The DNMR spectra of the title compounds bearing CONH2 and COCl substituents at the azepine nitrogen have been obtained at 200 MHz and simulated using the DNMR 3 program. Activation energies for seven-membered ring 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 methanol, and for 3 (X=NH2) in chloroform. For 1 (X=NH2) and 3 (X=NH2) such ring inversion involves two identical conformers and introduces an effective symmetry plane, while for 1 (X=Cl) it occurs between two non-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 more stable conformers with a quasi-axial oxirane ring. The crystal structure 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 presence of a COCl group in place of a CONH2 one at the azepine nitrogen introduces an asymmetry in the structure of the seven-membered ring.
|Autori interni:||CHIAPPE, CINZIA|
|Autori:||BELLUCCI G; CHIAPPE C; MARCHETTI F|
|Titolo:||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|
|Anno del prodotto:||1995|
|Appare nelle tipologie:||1.1 Articolo in rivista|