On the reaction of N-vinyliminophosphoranes. Part 11. Convenient synthesis of 9 H-cyclohepta[b]pyridines and pyridotropones

Abstract

Thermal reaction of tributyl(cyclohepta-1,3,5-trienylimino)phosphorane with α,β-unsaturated ketones led to a Michael-type C–C bond formation and subsequent aza-Wittig reaction to give 9H-cyclohepta[b]pyridine derivatives in good yields. The 9H-cyclohepta[b]pyridine derivatives were oxidized conveniently by t-butyl hydroperoxide in the presence of catalytic chromium trioxide to give two or three isomers of the pyridotropones in good to moderate combined yields.