Base catalysed rearrangements involving ylide intermediates. Part 10. The effects of torsional strain in the transition state upon [1,2] and [3,2] rearrangements
作者:W. David Ollis、Ian O. Sutherland、Yodhathai Thebtaranonth
DOI:10.1039/p19810001963
日期:——
sigmatropic rearrangements of the bicyclic ammonium ylides (8), (11), and (14) are inhibited by the bicyclic framework which prevents correct orbital alignment for π-bonding in the transition state for a concerted [3,2] sigmatropic rearrangement or in the vinylogous nitroxide component of the radical pair required as an intermediate in a [1,2] sigmatropic rearrangement. The ylides (14a) and (14d), based upon
双环铵盐(8),(11)和(14)的[3,2]和[1,2]σ重排被双环框架所抑制,这防止了过渡态π键的正确轨道对准用于协调的[3,2]σ重排或作为[1,2]σ重排的中间体所需的自由基对的乙烯基亚硝酸盐组分。基于1-氮杂双环-[3.3.1]壬烷体系的亚基(14a)和(14d)是唯一经历纯净[3,2]重排的双环烯丙基亚基,其涉及外向过渡态,或者完全(14a)或主要(14d)。