Visible-Light-Induced Three-Component CH2 Insertion and Trifluoroethylation of Quinoxalin-2(1H)-ones

Quinoxalin-2(1H)-ones represent an important class of nitrogen-containing heterocycles. We have developed a three-component strategy enabling the insertion of a methylene (CH2) unit, which was successfully applied to the trifluoroethylation of quinoxalin-2(1H)-ones. In this reaction, trifluoromethylsulfonyl-pyridinium (TFSP) served as the trifluoromethyl source and acetone provided the CH2 moiety, thereby introducing trifluoroethyl at the C3 position of quinoxalin-2(1H)-ones. This method is distinguished by its broad substrate scope with good yields, metal-free and mild reaction conditions, and remarkable step economy that seamlessly cascades C-H alkylation, trifluoromethylation, and deacetylation. Gram-scale experiments confirmed its practicality for potential large-scale applications. The reaction mechanism was systematically investigated, with key intermediates experimentally captured and characterized and further corroborated by DFT calculations.