SYNTHESIS OF NOVEL SUBSTITUTED PYRIDAZIN- 6(1H)-ONES

Arylhydrazono acetamides 1 react with chloroacetic acid chloride to gi ve N-chloroacetyl derivatives 2. Subsequent reaction with pyridines fo llowed by ring closure yield 1-(4-amino-6-oxopyridazin-5-yl)-pyridiniu m chlorides 3. Analogously, 1-(6-oxo-pyridazin-5-yl)-pyridinium chlori de (5) and 6-oxo-5-pyridinio-pyridazin-4-olate (4) are formed from phe nylhydrazono derivatives and pyridine. Treatment of 3 and 4 with hydra zinium hydrate gives 4,5-diamino-6-oxo-pyridazin-3-carbohydrazides 6 a nd 5-amino-4-hydroxy-pyridazin-6(1H)-one (8). An analogous ring cleava ge of 3e and 5 gives rise to 4,5-diamino- and 5-amino-pyridazin-6(1H)- ones 7. On treatment of the pyridinium salts 3 with caustic soda in wa ter, nucleophilic addition of the amino group to the pyridinium ring t akes place and stable dehydrated products 9 are isolated.