Palladium(II) N^O Chelating Complexes Catalyzed One-Pot Approach for Synthesis of Quinazolin-4(3<i>H</i>)-ones via Acceptorless Dehydrogenative Coupling of Benzyl Alcohols and 2-Aminobenzamide
Sundarraman Balaji, Gunasekaran Balamurugan, Rengan Ramesh, David Sémeril
Abstract
A convenient protocol for the one-pot synthesis of quinazolin-4(3H)-ones using palladium(II) complexes via dehydrogenative coupling of readily available benzyl alcohols and 2-aminobenzamide has been described. New structurally related Pd(II) N^O chelating complexes of general configuration [Pd(L)Cl(PPh3)] (where L = dimethylamino benzoylhydrazone ligands) have been designed and synthesized. The formation of the complexes has been recognized by analytical and spectral methods (FT-IR, NMR, HR-MS). The presence of a square-planar geometry around the palladium(II) ion was confirmed by single crystal X-ray diffraction study. A wide range of substituted quinazolinones have been successfully achieved from a diverse range of benzyl alcohols in good to excellent yields using 1.0 mol % of catalyst loading under aerobic conditions. Furthermore, control experiments reveal that the dehydrogenative coupling reaction involves initially the formation of an aldehyde intermediate and subsequent formation of a cyclic aminal intermediate.