CONFORMATIONAL PROCESSES AND SYMMETRY IN N-SUBSTITUTED 10,11-DIHYDRO-5H-DIBENZ[B,F]AZEPINE AND 1A,10B-DIHYDRO-6H-DIBENZ[B,F]OXIRENO[D]AZEPINE DERIVATIVES

The DNMR spectra of the title compounds bearing CONH2 and COCl substit uents at the azepine nitrogen have been obtained at 200 MHz and simula ted using the DNMR 3 program. Activation energies for seven-membered r ing inversion of 16.5(0.2), 16.3(0.2), and 15.5(0.2) kcal mol(-1) have been calculated, respectively, for diols 1 (X=NH2) and 1 (X=Cl) in me thanol, and for 3 (X=NH2) in chloroform. For 1 (X=NH2) and 3 (X=NH2) s uch ring inversion involves two identical conformers and introduces an effective symmetry plane, while for 1 (X=Cl) it occurs between two no n-equivalent conformers having a population ratio of 72:28. Epoxides 2 (X=NH2) and 2 (X=Cl) show temperature-independent NMR spectra between -25 and + 50 degrees C, being probably present in solution in the mor e stable conformers with a quasi-axial oxirane ring. The crystal struc ture of 2 (X=NH2) has been determined: space group Pbcn, a = 11.111 (3 ), b = 14.692 (3), c = 15.224 (4) Angstrom, final R value 0.0477. The NMR data, as well as X-ray single-crystal analysis, show that the pres ence of a COCl group in place of a CONH2 one at the azepine nitrogen i ntroduces an asymmetry in the structure of the seven-membered ring.