Developments in transfer hydrogenations of aromatic ketones catalyzed by boron compounds

Boron complexes BL1 and BL2 were prepared from O-donor ligands, 2,2′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L1) and 2,2′-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L2). The complexes were fully characterized by 1H and 13C NMR, LC-MS/MS, TGA/DTA, UV-Vis, elemental analysis, SEM, and FTIR. The transfer hydrogenation of acetophenone derivatives was investigated by the boron complexes in the presence of isoPrOH, as the hydrogen source, under basic condition with NaOH. The results showed that the boron complexes were promising catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M isoPrOH solution (up to 99%). Both steric and electronic factors of this class of molecules had a significant impact on the catalytic properties.