Three-component coupling approach for the synthesis of 4H-pyrans and pyran-annulated heterocyclic scaffolds utilizing Ag/TiO2 nano-thin films as robust recoverable catalyst

Abstract

As a segment of ongoing surveys and with the aim of expansion of environmentally benign processes, a series of biologically varied type of substituted 2-amino-3-cyano-4<em>H</em>-pyrans and pyran-annulated Scaffolds have been synthesized by tandem Knoevenagel-cyclocondensation of aldehydes, malononitrile, and C-H-activated acidic compounds in aqueous ethanol in the presence of Ag/TiO₂ nano-thin films as an eco-friendly, recyclable, and, robust catalyst at 60°C. The salient features of this protocol are mild reaction conditions, producing target compounds in high yields, short reaction times, high atom economy, eco-friendly catalyst, easy isolation of products and no column chromatographic separation. Also, it is observed that the catalyst is highly stable during the reaction and several reuse times without observable loss in catalytic performance.