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Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions.
Chemistry. 2004 Nov 05; 10(22):5640-8.C

Abstract

Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides--as well as primary ones--to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.

Authors+Show Affiliations

Ohmiya H
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Tsuji T
No affiliation info available
Yorimitsu H
No affiliation info available
Oshima K
No affiliation info available

MeSH

AlkylationBenzeneCarbonCatalysisChloratesCobaltCross-Linking ReagentsCyclizationFree RadicalsLigandsMagnesium CompoundsMolecular StructurePentanonesPropaneTemperature

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15457521

Citation

Ohmiya, Hirohisa, et al. "Cobalt-catalyzed Cross-coupling Reactions of Alkyl Halides With Allylic and Benzylic Grignard Reagents and Their Application to Tandem Radical Cyclization/cross-coupling Reactions." Chemistry (Weinheim an Der Bergstrasse, Germany), vol. 10, no. 22, 2004, pp. 5640-8.
Ohmiya H, Tsuji T, Yorimitsu H, et al. Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions. Chemistry. 2004;10(22):5640-8.
Ohmiya, H., Tsuji, T., Yorimitsu, H., & Oshima, K. (2004). Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions. Chemistry (Weinheim an Der Bergstrasse, Germany), 10(22), 5640-8.
Ohmiya H, et al. Cobalt-catalyzed Cross-coupling Reactions of Alkyl Halides With Allylic and Benzylic Grignard Reagents and Their Application to Tandem Radical Cyclization/cross-coupling Reactions. Chemistry. 2004 Nov 5;10(22):5640-8. PubMed PMID: 15457521.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions. AU - Ohmiya,Hirohisa, AU - Tsuji,Takashi, AU - Yorimitsu,Hideki, AU - Oshima,Koichiro, PY - 2004/10/1/pubmed PY - 2006/5/18/medline PY - 2004/10/1/entrez SP - 5640 EP - 8 JF - Chemistry (Weinheim an der Bergstrasse, Germany) JO - Chemistry VL - 10 IS - 22 N2 - Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides--as well as primary ones--to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides. SN - 0947-6539 UR - https://www.unboundmedicine.com/medline/citation/15457521/Cobalt_catalyzed_cross_coupling_reactions_of_alkyl_halides_with_allylic_and_benzylic_Grignard_reagents_and_their_application_to_tandem_radical_cyclization/cross_coupling_reactions_ DB - PRIME DP - Unbound Medicine ER -