Photocatalytic 1,3-Difluoroalkylcarboxylation of Alkenes by Triple Kinetic-Controlled Radical Self-Ordering

Abstract

A transition metal-free protocol for the unsymmetrical radical 1,3-difunctionalization of alkenes has been established for the first time in the form of 1,3-difluoroalkylcarboxylation by a photocatalytic radical three-component reaction of allyl formates, trifluoroacetanilides, and cesium formate. This reaction employs formate as the carboxylating reagent and trifluoroacetanilide as the difluoroalkylating reagent via C-F bond activation. As a result, a series of previously inaccessible unsymmetrical difluorinated adipic acid derivatives can be easily and efficient prepared. Mechanism studies reveal that a triple-kinetic controlled radical self-ordering is the key core for this unique reaction. This radical sorting involves fast initiation of CO2 radical anion and its chemoselective addition and reduction, followed by the slow generation of fluoroalkyl radical and its chemo-/regioselective addition. Notably, this strategy is also suitable for the 1,3-difluoroalkylcarboxylation of unsymmetrical and cyclic alkenes by diastereoselectively constructing two or three consecutive stereocenters.