2-Alkyl-3,5-diaryl-1,3,4-thiadiazolium perchlorates and reactions thereof

Abstract

2-Alkyl- and 2-aryl-3,5-diaryl-1,3,4-thiadiazolium perchlorates can be prepared from N′-arylbenzothiohydrazides by reaction with (a) a carboxylic anhydride–perchloric acid mixture or (b) a nitrile–perchloric acid mixture.

The 2-methyl-3,5-diaryl-1,3,4-thiadiazolium salts can be deprotonated to methine bases which can be trapped by carboxylic anhydrides, thiobenzoylthioglycolic acid, and 1-fluoro-2,4-dinitrobenzene to yield the corresponding derivatives of the methine base; in one instance, the methine base was shown to dimerize in the absence of a trapping agent. Treatment with triethylamine–methanol (or ethanol) gives the 2-alkoxy-2-alkyl-3,5-diaryl-1,3,4-thiadiazole which is also a source of the (trappable) methine base on thermolysis. The 2-aryl series of thiadiazolium salts gives analogous 2-alkoxythiadiazoles under these conditions.