Through sequential Claisen- and Cope rearrangements the chainlengthening of allylic alcohols by one isoprene unit was achieved. Treatment of (E)-1a first with lithium N-cyclohexyl-N-isopropylamide at −70°, followed by trimethylsilylchloride and warming up to room temperature yielded after work-up 3a (R = H), which rearranged at 156° in high yield to (E/Z)-4a. An analogous reaction sequence transformed
通过连续的Claisen和Cope重排,实现了烯丙基醇通过一个
异戊二烯单元的链延长。首先在-70°C下用N-环己基-N-异丙基
氨基
锂处理(E)-1a,然后在处理3a(R = H)后将其加热到室温,然后在156°C下重排3a(R = H)产率为(E / Z)-4a。类似的反应序列由6转化为8。选择
N-甲基苯胺基
锂作为碱(E / Z)-9,选择性地重排为12,然后将其转化为Cecropia少年激素前体(E / Z)-4b。