Conformational NMR study of N-substituted-1,3,4,5-tetrahydro-1H-2-benzazepines

Abstract

The variable temperature (298–179 K) ¹H NMR spectra of N-substituted 2-benzazepines (compounds 2–7) correspond to two puckered mirror-image (enantiomorphic) conformations, with a single chair-to-chair interconversion barrier for the benzazepine ring of ca. 11 kcal mol⁻¹ in CD₂Cl₂ solution. A similar interconversion was detected for 1,3,4,5-tetrahydro-N-methylbenzazepine (compound 1), of lower symmetry. The conformations of compounds 1–7 were assigned on the basis of the magnitude of ¹H-¹H vicinal coupling constants. The ¹H and ¹³C NMR spectral assignments were determined by ¹H–¹H COSY, ¹H–¹³C COSY, and NOESY experiments.