An insight on the influence of surface Lewis acid sites for regioselective C-H bond C-3-cyanation of indole using NH4I and DMF as combined cyanide source over Cu/SBA-15 catalyst

The dispersed on mesoporous SBA-15 has demonstrated the regioselective C-H bond C-3-cyanation of indoles by in-situ generation of -CN using DMF and NH4I in presence of O-2. Pyridine adsorbed diffuse reflectance infrared spectroscopy (DRIFTS) results revealed that surface Cu2+ species are acting as Lewis acid sites in the in-situ generation of cyano-group for the synthesis of indole nitriles. A direct correlation between Cu metal surface area and the indole nitrile yields are established and the dual role of copper is substantiated by N2O titration and XPS techniques. The 10 wt%Cu/SBA-15 demonstrated superior performance when compared to Pd, Ru supported on SBA-15. The 10 wt%Cu/SBA-15 catalyst showed consistent activity and selectivity after the 4th cycle. (C) 2017 Elsevier B.V. All rights reserved.