Solvent-free direct ortho C-acylation of phenolic systems by methanesulfonic acid as catalyst

The use of methanesulfonic acid as a Brønsted acid for direct ortho-acylation of phenols and naphthols proves to be a convenient, more general and direct route to various hydroxyaryl ketones. The route is regioselective, leading to ortho C-acylated products in satisfactory to high yields in most cases. The solvent free reactions described below exhibited environmentally benign in terms of faster reaction, benign conditions and higher yield of the desired products. The influence of the temperature, the ratios of the reactants and the amounts of MSA were investigated. However, after a 10-18 minute reaction time at 60-100 °C, selectivity to over 98% ortho acylation products was obtained. This method represents an environmentally benign acylation route, because MSA is biodegradable acid which can easily be separated from the reaction mixture via decantation.