Intramolecular cyclization of beta,beta-difluorostyrenes bearing an iminomethyl or a diazenyl group at the ortho position: synthesis of 3-fluorinated isoquinoline and cinnoline derivatives

Abstract

o-Formyl-substituted beta,beta-difluorostyrenes readily react with NH(2)OH.HCl or NH(4)OAc to afford 3-fluoroisoquinoline derivatives in good yield via (i) the formation of the corresponding oximes or imines and (ii) subsequent intramolecular replacement of a vinylic fluorine by the sp(2) nitrogen of the iminomethyl group (HON=CH- or HN=CH-). Beta,beta-Difluorostyrenes bearing an o-diazenyl group (HN=N-), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines.