Asymmetric Vinylogous Mannich Reaction of Silyloxy Furans with <i>N</i>-<i>tert</i>-Butanesulfinyl Ketimines

A highly regio- and diastereoselective TMSOTf promoted vinylogous Mannich reaction for the synthesis of chiral quaternary 3-amino­oxindole butenolides from 2-silyloxy furans and chiral ketimines is described. The method is found to be very efficient and also provides a facile access to sterically challenging 3-amino­oxindole butenolides bearing two quaternary centers in continuation. Further, the versatility of the method is demonstrated by the 1,4-addition of nucleophiles on the sterically congested butenolide substructure.本研究报道了一种以三氟甲磺酸三甲基硅酯（trimethylsilyl trifluoromethanesulfonate, TMSOTf）为促进剂的高区域选择性与非对映选择性插烯曼尼希反应，可用于由2-硅氧基呋喃与手性酮亚胺出发合成手性季碳3-氨基氧化吲哚丁烯内酯。该方法展现出优异的反应效率，还可便捷制备带有两个连续季碳中心、空间位阻极具挑战性的3-氨基氧化吲哚丁烯内酯产物。进一步地，通过在空间位阻拥挤的丁烯内酯子结构上开展亲核试剂的1,4-加成反应，验证了该方法的通用性。