Ligand-Controlled Intramolecular Carbonylative Cyclization of 1,1-Diethynyl Acetates: New Entry to the Functionalized 4-Cyclopentene-1,3-diones

The carbonylative cyclization of 1,1-diethynyl acetates mediated by Phbox/Pd(TFA) 2 afforded a functionalized 4-cyclopentene-1,3-dione as a major product. In the absence of box ligand, a methoxycarbonylated orthoester was obtained predominantly.