Thiapyran-2-thiones, synthesis

Besides being useful precursors to pyrroles pyridine-2-ones -4-ones, -4-thiones. and -4-imines 4-alkylidene-dihydropyridines thiophenes 1,2,4-triazoles thiapyrane-2-thiones, isoquinoline-3-ones isoben-zothiophenes and 4-mercaptoimidazolium hydroxide inner salts, mesoionic thiazoles are potentially useful in the construction of molecules with herbicidic (39). central nerve stimulating, and antiinflammatory properties (40,41). Application in dye synthesis has likewise been reported (42). 

Thiapyran derivatives can be prepared from preformed organoiron and -cobalt complexes as in Scheme 160 the organocobalt complex (136) can be used as an intermediate in the synthesis of 1,2-dithia cyclopent-4-en-3-thione (See Scheme 122 in Section IV,H.)... 

The 4 -thiapyran-4-thione route to thiathiophthens has been modified so as to yield 6a-selenahthiopthens (35). The intermediate selenoketones (38) are unstable, but react satisfactorily with sodium sulphide in aqueous dimethyl sulphoxide to give dianions which are oxidized, as in the original synthesis, with ferricyanide. N.m.r. data on 6a-selenathiophthen, and on its 3,4-dimethyl and 2,5-diphenyl derivatives, indicate real or time-averaged... 

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