Oxaziridine reactions acid-catalyzed

Acid-catalyzed hydrolysis of A-aryloxaziridines may proceed via cleavage of either the C—O or N—O bonds, depending upon the ring substitution pattern. These reactions are usually discussed in terms of initial protonation at the oxaziridine oxygen atom <77JHC1393>. Acid-catalyzed isomerization to nitrones has also been reported <64HC(19)624>. 

Sulfoxide linkers can be synthesized via addition of a sulfoxide linker to the resin or via transformation of a sulfide linker to the corresponding oxo-derivative. Many oxidation reagents like ozone or mCPBA to convert thioethers are very unselective regarding sulfoxide/sulfone formation but methodologies like acid-catalyzed oxaziridine oxygen transfer [298], H2O2/HFIP oxidation [299] or reaction with a fBuOOH/CSA-mixture [300] can be applied successfully. 

Enantiomeric purities ranging from 20 to 80% have been reported for the acid-promoted asymmetric oxidation of sulfides to sulfoxides by binaphthyl-derived oxaziridines has been described <2007T6232>. A novel amino hydroxylation of olefins has been developed using /ra t-2-phenylsulfonyl-3-phenyloxaziridine 33 <2007JA1866>. The reaction, which is catalyzed by copper(ll) salts, affords good yields of the product. Oxidation of aldimines to oxaziridines using alumina-supported M0O3 catalyst and anhydrous /-butyl hydroperoxide (TBHP) has been described. Yields are excellent. 

Hydrolysis by Emmons path 2 has been suggested" as a method for converting amines to ketones, the acid counterpart of a base-catalyzed procedure cited previously. The oxaziridines were obtained by oxidation of the product from amines and acetone, and hydrolyzed with 2M hydrochloric acid at room temperature for 40 hours. The only aliphatic aldehyde produced was not stable under these conditions. This reaction has received further study. ... 

Heteropoly acids (HPAs) such as 12-phosphomolybdic acid (PMA) and 12-phosphotungstic acid (PWA) function as a catalyst in the aziridination of alkenes with chloramine-T (Scheme 2.37) [56]. PMA catalyzed the reaction most efficiently in the presence of a quaternary ammonium cocatalyst and molecular sieves, affording aziridine products in good yields. The low stereospecificity of the reaction indicates the stepwise mechanism. The authors proposed the involvement of metallo-oxaziridine 22 as an intermediate. 

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