Using unactivated alkylsulfinic acids as an alkyl radical source, a novel and highly practical visible-light-assisted synthetic methodology for the alkylation/annulations of a series of N-arylacrylamides into corresponding 3,3-dialkylindolin-2-ones has been developed. This approach does not require a photosensitizer or any metal reagents because the development of an electron donor-acceptor complex between alkylsulfinates and 2-isocyano-1,1'-biphenyl (catalytic electron acceptor) allows, under visible-light irradiation, the preparation of desired products in good yields. The mildness, gram-scale synthesizability, lack of toxic organic solvents and a transition metal, as well as suitability for the synthesis of bioactive compounds (used as progesterone antagonist and anti-depressant) are a few noteworthy features of this procedure. Furthermore, alkylsulfinic acids are stable, safe, easily handled, and readily available than other alkyl radical donors (like N-(acyloxy)phthalimides and Katritzky salts) reported in the literature.

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