A useful synthesis of 3-halogeno-1-azabutadiene derivatives, and their applicability in the preparation of heterocycles

Abstract

Azabutadiene derivatives (1) are halogenated in a selective manner with N-chlorosuccinimide or N-bromosuccinimide at the C_β-enamine carbon. The resultant halogenated compounds (3) are suitable precursors for the synthesis of 2-oxopyrimidines and 1,2,6-thiadiazine S-oxides containing a halogen at C-5 and C-4 respectively, and also for substituted 4-chloro- and 4-bromo-pyrazoles.