C-H Bond Cleavage-Enabled Aerobic Ring-Opening Reaction of in Situ Formed 2-Aminobenzofuran-3(2H)-ones

A C-H bond cleavage-enabled areobic ring-opening reaction of 2-aminobenzofuran-3(2H)-ones formed in situ by hemiacetals with a variety of amines is reported. The simple one-pot reaction provides an alternative approach to o-hydroxyaryl glyoxylamides in excellent yields of up to 97%. Alkylamines react with hemiacetals via a catalyst-free deydration condensation to generate 2-aminobenzofuran-3(2H)-ones. The in situ formed semicyclic N,O-acetals undergo a same amine-initiated C-H bond hydroxylation with air under mild conditions to afford ring-opening products. Similar, Arylamines are investigated as substrates for a two-step tandem process involving a DPP-catalyzed condensation followed by Et2NH-mediated C-H hydroxlation. Unlike the previously reported functionalizaiton of N,O-acetals via C-O or C-N cleavage, the aerobic oxidative C-H hydroxylation in this reaction, which is promoted by stoichiometric alkylamines as both a Lewis base and a reductant at room temperature under atmospheric air, proceeds via α-carbonyl-stabilized carbanion intermediates from C-H cleavage of N,O-acetals.