Cobalt-Catalyzed Cross-Coupling Reactions of Alkyl Halides with Allylic and Benzylic Grignard Reagents and Their Application to Tandem Radical Cyclization/Cross-Coupling Reactions
作者:Hirohisa Ohmiya、Takashi Tsuji、Hideki Yorimitsu、Koichiro Oshima
DOI:10.1002/chem.200400545
日期:2004.11.19
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
公开了烷基卤化物与烯丙基格利雅试剂的钴催化的交叉偶联反应的细节。氯化钴(II)和1,2-双(二苯基膦基)乙烷(DPPE)或1,3-双(二苯基膦基)丙烷(DPPP)的组合适合作为预催化剂,并允许使用仲和叔烷基卤化物作为主要试剂-可用作烯丙基格氏试剂的偶联伙伴。该反应提供了季碳中心的简便合成,而钯,镍和铜催化剂几乎是不可能的。苄基,甲基烯丙基和巴豆基格氏试剂均可以与卤代烷偶联。苄基化肯定需要DPPE或DPPP作为配体。反应机理应包括由母体烷基卤生成烷基。可以根据串联自由基环化/交叉偶联反应来解释该机理。此外,还描述了5-烷氧基-6-卤代-4-氧杂-1-氧杂-1-己烯衍生物的偶发串联自由基环化/环丙烷化/羰基烯丙基化。以碳为中心的自由基的中间体导致母体烷基卤化物的原始立体化学丧失,从而产生了外消旋烷基卤化物不对称交叉偶联的可能性。