BIS(BENZO[4,5]THIENO)[3,2-C-2',3'-E][1,2] DITHIINE, A VALENCE ISOMER OF DITHIOXO-THIOINDIGO

Citation
W. Schroth et al., BIS(BENZO[4,5]THIENO)[3,2-C-2',3'-E][1,2] DITHIINE, A VALENCE ISOMER OF DITHIOXO-THIOINDIGO, Chemische Berichte, 127(2), 1994, pp. 401-408
Citations number
101
Categorie Soggetti
Chemistry
Journal title
ISSN journal
00092940
Volume
127
Issue
2
Year of publication
1994
Pages
401 - 408
Database
ISI
SICI code
0009-2940(1994)127:2<401:BDAVIO>2.0.ZU;2-E
Abstract
3-Mercaptobenzo[b]thiophene (1) is transformed with assistance of base s, especially of amines, into the benzo[b]-thieno-annellated 1,2-dithi ine 6 and not into the originally claimed ''Dithioxo-thioindigo'' tran s-3. Primarily, the formation of 6 from 1 involves oxidation to the di sulfide 4 which may also be used separately. Conceivable rationalizati ons are discussed. The same compound is accessible (in lower yield) by thionation of thioindigo with the aid of the Lawesson reagent. X-ray elucidation of 6 reveals a non-planar structure of the cyclic disulfid e with a dihedral C-S-S-C-angle of 53-degrees. Despite of the absence of any established chromophoric moiety, 6 is deeply red in the crystal and in solution, as it is representative for the ''undisturbed'' 1,2- dithiine system. Contrary to the usual behaviour of the non-annellated 1,2-dithiines, 6 displays no spontaneous sulfur extrusion under mild conditions, but only at high temperatures and in the presence of sulfu r-binding agents, leading to the benzo[b]thieno-annellated thiophene 2 2, Moreover, 6 may be reduced to the dithiol 14 (or 13, respectively) and regenerated exclusively from this by oxidation. Further characteri stic reactions of 6 are described (e.g. to the sulfoxide 18, to the py ridazine 19, and to the thiophosphoric ester 21).