Ligand-Controlled Regioselective Alkoxycarbonylation of Nonfunctionalized Unsymmetric Internal Alkynes

Pd-catalyzed alkoxycarbonylation of internal alkynes provides a straightforward access to α,β-disubstituted acrylic esters. Compared with the well-established regioselective alkoxycarbonylation of terminal alkynes, the regioselective hydrocarboxylation of non-functionalized unsymmetric internal alkynes was more challenging owing to the delicate differences of properties between the two substituents. Herein, by using either monophosphine ligand based on 2,3-dihydrobenzo[d][1,3]oxaphosphole motif or bidentate ligand Ph-Phox, the regioselective alkoxycarbonylations of aryl-aryl, aryl-alkyl and alkyl-alkyl disubstituted alkynes were achieved, giving a diversity of trisubstituted α,β-unsaturated carboxylic esters with moderate to excellent yields and high regioselectivity. The synthetic utility of obtained α,β-disubstituted acrylic esters was demonstrated.