Asymmetric unbridged nitrogen. 39. Configuration and conformations of N-substituted perhydro-1, 3,2-dioxazines

The stereochemical peculiarities of N-substituted perhydro-1,3,2-dioxazines were analyzed thoroughly on the basis of NMR spectroscopic data, the results of x-ray diffraction analysis, and quantitative MO theory. It is shown that in solutions and in the crystalline state these compounds exist in a chair conformation with an equatorial orientation of the substituents in the 2 and 4 positions; the high degree of crimped character of the heteroring (the angle of inflection along the 0...0 line is 70.3°) is due to repulsion of the unshared electron pairs of the N and 0 atoms and n- interactions. An increase in the n- interaction in dialkoxy amines and acetals on passing from C_s to C₂ symmetry of the molecules was demonstrated.See 1] for communication 38. Communication 39 is also communication 25 of the series Geminal systems. See 2] for communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1341–1347, October, 1985.