Photocatalytic decarboxylative alkylations mediated by triphenylphosphine and sodium iodide

Abstract

Crowdsourcing a chromophore Photoredox catalysis is widely used to accelerate chemical reactions by channeling the energy in visible light. However, most implementations rely on expensive chromophores to absorb light. Fu et al. now show that a pair of cheap components acting in concert can induce these reactions, despite not being strong visible absorbers individually. The combination of sodium iodide and triphenylphosphine allowed photoinduced electron transfer to catalyze a variety of alkylations. Science, this issue p. 1429 A cheap combination of sodium iodide and triphenylphosphine can act as an electron-transfer catalyst under visible light. Most photoredox catalysts in current use are precious metal complexes or synthetically elaborate organic dyes, the cost of which can impede their application for large-scale industrial processes. We found that a combination of triphenylphosphine and sodium iodide under 456-nanometer irradiation by blue light–emitting diodes can catalyze the alkylation of silyl enol ethers by decarboxylative coupling with redox-active esters in the absence of transition metals. Deaminative alkylation using Katritzky’s N-alkylpyridinium salts and trifluoromethylation using Togni’s reagent are also demonstrated. Moreover, the phosphine/iodide-based photoredox system catalyzes Minisci-type alkylation of N-heterocycles and can operate in tandem with chiral phosphoric acids to achieve high enantioselectivity in this reaction.