meso-Phbox-Pd(II) catalyzed tandem carbonylative cyclization of 1-ethynyl-1-propargyl acetate

Palladium(II) catalyzed carbonylation of 1-ethynyl-1-propargyl acetate 1 is described; in the absence of the bisoxazoline (box) ligand, the second triple bond did not react, affording cyclic orthoesters 3 and 4. The use of meso-Phbox-Pd(II) strikingly changed the course of the reaction, yielding bicyclic lactone 2 by tandem carbonylative cyclization as a result of insertion of the second triple bond.