Isothiazolo [3, 4-b] pyridine was synthesized from 2-aminonicotinonitrile in three steps: by the reaction with ammonia and hydrogen sulfide to produce 2-aminothionicotinamide; oxidative cyclization with hydrogen peroxide to give 3-aminoisothiazolo [3, 4-b] pyridine, followed by diazotization and reduction with hypophosphorous acid. 3-Aminoisothiazolo [4, 3-b] pyridine was prepared in a similar way from 3-aminopicolinonitrile via 3- ...