Anomalous Z-isomer content in Wittig reaction products from keto-stabilised ylides with ortho-heteroatom substituted benzaldehydes
作者:Peter A. Byrne、Lee J. Higham、Pádraic McGovern、Declan G. Gilheany
DOI:10.1016/j.tetlet.2012.09.123
日期:2012.12
Wittig reaction products of keto-stabilised ylides with ortho-substituted benzaldehydes are found to show significantly higher than expected Z-alkene content (up to 50%) compared to analogous reactions of the same ylides with benzaldehyde itself. A cooperative effect is seen whereby the unusual Z-content is further augmented if the ylide bears greater steric bulk in the α′-position. These results are
与相同的酰基化物与苯甲醛本身的类似反应相比,发现酮稳定的酰基化物与邻位取代的苯甲醛的维蒂希反应产物显示出显着高于预期的Z-烯烃含量(高达50%)。观察到协同作用,如果叶立德在α'-位置具有较大的空间体积,则异常Z含量会进一步增加。这些结果与我们先前关于所有内鎓盐类型与带有β-杂原子的醛的反应的观察结果一致。值得注意的是,以前仅在半稳定化的基团上才能看到的协同作用现已扩展到稳定化的基团。Z都异常增加-含量和协同作用可以在Wittig反应的[2 + 2]环加成机理内合理化。