Pyridazine chemistry. Part 33. 5-Aminopyridazin-4-yl o-fluorophenyl ketone as a key intermediate in the syntheses of diaza analogues of acridone, xanthone, and thioxanthone

Abstract

Facile syntheses of pyridazino[4,5-b]quinolin-10(5H)one (2) and 5-substituted derivatives thereof [(5a),(5b)] are described. 5-(o-Fluorobenzoyl)pyridazin-4(1H)one (9), readily accessible from the title amino ketone (1) by a N-benzylation–hydrolysis–debenzylation sequence, serves as an intermediate in high-yield syntheses of 10H-[1]benzopyrano[2,3-d] pyridazin- 10-one (10) and 10H-[1]benzothiopyrano[2,3-d]pyridazin-10-one (11).