Strontium arsenate pyrochlore and its doped sample (Sr2As2EuxO7+δ) as recyclable heterogeneous catalysts in one-pot, three-component synthesis of 2-amino-4H-chromene derivatives under microwave irradiation.

In this paper, a very effective method for the synthesis of 2-amino-4H-Chromene derivatives has been reported. These derivatives were obtained during a one-pot, three-component condensation reaction between aromatic aldehydes, malononitrile and β-naphthol in the presence of water as an environmentally friendly solvent and under microwave irradiation using heterogeneous nanocatalysts Sr2As2O7 and Sr2As2EuxO7+δ. This is the first report of using of the mentioned catalysts in the synthesis of Chromen derivatives. These catalysts were synthesized using the solvothermal method at 180 oC for 24 h and were characterized by various techniques such as UV-Vis, PXRD, FTIR, FESEM, and EDX.  To carry out the catalytic reaction, the reaction conditions were optimized and it was determined that when 15 mg of catalyst, water as solvent and microwave irradiation time (6 minutes) were used, a higher efficiency was obtained. Investigations showed that the aromatic aldehydes containing electron-donating and electron-withdrawing groups can produce the corresponding products, but the reaction efficiency with aldehydes with electron-withdrawing groups is higher (97-99%). The synthesized catalysts can be easily recycled and reused 4 times without significant decrease in catalytic activity. After the fourth step, the reaction efficiency was 71% for Sr2As2O7 and 73% for the doped sample. The advantages of this method are the use of environmentally friendly solvent, short reaction time, easy separation and production of products with high efficiency.