Synthesis of Angular 7,8-Pyridazinocoumarins via the Transformation of a Hydroxy Group into a Carbonyl Group

The synthesis of angular 7,8-pyridazinocoumarins (2H-pyrano[2,3-f]phthalazin-2-ones) is reported via the oxidation of 8[1-(acylhydrazono)ethyl]-7-hydroxycoumarin with (diacetoxyiodo)benzene and subsequent treatment of the derived 7,8-diacylcoumarins with hydrazine. The procedure involves transformation of a hydroxy group into an acyl group and formation of a new C-C bond.