Synthesis of hydrazones derived from 2-substituted-10-carboxyphenothiazine hydrazides

2-Substituted-10-carboxyphenothiazine hydrazides 3 were found to yield hydrazones 5 on reaction with aromatic aldehydes. However, a similar reaction of hydrazides 3 with aliphatic ketones in refluxing ethanol failed to give the expected hydrazones 6 . The corresponding phenothiazines 1 were isolated in this reaction, apparently through alcoholysis of the amide bond to the ring nitrogen atom in 3 .