Conformational Analysis of (S)-4,5,6,7-Tetrahydro-5-Methylimidazo [4,5,1-jk][1,4]-Benzodiazepin-2(1H)-one (R78362)

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Abstract
The solution and solid state conformation of (S)-4,5,6,7-tetrahydro-5-methylimidazo [4,5,1-jk][1,4]-benzodiazepin-2(1H)-one (R78362) have been investigated by low temperature NMR and x-ray diffraction studies. The 1H NMR spectrum of R78362 shows no evidence of the presence of multiple conformers in the temperature range 340K - 177K. Molecular mechanisms and semiempirical molecular orbital calculations suggest that the nitrogen and ring inversion barriers of R78362 are small and thus a time-averaged 1H NMR spectrum is probably occurring at 298K. The x-ray diffraction data indicated that there were two independent molecules in the asymmetric unit of the crystal. The two molecules had similar conformations with the benzoimidazole ring being planar and the diazepine ring in a “half-chair” conformation.