Thieno -1,3-dithiole-2-thione

Thieno[2,3-r 1-l,2,3-thiadiazoles 40a-f heated with CS2 in a double compartment autoclave produced thieno[2,3-rfl-l,3-dithiol-2-thiones 41a-f <2001MOL145>. In addition to the thermolysis product 41e, thieno[2,3- / -l,2,3-thia-diazoles 40e also produced bisthieno[2,3-/ 2, 3 -< ][l,4]dithiine 42 in 36% yield (Equation 3). 

The intermolecular Diels-Alder reactions of 1,3-dithioles (163) with DMAD and DEAD produced the first 7//-thieno[2,3-c]thiopyran-7-thiones (164) and 47/-thieno [3.2-c]thiopyran-4-thiones (165), the structures of which were confirmed by X-ray diffraction. Further work on the mechanism of the cycloaddition and subsequent rearrangement is in progress (Scheme 46).191... 

Dichloro-l,2-dithiole-3-thione (1) undergoes 1,3-cycloaddition with DMAD to give the adduct (2).1 On further heating with alkynes, regiospecific cycloaddition and molecular rearrangement occur with loss of chlorine to give 7//-thieno[2,3-c]thiopyran-7-thiones (3) and 4//-thieno[3,2-c]thiopyran-4-thiones (4). 

Upon treatment with CS2 at 170°C, 4,6-dihydro thieno[3,4-d]-l,2,3-thiadiazole (70) yielded 4,6-dihydrothieno[3,4-(/]-1,3-dithiole-2-thione (71), which was a useful intermediate for the synthesis of a novel organic conductor <89TL7249>. 

Thieno-l,3-dithiolane-2-thione (62ACS105) was prepared by a convenient one-flask reaction in which 3,4-dibromothiophene was twice treated with BuLi followed by elemental sulfur at —78 °C to provide the dilithio intermediate. This sequence was followed by the addition of an excess of CS2 and 2N NaOH (equation 8). Alternatively, the dilithio intermediate could be protonated, and the resulting dithiole allowed to react with thiocar-bonyldiimidazole (81CC920). 

Dithioles 480 undergo cycloaddition with alkynes, and subsequent rearrangement with loss of CI2 gives IH-thieno[2,3-f]thiopyran-7-thiones 481 and 4//-thieno[3,2-f]thiopyran-4-thiones 482 as an isomeric mixture (Scheme 80) <20050L791>. 

Vinyl-l,2-dithiole-3-thiones react with sulfur to form thieno[3,2-c]-1,2-dithiole-3-thiones (134).186 188 4-Amino-l,2-dithiole-3-thiones can be N-alkylated and N-acylated.189... 

Dithiolium cations (3) form radicals under the thermal conditions of mass spectroscopy (Section 3.11.3.4), and carbenes may be involved in the formation of l,2-dithiole-3-thiones and thieno[3,2-Z>]thiophenes by thermolysis of 2-iodo-l,2-dithiolium salts (29a) <8ILA1729>. 

Dithioles. Diselenoles. and Dltelluroles.- Treatment of ethyl benzoylacetate with Lawesson s reagent (188) gives the l,2-dithiole-3-thione (189) 197 the latter reacts with arenediazonium fluoroborates to yield the 1,2-dithioliua salts (190 R = aryl). The action of -methylbenzylidenemalononitrile, PhMeC C(CN)2, on the methylthio-analogue (190 R = Me) leads to a mixture of the condensation product (191) and the thieno[3,2-b]thiopyranimine (192).199 The mesoionic dithiolium oxide (193) has been prepared from -dichloroacetone and sulphur, followed by methylation. 

Refluxing cyclopropenethione 90 with 4,5-disubstituted l,2-dithiol-3-thiones 94 in anhydrous benzene in the dark is accompanied by the elimination of two sulfur atoms to form thieno[3,2-Z)]thiophenes 95 (82LA315). 

In an extension of the familiar addition reaction of l,2-dithiole-3-thiones and acetylenes, dibenzoylacetylene has been shown to yield products of the expected type (18 X = CH). An attempt to utilize the adjacent carbonyl groups to generate the fused thieno-system (19 X = CH) failed, although the reaction succeeded with the nitrogen analogue (18 X = N), which, on... 

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