Vibrational, NMR, photoelectron spectra and conformational analysis of seven-membered heterocycles

The article covered are the general principles of conformational analysis of 7-membered 1,3-dihetero-2-phosphepines and -silepines with one planar unit by means of spectral methods. The quantitative description of all possible conformers is given. Spectral criteria (the most informative bands in vibrational spectra, the shift difference and vicinal couplings in NMR spectra) for structural investigations are derived and on their basis the conformational condition is established depending on the nature of planar units and heteroatoms. © 1990