Regioselective and Asymmetric Diels−Alder Reaction of 1- and 2-Substituted Cyclopentadienes Catalyzed by a Brønsted Acid Activated Chiral Oxazaborolidine
作者:Joshua N. Payette、Hisashi Yamamoto
DOI:10.1021/ja0735958
日期:2007.8.1
Cationic oxazaborolidine 2 affords Diels−Alder adducts of ethyl acrylate and 2-substituted cyclopentadienes, derived from the corresponding mixture of regioisomers, as single isomers in excellent yields and enantioselectivities. Furthermore, Diels−Alder adducts of 1-substituted cyclopentadienes are obtained through a one-pot procedure whereby ethyl acrylate is initially employed to consume all 2-substituted
阳离子 oxazaborolidine 2 提供丙烯酸乙酯和 2-取代环戊二烯的 Diels-Alder 加合物,衍生自相应的区域异构体混合物,作为单一异构体,具有优异的产率和对映选择性。此外,1-取代环戊二烯的 Diels-Alder 加合物是通过一锅法获得的,其中最初使用丙烯酸乙酯消耗所有 2-取代环戊二烯。随后,加入各种 2,5-二取代苯醌以与剩余的 1-取代环戊二烯反应。值得注意的是,反应选择性地发生在与催化剂 2 配位的双键上,以高产率和优异的对映选择性提供含有相邻全碳四元立体中心的加合物。