Oxaziri dines

Nitrones can be formed upon treatment of secondary amines with an oxaziri-dine salt (23) generated from dihydroisoquinoline (Scheme 2.10) (79). 

Photochemical Rearrangement Isomerization of nitrones to oxaziri-dines is a general reaction of various cyclic and acyclic nitrones (447-449). When this reaction is reversible, many transformations of nitrone to oxaziridine and back to nitrone can be carried out without decomposition. This reaction is of special interest in view of light energy accumulation (450, 451). 

Sometimes the reaction medium is not sufficiently oxidizing to allow the complete rearomatization of the a-complex, which can dimerize. This was observed in the alkylation of pyridine and pyrazine by oxaziri-dines the products (1 and 2) of the dimerization of the a-complex and subsequent oxidation were also formed. ... 

A plausible reaction mechanism is that oxidative cleavage of tosylhydrazones is initiated by oxidation of the imino double bond of the tosylhydrazones with 51 to an oxaziri-dine derivative, which may be immediately converted to the carbonyl compound by a fragmentation reaction induced by 02 (equation 81). 

The antibiotic ( + )-kjellmanianone (2) has been prepared by asymmetric hydroxylation of the sodium enolate of the P-keto ester 1 with several (camphoryl)oxaziri-dines. The highest enantioselectivity (68.5% ee) was obtained by use of the p-(trifluoromethyl)benzyl derivative 3.3... 

Irradiation of crystalline host-guest complexes of the nitrones 23 with the axle-wheel-type host compound (R,R)-( — )-4 gave the optically active oxaziri-dines 24 (Scheme 6) [48]. In particular, the enantioselectivities for the formation of 24d and 24e were perfect. 

An alternative to the Bach procedure (BocN3/FeCl2) for the synthesis of Boc-protected sulfimides was developed in 2002 (Scheme 76) [171]. Oxaziri-dine 312, prepared from diethyl ketomalonate, was found to iminate allylic sulfides 309 at low temperatures. The resulting allyl sulfimide (not shown) immediately rearranged to protected amines 313 in high yields. The possibility of preparing a-amino acid derivatives like 314 is a noteworthy feature although the compounds are, of course, racemic. 

Oxidation of Oxaphospholenes. Reaction of oxaphos-pholene (5) with (+)-[(8,8-dichlorocamphoryl)sulfonyl] oxaziri-dine (2) affords p-hydroxy-y-keto-phosphonate in 49% ee with undetermined absolute configuration (eq 3). Higher temperatures accelerate the reaction but lower the stereoselectivity. 

Sulfones are valuable intermediates for the synthesis of chemically and biologically useful molecules. Traditionally, they are prepared by oxidation of sulfides with nitric acid, KMnO, MnO, NaClO, m-chloroperbenzoic acid, sodium metaperiodate, bromine, dinitrogen tetraoxide, oxaziri-dine, benzeneseleninic peracid, tert-butyl hydroperoxide, sulfinyl peroxy compounds, iodosobenzene diacetate and 4-methylmorpholine N-oxide/ osmium tetroxide. 

In the field of asymmetric a-hydroxylation reactions, early developments required multistep procedures, where the substrates were activated via enol or enolate intermediates. More recently, it has been demonstrated that the hydroxylation of p-keto esters could be achieved directly, by using oxaziri-dines. In this area, advances have been made with highly enantioselective nickel-catalysed a-hydroxylations of cyclic and acyclic p-keto esters, as well as... 

Cl4H12N2O5S, trans-2-(p-Toluenesulphonyl)-3-(m-nitrophenyl)oxaziri-dine, 44B, 341... 

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