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.

Graphical abstractWe report that 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 solution. The catalyst is very efficient with good yield for aromatic nitriles. The mono- and di-addition products from dicynaobenzene can be selectively synthesized.Figure optionsDownload full-size imageDownload as PowerPoint slide