Access to phthalazinones via palladium-catalyzed three-component cycloamino-carbonylation of 2-formylaryl tosylates, hydrazines and CO

The palladium-catalyzed three-component cycloaminocarbonylation of 2-formylaryl tosylates with hydrazines and carbon monoxide has been established, which provides an efficient method for synthesis of substituted phthalazinones. In addition, by applying this protocol as the key step, Hydralazine can easily be synthesized in 65% yield.