Base catalysed rearrangements involving ylide intermediates. Part 9. The rearrangement reactions of cyclic allylic ammonium and sulphonium ylides
作者:Sivapathasuntharam Mageswaran、W. David Ollis、Ian O. Sutherland
DOI:10.1039/p19810001953
日期:——
allylic ammonium ylides (22) and (47) and sulphonium ylide (53) are isolable, usually as crystalline solids, because their [3,2] sigmatropic rearrangements are inhibited by the strain associated with the bicyclic transition state of a concerted reaction mechanism. The tetrahydropyridinium (22) and dihydrothiopyranium (29) ylides undergo a thermal [3,2] rearrangement, but, the pyrrolinium ylide (47) rearranges
烯丙基铵化铵(22)和(47)以及化铵(53)通常是结晶固体,是可分离的,因为它们的[3,2]σ重排被与协同反应机制的双环过渡态相关的应变所抑制。 。四氢吡啶鎓(22)和二氢硫代吡啶鎓(29)的基团进行热[3,2]重排,但是吡咯内鎓盐(47)通过[1,2]而不是[3,2]σ途径重排。二氢噻吩叶立德(53)既不进行[1,2]也不进行[3,2]σ重排,而是以双分子的方式反应,最终生成1,3-二烯,2,5-二氢噻吩和丁酸酯。杂环(55)。酰基(22)和(29)的[3,2]重排主要遵循内切-导致产物(23)和(31)的单一非对映异构体的途径;类似的无环铵化铵没有显示出这种强烈的内在偏爱性。