Thiol is known to act as a hydrogen atom transfer catalyst working in synergy with a photocatalyst in photoredox catalysis, but we report herein that an arene thiolate with an appropriate substituent can be photoactivated under visible light to function as both a strongly reducing electron-donating redox catalyst and a HAT catalyst to enable catalytic C−F activation of trifluoromethyl substrates for selective hydrodefluorination and coupling with various alkenes in the presence of formate salts. These reactions demonstrate the promising utility of arenethiolates as dual function photocatalysts. The synthetic utility of this method is demonstrated by the broad scope of amenable trifluoromethyl substrates, including trifluoromethylated (hetero)arenes, trifluoroacetates, and trifluoroacetamides, which exhibited high levels of chemoselectivity. The reaction efficacy allows site-selective late-stage functionalization of multitrifluoromethylated bioactive compounds and pharmaceuticals
Under visible light irradiation, o-phosphinophenolate functions as an easily accessible photoredox catalyst to activate trifluoromethyl groups in trifluoroacetamides, trifluoroacetates, and trifluoromethyl (hetero)arenes to deliver corresponding difluoromethyl radicals. It works in relay with a thiol hydrogen atom transfer (HAT) catalyst to enable selective defluoroalkylation and hydrodefluorination. The reaction allows for the facile synthesis of a broad scope of difluoromethylene-incorporated carbonyl and (hetero)aromatic compounds, which are valuable fluorinated intermediates of interest in the pharmaceutical industry. The ortho-diphenylphosphino substituent, which is believed to facilitate photoinduced electron transfer, plays an essential role in the redox reactivity of phenolate. In addition to trifluoromethyl groups, pentafluoroethyl groups could also be selectively defluoroalkylated.
o-Phosphinophenolate and o-phosphinothiophenolate are potent photocatalysts with strong reducing ability to activate aryl chlorides and bromides under visible light for borylation, arylation, and phosphorylation. Experimental and theoretical studies revealed that the o-diphenylphosphino substituent results in a narrow optical gap and facilitates intersystem crossing to access triplet states, which promote phenolate and thiophenolate to function as effective visible-light-photoredox catalysts. The results presented herein suggest promising utility of synthetically modified phenolates and thiophenolates as photoredox catalysts.
Enamides and silyl enol ethers were alkylated to deliver products of N-acyl imines and ketones in the presence of a catalytic amount of N-tetrabutylammonium iodide under irradiation of purple light...
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