半稳定磷叶立德和亚胺高选择性合成卤代烯烃

半稳定磷叶立德分别和合适的磺酰基活化的亚胺在温和的反应条件下得到高选择性的卤代烯烃产物,对于芳香族、杂芳环、α,β-不饱和以及脂肪族亚胺产物都可以得到良好的收率。除此之外,我们还以良好的收率选择性合成了单一构型的一系列的氯代和碘代烯烃产物。该反应机理和Wittig反应类似,反应通过2+2]环加成生成中间体然后消除得到产物,产物的ZE选择性和氮原子上磺酰基团的性质有关。

Stereoselective synthesis of disubstituted alkenyl halides via semistabilized triphenylphosphonium Ylides with imines

A broad range of N-sulfonyl aromatic,heteroaromatic,alpha,beta-unsaturated,and aliphatic imines reacted with semistabilized phosphonium ylides to afford an array of both(Z)-and(E)-isomers of alkenyl bromides in good yields and with greater than 99∶1 stereoselectivity.Moreover,this tunable protocol had been successfully applied to the highly stereoselective synthesis of alkenyl chloride,and alkenyl iodides.The olefination reaction could potentially proceed through a Wittig-type reaction pathway involving formal2+2]cycloaddition to generate a 1,2-azaphosphetane intermediate followed by elimination of an iminophosphorane yielding an alkene,wherein the N-sulfonyl groups serve as powerful handles to finely tune stereoselectivity.