Transition metal-free annulative vinylene transfer via the 1,3-dipolar reaction of N -ylides: access to benzo-fused indolizines.

An efficient metal-free annulative vinylene transfer protocol for the synthesis of benzo-fused indolizines via 1,3-dipolar cycloadditions of N -ylides with vinylene carbonate has been developed. Vinylene carbonate serves as an acetylene surrogate without any external oxidant involved. This transformation leads to the direct construction of versatile benzo-fused indolizine derivatives in moderate to good yields.