Photoredox-catalyzed self-dimerization and cross-addition as well as Zn(OTf)2-mediated nucleophile coupling: a novel route to structurally diverse 2,2-disubstituted indolin-3-ones

An efficient protocol for the synthesis of 2,2-disubstituted indolin-3-ones from both 2-aryl and 2-alkyl indoles via photoredox-catalyzed self-dimerization and cross-addition as well as Zn(OTf)2-mediated nucleophile coupling is described. The photoredox reactions feature low catalyst loading, mild reaction conditions, and broad functional group tolerance, generating indolin-3-ones in moderate to excellent yields. The Zn(OTf)2-mediated transformation using indolin-3-one dimer as a newly active species provides a much gentle way to access structurally diverse indolin-3-ones.