STEREOCHEMICAL STUDIES OF 1,2-DI(THIO)ACETAMIDOCYCLOHEXANES AND THEIRN,N-DIMETHYL DERIVATIVES BY NMR AND CD SPECTROSCOPY AND BY MOLECULAR MECHANICS CALCULATIONS
Azq. Khan et al., STEREOCHEMICAL STUDIES OF 1,2-DI(THIO)ACETAMIDOCYCLOHEXANES AND THEIRN,N-DIMETHYL DERIVATIVES BY NMR AND CD SPECTROSCOPY AND BY MOLECULAR MECHANICS CALCULATIONS, Acta chemica Scandinavica, 50(10), 1996, pp. 938-951
The configurations and conformations of cis- and trans- 1,2-di (thio)
acetamidocyclohexane and their N,N'-dimethyl derivatives have been stu
died by H-1 and C-13 NMR spectroscopy, using chemical shifts and coupl
ing constants, difference NOE H-1 NMR spectra and 2D H-1-C-13 NMR corr
elation spectra. For the trans compounds, the Z,Z configuration of the
(thio)amide groups with equatorial (thio)acetamido groups was found t
o be strongly preferred. For the cis compounds, E,Z configurations of
the (thio)amide groups with axial E and equatorial Z groups were found
to be preferred. Empirical force-held calculations with the MM2(91) f
orce field led to predictions for the most stable configurations and c
onformations, mostly in very good agreement with those obtained by NMR
spectroscopy. CD spectra recorded for the trans-(R,R)-N-methyl compou
nds in acetonitrile solution agreed well with those calculated on the
basis of geometries from force-field calculations. The CD spectra calc
ulated for the trans-(R,R)-NH- compounds and for the cis-monothio comp
ounds showed poor agreement with the experimental spectra.