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The design, structural characterization, and evaluation of a unique class of 1,2,3-benzoxathiazine-based oxaziridines as potent O-atom transfer agents for catalytic C-H hydroxylation and alkene epoxidation are described. Turnover of this reaction is made possible by employing a diaryl diselenide cocatalyst and urea.H2O2 as the terminal oxidant. Oxidation of saturated hydrocarbons is strongly biased toward 3 degrees C-H bonds even in systems possessing a significantly greater number of methylene groups. In addition, the benzoxathiazine catalyst is effective for epoxidation of terminal and electron-deficient olefins. Collectively, these findings represent an important first step toward the advancement of general methodology for selective C-H oxidation.

Substituted benzoxathiazines function as catalysts for the selective hydroxylation of tertiary C-H bonds. Mechanistic studies have revealed an unanticipated disparity between oxaziridine reactivity and catalyst performance and have given way to a new catalyst and an aqueous H(2)O(2) reaction protocol that greatly facilitate such transformations (see scheme).

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Catalytic reaction processes for selective C À H bond hydroxylation are at the fore of modern synthetic chemical methods development. Such technologies attempt to mimic the extraordinary performance and precision of enzymatic systems. [1] Following this approach, most inventions have relied on transition-metal based complexes to support reactive metaloxo or metal-peroxo species that can effect the desired C À H oxidation event. [2,3] Far fewer catalytic methods make use of strained, electrophilic organic heterocycles (e.g., dioxiranes and oxaziridines). [4,5] We have capitalized on the unique properties of oxaziridines-ease of synthesis, modularity of design, tunable reactivity-and have described the first example of an oxaziridine-based catalytic process for C À H hydroxylation. [6,7] In contrast to most metal-mediated hydroxylation reactions, for which the high, indiscriminant reactivity of the oxidant often limits product selectivity and catalyst turnover, our first-generation oxaziridine system is hampered by its modest activity, thus restricting its use to a very small number of substrates. As such, we have sought new catalyst designs with enhanced performance and application potential. Mechanistic insights gained through computational and kinetics experiments have made possible the advent of a catalyst for CÀH hydroxylation that: 1) can be employed with a number of architecturally diverse substrates; 2) displays positional selectivity towards tertiary C À H bonds; and 3) functions under aqueous conditions with H 2