N‑Heterocyclic Carbene-Catalyzed [3+4] Cycloaddition and Kinetic Resolution of Azomethine Imines

The
first N-heterocyclic carbene (NHC)-catalyzed
[3+4] cycloaddition of azomethine imines and enals is disclosed. Oxidative
catalytic remote activation of enals affords 1,4-dipolarophile intermediates
that react with 1,3-dipolar azomethine imines to generate dinitrogen-fused
seven-membered heterocyclic products with high optical purities. Our
approach also provides effective kinetic resolution of azomethine
imines, in which the substrate chiral center that is remote from the
NHC catalyst can be well resolved.

本发明涉及一种首例N-杂环卡宾（NHC）催化的[3+4]环加成反应，该反应以亚胺亚甲基和烯醛为底物。通过氧化催化远程激活烯醛，可获得1,4-二极性中间体，进而与1,3-二极性亚胺亚甲基反应，生成高光学纯度的氮气桥连七元杂环产物。此外，本研究方法还实现了亚胺亚甲基的高效动力学拆分，其中远离NHC催化剂的底物手性中心得以有效分辨。