Copper Exchanged SiO2/Al2O3 Catalyst Prepared by Sol-Gel Method for Intermolecular Hydroamination of Terminal Alkynes

Catalytic hydroamination of terminal alkynes with amines is the most attractive C-N bond forming method. Intermolecular hydroamination of terminal alkynes with aromatic amine has been carried out using Cu- exchanged SiO2/Al2O3 as a heterogeneous catalyst. SiO2/Al2O3 with Si/Al ratio 12.5 has been prepared by novel sol-gel method using tetraethyl orthosilicate and aluminium sec-butoxide as Si and Al precursors respectively. The catalyst has been extensively characterized using various physicochemical and spectroscopic techniques viz., X-ray diffraction analysis, BET surface area, NH3-TPD, FTIR of adsorbed pyridine and 29Si and 27Al NMR. The catalyst showed very high conversion up to 97% and turnover number of 335 for intermolecular hydroamination of terminal alkynes with amines. The reaction proceeded smoothly with highly selective Markonikov addition product.