Herein, we report a catalytic radical-Smiles rearrangement
system
of arene migration from ether to carboxylic acid with riboflavin tetraacetate
(RFT), a readily available ester of natural vitamin B2, as the photocatalyst
and water as a green solvent, being free of external oxidant, base,
metal, inert gas protection, and lengthy reaction time. Not only the
known substituted 2-phenyloxybenzoic acids substrates but also a group
of naphthalene- and heterocycle-based analogues was converted to the
corresponding aryl salicylates for the first time. Mechanistic studies,
especially a couple of kinetic isotope effect (KIE) experiments, suggested
a sequential electron transfer-proton transfer processes enabled by
the bifunctional flavin photocatalyst.