Visible-light-driven indation of aryl halides: arylindium(iii) reagents bridging single- and two-electron reactivity

A photoinduced indation of aryl and alkyl halides enabling efficient access to organoindium reagents is described. The method is operationally simple, exhibits broad functional group tolerance, is insensitive to air and moisture, and proceeds in high yields. The transformation can be achieved with or without a photocatalyst. It was proposed that starting from indium(i) bromide and bromide anion, a highly active low-valent indium species is formed under irradiation with 400, 455, and even 520 nm LEDs, which is capable of performing halogen atom transfer (XAT) to generate aryl radicals, finally leading to arylindium reagents. This reactivity mode is exceptionally rare for metals in main-group chemistry and typically associated with transition metals. The arylindium reagents can, in turn, serve as aryl radical precursors under photoredox conditions, establishing a reversible interplay between the formation and cleavage of the carbon-indium bond. This dual reactivity unlocks an unprecedented reactivity mode for arylindium reagents as radical sources in photocatalysis.