Regio- and stereo-selectivity in the reaction of methyl 4,5-epoxy-2-hexenoate with methylcopper reagents
作者:Toshiro Ibuk、Miwa Tanak、Hisao Nemoto、Yoshinori Yamamoto
DOI:10.1016/0040-4020(89)80071-7
日期:1989.1
The reaction of 4,5-epoxy-2-hexenoate (3) with methylcopper, dimethylcuprate, and their BF3, complexes gave predominantly the γ-methylated product (5) via SN2 process, while the reaction with methylcyanocuprate, higher order dimethylcyanocuprate and their BF3 complexes afforded preferentially the α-methylated product (4) via SN2 ' process. Anti-diastereoselectivity was observed regardless of the substitution
4,5-环氧-2-己烯酸酯(3)与甲基铜,二甲基铜酸酯及其BF 3配合物的反应主要通过S N 2过程得到的γ-甲基化产物(5),而与甲基氰脲酸酯的反应则更高级通过S N 2'方法,优先得到二甲基氰基丙二酸酯及其BF 3络合物,得到α-甲基化产物(4)。无论取代模式如何,均观察到抗非对映选择性。BF 3 ·OEt 2的存在降低了抗选择性,在某些情况下,在BF 3 ·OEt过量的情况下观察到相反的同-非对映选择性2。在CNDO / 2计算的基础上讨论了这些区域选择性和立体选择性。