Methylenecyclopropane Ring Formation/Opening Cascade for the Synthesis of Indolizines.

A unique strategy toward the synthesis of polysubstituted indolizines has been developed. When 2-pyridinyl-2-(2'-bromoallyl)-1-carboxylates were treated with Cs2CO3, the starting material went through a methylenecyclopropane ring formation/opening cascade, and the corresponding indolizines were obtained in moderate to good yield as a single regioisomer.