Polyoxoniobates as a superior Lewis base efficiently catalyzed Knoevenagel condensation

Knoevenagel condensation of various substrates with malononitrile and ethyl cyanoacetate were efficiently catalyzed by classical Lindqvist K7HNb6O19·13H2O (Nb6) at mild conditions, respectively, which is in good consistent with the results of DFT calculation. Catalysis study and kinetic test indicated the superior basic catalysis. Moreover, a proper mechanism speculates that the most negative charged terminal oxygens would be pivotal in this transformation according to Natural population analysis. In addition, Nb6 is easily prepared and convenient for producing the pure compounds with large capacity, which may provide the potential in its application.