Palladium(ii) N,N,O-pincer type complex-mediated dehydrogenative coupling of alcohols to quinazolines

Abstract

A new palladium(II) N,N,O-pincer type complex-promoted one-pot cascade synthesis of quinazolines through the dehydrogenative coupling of easily available alcohols and 2-aminobenzylamine is reported. A distinct set of Pd(II) complexes (1–2) was synthesized and characterized by analytical and spectral techniques. The single crystal X-ray diffraction study confirms square planar geometry around the palladium ion. A diverse range of quinazoline derivatives was fabricated with excellent yields using 0.5 mol% Pd(II) catalyst loading. The catalytic coupling process was performed under aerobic conditions and water is the only by-product. With data from the control experiments, a plausible mechanism for the dehydrogenative coupling reaction was proposed via a cyclic aminal intermediate through the oxidation of alcohol to aldehyde. The gram-scale synthesis proves the effectiveness of the presented protocol.