Palladium-catalyzed alkyne hydrocarbonylation under atmospheric pressure of carbon monoxide in the presence of hydrosilane

Abstract

An ultramild reaction condition for the hydrocarbonylation of alkynes, which is performed under atmospheric pressure of CO in the absence of acids, has been developed. Palladium hydride (Pd-H) generated from triethylsilane (Et₃SiH) rather than the traditionally used strong acid (HX) is applied for the first time in this transformation. In addition, an unusual counteranion-controlled linear and branch selectivity for terminal alkynes is observed under otherwise identical conditions. A wide range of 1,1-, 1,2-, and 1,2,2-substituted α,β-unsaturated thioesters or amides are regioselectively obtained from terminal and internal alkynes in moderate to excellent yields. Furthermore, the first enantioselective construction of indolone derivatives with a C–N chiral axis is achieved when using 2-(tert-butyl)-N-(2-alkynylphenyl)aniline as the substrate in the presence of TMS-SYNPHOS as the chiral ligand.