Regioselective homogeneous hydrogenation of quinoline by use of pyrazolyl borate ligand and transition metal complexes as a precatalyst

In situ regioselective quinoline hydrogenation with transition metal comple xes, such as [Rh(COD)Cl](2), [Lr(COD)Cl](2), [Ir(COE)(2)Cl](2) and RuCl2(CH 3CN)(4) stabilized with the ligands tris-pyrazolyl berates Tp = NaHB(pz)(3) and Tp* = KHB(pz*)(3) (pz* = 3,5 -dimethylpyrazolyl), via one pot reaction is described. The results are compared to those carried out with the compl ex TpIr(Ethylene)(2). The system formed by the complex [Rh(COD)Cl](2) with the ligand Tp is the most efficient and regioselective catalyst precursor f or this reaction. Influence of the type of Tp ligand in the activity of thi s system was observed. The complex TpIr(Ethylene)(2) shows catalytic activi ty in the hydrogenation, with strong influence of temperature, H-2 pressure and a polar solvent such as MeOH favors the formation of the active specie s. (C) 1999 Elsevier Science B.V. All rights reserved.