Stereochemisty. Part III. Conformation of eight-membered heterocyclic rings. Conformation of NN-diphenyl-3,7-diaza-1,5-dithiacyclo-octane in dioxan solution

Abstract

A general method for defining the geometry of non-rigid ring systems has been developed by a modification of literature methods. Using this method, the resultant moments of different conformers of NN-diphenyl-3,7-diaza-1.5-dithiacyclo-octane have been calculated. These compounds prefer a crown conformation in dioxan solution with a diequatorial disposition of the substituents on nitrogen.WHEREAS conformational analysis of eight-membered alicyclic systems has received considerable attention 1-12 substituted and heterocyclic eight-membered ring systems present a more complex picture.13 With a view to studying their conformation and stereochemistry, we have prepared NN-diphenyl-3,7-diaza-l,5-dithiacyclooctane (la) and its 9-bromo and $-methyl derivatives. We have measured the dipole moments of these compounds. Molecules with many polar bonds may be expected to have different resultant moments in different conformations. We thought a comparison of the 6-S-7 N L-QR LJ (1) a ; R = H b; R=Br C; R=CH3 experimental resultant moment with that calculated for different conformations might give definitive information about the conformational preference in solution.The experimental values of the dipole moments are given in Table 1.and ' equatorial ' refers to the bond that makes the larger angle.

Conformations of 1,3,3,5,7,7-Hexamethyl-1,5-diazacyclooctane and Its Bis-BH3 Adduct. Mono- and Bis-BH3 Adducts of Di-Tertiary Amines

“…The conformations preferred by heteroatom-substituted eight-membered rings are quite varied, but nitrogen-substituted eight-membered rings seem to prefer the chair-chair. For example, 3,7-diphenyl-3,7-diaza-1,5-dithiacyclooctane exists mainly as a chair-chair in solution. , The close analogue 3,7-dimethyl-3,7-diaza-1,5-dithiacyclooctane is also a chair-chair, with methyls axial, in the solid state . Choi et al.…”

“…For example, 3,7-diphenyl-3,7-diaza-1,5dithiacyclooctane exists mainly as a chair-chair in solution. 28,29 The close analogue 3,7-dimethyl-3,7-diaza-1,5dithiacyclooctane is also a chair-chair, with methyls axial, in the solid state. 30 Choi et al 31 found by X-ray crystallography a distorted chair-chair for 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane.…”