Alkylation of 2-methylquinoline with alcohols under additive-free conditions by Al2O3-supported Pt catalyst

Supported metal nanoparticle catalysts are studied for alkylation of 2-methylquinoline with benzyl alcohol under additive-free conditions in N2 atmosphere. Among various metal-loaded Al2O3 catalysts and supported Pt catalysts, Pt metal nanocluster loaded-Al2O3 pre-reduced in H2 at 500 °C shows highest yield (82%) of the product (2-phenethyl-quinoline). The catalyst is reusable, shows higher turnover number than a previous homogeneous catalyst, and shows good to moderate yield for alkylation of 2-methylquinoline with various alcohols. The reaction is driven by the borrowing-hydrogen pathway, in which aldehyde formed by dehydrogenation of alcohol undergoes aldol condensation with 2-methylquinoline to give the alkene intermediate which is finally hydrogenated by Pt-H species.