Thionation of N-methyl- and N-unsubstituted thiazolidine enaminones *

The potential of directional non-bonded 1,5-type S... O interactions to initi- ate the incipient stage of an in situ rearrangement of N-unsubstituted thiazolidine enaminones to functionalized 1,2-dithioles has been demonstrated. The spectral characteristics, as well as X-ray structural analysis of a selected rearranged product, indicate that a dynamic interconversion occurs in solution between the 1,2-dithiole and the 3,3a 4 ,4-trithia-1-azapentalene bicylic form. The lack of the rearrangement in the case of a N-methyl substituted enaminone precursor is attributed to an unfa- vorable methyl migration in the last reaction step.