Diazepines. Part XVI. Nuclear magnetic resonance spectra of 2,3-di-hydro-1H-1,4-diazepinium salts

Abstract

The n.m.r. spectra of a number of 2,3-dihydro-1H-1,4-diazepinium perchlorates are discussed. They indicate that the dihydrodizepinium cation has a half-chair shape which inverts rapidly at room temperature, but inversion is slow at lower temperatures. Variable temperature kinetic studies of the inversion show that it is facilitated by the presence of larger groups at the 6-position, but is independent of the electronic nature of these substituents. There appears to be complete delocalisation in the unsaturated portion of the molecule, and the 6-position has a greater electron density than the 5(7)-positions.