Base catalysed rearrangements involving ylide intermediates. Part 9. The rearrangement reactions of cyclic allylic ammonium and sulphonium ylides
Base catalysed rearrangements involving ylide intermediates. Part 9. The rearrangement reactions of cyclic allylic ammonium and sulphonium ylides
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涉及叶立德中间体的碱催化重排。
DOI：
10.1039/p19810001953
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
I. Sutherland
中科院分区：
文献类型：
--
作者：
S. Mageswaran;W. Ollis;I. Sutherland
烯丙基酰化铵（22）和（47）以及酰化磺铵（53）是可分离的，通常作为结晶固体，因为它们[3,2]的异位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（22）和二氢硫代吡啶（29）基基经过热[3,2]重排，但吡啶基（47）基基通过[1,2]而不是[3,2]信号通路重排。二氢噻吩基醚（53）不发生[1,2]或[3,2]异位重排，而是以双分子方式反应，最终生成丁-1,3-二烯、2,5-二氢噻吩和杂环（55）。酰基（22）和（29）的[3,2]重排主要遵循内通路，导致产物（23）和（31）的单一非对映异构体；类似的无环酰化铵没有表现出这种强烈的内端偏好。
The 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 by a [1,2], rather than a [3,2], sigmatropic pathway. The dihydrothiophenium ylide (53) does not undergo either a [1,2] or [3,2] sigmatropic rearrangement but instead reacts in a bimolecular fashion to give eventually buta-1,3-diene, 2,5-dihydrothiophen, and the heterocycle (55). The [3,2] rearrangements of the ylides (22) and (29) follow predominantly an endo-pathway leading to a single diastereoisomer of the products (23) and (31); this strong endo preference is not shown by analogous acyclic ammonium ylides.