Synthesis of new pyridazino[4,5-c]isoquinolinones by Suzuki cross-coupling reaction

Suzuki cross-coupling reaction of 2-alkyl(methyl and benzyl)-5-chloro-4-methoxy- and 2-alkyl(methyl and benzyl)-4-chloro-5-methoxypyridazin-3(2H)-ones with 2-formylphenylboronic acid afforded the corresponding biaryl products which were cyclized with ammonia to yield hitherto undescribed pyridazino[4,5-c]isoquinolinones. Removal of the N-benzyl protective group in position 2 yielded the unsubstituted tricyclic pyridazinones.