5-Morpholino-1,2,3,4-thiatriazole as a Sulfur-Transfer reagent in the reactions with Thioketones

Abstract

The thermal decomposition of 5-morpholino-1,2,3,4-thiatriazole (7), which leads to the extrusion of an active form of sulfur, in the presence of different thioketones is described. The interception of the S-atom by the C=S bond leads to in situ formation of an elusive thiocarbonyl S-sulfide of type 5. This
intermediate is a prone 1,3-dipole, which undergoes effectively [2+3] cycloadditions with thioketones to yield 1,2,4-trithiolane derivatives in a regioselective manner. Unexpectedly, 3,3-dichloro-2,2,4,4-tetramethyl-3-thioxocyclobutanone (1c) does not lead to the expected symmetrical 1,2,4-trithiolane. This result can be explained by the reduced stability of the corresponding thiosulfine 5c. Three-component reactions, which were carried out in the presence of equimolar amounts of two different thioketones, result in the formation of 'mixed' 1,2,4-trithiolanes of type 8.