Transfer hydrogenation of aryl ketones with homogeneous ruthenium catalysts containing diazafluorene ligands

Abstract

Novel cationic ruthenium(II) complexes bearing a 4,5-diazafluorene unit and p-cymene as ligands have been synthesised. The complexes were characterised based on elemental analysis and Fourier transform infrared and nuclear magnetic resonance spectroscopies. The synthesised Ru(II) complexes were employed as pre-catalysts for the transfer hydrogenation of aromatic ketones using 2-propanol as both hydrogen source and solvent in the presence of NaOH. All complexes showed high catalytic activity as catalysts in the reduction of substituted acetophenones to corresponding secondary alcohols. The products of catalysis were obtained with conversion rates of between 80 and 99%. Among the seven new complexes investigated, the most efficient catalyst showed turnover frequencies in the range 255-291 h(-1) corresponding to 85 to 97% conversion, respectively. Copyright (C) 2016 John Wiley & Sons, Ltd.