Chiral Amino Siloxy Dienes in the Diels−Alder Reaction: Applications to the Asymmetric Synthesis of 4-Substituted and 4,5-Disubstituted Cyclohexenones and the Total Synthesis of (−)-α-Elemene
作者:Sergey A. Kozmin、Viresh H. Rawal
DOI:10.1021/ja9921930
日期:1999.10.1
amino siloxy diene containing a C2-symmetric 2,5-diphenylpyrrolidine auxiliary was found to provide high diastereofacial control, even at or above room temperature. Upon hydrolysis of the cycloadducts, 4-substituted and 4,5-disubstituted cyclohexenones were obtained with ee's ranging from 85% to >98%. A simple model based primarily on steric arguments was developed to rationalize and predict the absolute
描述了手性 1-amino-3-siloxy-1,3-butadienes 在 Diels-Alder 反应中的制备、反应性和非对映选择性的研究。这些二烯很容易从相应的对映体纯取代吡咯烷以良好的收率制备。所有描述的二烯在温和的反应条件下很容易与几种活化的亲二烯体发生环加成反应。发现含有 C2 对称 2,5-二苯基吡咯烷助剂的氨基甲硅烷氧基二烯即使在室温或室温以上也能提供高度的非对映面控制。环加合物水解后,得到 4-取代和 4,5-二取代的环己烯酮,ee 的范围为 85% 至 >98%。开发了一个主要基于空间参数的简单模型,以合理化和预测通过该序列获得的最终产品的绝对构型。该方法的合成效用通过 (-)-α-榄香烯的简明对映选择性合成来说明。该合成还有助于建立...