Mass spectrometry of 2-substituted-4-arylthiazoles. II--Identification of microsomal nitroreduction product by mass spectrometry.

Electron impact fragmentation of 2-methyl-4-(4-nitrophenyl)-thiazole and 2-amino-4-(4-nitrophenyl)-thiazoles were studied. Prominent fragment ions result from: (1) elimination of an NO2 radical and of a neutral NO molecule; (2) 1,2 cleavage of the thiazole ring in both compounds to give a phenoxythiirene ion; and (3) subsequent cleavage of this phenoxythiirene ion to give the common ions [C7H5]+ and [C5H3]+. An anaerobic microsomal nitroreduction product of 2-methyl-4-(4-nitrophenyl) thiazole was isolated and its structure was determined by electron impact, chemical ionization and high resolution mass spectrometry to be 2-methyl-4-(4-aminophenyl)-thiazole.