α‑Regioselective Asymmetric [3 + 2] Annulations of Morita–Baylis–Hillman Carbonates with Cyclic 1‑Azadienes and Mechanism Elucidation

An α-regio-, diastereo-, and enantioselective [3 + 2] annulation reaction of Morita–Baylis–Hillman carbonates of isatins and activated alkenes with a bulky electron-withdrawing 1,2-benzoisothiazole 1,1-dioxide or 1,2,3-benzoxathiazine 2,2-dioxide motif is reported, furnishing an array of spirooxindoles (>19:1 dr, up to >99% ee) catalyzed by cinchona-derived tertiary amines. Density functional theory calculation studies have been conducted to elucidate the originality of the α-regioselective annulations.

本文报道了一种兼具α-区域选择性、非对映选择性与对映选择性的[3+2]环化反应：以靛红的莫里塔-贝利斯-希尔曼（Morita–Baylis–Hillman）碳酸酯与带有大位阻吸电子1,2-苯并异噻唑-1,1-二氧化物（1,2-benzoisothiazole 1,1-dioxide）或1,2,3-苯并氧噻嗪-2,2-二氧化物（1,2,3-benzoxathiazine 2,2-dioxide）结构单元的活化烯烃为反应底物，在金鸡纳碱衍生的三级胺催化下，可得到一系列螺环氧化吲哚（spirooxindoles）产物，其非对映选择性比例（diastereomeric ratio, dr）>19:1，对映体过量百分比（enantiomeric excess, ee）最高可达>99%。本研究通过密度泛函理论（Density Functional Theory, DFT）计算，阐明了该α-区域选择性环化反应的独特性。