Pd(II)—dppb and syngas catalyze regioselective hydroesterification of terminal alkynes under neutral conditions

Palladium(II) regioselectively catalyzes the hydroesterification of terminal alkynes under syngas forming α,β-unsaturated esters 3 and 4 in excellent chemical yields under neutral conditions. The high selectivity for the linear ester 4 was obtained with a catalytic system that includes Pd(II), 1,4-bis(diphenylphosphino)butane (dppb) and CO/H2 in CH2Cl2 as solvent. The control of the regioselectivity depends strongly upon the type of ligand, the solvent and the use of the syngas mixture.