Hydroalkylation and hydroacylation of trifluoromethyl olefins by N-centered direct hydrogen atom transfer photocatalysis

Abstract

The selective functionalization of trifluoromethyl olefins, while keeping the essential trifluoroalkyl moiety intact, remains a synthetic challenge. In this study, we report the use of an acridinium amidate as a direct hydrogen atom transfer (d-HAT) photocatalyst for the mild and selective hydroalkylation and hydroacylation of fluorinated olefins. The unique nature of this type of N -centered radical d-HAT system allows an efficient HAT process with a variety of substrates, as well as a single-electron transfer (SET) to obtain the corresponding α-CF 3 carbanion intermediate, while the undesired, typically occurring β-fluoro elimination leading to gem -difluoroalkanes when employing α-trifluoromethyl alkenes as radical acceptors is suppressed by a facilitated last protonation step. This method gives ready access to trifluoromethyl alkanes and can be extended to other fluorinated olefins and to post- and late-stage modifications of pharmaceutically relevant compounds, expanding the toolbox for sustainable and efficient synthesis of highly functionalized fluorinated derivatives under visible light photocatalysis.