ChemInform Abstract: Solid‐State Structures of cis‐ and trans‐1‐Cyclohexyl‐2‐phenyl‐3(p‐toluyl)aziridines.

Abstract

Solid‐state structures have been determined for cis‐ and trans‐1‐cyclohexyl‐2‐phenyl‐3‐(p‐toluyl)aziridines using single‐crystal X‐ray diffraction techniques. The cis isomer crystallizes in the centrosymmetric monoclinic space group P21/c (No. 14), with a = 18.669(3)Å, b = 5.709(1)Å, c = 17.412(2)Å, β = 96.29(1)° and Z = 4; the trans isomer crystallizes in the noncentrosymmetric orthorhombic space group Pna21 (No. 33), with a = 17.089(2)Å, b = 18.729(3)Å, c = 5.749(1)Å and Z = 4. Full‐matrix least‐squares refinement of the structural parameters led to the following final agreement factors: R1 (unweighted, based on F) = 0.040 and R2 (weighted, based on F) = 0.054 for the 2592 independent reflections of the cis isomer having 2θMoK¯α <55° and I>3σ1, and R1 = 0.033 and R2 = 0.031 for the 1504 independent reflections of the trans isomer having 2θMoK¯α <55° and I>3σ1. The statistically significant differences that exist between the two isomers for two bond lengths and ten bond angles (p < 0.05) appear to be the direct result of the p‐toluyl group orientation with respect to the cyclohexyl and phenyl substituents. In the cis isomer it is anti with respect to the N‐cyclohexyl group and cis with respect to the phenyl group, whereas in the trans isomer it is syn with respect to the N‐cyclohexyl and trans with respect to the phenyl group. Three‐ring to carbonyl hyperconjugation is correlated with stereoelectronic interactions in the trans isomer. Bonding, determined by X‐ray and nmr studies, is discussed for the three‐membered aziridine ring proper; while bonding, determined by X‐ray studies, is discussed for substituents of the aziridine ring. These aziridinyl ketone compounds are of importance as potential mammalian DNA alkylating anti‐tumor agents in solid‐state solid‐state systems. To date only a trans isomer has demonstrated this biological activity in tumor‐bearing rats.