Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China.
J Am Chem Soc. 2010 Apr 14;132(14):5018-20. doi: 10.1021/ja910238f.
The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph(3)P horizontal lineCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, alpha,beta-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
涉及三苯基膦叶立德（Ph(3)P 水平条 CHR）与醛的直接烯烃化的 Wittig 反应可以说是最常用的烯烃合成方法，但对于半稳定的三苯基膦叶立德（R = 芳基或乙烯基），通常会得到 Z-和 E-烯烃的混合物。我们开发了一种简单有效的方法，通过用具有与醛不同的电子和空间性质的 N-磺酰亚胺代替 Wittig 反应中使用的醛，显著提高立体选择性。一系列具有适当 N-磺酰基的芳香族、α，β-不饱和和脂肪族亚胺在温和的反应条件下与各种亚苄基三苯基膦或烯丙基三苯基膦顺利地进行烯烃化反应，以良好至优异的收率得到一系列共轭烯烃的 Z-和 E-异构体，立体选择性大于 99:1。此外，该可调谐方案已成功应用于两种抗癌药物 DMU-212 和其 Z-异构体的高立体选择性合成。
