Photoexcited Na2 eosin Y as direct hydrogen atom transfer (HAT) photocatalyst promoted photochemical metal-free synthesis of tetrahydrobenzo[b]pyran scaffolds via visible light-mediated under air atmosphere

Abstract

Backgroundeosin Y is a metal-free organic dye with easy availability that has gained a wide application in recent years, having economic and ecological superiority for substituting transition-metal-based photocatalysts. Methoda green three-component tandem strategy for synthesizing tetrahydrobenzo[b]pyran scaffolds through Knoevenagel-Michael cyclocondensation is reported using Na2 eosin Y-derived photoexcited states functions as a direct hydrogen atom transfer (HAT) catalyst via visible light-mediated in aqueous ethanol at ambient temperature under air atmosphere. Findingsthis study paves the new role for further use of a metal-free organic dye with commercial availability and inexpensiveness, Na2 eosin Y in photochemical synthesis with use of the lowest amount of catalyst, energy-effectiveness, excellent yields, operational simplicity, time-saving aspects of the reaction and high atom economy, thus meeting some features of sustainable and green chemistry.