Journal of the American Chemical Society, Vol.140, No.32, 10282-10288, 2018
Selective Palladium-Catalyzed Carbonylation of Alkynes: An Atom Economic Synthesis of 1,4-Dicarboxylic Acid Diesters
A class of novel diphosphine ligands bearing pyridine substituents was designed and synthesized for the first time. The resulting palladium complexes of L1 allow for chemo- and regioselective dialkoxycarbonylation of various aromatic and aliphatic alkynes affording a wide range of 1,4-dicarboxylic acid diesters in high yields and selectivities. Kinetic studies suggest the generation of 1,4-dicarboxylic acid diesters via cascade hydroesterification of the corresponding alkynes. Based on these investigations, the chemo- and regioselectivities of alkyne carbonylations can be controlled as shown by switching the ligand from L1 to L3 or L9 to give alpha,beta-unsaturated esters.