[ { "id": "authors:8844x-eat13", "collection": "authors", "collection_id": "8844x-eat13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200507-083516909", "type": "article", "title": "Electron acceptors promote proton\u2013hydride tautomerism in low valent rhenium \u03b2-diketiminates", "author": [ { "family_name": "Lohrey", "given_name": "Trevor D.", "orcid": "0000-0003-3568-7861", "clpid": "Lohrey-T-D" }, { "family_name": "Fostvedt", "given_name": "Jade I.", "orcid": "0000-0002-6445-8569", "clpid": "Fostvedt-J-I" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Arnold", "given_name": "John", "orcid": "0000-0001-9671-227X", "clpid": "Arnold-J" } ], "abstract": "We report a series of \u03b2-diketiminate (BDI) complexes in which tautomeric rhenium(III) hydride and rhenium(I) protio-BDI species readily interconvert between the solid and solution states. This phenomenon, which is only operative when an electron-accepting ligand is bound to rhenium, was investigated by a combination of experimental and computational methods.", "doi": "10.1039/c9cc09475j", "issn": "1359-7345", "publisher": "Royal Society of Chemistry", "publication": "Chemical Communications", "publication_date": "2020-04-04", "series_number": "26", "volume": "56", "issue": "26", "pages": "3761-3764" }, { "id": "authors:8j9yb-dny05", "collection": "authors", "collection_id": "8j9yb-dny05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191217-113649566", "type": "article", "title": "John E. Bercaw: a joint appreciation", "author": [ { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Labinger", "given_name": "Jay A.", "orcid": "0000-0002-1942-9232", "clpid": "Labinger-J-A" } ], "abstract": "An appreciation of John Bercaw from two of his long-time colleagues and friends.", "doi": "10.1016/j.poly.2019.114307", "issn": "0277-5387", "publisher": "Elsevier", "publication": "Polyhedron", "publication_date": "2020-02-01", "volume": "177", "pages": "Art. No. 114307" }, { "id": "authors:2vqrp-rz057", "collection": "authors", "collection_id": "2vqrp-rz057", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191204-090016184", "type": "article", "title": "Controlling dinitrogen functionalization at rhenium through alkali metal ion pairing", "author": [ { "family_name": "Lohrey", "given_name": "Trevor D.", "orcid": "0000-0003-3568-7861", "clpid": "Lohrey-T-D" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Arnold", "given_name": "John", "orcid": "0000-0001-9671-227X", "clpid": "Arnold-J" } ], "abstract": "The rhenium(I) salt Na[Re(\u03b7\u2075-Cp)(BDI)] can be cooled in solution under a dinitrogen atmosphere to selectively access complexes containing rhenium(III) centers bound to direduced, doubly-bonded N\u2082 (i.e. diazenide) fragments. We demonstrate this reactivity is critically dependent on ion pairing involving the Na\u207a ion in the starting material, as N\u2082 binding by Na[Re(\u03b7\u2075-Cp)(BDI)] proved to be much less favorable when the Na\u207a was sequestered by benzo-12-crown-4. The analogous chemistry of Na[Re(\u03b7\u2075-Cp)(BDI)] with carbon monoxide (CO) and 2,6-xylylisocyanide (XylNC) was also investigated, which provided structural and spectroscopic bases for determining the impact of ion pairing on \u03c0-acid activation in this system.", "doi": "10.1039/c9dt04489b", "issn": "1477-9226", "publisher": "Royal Society of Chemistry", "publication": "Dalton Transactions", "publication_date": "2019-12-28", "series_number": "48", "volume": "2019", "issue": "48", "pages": "17936-17944" }, { "id": "authors:esdd4-m4f05", "collection": "authors", "collection_id": "esdd4-m4f05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171219-094125728", "type": "article", "title": "Ronald Breslow (1931-2017)", "author": [ { "family_name": "Schepartz", "given_name": "Alanna", "clpid": "Schepartz-A" }, { "family_name": "Bergman", "given_name": "Robert", "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" } ], "abstract": "Ronald Breslow, Samuel Latham Mitchill Professor of Chemistry at Columbia University, passed away on October 25, 2017, at the age of 86. Breslow made remarkable contributions to the fields of physical-organic and bioorganic chemistry, including biological and biomimetic transformations, and the use of molecular recognition to control reaction selectivity.", "doi": "10.1002/anie.201711641", "issn": "1433-7851", "publisher": "Wiley", "publication": "Angewandte Chemie International Edition", "publication_date": "2018-01-02", "series_number": "1", "volume": "57", "issue": "1", "pages": "37" }, { "id": "authors:0f1ka-p0q34", "collection": "authors", "collection_id": "0f1ka-p0q34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100809-091734911", "type": "article", "title": "On the Development of Catalytic Carba-6\u03c0 Electrocyclizations", "author": [ { "family_name": "Bishop", "given_name": "Lee M.", "clpid": "Bishop-L-M" }, { "family_name": "Roberson", "given_name": "Russell E.", "clpid": "Roberson-R-E" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Trauner", "given_name": "Dirk", "orcid": "0000-0002-6782-6056", "clpid": "Trauner-D" } ], "abstract": "Hexatriene substrates substituted in the 2-position with carbonyl groups were studied in the context of catalytic 6\u03c0 electrocyclizations. The nature of the carbonyl group and the substitution pattern on the hexatriene have significant effects on the ability of these substrates to succumb to catalysis. A novel 2-formyl hexatriene dimerization was observed. The first example of a catalytic asymmetric carba-6\u03c0 electrocyclization is reported along with the discovery of an unusual kinetic resolution via a catalytic photochemical electrocyclic ring-opening.", "doi": "10.1055/s-0029-1218812", "issn": "0039-7881", "publisher": "Georg Thieme Verlag", "publication": "Synthesis-Stuttgart", "publication_date": "2010-07", "series_number": "13", "issue": "13", "pages": "2233 -2244" }, { "id": "authors:h4hmn-te821", "collection": "authors", "collection_id": "h4hmn-te821", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170125-103406029", "type": "article", "title": "Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C\u2212H Bond Activation", "author": [ { "family_name": "Lewis", "given_name": "Jared C.", "clpid": "Lewis-J-C" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Ellman", "given_name": "Jonathan A.", "clpid": "Ellman-J-A" } ], "abstract": "Nitrogen heterocycles are present in many compounds of enormous practical importance, ranging from pharmaceutical agents and biological probes to electroactive materials. Direct functionalization of nitrogen heterocycles through C\u2212H bond activation constitutes a powerful means of regioselectively introducing a variety of substituents with diverse functional groups onto the heterocycle scaffold. Working together, our two groups have developed a family of Rh-catalyzed heterocycle alkylation and arylation reactions that are notable for their high level of functional-group compatibility. This Account describes our work in this area, emphasizing the relevant mechanistic insights that enabled synthetic advances and distinguished the resulting transformations from other methods.\n\nWe initially discovered an intramolecular Rh-catalyzed C-2 alkylation of azoles by alkenyl groups. That reaction provided access to a number of di-, tri-, and tetracyclic azole derivatives. We then developed conditions that exploited microwave heating to expedite these reactions. While investigating the mechanism of this transformation, we discovered that a novel substrate-derived Rh\u2212N-heterocyclic carbene (NHC) complex was involved as an intermediate. We then synthesized analogous Rh\u2212NHC complexes directly by treating precursors to the intermediate [RhCl(PCy3)2] with N-methylbenzimidazole, 3-methyl-3,4-dihydroquinazoline, and 1-methyl-1,4-benzodiazepine-2-one.\n\nExtensive kinetic analysis and DFT calculations supported a mechanism for carbene formation in which the catalytically active RhCl(PCy3)2 fragment coordinates to the heterocycle before intramolecular activation of the C\u2212H bond occurs. The resulting Rh\u2212H intermediate ultimately tautomerizes to the observed carbene complex. With this mechanistic information and the discovery that acid cocatalysts accelerate the alkylation, we developed conditions that efficiently and intermolecularly alkylate a variety of heterocycles, including azoles, azolines, dihydroquinazolines, pyridines, and quinolines, with a wide range of functionalized olefins. We demonstrated the utility of this methodology in the synthesis of natural products, drug candidates, and other biologically active molecules.\n\nIn addition, we developed conditions to directly arylate these heterocycles with aryl halides. Our initial conditions that used PCy3 as a ligand were successful only for aryl iodides. However, efforts designed to avoid catalyst decomposition led to the development of ligands based on 9-phosphabicyclo[4.2.1]nonane (phoban) that also facilitated the coupling of aryl bromides. We then replicated the unique coordination environment, stability, and catalytic activity of this complex using the much simpler tetrahydrophosphepine ligands and developed conditions that coupled aryl bromides bearing diverse functional groups without the use of a glovebox or purified reagents. With further mechanistic inquiry, we anticipate that researchers will better understand the details of the aforementioned Rh-catalyzed C\u2212H bond functionalization reactions, resulting in the design of more efficient and robust catalysts, expanded substrate scope, and new transformations.", "doi": "10.1021/ar800042p", "pmcid": "PMC2610463", "issn": "0001-4842", "publisher": "American Chemical Society", "publication": "Accounts of Chemical Research", "publication_date": "2008-08-01", "series_number": "8", "volume": "41", "issue": "8", "pages": "1013-1025" }, { "id": "authors:h74bp-p9432", "collection": "authors", "collection_id": "h74bp-p9432", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120727-104851305", "type": "article", "title": "Identification of Binuclear Acyl Complexes as Intermediates in the CO-induced Conversion of [(\u03b7^5-C_5H_5)Co(CO)(Me)]_2 into Acetone, and [(\u03b7^5-C_5H_5)Co(CO)(Et)]_2 into Pentan-3-one", "author": [ { "family_name": "White", "given_name": "Mary Anne", "orcid": "0000-0001-8142-0004", "clpid": "White-M-A" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "abstract": "Studies of the carbonylation of [(\u03b7^5-C_5H_5)Co(CO)(R)]_2(R = Me, Et) at temperatures below ambient have revealed that these complexes may be converted into ketones via binuclear diacyl complexes [(\u03b7^5-C_5H_5)Co(CO)(COR)]_2; the postulated mechanistic pathway circumvents the earlier-identified intermediate (\u03b7^5-C_5H_5)Co(CO)R_2, and involves alkyl transfer from a Co^(II) acyl complex as a critical step.", "doi": "10.1039/c39790001056", "issn": "0022-4936", "publisher": "Royal Society of Chemistry", "publication": "Journal of the Chemical Society. Chemical Communications", "publication_date": "1979", "series_number": "23", "volume": "1979", "issue": "23", "pages": "1056-1058" }, { "id": "authors:hjkyb-qx780", "collection": "authors", "collection_id": "hjkyb-qx780", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120813-144839283", "type": "article", "title": "Cationic Cyclization Involving a Remote Allene Function in the\n Trifluoroethanolysis of Hepta-5,6-dienyl Toluene-p-sulphonate", "author": [ { "family_name": "Sekera", "given_name": "Michael H.", "clpid": "Sekera-M-H" }, { "family_name": "Weissman", "given_name": "Ben-Avi", "clpid": "Weissman-B-A" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "abstract": "The remote allene function participates efficiently in the trifluoroethanolysis of hepta-5,6-dienyl toluene-p-sulphonate, leading to the cyclized 2-methylenecyclohexyl cation.", "doi": "10.1039/C39730000679", "issn": "0022-4936", "publisher": "Royal Society of Chemistry", "publication": "Journal of the Chemical Society. Chemical Communications", "publication_date": "1973", "series_number": "18", "issue": "18", "pages": "679-680" }, { "id": "authors:av3sc-qs284", "collection": "authors", "collection_id": "av3sc-qs284", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120808-141846921", "type": "article", "title": "Effect of 2-Substitution on the Rearrangement of 1-Cyclopropylvinyl Cations", "author": [ { "family_name": "Kelsey", "given_name": "Donald R.", "clpid": "Kelsey-D-R" }, { "family_name": "Bergman", "given_name": "Robert G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" } ], "abstract": "2-Substitution in 1-cyclopropylvinyl cations\nproduces a steric effect on cation generation and solvent\ntrapping, but an electronic charge-stabilizing effect\non cyclopropyl-to-cyclobutyl rearrangement.", "doi": "10.1039/C39730000589", "issn": "0022-4936", "publisher": "Royal Society of Chemistry", "publication": "Journal of the Chemical Society. Chemical Communications", "publication_date": "1973", "volume": "16", "pages": "589-590" }, { "id": "authors:97b35-xgq83", "collection": "authors", "collection_id": "97b35-xgq83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120814-151623508", "type": "article", "title": "3-Oxabicyclo[3,2,0]hepta-1,4-diene", "author": [ { "family_name": "Bergman", "given_name": "R. G.", "orcid": "0000-0002-3105-8366", "clpid": "Bergman-R-G" }, { "family_name": "Vollhardt", "given_name": "K. Peter C.", "clpid": "Vollhardt-K-P-C" } ], "abstract": "3-Oxabicyclo[3,2,0]hepta-1,4-diene (3) has been synthesized by partial hydrogenation of 3-oxabicyclo-[3,2,0]hepta-1,4,6-triene (2).", "doi": "10.1039/C39730000214", "issn": "0022-4936", "publisher": "Royal Society of Chemistry", "publication": "Journal of the Chemical Society. Chemical Communications", "publication_date": "1973", "series_number": "6", "volume": "1973", "issue": "6", "pages": "214-215" } ]