A New Approach to Promoting Sluggish Diels−Alder Reactions: Dihapto-Coordination of the Diene
作者:Weijun Liu、Fei You、Christopher J. Mocella、W. Dean Harman
DOI:10.1021/ja0553654
日期:2006.2.1
and various enones and enals (methyl vinyl ketone, ethyl vinyl ketone, methacrolien) is accomplished at room temperature in yields ranging from 51 to 68% without the use of Lewis acids, high pressures, or microwave reactors. This normally sluggish cyclization is accomplished by precoordination of the diene to a pi-basic molybdenum complex. The eta2-bound metal is thought to promote a Michael reaction
1,3-环己二烯与各种烯酮和烯醛(甲基乙烯基酮、乙基乙烯基酮、甲基丙烯醛)之间的环加成反应在室温下完成,收率范围为 51% 至 68%,无需使用路易斯酸、高压或微波反应器. 这种通常缓慢的环化反应是通过将二烯预先配位为 pi-碱性钼络合物来完成的。据认为,与 eta2 结合的金属会促进二烯的未配位部分与烯酮之间的迈克尔反应,然后所得的烯醇化物闭合形成环烯烃产物。有机环加合物通过用空气或三氟甲磺酸银氧化以接近定量的产率去除。对于更多空间位阻的烯酮(例如,氧化亚甲基)和丙烯酸甲酯,所需的结果需要使用 BF3.OEt2,