Journal of Molecular Catalysis A-Chemical, Vol.304, No.1-2, 135-138, 2009
Tungstates: Novel heterogeneous catalysts for the synthesis of 5-substituted 1H-tetrazoles
Most heterogeneous Catalysts utilized for the formation of 5-substituted 1H-tetrazoles contain zinc as the metal core at the catalytically active site. In this paper, we report that the tungstate MWO4 (M = Ba, Ca, Zn, Cd, Cu. Na, H) can catalyze the [2+3] cycloaddition reaction of nitriles with sodium azide to produce 5-substituted 1H-tetrazoles in DMF The catalyst is very efficient, affording good yield of aromatic nitriles and can be reused for several cycles. The mono- and di-addition products from dicyanobenzene can be selectively synthesized, which is a development being reported for the first time. The mechanism of the catalysis may originate from the nitrile group coordinating With the unsaturated W atoms, formed by oxygen vacancies on the surface of solid tungstates. (c) 2009 Elsevier B.V. All rights reserved.