Synthesis of 5-(2-Phenylethenyl)indolizines by Selective Intermolecular 1,3-Dipolar Cycloaddition of 2-(2-Phenylethenyl)pyridinium N-Ylide with Alkenes Promoted by Tetrakis-pyridine Cobalt(II) Dichromate

Abstract

Intermolecular 1,3-dipolar cycloadditions of 2-(2-phenylethenyl)pyridinium N-ylides (3a–d) with electron-deficient alkenes (5a–d) were carried out selectively in the presence of tetrakis-pyridine cobalt(II) dichromate to yield 5-(2-phenylethenyl)indolizines (6a–j) in moderate yields (48–63%).