CYCLOPENTA-1,2,3-DITHIAZOLES AND RELATED-COMPOUNDS

Treatment of 3-phenylinden-1-one oxime 6 with disulfur dichloride give s the indenodithiazole 2 directly in 58%; in the presence of Hunig's b ase the yield rises to 90%. Indenone oxime 9 and indanone oxime 11 wit h disulfur dichloride both give the chlorinated indenodithiazole 10, i n up to 80% with Hunig's base. Similarly, cyclopentanone oxime gives t he deeply violet trichlorocyclopentadithiazole 13 (ca. 25%) at 4-degre es-C in tetrahydrofuran with Hunig's base or in dimethylformamide with out added base. A mechanism (see Scheme 1) is proposed for this extens ive transformation in which a simple saturated oxime is converted into a highly functionalised heteroaromatic compound by the formation of 7 new bonds; this mechanism is based on the activation to chlorodeproto nation of all the cyclopentane positions, in turn, by the dithiazole r ing. Analogously, cycloheptanone oxime 17 gives the red pentachlorocyc loheptadithiazole 21, by the formation of 10 new bonds, and now di-, t ri-, and tetrachloro intermediates, 18-20, can also be isolated; tetra hydrobenzocycloheptenone oxime 22 gives the analogous dichloro 23 and trichloro 24 compounds, and the acyclic oxime 25 gives the monocyclic dithiazole 27, all in modest yield. The chlorine in compound 10 is dis placed by morpholine and pyrrolidine, but similar displacements in the trichloro compound 13 are unsuccessful since its heterocyclic ring is destroyed by nucleophiles. The pentachloro compound 21 is more stable than 13 towards nucleophiles, but less stable towards m-chloroperbenz oic acid, and these observations are explained in terms of the dipolar structures 13a and 21a.