Fused 1,2-dithioles, V: Carbenoid anions as intermediates in reactions of pyrrothines and their heteroanalogues.

Pyrrothines like thiolutine and other bicyclic 1,2-dithioles of type 1 when unsubstituted in 3-position are marked by their CH acidity. In the presence of weak bases such as triethylamine the pyrrothine 4 degraded via its anion to a thioketene trapped as the 1,3-dithietane 5. The carbenoid anions of several compounds 1 reacted with elemental sulphur forming enthiolates whose alkylation led to the corresponding thioethers or, in the case of the thiolactam 9, to the bicyclic trithiones 10 and 11. In the same manner selenides can be obtained via intermediate selenolate ions. Introduction of an aryl- or heteroarylmercapto group into compounds 1 was achieved directly by reaction of the corresponding anions with suitable disulphides. Though there may be structural limitations, this sulphurization reaction can be extended to 3-unsubstituted trithiones. The new compounds exhibited significant activity against Mycobacterium tuberculosis in the primary screening.