A green and clean pathway: one pot, multicomponent, and visible light assisted synthesis of pyrano[2,3-c]pyrazoles under catalyst-free and solvent-free conditions

Abstract

A mild, eco-efficient and metal-free synthetic protocol for the production of biologically significant scaffold dihydropyrano[2,3-c]pyrazoles via reaction between ethylacetoacetate (1), hydrazine hydrate (2), aromatic aldehydes (3) and malononitrile (4) as reactants and exploiting visible light as a reaction promoter has been developed. Cost effectiveness, nontoxicity, being catalyst-free and solvent-free, the easy-availability of reactants and non-involvement of specific glasswares and a photo-reactor system are some of the significant traits of the present protocol. The scope of the current methodology is further extended by using diethyl acetylene dicarboxylate (6) as a reactant in place of ethylacetoacetate.