CRYSTAL-STRUCTURE OF THE SYN-DIAXIAL CONFORMER OF 2,2-DIPHENYL-1,3-DITHIANE CIS-1,3-DIOXIDE

The lower melting 1, 3-dioxide of 2, 2-diphenyl-1, 3-dithiane has been determined to be the cis diastereomer by 1 and l3C NMR spectroscopy and by single-crystal X-ray diffraction rather than trans as reported in the literature. The molecule exists in the conformation in the crystal which has both sulfoxide oxygens axial in spite of the significant electrostatic repulsions attending this conformation. The preference for the observed conformation appears to result from van der Waals interactions involving the two C (2)-phenyl substituents with each other and with the two oxygens. Crystals of the dioxide conform to space group P21/n, with a = 9.635 (2), b = 10.096 (3), c = 14.798 (4) Á, β = 98.86 (1)°, and Z = 4. The structure was solved by direct methods, and least-squares refinement gave R = 0.052 for 1680 independent significant reflections measured by counter diffractometry. © 1979, American Chemical Society. All rights reserved.