“Clip-cycle” synthesis of 2-pyridazinones bearing enaminonitrile moiety from thioesters and dicyanohydrazones

The "clip-cycle" synthesis of 2-pyridazinones containing enaminonitriles from thioesters with dicyanohydrazones is achieved through a AgOAc-promoted acylation-cyclization-tautomerization cascade reaction. Moreover, the obtained 2-pyridazinones are further transformed into biologically significant bicyclic-fused pyridazinones exhibiting intriguing fluorescence emission properties. Additionally, quantum chemical calculations were performed to provide a rational explanation for the observed photophysical characteristics.