Electron-Donor–Acceptor Complex-Enabled Flow Methodology for the Hydrotrifluoromethylation of Unsaturated β-Keto Esters
Gabriel M. F. Batista, Pedro P. de Castro, Hélio F. Dos Santos, Kléber T. de Oliveira, Giovanni W. Amarante
Abstract
A novel electron-donor-acceptor (EDA) complex-enabled flow photochemical hydrotrifluoromethylation of unsaturated β-keto esters is described. The developed protocol has an easy experimental procedure and does not require the use of transition-metal-based photocatalysts, allowing the isolation of 14 new compounds in up to 86% yield. Control experiments and computational studies revealed that the reaction proceeds through a Michael-type 1,4-addition of a trifluoromethyl radical, followed by a proton transfer step. Furthermore, the reaction could be scaled up to 1 mmol, and the final product could be employed in the preparation of an isoxazolone and a pyrazolone as trifluoro-substituted heterocycles.