Formal [4 + 2] Cycloaddition of Donor−Acceptor Cyclobutanes and Aldehydes: Stereoselective Access to Substituted Tetrahydropyrans
作者:Andrew T. Parsons、Jeffrey S. Johnson
DOI:10.1021/ja906755e
日期:2009.10.14
diastereoselective synthesis of 2,6-cis-disubstituted tetrahydropyrans (THPs) via Lewis acid-catalyzed formal [4 + 2] cycloaddition of donor-acceptor cyclobutanes and aldehydes has been developed. THP products are formed in up to 96% yield and 99:1 diastereoselectivity. Aromatic, cinnamyl, and aliphatic aldehydes are competent dipolarophiles in this system. This methodology was extended to a [[2 + 2] + 2] cycloaddition
通过路易斯酸催化的供体-受体环丁烷和醛的正式 [4 + 2] 环加成,2,6-顺式二取代四氢吡喃 (THP) 的高度非对映选择性合成已被开发出来。THP 产物的产率高达 96%,非对映选择性为 99:1。芳香醛、肉桂醛和脂肪醛在该系统中是有能力的亲偶极体。该方法扩展到 4-甲氧基苯乙烯、二甲基亚甲基丙二酸酯和醛的 [[2 + 2] + 2] 环加成反应,直接提供 THP,无需事先分离环丁烷。