已经建立了2,2'-二酯氮丙啶与3,4-二氢吡喃衍生物和非环烯醇醚的高度非对映和对映选择性[3 + 2]环加成反应。以中等至高产率(高达94%)和良好的立体选择性(> 19:1 dr,高达95.5:4.5 er)生成了各种旋光的八氢吡喃并[2,3- c ]吡咯和3-甲氧基吡咯烷衍生物。该方法还用于d-半乳糖衍生物的高度非对映选择性合成中。八氢吡喃并[2,3- c ]吡咯的绝对构型表明,在最后的环化步骤中,使用3,4-二氢吡喃和6-烷基取代的吡咯为底物的反应给出了反向的非对映异构。
Chiral Phosphoric Acid Catalyzed Addition of Dihydropyrans to N-Acyl Imines: Stereocontrolled Access to Enantioenriched Spirocyclic Oxazoletetrahydropyrans with Three Contiguous Stereocenters
摘要:
Dihydropyran derivatives readily undergo addition to N-acyl imines in the presence of chiral phosphoric acids. This addition process yields an attractive product that is capable of a tandem oxidative-cyclization via an epoxide intermediate.