Synthesis of allomaltol containing pyridazines and their photochemical transformation into substituted benzo[h]pyrano[2,3-f]cinnolin-8-ones

Abstract

In this study, we developed an efficient two-step approach for the synthesis of novel terarylenes featuring an allomaltol substituent and a pyridazine bridge and investigated their photochemical behavior. The proposed strategy is based on the initial reaction of methylene-active allomaltol derivatives with aromatic arylglyoxals, followed by condensation of the resulting diaroylethene with hydrazine. It was found that the obtained terarylenes do not undergo any photochemical transformations under UV irradiation. However, modification of the hydroxyl group through acylation overcomes this limitation and directs the photoreaction toward 6π-electrocyclization. This study provides a convenient method for accessing previously unknown benzo[h]pyrano[2,3-f]cinnolin-8-one derivatives and demonstrates that their acylated precursors can serve as efficient photoacid generators.