Organocatalytic C-H Hydroxylation

Significance

Based on the authors’ previous work in this field (J. Am. Chem. Soc. 2005, 127, 15391) a second-generation oxaziridine 2-mediated catalytic process for C-H hydroxylation is reported. The revised reaction protocol features the use of aqueous H₂O₂ in AcOH-H₂O (1:1), conditions which efficiently generate the reactive oxaziridine intermediate 2 in situ from the benzoxa­thiazine catalyst 1. Among all catalysts 1 tested, catalyst 1e (R = C₆F₅) turned out to be the most effective suggesting hydrophobic catalyst-substrate aggregation as proposed by the authors. Mechanistically, oxaziridine-mediated electrophilic O-atom insertion into C-H bonds likely proceeds in a concerted, asynchronous fashion.