Oxaziridines

Biographical Sketches

Jitendra Kumar Mishra was born in 1980 in Gorakhpur (U.P.), ­India. He completed his B.Sc. (1999) and M.Sc. (2001) degrees in organic chemistry from D.D.U. Gorakhpur University, Gorakhpur. He is currently working as a DRDO-JRF for his Ph.D. degree under the supervision of Prof. M. P. Kaushik at the Defence Research and Development Establishment in Gwalior, India.

Introduction

Oxaziridines were first discovered in 1956 [1] and have been widely investigated, principally for two reasons. The ­presence of an inherently weak N-O bond in a strained ring promised a group of compounds of unusually high ­reactivity. In addition, this system possesses the structural elements that seem to be required in order to observe ­stereochemical isomerism at nitrogen: ring strain and an atom with unshared electron pairs attached to the ­nitrogen.

Oxaziridines can be used as both oxygenating and aminating agents in their reactions with a wide variety of nucleophiles. Oxaziridines with small groups on N, for example hydrogen or methyl, act as aminating agents, whereas those with bulky or electron withdrawing groups on N preferentially transfer the oxygen atom. Oxaziridine-­mediated processes are of interest due to the easy accessibility of the reagents and their potential for asymmetric ­induction.

Abstracts

(A) For asymmetric oxygenation of chiral imide enolates: Evans and coworkers have found that the a-hydroxylation reactions of chiral enolates derived from oxazolidinone carboximide proceed with exceptional facility with the oxidant 2-(phenyl­sulfonyl)-3-phenyl oxaziridine. The following carboximides were transformed into their respective Z-sodium enolates (1.2 equiv of NaN(Me3Si)2, THF, -78 °C) with slight excess of oxaziridine. [2]
(B) For asymmetric oxidation of ketone enolates: The reagent-controlled asymmetric oxidation of trisubstituted enolate anions can be done by enantiomerically pure camphorsulfonyl oxaziridine. [3]
(C) For epoxidation of alkenes: Epoxidation of alkenes are also possible by using oxaziridine. [4]
(D) For epoxidation of alkenes (with perfluorinated oxaziridines): Alkyl-substituted olefins are epoxidized by perfluoro-cis-2,3-­dialkyl oxaziridines under mild conditions. Similarly electron ­deficient substrates (e.g. a,b-enones) can also be epoxidized. [5]
(E) For amination of N-nucleophiles: Oxaziridines can be used as an aminating reagent for N-amination of 2° amines. [6]
(F) For N-acylamidation: Direct N-acyl transfer as a method for protected hydrazine syn­thesis has also been shown to proceed in good yield with a wide ­variety of substrates. [7]

References

• 1 Emmons WD. J. Am. Chem. Soc.  1956,  78:  6208 
• 2 Evans DA. Morrissey MM. Dorow RL. J. Am. Chem. Soc.  1985,  107:  4346 
• 3 Davis FA. Sheppard AC. Chen B.-C. Serajul Haque M. J. Am. Chem. Soc.  1990,  112:  6679 
• 4 Davis FA. Abdul-Malik NF. Awad SB. Harakal ME. Tetrahedron Lett.  1981,  22:  917 
• 5 Arnone A. Desmarteau DD. Novo V. Petrov VA. Pregnolato M. Resnati G. J. Org. Chem.  1996,  61:  8805 
• 6 Andreae S. Schmitz E. Synthesis  1991,  327 
• 7 Schmitz E. Fechner-Simon H. Schramm S. Liebigs Ann. Chem.  1969,  725:  1