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Abstract
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A simple, efficient, and environmentally benign route was developed for the preparation of 2-amino-3- cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans and 6-amino-5-cyano-4-aryl-1,4- dihydropyrano[2,3-c]pyrazoles from the condensation of various aldehydes, malononitrile, and 1,3- dicarbonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-1,3-cyclohexanedione) or 3-methyl-1- phenyl-2-pyrazoline-5-one, using NH4 H2PO4 /Al2O3 with good yields. The use of easily available catalyst, shorter reaction times, better yields, the simplicity of the reaction, the heterogeneous system, and the easy work up are the advantages of the present method. Characterization of the catalyst was performed by FT-IR spectroscopy, X-ray diffraction (XRD) techniques, thermal analysis (TG/DTG) and Transmission electron microscopy (TEM)
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