Base-Mediated Synthesis of 4,5-Disub-stituted Furan-2(5H)-ones

Significance

Reported is a route to furan-2(5H)-ones by cyclization of acetyl propargylic esters, involving an intriguing acyl shift, cyclization and decarbonylation sequence. The starting materials can be synthesized from the corresponding alkyne carboxylic acids and 2-haloacetophenones. Reaction conditions are mild, the substrate scope is quite good, and the yields range from poor to excellent. The reaction fails when R^² = Alk. Refreshingly, proof for the mechanism involving deuterium (both solvent and substrate) and ^¹³C labeling, isolation, and successful reaction of the cyclized pre-decarbonylation product is provided.