A Green Access to Tetrahydro-1H-pyrano[2,3-d] pyrimidines: Visible-Light-Triggered and Ethylene-Glycol-Mediated Multicomponent One-Pot Process

Efficient and environmentally benign heterocyclization via Knoevenagel condensation followed by [4+2] cycloaddition resulting the synthesis of tetrahydro-1H-pyrano[2,3-d]pyrimidine derivatives starting from 2-thiobarbutiric acid, aldehydes and alkyne has been reported. Easily available ethylene glycol was used as a green promoting medium as well as solvent for the reaction progress. This methodology offers a metal and base free approach which endowed high yields with mild reaction conditions and better functional group tolerating ability. Further visible light as a source of energy, recyclability and reuse of ethylene glycol add the methodology a wide scope.