Fabrication of porous ultrathin carbon nitride nanosheet catalysts with enhanced photocatalytic activity for N- and O-heterocyclic compound synthesis

A simple and efficient photocatalytic method for the synthesis of dihydropyrimidinones (DHPMs) and their derivatives via porous ultrathin carbon nitride nanosheets (p-CNNs) without solvents was demonstrated. The yields of 3,4-dihydropyrimidin-2(1H)-ones/thiones and their derivatives were up to 97.0%. Furthermore, the yield of 5-ethoxycarbonyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one in the 10th cycle retained 98.9% of its 1st value. Considering the environmental and economic benefits, this work exhibits various merits including excellent yields, environmental friendliness, inexpensiveness, and avoiding the use of solvents and metal-based photocatalysts. In addition, the excellent performance of the p-CNNs and environmentally benign reaction system have also been checked by the photocatalytic synthesis of 12-phenyl-9,9-dimethyl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one and 5-phenyl-1(4-methoxyphenyl)-3[(4-methoxy-phenyl)-aminol]-1H-pyrrol-2(5H)-one. This work paves a new way for carrying out a three-component reaction using metal-free photocatalysts under mild reaction conditions.