Catalytic hydrotrifluoromethylation of styrenes and unactivated aliphatic alkenes via an organic photoredox system

Abstract

Herein is presented a direct method for the metal-free hydrotrifluoromethylation of alkenes. The method relies on the single electron oxidation of a commercially available sodium trifluoromethanesulfinate salt (CF 3 SO 2 Na, Langlois reagent) by N-Me-9-mesityl acridinium as a photoredox catalyst. Methyl thiosalicylate is used as a substoichiometric H-atom donor for aliphatic alkenes, and thiophenol is used as a stoichiometric H-atom donor for styrenyl substrates. The substrate scope for the transformation is broad, including mono-, di-and trisubstituted aliphatic and styrenyl alkenes, with high regioselectivity in nearly all cases examined.Scheme 1 Proposed hydrotrifluoromethylation method using photoredox catalysis.

Free‐Radical Multicomponent Processes

“…Hydroxytrifluoromethylation of styrenes and unactivated olefins (e.g., 58) was thus shown to provide the corresponding fluorinated product (e.g., 60) in moderate to good yields, using Langlois's reagent (CF 3 SO 2 Na) as a CF 3 source and the mesityl acridinium 59 as the photoredox catalyst (Scheme 14.15) [44]. Trifluoroethanol (TFE) served both as a cosolvent and as the hydrogen source (TFE C-H bond) and thus as a third component.…”

Visible-light-mediated trifluoroethylation of 2-isocyanobiaryl with trifluoroethyl iodide: Synthesis of 6-trifluoroethyl-phenanthridines

“…Recently, visible-light photocatalyzed direct trifluoromethyl ation of arenes, heteroarenes, arylboronic acids and alkenes have been explored [32][33][34][35][36][37]. In contrast to these impressive progresses, until recently there were rather few practical methods for related visible-light photocatalyzed trifluoroethylation.…”

Hydrotrifluoromethylation and iodotrifluoromethylation of alkenes and alkynes using an inorganic electride as a radical generator

“…The deuterated products (2a 0 , 4a 0 and 6a 0 ) were exclusively formed from the reactions, clearly confirming that the hydrogen of the -OH group on the ethanol is the actual source of hydrogen in this process. Namely, no hydrogen abstraction from a-C-H bond of ethanol occurred 34,35 .…”

“…In particular, the literature contains only a few reports of the hydrotrifluoromethylation of alkenes and alkynes [34][35][36][37] . Here, we report an environmentally benign, efficient and simple method for a radical-initiated hydrotrifluoromethylation reaction with alkenes and alkynes using the inorganic electride [Ca 2 N] þ Á e À as an electron donor.…”