Trifluoromethyl-containing organic compounds have found widespread applications in various areas such as pharmaceuticals, agrochemicals and materials science. Fluoroform is the cheapest and most atom-economical trifluoromethyl source, but chemically inert. The use of fluoroform in trifluoromethylation reactions remains a formidable challenge. In this work, with a trifluoromethylboron complex derived from fluoroform as the trifluoromethylating reagent, the hydrotrifluoromethylation of styrenes, acrylates and acrylamides is successfully accomplished under photoredox catalytic conditions. Thus, with potassium bis(trimethylsilyl)amide (KHMDS) as the base, the reaction of fluoroform with (4-methoxyphenyl)boronic acid pinacol ester at room temperature (r.t.) leads to the corresponding trifluoromethylboron complex in 59% yield as a white solid stable in air and moisture. With the ate complex as the trifluoromethylating reagent, 1,2,3,5-tetrakis(carbazol-9-yl)-4,6- dicyanobenzene (4CzIPN) as the photocatalyst and benzoic acid as the proton source, the reaction of styrenes in N,N-dimethylacetamide (DMA) at r.t. under blue light irradiation provided the corresponding anti-Markovnikov hydrotrifluoromethylation products in satisfactory yields. The protocol is also applicable to various acrylates as well as acrylamides, furnishing the expected ꞵ-trifluoromethylated esters or amides. A wide functional group compatibility is observed. The reaction is efficient and highly regioselective. In addition, the pinacol boronate generated along with the hydrotrifluoromethylation products can be recovered and reused. A redox-neutral mechanism is proposed, which involves the oxidative generation of CF₃ radicals, addition to C=C bonds, subsequent single electron reduction and protonation.

Key words: trifluoromethylation, fluoroform, trifluoromethylboron complex, photocatalysis, hydrotrifluoromethylation