Lewis acid mediated asymmetric Diels–Alder reactions of chiral 2-phosphonoacrylates
作者:Jia-Liang Zhu、Po-Erh Chen、Hue-Wen Huang
DOI:10.1016/j.tetasy.2012.11.021
日期:2013.1
2-Phosphonoacrylates containing four chiral alcohol auxiliaries were efficiently prepared and evaluated in Lewis acid mediated Diels–Alder reactions. Under the activation of SnCl4, all reactions performed in CH2Cl2 at −65 °C exclusively afforded the endo (endo-to-carboxylate) cycloadducts with dr’s ranging from 50:50 to >99:1. The best facial selectivity was obtained from the substrate bearing a (−)-phenylmenthyl
含有四种手性醇助剂的2-膦酸酯已通过路易斯酸介导的Diels-Alder反应进行了高效制备和评估。在SnCl 4的激活下,在CH 2 Cl 2中于-65°C进行的所有反应仅得到dr's为50:50至> 99:1的内(内-羧化)环加合物。从带有(-)-苯基薄荷基的底物获得最佳的面部选择性,得到的加合物为(dr> 99:1)或几乎为(dr = 99:1)单一非对映异构体。描述了用于阐明环加合物的结构以及观察到的立体选择性的合理化的详细策略。