2‐Arylbenzyl Methyl Ethers as Precursors for the Tandem Synthesis of Benzo[c]coumarins Over Heterogeneous Visible‐Light Photoredox Catalysis with Graphitic Carbon Nitride (g‐C₃N₄)

Abstract

Utilizing readily accessible 2-arylbenzyl methyl ethers as precursors, an unprecedented three reactions in one-pot protocol for the synthesis of benzo[c]coumarins over heterogeneous visible-light photoredox catalysis with graphitic carbon nitride (g-C 3 N 4 ) has been developed. Also, a possible reaction mechanism has been explored. Upon irradiation, g-C 3 N 4 converts molecular oxygen into superoxide radical anion, which facilitates the benzylic oxidation of 2arylbenzyl methyl ethers into methyl [1,1'-biaryl]-2-carboxylate. The required benzo[c]coumarins are then produced through the hydrolysis and dehydrogenative lactonization of methyl [1,1'-biaryl]-2-carboxylate. The main attributes of this transformation include mildness, convenience in catalyst recovery and reuse, compatibility with lithium persulfate produced from the spent lithium-ion batteries, works in aqueous medium, and is a multiple CÀ H functionalization processes happen via three reactions (oxidation, hydrolysis and dehydrogenative lactonization) in one-pot at ambient conditions.

Convenient synthesis of 2-chloro-3-substituted quinoxalines by visible-light-induced radical cascade cyclization of ortho-diisocyanoarenes with sulfinic acids

“…Visible-light-driven synthesis, which has been the subject of recent studies, offers a low-cost, efficient, and environmentally safe method. 11 Typically, a dye (catalyst) absorbs the energy of visible-light and uses it to transform reactants into products through routes for either energy transfer or electron transfer. 12 Several visible-light-induced synthetic methods without an external dye (catalyst) have also been developed employing the photochemical activity of different electron donor–acceptor (EDA) complexes.…”