Synthesis of new boron complexes: application to transfer hydrogenation of acetophenone derivatives

Abstract

Two new boron complexes were synthesized from N-[3-(methylmercapto)aniline]-3,5-di-tert-butylsalicylaldimine (LH) with boron reagent BPh3 or BF3 center dot Et2O. These boron complexes are stable and easily soluble in protic solvents such as ethanol (C2H5OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl3), dichloromethane (CH2Cl2) and tetrahydrofuran (THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic activities of complexes [LBPh2], 2, and [LBF2], 3, in the transfer hydrogenation of acetophenone derivatives were tested. Stable boron complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in good conversions up to 99% in the presence of iso-PrOH/KOH. Copyright (C) 2011 John Wiley & Sons, Ltd.