Transitional activation phenomena: synthesis of the 4H-benzo[e][1,3,4]-thiadiazine ring

Abstract

A synthesis of 1,3,4H-benzothiadiazine derivatives from α-bromo- and α-chlorobenzaldehyde 2,4-dihalogenophenylhydrazones and potassium thioacetate is described. The process involves displacement of ortho-halogen, considered to be transiently activated during the course of reaction : the ease of displacement of ortho-halogen is F > Br > Cl.

The bis-[α-(2,4-dihalogenophenylhydrazono)benzyl] sulphide, for which a second synthesis is described, accompanies the thiadiazine in most cases.