Fischer indole synthesis over hydrous zirconia-supported niobium oxide

Abstract

Supported niobium oxides are investigated as green catalysts for Fischer indole reaction. By means of wet impregnation, 1040 wt-% Nb2O 5 were loaded onto hydrous zirconia as a support. Pore size distribution curves showed that the niobium oxide overlayer was uniformly dispersed onto the mesoporous support. Samples with close to a monolayer coverage of niobium oxide had the highest activity in the Fischer indole reaction of phenylhydrazine with both 3-heptanone and cyclohexanone. A coverage higher than a monolayer led to lower activity. In comparison, the supported catalysts were more active than bulk niobium oxide or a sample prepared by co-precipitation of hydrous zirconia and niobium oxide. © CSIRO 2009.