On the Reaction of (Vinylimino)phosphoranes. Part 17. Preparation of N-Vinylcarbodiimides and Their Cycloaddition with Several Dienophiles to Give Pyridine Ring System

Article abstract of DOI:10.1246/bcsj.64.1325

The aza-Wittig reaction of (vinylimino)triphenylphosphorane and its several derivatives was examined to give N-phenyl-N'-vinylcarbodiimide and its derivatives, all of which underwent a <4+2> cycloaddition reaction with electron-rich dienophiles (enamines) and/or electron-deficient dienophiles (activated acetylenes), resulting in the formation of a pyridine ring system.The regioselectivity of the cycloaddition reaction could be rationalized on the basis of a frontier orbital consideration.