Quinolone analogues 8 [1‐6]. Synthesis of 3‐aminopyridazino‐[3,4‐ b ]quinoxalin‐4(l H )‐one

The 3‐amino‐1‐methylpyridazino[3,4‐ b ]quinoxalin‐4(1 H )‐one 6 and N ‐(1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐ b ]quinoxalin‐3‐yl)carbamates 17a,b were synthesized from the 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐ b ]quinoxa‐line‐3‐carboxylate 1b via the 1,5‐dihydro‐4‐hydroxy‐1‐methylpyridazino[3,4‐ b ]quinoxaline‐3‐carbohydrazide 13b and then 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐ b ]quinoxaline‐3‐carboxazide 8 . Heating of compound 13b and arylalde‐hydes afforded the 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐ b ]quinoxaline‐3‐carbo(2‐arylmethylene)hydrazides 14a‐d.