Synthesis of imine and reduced imine compounds containing aromatic sulfonamide: Use as catalyst for in situ generation of ruthenium catalysts in transfer hydrogenation of acetophenone derivatives

Three imine and three reduced imine ligands containing aromatic sulfonamide (2-7) were isolated by a simple method and characterized by FT-IR, NMR, and elemental analysis. Meanwhile, the interaction of 2-7 ligands with [(p-cymene)RuCl2](2) was analyzed in situ by UV-vis spectrophotometer. The in situ generated catalytic system derived from N-(2-(benzylideneamino)phenyl)-2,4,6-trimethyl-benzenesulfonamides and N-(2-(benzylamino)phenyl)-2,4,6-trimethyl-benzenesulfonamides with [(p-cymene)RuCl2](2) was used as a catalyst in the transfer hydrogenation (TH) of p-substituted acetophenone derivatives. The catalytic systems displayed high activities, which increased in the order 7 < 4 < 5 < 6 < 1 <2 <3. The best activity for the TH of 4-chloroacetophenone was provided with the [(p-cymene)RuCl2](2)/ligand (3) catalytic system (turnover frequency values: 720h(-1) for 10 min on S/C: 500/1). (C) 2013 Elsevier B.V. All rights reserved.