Dithiols. Part 28. Conversion of 1,3-dithiolan-2-ones, 1,3-oxathiolan-2-ones, and 1,3-oxathiolan-2-thiones into 1,3-dithiolan-2-thiones

Abstract

Reaction of cis-perhydro-1,3-benzodithiol-2-one with potassium O-methyl dithiocarbonate gives cis-perhydro-1,3-benzodithiole-2-thione; a mechanism involving cyclohexane-cis-1,2-dithiol as an intermediate is proposed. Similar reactions on the cis- and on the trans-forms of 4,5-dimethyl-1,3-oxathiolan-2-one, 4,5-dimethyl-1,3-oxathiolan-2-thione, 4,5-bis(benzyloxymethyl)-1,3-oxathiolan-2-one, and 4,5-bis(benzyloxymethyl)-1,3-oxathiolan-2-thione likewise give high yields of the corresponding trithiocarbonates with retention of configuration; the suggested mechanism requires attack on the carbonyl or thiocarbonyl group, and the formation of an intermediate episulphide, a proposal supported by the finding that cis-perhydro-1,3-benzoxathiole-2-thione, which for steric reasons cannot form an episulphide by such a mechanism, gives no cis-perhydro-1,3-benzodithiole-2-thione.