Reaction of heteroarenes and 3-alkenyl oxindoles: Synthesis of stereodefined tetrasubstituted alkenes

A novel protocol mediated by DBU for the construction of sp2 C–N bond between 3-alkenyl oxindoles and indazole/benzotriazole has been successfully accomplished. But the cascade reaction of 3-alkenyl oxindoles with benzimidazole leads to the formation of sp2 C-C coupling products under similar conditions. Starting from 3-alkenyl oxindoles, various stereodefined aromatic substituted 3-alkenyl oxindoles can be obtained under simple conditions without contamination by transition-metal residues.