CHIROPTICAL PROPERTIES OF C2-SYMMETRICAL N-HALOAZIRIDINES - CHIRAL RULES FOR THE N-HALOAZIRIDINE CHROMOPHORE

N-Chloro (a) and N-bromo (b) derivatives of C2-symmetric aziridines (2 S,3S)-1-halogen-2,3-dimethylaziridines 1a,b and 2S,3S)-1-halogen-2,3-b is(alkoxycarbonyl)aziridines 2a,b and 3a,b were obtained. Haloaziridin es 1a,b are an example of the ''pure'' N-haloaziridine chromophore whi ch has the first Cotton effect (CE) in the region of 260-300 nm. A qua drant rule which connects the first CE sip with the stereochemical env ironment 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 rever se quadrant rule.