Copper- and Amine-free Sonogashira Cross-Coupling in the Presence of Ligandless Pd-containing Catalyst

Abstract

In this work, the effect of reaction conditions (temperature and composition of the reaction mixture) on the Cu-free Sonogashira cross-coupling of 4-iodoanisole (IAn) and phenylacethylene using nanoparticulate ligandless palladium catalyst based on hyper-cross-linked aromatic polymer (HAP) was studied. Main idea of the study is the ability of HAP to stabilize small Pd nanoparticles that allows developing effective catalysts. It was shown that > 99 % conversion of IAn can be achieved in the presence of Pd/HAP for 1 h at 90 ?? at the absence of amines and copper while using DMSO as a medium. DMSO allowed high solubility of all the reaction components and likely played a role of ligand in the Sonogashira reaction cycle. After the reaction, the cross-coupling product (1-methoxy-4-(phenylethynyl)benzene) was purified, its structure was confirmed by NMR.