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

摘要

o-Formyl-substituted β,β-difluorostyrenes readily react with NH_2OH·HCl or NH_4OAc 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-). β,β-Difiuorostyrenes bearing an o-diazenyl group (HN=N-), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines.