Synthesis of -Hydroxy and -Alkoxy Esters Enabled by a Visible-Light-Induced O-H Insertion Reaction of Diazo Compounds

A visible-light-induced O-H insertion reaction of diazo compounds is reported. This synthetic method, unlike conventional pathways, does not rely on transition metals, Lewis acids, or Bronsted acids; does not use any catalyst; and produces valuable alpha-hydroxy and alpha-alkoxy esters in good yields of up to 98%. The protocol exhibits a broad substrate scope and good functional-group tolerance. Notably, a gram-scale synthesis has been performed in a photochemical continuous-flow mode.