Acridine yellow G as a photo-induced electron transfer catalyzed radical metal-free synthesis of tetrahydrobenzo[b]pyran scaffolds in an aqueous media

We established a green approach for the radical synthesis of tetrahydrobenzo[b]pyran scaffolds by using Knoevenagel-Michael tandem cyclocondensation of aldehyde derivatives, malononitrile, and dimedone. Using visible light as a renewable energy source, a photo-induced electron transfer (PET) photocatalyst was exploited in an aqueous solution. A low-cost, readily available non-metal dye is the goal of this research. The photochemically catalyzed acridine yellow G (AYG) exhibits high yields, energy efficiency, and environmental friendliness, as well as speed-saving characteristics and ease of use. This allows for tracking of environmental and chemical variables over time. In this study, turnover number (TON) and turnover frequency (TOF) of tetrahydrobenzo[b]pyran scaffolds were determined. It is remarkable that gram-scale cyclization is feasible, indicating that it can be applied to industry.