NOVEL SYNTHESIS OF NITROGEN-HETEROCYCLES BY USING N-VINYLIMINOPHOSPHORANES

The chemical species containing nitrogen-phosphorus double bond are known as the iminophosphorane. We have prepared novel N-vinyliminophosphoranes by the reaction of vinyl azides with tertiary phosphines. The iminophosphoranes underwent enamine type C-C bond formation and following aza-Wittig reaction to give nitrogen heterocycles. The reaction of N-vinyliminophosphoranes with α, β-unsaturated ketones resulted in the formation of pyridines. The reaction was also applicable for the synthesis of [n] (2,4)pyridinophanes (n = 6-9) by using cyclic α, β-unsaturated ketones. In the reaction with α-bromoketones, preparation of pyrrole ring system was accomplished. Furthermore, the reaction with tropone derivatives and fulvene derivatives resulted in the formation of 1-azaazulene and 5-azaazulene ring systems. The chemical properties of these azaazulenes were also studied. These reactions are general and serve as a convenient route for the synthesis of pyridine, pyrrole and azaazulene ring systems. © 1990, The Society of Synthetic Organic Chemistry, Japan. All rights reserved.