Photoredox-Catalyzed\nCross-Coupling of In Situ Generated\nQuinoxalinones with Indoles for the Synthesis of Tertiary Alcohols

A visible\nlight-driven photoredox-catalyzed direct C(sp<sup>2</sup>)-H functionalization\nof N–H free indoles with quinoxalinones\ngenerated in situ from 2,2-dihydroxy-1<i>H</i>-indene-1,3(2<i>H</i>)-dione and phenylene-1,2-diamines has been reported with\nthe aid of Na<sub>2</sub>-Eosin Y as the photocatalyst and the Hünig\nbase as the sacrificial electron and proton donor. The reaction provides\neasy access to a variety of quaternary-centered C-3 selective indole-substituted\ntertiary alcohols in good yields. Mechanistic studies demonstrated\nthe realization of photoredox-catalyzed in situ quinoxalinone formation\nand their proton-coupled single electron reduction to the corresponding\nketyl radicals followed by cross-coupling with indoles. The potential\napplications of the synthesized tertiary alcohols in photoacid-catalyzed\ncarbon–carbon and carbon–sulfur bond-forming reactions\nfeature the key findings of the present work.