Thiocarbonyls. X. The Isomeric 2,4,6-Tris(halophenyl)-1,3,5-thianes

Nine pairs of isomeric 2,4,6-tris(halophenyl)-1,3,5-trithianes have been assayed in the crude state by n.m.r. techniques, and separated and purified by chromatography. Contrary to previous reports, the α-(cis, trans)-isomers are the major products in most cases. These compounds are shown to exist as puckered chair trithiane structures, even in the more hindered α-(cis, trans)-o-halophenyl cases, by the clear resolution of axial and equatorial trithiane ring protons in a ratio of 2:1. An o-halogen on an axial phenyl group in the α-isomers causes the aromatic group to exert an anisotropic deshielding effect on adjacent axial protons, so as to cause the axial and equatorial proton peaks to appear as a singlet in some solvents. Melting point differences, in several cases quite large, from those previously reported have been observed for six of the eighteen triaryltrithianes reported.