A STUDY OF NITROGEN- AND SULFUR-CONTAINING HETEROCYCLES. 41. SYNTHESIS AND SPATIAL STRUCTURE OF 3a-ALKYL-4,7-DICHLORO-1,2-DIOXOOXAZOLIDINOPYRIDOTHIAZINES

Article abstract of DOI:10.1007/BF00506390

The structure of the products of the chlorination of oxazolidino<3,2-f>pyrido<2,3-b><1,4>-thiazines has been studied with the aid of spectral methods.It has been shown that the chlorine atom substitutes position 4 of the tricyclic system (in the thiazine ring).It has been established on the basis of PMR and 13C NMR spectra that in solution the compounds obtained exist in the form of mixtures of two diastereomers with the cis and trans orientations of the substituents at the C_(3a) and C₍₄₎ carbon atoms of the tricyclic system in each case.The configurations of the diastereomers have been determined from the chemical shifts in the 13C NMR spectra and from the relaxation times in the PMR spectra.It has been shown that the isomer with the transoid arrangement of the substituents on the C_(3a) and C₍₄₎ atoms of the tricyclic system, which are included in a thiazine ring present in the "half-chair" conformation, is energically the more favorable.