Stereochemistry of α-halogeno-sulphoxides. Part IV. Halogenation of thian 1-oxides

Abstract

Chlorination of trans- and cis-4-p-chlorophenylthian 1-oxide [(I) and (II)] affords as main product 2ax-chloro-4eq-p-chlorophenylthian 1eq-oxide (IIIa), together with minor amounts of 2eq-chloro-4eq-p-chlorophenylthian 1ax-oxide (IVa). Bromination of (I) gives a similar mixture of the bromo-sulphoxides (IIIb) and (IVb). In the presence of silver nitrate the main products from the trans-substrate (I) are the 1ax-oxides (IV) and the only products from the cis-substrate (II) are the 1eq-oxides (III). The reactions in the absence and in the presence of silver ions seem to be subject to predominant thermodynamic and kinetic control, respectively.