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.