Abstract
2-Chloro-3-cyanopyridine compounds (2a, b), intermediates for the synthesis of thiamine were reacted with hydrazine hydrate to give the corresponding 1H-pyrazolo[3, 4-b]pyridine compounds (3a, b). The reaction of methyl 2-chloro-3-cyano-6-methylpyridine-4-carboxylate (5) with hydrazine hydrate afforded pyrido[3, 4-d]pyridazine compounds(6, 7). By refluxing with ethanol containing a small amount of H2SO4, 3-(ethoxycarbonylcyanomethylene)indolin-2(1H)-one was converted into ethyl 3-cyano-2-oxo-1, 2-dihydroquinoline-4-carboxylate(9). The reaction of hydrazine hydrate with 2-chloroderivative of (9) gave 1H-pyrazolo[3, 4-b]quino1ine compound (12).
