D-Glucose has been identified as an efficient C1 synthon in the synthesis of benzimidazoles from o-phenylenediamines via an oxidative cyclization strategy. Isotopic studies with 13 C 6 -D-glucose and D 2 O unambiguously confirmed the source of methine. The notable features of this method include the following: broad functional group tolerance, a biorenewable methine source, excellent reaction yields, a short reaction time, water as an environmentally benign solvent, and the synthesis of vitamin B 12 component on the gram scale.

Herein, we report the synthesis of methylenebridged bis-1,3-dicarbonyls from olefins and 1,3-dicarbonyls using a photoredox/nickel-catalyzed synergistic approach. Styrene is reported as methylene one-carbon (C1) synthons in the synthesis of bis-(β-dicarbonyls) for the first time. The deuterated study showed the incorporation of styrene-d 3 in the product by NMR and Mass analysis. Fluorescence quenching and cyclic voltammetry (CV) suggest that the reaction proceeds via an energy transfer process (EnT). The key aspects of the protocol are the use of benign photocatalyst fluorescein, peroxide-free, air as oxidant, broader substrate scope, and 56% to 99% product yields. The synthetic application of the product has been extended to construct tetrasubstituted pyridines in a sequential one-pot manner, bis-isoxazole, and bis-pyrazole.

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Highly functionalized quinazolin‐4(3H)‐ones were synthesized from reactions of N‐aryl‐2‐aminobenzamides with trialkylamines under photocatalytic conditions by using eosin Y (EY) as a catalyst. The reaction proceeds under mild conditions in aqueous acetonitrile and has a broad substrate scope. Mechanistic studies disclosed the electron‐donor nature of the intermediate 2,3‐dihydroquinazolin‐4(1H)‐one (3’) in the photocatalytic cycle to afford the 2,3‐disubstituted‐quinazolin‐4(3H)‐ones (3). This methodology has been extended to synthesize benzo [4,5] imidazole[1,2‐c] quinazolines and 3 aa on a large scale. Furthermore, the synthesis of potent central nervous system depressant (CNS) drug molecules such as methaqualone (3 la) and mecloqualone (3 pa) was also achieved successfully.