1.2- Dithiole-3-thiones reduction

Attempts to follow a published procedure for the preparation of 1,3 -dithiole-2-thione-4,5-dithiolate salts [1], involving reductive coupling of carbon disulfide with alkali metals, have led to violent explosions with potassium metal, but not with sodium [2], However, mixtures of carbon disulfide with potassium-sodium alloy, potassium, sodium, or lithium are capable of detonation by shock, though not by heating. The explosive power decreases in the order given above, and the first mixture is more shock-sensitive than mercury fulminate [3],... 

Many papers deal with both analytical determination and cathodic transformations of thiones (21). Thus, a four-electron reduction of OLTIPRAZ [4-methyl-5-(2-pyrazinyl)-l,2-dithiole-3-thione] produces several species that could account for the schistosomicidal activity of metabolites of the starting compound. The first two-electron reduction (in aqueous media) affords the scission of the S —S linkage and the thus formed dianion can be readily [197] alkylated by common alkyl halides. Let us note that the cathodic behavior of structure (21) was shown to be strongly influenced by the nature of substituents and particularly [198] by the electron-donating ability of Rh... 

In the past, TTF has been prepared from 1,3-dithiole-2-thione, which, by an oxidative step, was converted to a 1,3-dithiolylium salt followed by coupling with base.6 9,15 The present method uses a reductive sequence, thereby permitting milder conditions and better yields.16... 

Reaction of 4-fluoro5-5-(l,l,2,2-tetrafluoroethyl)-3//-dithiole-3-thione with 2equiv of Na2S affords 3,4-difluoro-2-mercapto-l,6,6aA-trithiapentalene after an acidic work-up. Further reduction with Na2S gives 3,5-difluoro-4-mercapto-2//-thiopyran-2-thione 507 in >30% overall yield. Methylation of the Na salt of the pentalene affords an 1 1 mixture of methylsulfanyl derivatives of a 2//-thiopyran-2-thione 508 and 4//-thiopyran-4-thione 509 (Scheme 190). DFT calculations predict the stability sequence for the thiones is 507 > 508 > 509 <2006JFC(127)774>. 

The reduction of benzo-l,2-dithiole-3-thiones (77b) to various polythiols (74ACS(B)827, 63LA(661)84) may be accomplished by lithium (78BEP867155), lithium aluminum hydride, or by catalytic hydrogenation, and Raney nickel hydrodesulfurization gives products by complete elimination of sulfur (B-66MI43100). 

Reaction of the immonium ion (157) with dihydrogen sulfide produces the l,3-dithiole-2-thione (158) while reduction of the ion (157) with sodium borohydride, followed by treatment with sulfuric acid, resulted in the formation of the 1,3-dithiolylium salt (48) (76S489). 

The l,3-dithiole-2-thione derivative (328) can be prepared by reduction of carbon disulfide with potassium in DMF under argon and subsequent alkylation with dimethyl sulfate (80CB1898). Other alkylating agents besides dimethyl sulfate can be used. 

The unsubstituted 1,3-dithiolylium salt (1) can be prepared by reaction of l,3-dithiole-2-thione (21) with peracetic acid in acetone or with hydrogen peroxide in acetic acid (76S489). Another method includes borohydride reduction of 2-methylthio-l,3-dithiolylium salts to the 2-methylthio-l,3-dithiole followed by acidification (76S489). 

Electrochemical reduction of CS2 in either DMF or MeCN yields the trithiocarbonate (16) and the 4,5-dimercapto-l,3-dithiole-2-thione (17) dianions, which on oxidation by iodine give the binary carbon sulfide C3S6 in good yields (equations 111 and 112). ... 

It was shown <1988BSF101, 1994JCS(P2)351> that thiacyl thioketenes are intermediates for the reductive dimerization of 5-alkylthio-l,2-dithiole-3-thiones with P(OMe)3 in refluxing benzene, giving rise to 2,4-bis(2-thioxoethylidene)-1,3-dithietanes, known as thioxodesaurins. Later, the intramolecular variant was applied successfully <1998CC1653>,... 

The stepwise reduction of 4-fluoro-5-(l,l,2,2-tetrafluoroethyl)-3//-l,2-dithiole-3-thione 153 with Zmolequiv of sodium sulfide, acting both as the reducing and nucleophilic reagent, has found use in a synthesis of the sodium salt of trithiapentalene 154 (Scheme 18), which was converted upon acidification into 3,4-difluoro-2-mercapto-l,6,6aA -trithiapentalene 155 in moderate yield <2006JFC(127)774>. 

The l,3-dithiole-2-thione 207 possessing vicinal bis(bromomethyl) groups was a precursor of the diene 208 by a reductive elimination using iodide (Equation 11) <1998CC2197, 2000TL2091, 2002JMC2137>. 

When an N-substituent at C-2 of 1,3-dithioles was replaced by an S-substituent, a similar reaction sequence led to formation of the bis(2,3-dithiabutane-l,4-diyl)TTF 686. Thus, methylation of the l,3-dithiole-2-thione 681 with MeOTf afforded the corresponding salt 682, which after reduction with NaBH4 produced the 1,3-dithiole 683. 

Reduction of l,3-dithiole-2-thione yields an anion-radical (150) whose ESR spectrum at low temperature has been measured the very low proton splitting (indicated in gauss) implies the spin population to be highly concentrated in the trithiocarbonate moiety. Consistent with this, no proton hyperfine splittings were resolved in the ESR spectrum of the anion-radical of benzo-l,3-dithiole-2-thione. ... 

Carbon-sulfur bonds are formed during the reduction of carbon disulfide in aprotic medium methylation of the product yields 4,5-bis(methylthio)-l,3-dithiole-2-thione (XXIX) [92] if this compound is ethylated with Meerwein s reagent, followed by electrochemical reduction and thermal elimination, tetrathiomethoxy tetrathiofulvalene (XXX) is produced [93]. The mechanism of the formation of XXIX has been discussed [94, 95], and it has been shown that carbon sulfide (CS) is not involved in the formation of XXIX [96]. 

Electrochemical reduction of 4,5-alkylthio-l,3-dithiol-2-ones in aprotic medium, followed by alkylation, gives tetraalkylthioethylenes in almost quantitative yield the same products are formed, albeit in lower yields, on the reduction of 4,5-alkylthio-l,3-dithiol-2-thiones [295]. 

The reduction of l,2-dithiole-3-thiones (7) by means of triethylsilane probably involves an addition of the silane to the thiocarbonyl group with subsequent opening of the ring and reaction with one further mole of triethylsilane123 (Eq. 4). 

Electrochemical reduction of 1,2-dithiole-3-thiones on a platinium electrode gives rise to the same products (see Section III,H). 

Polarographic studies of the reduction of the parent l,2-dithiole-3-thione (27) show two waves.169 The first one corresponds to a two-electron reduction of the thiocarbonyl group to a thiol followed by an oxidation to disulfide 121. The second wave is a catalytic hydrogen wave. The reduction could not be carried out on a preparative scale owing to reactions with the mercury electrode. 

The preparative reduction, polarography, and cyclic voltammetry of 5-methyl-l,2-dithiole-3-thione have been studied.171 The results obtained are in agreement with a one-electron reduction of the thiocarbonyl group to a radical-anion, which could not be detected by ESR spectroscopy as it dimerizes too fast. The dimer is further reduced by a one-electron reduction to an anion in which the ring has been opened. (Scheme 12). The dianion could be isolated after methylation and was found to be identical with the compounds isolated by Maignan and Vialle by reduction with sodium sulfide.124 The dianion corresponds to the thioketonate dianion obtained by electrochemical reduction of 1,2-dithiolylium salts.172... 

Reduction of carbon disulfide also provides a starting point for the synthesis of these compounds. For small scale preparation the electrochemical reduction of CS2 in DMF on a platinum or mercury electrode offers a way for the preparation of 4,5-dithio-l,3-dithiole-2-thione dianion (248) (together with significant amounts of potassium trithiocarbonate (249)), which upon alkylation gives access to 4,5-bis(alkylsulfanyl)-1,3-dithiole-2-thiones (252) (Scheme 51) <74J A945,74JOC511,81JOC775). How-... 

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