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

Two new boron complexes were synthesized from N ‐[3‐(methylmercapto)aniline]‐3,5‐di‐ tert ‐butylsalicylaldimine ( LH ) with boron reagent BPh 3 or BF 3 .Et 2 O. These boron complexes are stable and easily soluble in protic solvents such as ethanol (C 2 H 5 OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl 3 ), dichloromethane (CH 2 Cl 2 ) and tetrahydrofuran (THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic activities of complexes [LBPh 2 ], 2 , and [LBF 2 ], 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 © 2011 John Wiley & Sons, Ltd.