Green catalyst access to thieno [2, 3-b] pyridines derivatives

The current study focuses on the use of tungstovanadophosphoric heteropoly acid H4PW11VO40 center dot 8 H2O (PVW) with Keggin structure and supported on acid activated (PVW/AAM) in the synthesis of new substituted Thieno [2, 3-b] pyridines derivatives. The suggested protocol is an easy, environmentally friendly method for synthesis of thieno [2,3-b] pyrimidine derivatives obtained from 3-cyano-2-aminothiophene as building blocks under solvent-free reactions condition. Excellent product yields of substituted Thieno [2, 3-b] pyridine derivatives (60%-97%) were achieved using the synthesized PVW/AAM catalyst. The current processes provide benefits including a quicker reaction time, an easy set-up, and high yields. Spectroscopic data (IR, H+ and C-13 NMR spectra) have revealed the structural details of all target compounds. The catalyst was characterized by X-ray diffraction, BET and Fourier-transformed infrared spectroscopy. X-ray diffraction showed that PVW was correctly incorporated on an acid activated clays support. In comparison to the parent, Tungstovanadophosphoric acid, the PVW supported acid activated montmorillonite provided increased Lewis acid site density, redox characteristics, and surface area. Due to the recoverability of heterogeneous catalysts, the heterogenization of homogeneous catalysts is very attractive. In addition, the produced catalysts can be simply removed from the reaction system and reused six times more effectively.