The synthesis of alkenes via epi-phosphonium species: 1. An anti-Wittig elimination
作者:Nicholas J. Lawrence、Faiz Muhammad
DOI:10.1016/s0040-4020(98)00959-4
日期:1998.12
syn-isomers upon treatment with phosphorus trichloride and triethylamine give E and Z alkenes respectively, by an anti elimination. This is in marked contrast to the syn Horner-Wittig elimination of the corresponding 1,2-phosphinoyl alcohols. The 1,2-phosphinyl alcohols 11 were prepared by the reduction of 1,2-phosphinoyl alcohols with cerium(III) chloride/lithium aluminium hydride. The anti elimination is
反-1,2-氧膦醇11和它们相应的顺式处理时-异构体与三氯化磷和三乙胺给予Ë和Ž分别烯烃,由抗消除。这与相应的1,2-膦酰基醇的合成的霍纳-维蒂希(Honer-Wittig)消除形成鲜明对比。通过用氯化铈(III)/氢化铝锂还原1,2-膦酰基醇来制备1,2-膦酰基醇11。通过消除瞬态表epi物种的形成来解释抗消除。意外的E描述了在氯化铈(III)/氢化铝锂还原期间,其中二苯基膦酰基与芳基相邻的1,2-膦酰基醇的-选择性Horner-Wittig消除。这导致了抗有丝分裂剂E -combretastatin A-4的合成。还描述了由相应的膦-硼烷配合物合成1,2-膦基醇的方法。