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

o-Formyl-substituted β,β-difluorostyrenes readily react with NH₂OH·HCl or NH₄OAc 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 sp² nitrogen of the iminomethyl group (HONCH– or HNCH–). β,β-Difluorostyrenes bearing an o-diazenyl group (HNN–), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines.