Thiazolo [3,2-a] pyridinium salts

The sulfides formed by the reaction of α-halo ketones or α-halo acetals with 2-mercaptopyridine may be cyclized in good yield to form thiazolo[3, 2-a]pyridinium salts. The presence of chloro or nitro substituents on the pyridine ring does not interfere with the synthesis. Nitration of 3-methylthiazolo[3, 2-a]pyridinium perchlorate has been found to occur at position 8.