Synthesis of diverse 4,5-dihydro-3(2H)-pyridazinones on Wang resin

An efficient solid-phase synthesis of structurally diverse 4,5-dihydro-3(2H )-pyridazinones is described using readily available substituted 4-oxo-buta noic acids. Polymer-supported gamma -ketoesters prepared from Wang resin re acted with several hydrazines to afford the corresponding hydrazones. A pro tocol developed in mild conditions without isolating the intermediate hydra zone led to pyridazinones in good yields after a cyclization cleavage appro ach. This successful strategy represents an attractive method for a rapid s ynthesis of heterocyclic libraries for biological evaluation.