\nproducts from both reactions are identical; however the proportions \r\nvary greatly. Greater than 95% of the product from the diazo compound \r\nis the cyclopropene, and the remainder of the product is\r\nisoprene and isopropylacetylene in a 5:2 ratio, with trace gem-dimethyl\u00adallene.\t\r\nThe products from isomerization of the cyclopropene are isopropylacetylene, \r\nisoprene, and gem-dimethylallene in a ratio of\r\n500:50:1. From these data it is concluded that two intermediates\r\nexist for the isomerization, gem-dimethylvinylcarbene, (CH3)2C=CH CH,\r\nand a 90\u00b0 rotamer, designated as a diradical, (CH3)2\u010aCH=\u010aH.\r\nRelative rates of interconversion and cyclization and an energy surface are \r\ndetermined and the results are compared with Huckel and CNDO/2 \r\ncalculations on vinylcarbene.
\r\n\r\n\r\nPART II. Interaction of Remote Functional Groups in the Ion Chemistry of Bifunctional Ethers
\r\n\r\n\r\nAn Ion Cyclotron Resonance examination of bifunctional ethers of \r\nthe form CH3O(CH2)nOR, where n = 1 - 6 and R = H, CH3, or C2H5,\r\nreveals a large number of mass spectral processes and ion-molecule\r\nreactions in which the interaction of remote functional groups plays a\r\nprominent role.\tChainlength effects are particularly pronounced:\r\n6-member cyclic intermediates are inf erred in rarrangements of odd\u00ad electron species, \r\nwhile larger cycles appear pref erred in rearrange\u00adments of \r\nmany even electron species.
", "doi": "10.7907/0b6f-h333", "publication_date": "1973", "thesis_type": "phd", "thesis_year": "1973" }, { "id": "thesis:11175", "collection": "thesis", "collection_id": "11175", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09072018-101527022", "primary_object_url": { "basename": "Kelsey_DR_1973.pdf", "content": "final", "filesize": 192136440, "license": "other", "mime_type": "application/pdf", "url": "/11175/1/Kelsey_DR_1973.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Studies on Cycloproply-Stabilized Vinyl Cation Intermediates. II. Molecular Orbital Calculations on Cationic Intermediates and Displacement Reactions. III. On the Complexation of NMR Lanthanide Shift Reagents with Organic Substrates", "author": [ { "family_name": "Kelsey", "given_name": "Donald Ross", "clpid": "Kelsey-Donald-Ross" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "I. The heterogeneous and homogeneous silver-catalyzed acetolyses of E- and Z-1-cyclopropyl-1-iodopropene (1E and 1Z, R = methyl), E- and Z-1,2-dicyclopropylethylene (1E and 1Z, R = cyclopropyl), E- and Z-1-cyclopropyl-3-ethyl-1-iodopentene (1E and 1Z, R = 3-pentyl), and 1-iodo-3,4-hexadiene (4) are examined in detail. The acetate product distributions reveal small, but important, contributions of heterogeneous catalysis, clearly show overall net inversion of geometry in the formation of the corresponding vinyl acetates under homogeneous conditions, and reveal selectivity in the cyclopropyl ring-opening rearrangements of the intermediate vinyl cations. The results are consistent with the intervention of non-equilibrated ion-pair intermediates which undergo both some solvent trapping and ring-opening rearrangement with net inversion and dissociation to linear, sp-hybridized vinyl cations. It is also found that the steric\r\neffects of the \u03b2-alkyl substituents R are important in determining the extent of ion-pair contribution. The product distributions are also highly dependent upon the R substituent, with the ratio of vinyl acetates to rearranged cyclobutyl-type acetates decreasing as R changes from hydrogen, to 3-pentyl, to methyl, to cyclopropyl. It is shown that this is consistent with the conjugative electron-releasing ability of R in stabilizing the transition state for rearrangement of the vinyl cations, whereas the initial ionizations of the vinyl iodides (Z isomers) qualitatively depend upon the inductive electronic properties of R. Other electronic and steric effects of substituent R are discussed.
\r\n\r\nIt is also shown that 1E and 1Z, R = cyclopropyl, with deuterium label in the \u03b2-cyclopropyl ring, undergo reaction with no isotopic scrambling, indicating the absence (< 0.2%) of 1,2-hydride shift across the double bond in the 1,2 dicyclopropylvinyl cation. A similar result (< 1% rearrangement) is found for the 1,2-dicyclopropylethyl cation. These results are discussed in terms of \u03c3-delocalization of the cyclopropyl rings adjacent to the cationic centers.
\r\n\r\nII. This part has been published in full, see D.R. Kelsey and R.G. Bergman, Journal of the American Chemical Society, 93, 1953 (1971).
\r\n\r\nIII. An explicit treatment of the complexation equilibrium between organic substrates and the lanthanide nmr shift reagents is developed. It is shown that for a single equilibrium, plots of the observed shifts of two substrate protons, i and j, against one another must be linear with slopes that reflect the ratios (\u0394maxi/\u0394maxj) of the chemical shifts in the bound complex. This \"internal standard proton\" method is applied to sixteen vinyl and eleven allyl acetates using the acetoxy methyl protons as standard and Eu(fod)3 shift reagent. Characteristic slopes are obtained which depend upon the stereochemical relationships to the reference group. The method is shown to be a valuable and reliable means of establishing substrate structures even for isomeric mixtures, since impurities and concentrations have little effect.
\r\n\r\nIt is shown that at large ratios of substrate to reagent concentrations, St/Et, a plot of reciprocal observed shift, 1/\u0394obsd, against the total substrate concentration, St, should be linear if a 1:1 stoichiometry obtains. The plots of the data for representative substrates (allyl acetate, isopropenyl acetate, 2-butanone, tetrahydrofuran, 2-propanol, and dimethyl sulfoxide) with Eu(fod)3 show excellent linearity and estimated bound chemical shifts, \u0394max, and equilibrium constants, K, are obtained. The results for dimethyl sulfoxide suggest that the major complex stoichiometry is 1:1 at room temperature, even though the literature data suggest formation of a 2:1 (DMSO: Eu(fod)3) complex at low temperatures. It is observed that the limiting observed shifts, \u0394lim, obtained at high Et/St ratios are generally less than the \u0394max values. This and other observations are discussed in terms of non-ideal solution behavior at high reagent concentrations. A bibliography of 240 references is included.
", "doi": "10.7907/QV6K-J118", "publication_date": "1973", "thesis_type": "phd", "thesis_year": "1973" }, { "id": "thesis:9646", "collection": "thesis", "collection_id": "9646", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04042016-112239738", "primary_object_url": { "basename": "DAmore_mb_1972.pdf", "content": "final", "filesize": 60204677, "license": "other", "mime_type": "application/pdf", "url": "/9646/1/DAmore_mb_1972.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Bicyclo[3.2.0]Hepta-1,4,6-Triene: Synthesis, Thermal Rearrangement, and Anion Formation", "author": [ { "family_name": "D'Amore", "given_name": "Michael Brian", "clpid": "D'Amore-Michael-Brian" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In order to determine the properties of the bicycloheptatrienyl anion (Ia) (predicted to be conjugatively stabilized by H\u00fcckel Molecular Orbital Theory) the neutral precursor, bicyclo[3. 2. 0] hepta-1, 4, 6-triene (I) was prepared by the following route.
\r\n\r\nReaction of I with potassium-t-butoxide, potassium, or lithium dicyclohexylamide gave anion Ia in very low yield. Reprotonation of I was found to occur solely at the 1 or 5 position to give triene II, isolated as to its dimers.
\r\n\r\nA study of the acidity of I and of other conjugated hydrocarbons by means of ion cyclotron resonance spectroscopy resulted in determination of the following order of relative acidities:
\r\n\r\nH2S \u02c3 C5H6 \u02c3 CH3NO2 \u02c3 1, 4- C5H8 \u02c3 I \u02c3 C2H5OH \u02c3 H2O;\r\ncyclo-C7H8 \u02c3 C2 H5OH; \u0444CH3 \u02c3 CH3OH
\r\n\r\nIn addition, limits for the proton affinities of the conjugate bases were determined:
\r\n\r\n350 kcal/mole \u02c2 PA(C5 H5-) \u02c2 360 kcal/mole
\r\n\r\n362 kcal/mole \u02c2 PA(C5H7-, Ia, cyclo-C7H7-) \u02c2 377 kcal/mole PA(\u0444CH2-) \u02c2 385 kcal/mole
\r\n\r\nGas phase kinetics of the trans-XVIII to I transformation gave the following activation parameters: Ea = 43.0 kcal/mole, log A = 15.53 and \u2206S\u01c2 (220\u00b0) = 9.6 cu. The results were interpreted as indicating initial 1,2 bond cleavage to give the 1,3-diradical which closed to I. Similar studies on cis-XVIII gave results consistent with a surface component to the reaction (Ea = 22.7 kcal/mole; log A = 9.23, \u2206S\u01c2 (119\u00b0) = -18.9 eu).
\r\n\r\nThe low pressure (0.01 to 1 torr) pyrolysis of trans-XVIII gave in addition to I, fulvenallene (LV), ethynylcyclopentadiene (LVI) and heptafulvalene (LVII). The relative ratios of the C7H6 isomers were found to be dependent upon temperature and pressure, higher relative pressure and lower temperatures favoring formation of I. The results were found to be consistent with the intermediacy of vibrationally excited I and subsequent reaction to give LV and LVI.
\r\n\r\n", "doi": "10.7907/HJ5M-D411", "publication_date": "1972", "thesis_type": "phd", "thesis_year": "1972" }, { "id": "thesis:5724", "collection": "thesis", "collection_id": "5724", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04202010-094744901", "primary_object_url": { "basename": "Bruckner_jr_1971.pdf", "content": "final", "filesize": 1509768, "license": "other", "mime_type": "application/pdf", "url": "/5724/1/Bruckner_jr_1971.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Study of the Preparation of Tricyclo[4,1,0,0\u00b3,\u2077]heptane and the 6-Halofulvenes", "author": [ { "family_name": "Bruckner", "given_name": "Joseph Robert", "clpid": "Bruckner-Joseph-Robert" } ], "thesis_advisor": [ { "family_name": "Bergman", "given_name": "Robert G.", "clpid": "Bergman-R-G" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Part I:
\r\nThe literature synthesis, with some modifications, of tricyclo[ 4, 1, 0, 03,7]heptane was undertaken. While considerable difficulty was encountered in the final reaction involving a sodium borohydride reduction, far more successful results were obtained when lithium aluminum hydride was used instead as the reducing agent. The hydrocarbon can be stereospecifically deuterated at various points in the reaction sequence and once labeled, can be pyrolyzed and its products studied to determine the extent of orbital symmetry restrictions on the pyrolytic rearrangement process.
Part II:
\r\nIn efforts to produce the mono- and diadducts of dichloro- and dibromocarbene to cyclopentadiene, it was found that the respective 6-halofulvenes were being produced instead. Depending upon the conditions used, varying amounts of halobenzene and 1, 1-dihalo-2, 2- dimethylcyclopropane could be produced as other major reaction products. The fulvenes were obtained in best yield using haloform as the dihalocarbene precursor and potassium tert-butoxide as the base. Ethyl trichloroacetate and phenyl (bromodichloromethyl) mercury were also used with various bases to generate dichlorocarbene, but these methods were unsuccessful in producing the 6-chlorofulvene.
I. Structure and Reactions of the 1-Cyclopropyvinyl Cation
\r\n\r\nThe unusual solvolytic reactivity of cyclopropylcar\u00adbinyl derivatives suggested that cyclopropyl substitution should stabilize vinyl cations; accordingly, it has been shown that 1-cyclopropylvinyl iodide ionizes readily under solvolytic conditions, with or without silver catalysis.\r\nComparative kinetic measurements show that the cyclopropyl\r\ngroup enhances the uncatalyzed solvolysis rate by a factor greater than 1.2 x 103, apparently by delocalizing the incipient positive charge. The major products result from reactions of the 1-cyclopropylvinyl cation with solvent, but partial rearrangement of this intermediate to the 2-methyl-enecyclobutyl cation occurs in acetic acid. The enthalpy of activation for this rearrangement exceeds that required for solvent trapping by 2.2 kcal/mol. A small yield of 3,4-pentadien-l-yl acetate may involve rearrangement to the 3,4-pentadien-l-yl cation. Comparative product studies show that 1-cyclopropylvinyl cation is also the major intermediate in the solvolysis of 3,4-pentadien-l-yl derivatives but is not involved in solvolyses of 2-methylenecyclobutyl or\r\n1-cyclobutenylcarbinyl halides.\tThere appears to be a difference between the 2-methylenecyclobutyl cation resulting from rearrangement and that obtained on direct solvolysis.
\r\n\r\nII. Interaction of the Face of a Cyclopropane Ring with Positively Charged Carbon
\r\n\r\nIn order to evaluate the nature of the title interaction,\r\nthe solvolytic reactivities of 4-tricyclyl, 1-apocamphyl,\r\nand 1-methyl-4-tr icyclo[2.2.2.02.6]octyl derivatives were compared. Solvolysis of the trifluoromethanesulfonates (triflates) in 60% aqueous ethanol (buffered) provided good first-order kinetic and Arrhenius data. Extrapolated to 25\u00b0 the relative rates for these substrates (in the order given above) are 1.0, 2.84 x 104, and 5.45 x 107. In\r\neach case, product studies showed that no rearrangement\r\ntook place, and incorporation of 18O-in 4-tricyclenol on solvolysis of 4-tricyclyl triflate in isotopically enriched medium showed that even under the most forcing conditions, carbon-oxygen rather than sulfur-oxygen bond cleavage was occurring. Since the rate data are well rationalized by semiempirical calculations that consider only relative strain energies, interaction of an incipient carbonium ion with the face of a cyclopropane ring apparently affords no significant stabilization.
\r\n\r\n", "doi": "10.7907/9A8S-1W54", "publication_date": "1971", "thesis_type": "phd", "thesis_year": "1971" } ]