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J . Am. Chem. SOC.1993,115, 10267-10274
Chiroptical Properties of C2-Symmetric N-Haloaziridines, Chiral Rules for the N-Haloaziridine Chromophore G. V. Shustov,**tA. V. Kachanov,f V. A. Korneev,+R. G. Kostyanovsky,f and A. Rauk.4 Contribution from the Institute of Chemical Physics, Russian Academy of Sciences, 117977, Moscow, Russia, and Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N I N 4 Received May 13, 1993”
Abstract: N-Chloro (a) and N-bromo (b) derivativesof Cz-symmetricaziridines(2!?,3S)- l-halogen-2,3-dimethylaziridines la,b and (2S,3S)- l-halogen-2,3-bis(alkoxycarbonyl)aziridines2a,b and 3a,b were obtained. Haloaziridines la,b are an example of the “pure” N-haloaziridine chromophore which has the first Cotton effect (CE) in the region of 260-300 nm. A quadrant rule which connects the first C E sign with the stereochemical environment of the chromophore is offered. Haloaziridinecarboxylic esters are a specific case of the N-haloaziridine chromophore. The second CE sign at 220-230 nm in the CD spectra of these compounds obeys a reverse quadrant rule.
Introduction Optically active aziridines are synthons for the preparation of amino acids’ and @-lactams,2are used as chiral reagents,) and show various biological activity? Optically active aziridines are often obtained by such methods as asymmetrical synthesis: kinetic resolution (fermentative catalysis): or resolution of racemates.’ In such cases the problem of the determination of absolute stereochemistry usually arises. This problemcould be easily solved by means of circular dichroism (CD) spectroscopy. However, the aziridine chromophore proper has its first dichroic absorption in the short-wavelength region (
