Diaziridines, chirality

Diaziridines also show slow nitrogen inversion, and carbon-substituted compounds can be resolved into enantiomers, which typically racemize slowly at room temperature (when Af-substituted with alkyl and/or hydrogen). For example, l-methyl-3-benzyl-3-methyl-diaziridine in tetrachloroethylene showed a half-life at 70 °C of 431 min (69AG(E)212). Preparative resolution has been done both by classical methods, using chiral partners in salts (77DOK(232)108l), and by chromatography on triacetyl cellulose (Section 5.08.2.3.1). 

A study of the chiral discrimination in diaziridine clusters has been carried out using DFT computational methods [38]. The most stable neutral structure corresponds to that with the monomers in alternated chirality. The proton transfer within the neutral diaziridine chain proceeds with high TS barriers. The protonation of the fist diaziridine of the chain tends to produce a spontaneous proton transfer from the first monomer to the second (Fig. 3.18). The studied processes of proton transfer in the charged system show small barriers. The proton transfer in the neutral or protonated systems produces an inversion of the chirality of the monomers as the process evolves along the chain producing chirality waves. Finally, the calculated ORP of the clusters is very dependent on the cluster size, cyclic or helix shape, and on the number of monomers that form the cluster. 

I. Alkorta et al., Chiral recognition in diaziridine clusters and the problem of racemization waves. J. Phys. Chem. A 111, 1096-1103 (2007)... 

Spirocyclic, chiral diaziridines 79 can be made by reaction of a chiral-substituted imine 77 with ethyl A -[(4-nitrobenzenesulfonyl)oxy]carbamate (Ns0NHC02Et, 78) (Scheme 27) <1998TL6391>. Interestingly, this reaction does not proceed when using the more traditional tosyl-substituted aminating agent. 

The formation of optically active 115 demonstrates that the chiral leaving group takes part in the rate-determining step of the diaziridine synthesis, which is an argument against a nitrene intermediate. 

Kostyanovsky, R.G. Shustov, G.V. Zaichenko, N.L. As3mimetrical nonbridgehead nitrogen. XXIII. Chiral 3,3-bis(trifluoromethyl)diaziridines. Tetrahedron 1982, 38,949. 

Jung, M. Schurig, V. Determination of enantiomerization barriers by computer simulation of interconversion profiles Enantiomerization of diaziridines during chiral inclusion gas chromatography. JACS 1992, 114 (2), 529-534. 

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