In the presence of tetrabutylammonium fluoride and molecular sieves (MS) 4 Å in DMF, an efficient autoxidation reaction of 2-oxindoles with ketones under air at room temperature has been developed. This approach may provide a green, practical, and metal-free protocol for a wide range of biologically important 3-hydroxy-3-(2-oxo-alkyl)-2-oxindoles.

A protocol to obtain a variety of 6-difluoromethylenephosphonated phenanthridines through a radical cyclization process was explored. These reactions, performed with the use of diethyl bromodifluoromethylphosphonate as a radical resource and 2-isocyanobiphenyls as radical acceptors, were smoothly triggered by visible-light photocatalysis. Electron-withdrawing and electron-donating groups were well tolerated, and the target molecules were obtained in excellent to moderate yields.

This paper reports a room temperature visible-light-driven protocol for the intermolecular [2+2] cycloadditions between coumarin-3-carboxylates and acrylamides analogs by an energy-transfer process. Using an iridium complex FIrPic as a photosensitizer and a 3 W blue LED as a light source, an array of cyclobutabenzocypyranones were prepared in moderate to excellent yields.

A metal-free and environmentally friendly aerobic aromatization photosensitized by organic dye eosin Y bis(tetrabutyl ammonium salt) (TBA-eosinY) has been developed. With the aid of K₂CO₃, the aerobic catalytic system converts 1,4-dihydropyridines to their corresponding pyridine derivatives efficiently under visible light irradiation (λ=450 nm) at room temperature.

The first aerobic oxidative coupling of resveratrol and its analogues by mesoporous graphitic carbon nitride as a bioinspired catalyst with visible light has been developed. With this method, δ-viniferin and its analogues were synthesized in moderate to high yield. The metal-free conditions, visible-light irradiation, and the ideal oxidant, molecular oxygen, make this coupling reaction environmental friendly and practical.

Both benzoxazole and benzimidazole are common heterocyclic scaffolds in biologically active and medicinally significant compounds. Reductive cyclization of ortho-substituted nitrobenzene derivatives provides an attractive route to benzoxazole or benzimidazole ring formation. Unfortunately, only a few synthetic methods by reductive cyclization ofortho-nitro compounds have been reported and the yields are rather low. In continuation of the development of biomimetic reductants in synthetically useful organic transformations, Hantzsch ester 1,4-dihydropyridine (HEH), analogues of NAD(P)H, has attracted a considerable amount of attention. Hence, we wish to report that benzoxazoles and benzimidazoles can be efficiently synthesized by the reaction of ortho-substituted nitrobenzene derivatives with HEH catalyzed by Pd/C. A range of functionalized ortho-nitrophenyl esters or ortho-nitrophenyl amides were efficiently reduced by HEH and cyclized to the corresponding benzoxazoles or benzimidazoles. Especially, working in the presence of the same substituents, benzimidazoles could be obtained in higher yields with respect to the corresponding benzoxazoles. Moreover, in the present work, the recycling of Pd/C was studied and was shown to maintain its high catalytic activity over five runs. On the basis of our experimental results and DFT calculations, a plausible reaction mechanism was proposed.