A chiral N-methylbenzamide:: Spontaneous generation of optical activity

1,2-Bis(N-benzoyl-N-methylamino)benzene (1) was crystallized from distilled ethyl acetate as chiral crystals belonging to space group P2(1)2(1)2(1). The optically active crystals of the two enantiomers were distinguishable morphologically, and their CD spectra in KBr were mirror images. In solution, several conformational isomers due to rotations of the Ar-N bonds and the amide bonds were observed. The major conformer corresponds to the crystal structure in which the two N-benzoyl groups exist on opposite sides of the central benzene ring (anti conformation) and the amide bonds are both cis. The enantiomers in solution could be distinguished from each other by H-1-NMR measurements in the presence of chiral 1,1'-bi-2-naphthol. Mixed crystals of 1 and (R)-1,1'-bi-2-naphthol were obtained from their 1:1 mixed solution in MeOH. An X-ray crystallographical analysis showed that the configuration of 1 in the mixed crystals was (R,R). H-1-NMR measurements of the mixed crystals at 178 K in CD2Cl2 showed the absolute configuration of 1 in the CD260-(+)-crystal to be (R,R). (C) 1999 Elsevier Science Ltd. All rights reserved.