Synthesis, NMR Spectroscopy and Molecular Modelling of the 2-Methyl-2,3,4,5-tetrahydro-1<i>H</i>-[1]benzothieno[2,3-<i>c</i>]azepine
A new approach to the preparation of condensed azepines was demonstrated with a case study of the 2-methyl-2,3,4,5-tetrahydro-1 H -[1]benzothieno[2,3- c ]azepine synthesis. The key stage of the synthesis protocol is the formation of an azepine ring under the Eschweiler-Clark reaction conditions. The Gibbs energy of activation for the inversion of azepine ring was determined by dynamic NMR 1H spectroscopy. Molecular modeling of the structure and evaluation of chemical shifts of 1H and 13C nuclei were performed for the 2-methyl-2,3,4,5-tetrahydro-1 H -[1]benzothieno[2,3- c ]azepine. The calculation of the magnetic shielding constants was performed by the standard GIAO method using the B3LYP/6-31G(d,p) optimized molecular geometry parameters. The solvent effect was taken into account in the PCM approximation. The calculated chemical shifts of the 1H and 13C nuclei for 2-methyl-2,3,4,5-tetrahydro-1 H -[1]benzothieno[2,3- c ]azepine are in good agreement with the experimental ones obtained from DMSO- d 6 solution.