Ruthenium-Catalyzed Dehydrogenative β‑Benzylation of 1,2,3,4-Tetrahydroquinolines with Aryl Aldehydes: Access to Functionalized Quinolines

Abstract

A new benzylation protocol, enabling straightforward access to β-benzylated quinolines, has been demonstrated. By employing readily available [RuCl₂(<i>p</i>-cymene)]₂ as a catalyst and O₂ as a sole green oxidant, various 1,2,3,4-tetrahydro­quinolines were efficiently converted in combination with aryl aldehydes into desired products in a step- and atom-economic fashion together with the advantages of excellent functional group tolerance and chemoselectivity, offering an important basis for the transformation of saturated <i>N</i>-heterocycles into functionalized <i>N</i>-heteroaromatics via a dehydrogenative cross-coupling strategy. Mechanistic investigations support that the reaction undergoes a monodehydrogenation-triggered β-benzylation mode