Cobalt-catalyzed cross-coupling reactions of alkyl halides with aryl Grignard reagents and their application to sequential radical cyclization/cross-coupling reactions
Reactions of alkyl halides with arylmagnesium bromides in the presence of cobalt(II)(diphosphine) complexes are discussed. Treatment of 1-bromooctane with phenylmagnesium bromide with the aid of a catalytic amount of CoCl2(dppp) [DPPP=1,3-bis(diphenylphosphino)propane] yielded octylbenzene in good yield. The reaction mechanism would include single electron transfer from an electron-rich cobalt complex
gallium hydride reagent, HGaCl2, was found to act as a radical mediator, like tributyltin hydride. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radicalcyclization of halo acetals was also successful with not only the stoichiometric gallium
Radical Cyclization Reactions with a Zirconocene-Olefin Complex as an Efficient Single Electron Transfer Reagent
作者:Kazuya Fujita、Hideki Yorimitsu、Koichiro Oshima
DOI:10.1055/s-2002-19777
日期:——
A zirconocene-olefin complex induced reductive radical cyclization of β-haloalkyl allyl acetals in THF. This complex served as a single electrontransferreagent to promote the cyclization. Furthermore, the reaction in DME afforded tetrahydrofuranylmethylzirconium species effectively.