B. Shainyan, I. Ushakov, L. L. Tolstikova
May 26, 2008
Citations
0
Influential Citations
9
Citations
Journal
Tetrahedron
Abstract
Abstract The stereodynamic behaviour of 1-(trifluoromethylsulfonyl)piperidine 1 , 4-(trifluoromethylsulfonyl)morpholine 2 , 1,4-bis(trifluoromethylsulfonyl)piperazine 3 and 4-(trifluoromethylsulfonyl)thiomorpholine 1,1-dioxide 4 was studied by low-temperature 1 H, 13 C and 19 F NMR spectroscopies. In acetone solution, compounds 1 , 2 and 4 were found to exist as mixtures of two conformers in the ratio of 4:1, 4:1 and 8:1, respectively, differing by orientation of the CF 3 group with respect to the ring. Compound 3 exists as a mixture of three conformers in the ratio of 3:28:69 also differing by the orientation of the two CF 3 groups. Unlike the previously studied N -trifyl substituted 1,3,5-triheterocyclohexanes, the preferred conformers of compound 1 and of 1,4-diheterocyclohexanes 2 – 4 are those with the CF 3 group directed outward from the ring, which is caused by intramolecular interactions of the oxygen atoms of the CF 3 SO 2 N groups with the equatorial hydrogens in the α-position. B3LYP/6-311+G(d,p) calculations of the energy, geometry and NMR parameters corroborate the experimental data. The calculated Perlin effects for all conformers of compounds 1 – 4 as well as those measured for the major conformers of compounds 3 and 4 were analyzed by the use of the NBO analysis.