Preparation of Functionalized Dialkylzincs via a Boron−Zinc Exchange. Reactivity and Catalytic Asymmetric Addition to Aldehydes
作者:Falk Langer、Lothar Schwink、Arokiasamy Devasagayaraj、Pierre-Yves Chavant、Paul Knochel
DOI:10.1021/jo961129n
日期:1996.11.15
The hydroboration of olefins with Et(2)BH provides diethyl(alkyl)boranes 2 which readily undergo a boron-zinc exchange with Et(2)Zn providing a range of polyfunctional primary, secondary, and benzylic diorganozincs. The resulting diorganozincs 3 have been reacted with various electrophiles (allylic halides, acid chlorides, alkylidenemalonates, ethyl propiolate, nitroolefins) in the presence of CuCN
烯烃与Et(2)BH的氢硼化反应生成的二乙基(烷基)硼烷2容易与Et(2)Zn进行硼-锌交换,从而提供了一系列多官能的伯,仲和苄基二有机锌。在CuCN.2LiCl存在下,使所得的二有机锌3与各种亲电试剂(烯丙基卤化物,酰氯,亚烷基丙二酸酯,丙酸乙酯,硝基烯烃)反应,具有极好的收率。用由非对映体纯的二乙基(烷基)硼烷制备的仲二烷基锌,发生硼-锌交换而失去立体化学。在手性催化剂55的存在下,将3-不对称地加成到醛中,提供了光学活性的多官能仲醇(50至超过96%ee)。