1.3- Dithiole-2-thiones, oxidation

Dithiole-2-thione (176) reacts with (V,A/-dichIorosulfonamides to give the 1,3-dithiol-2-ylidenesulfonamides (177) and (178) as well as the 1,3-dithiole-2-thione oxide (179). It has been established that the primary step in these reactions is nucleophilic attack of the exocyclic sulfur of the l,3-dithiole-2-thione on the chlorine of the amide to produce an ion pair which can react in three ways to furnish the l,3-dithiol-2-ylidenesulfonamides (79LA689). 

Few isothiazoles undergo simple cycloaddition reactions. 4-Nitroisothiazoles add to alkynes (see Section 4.17.7.4). With 5-thiones (84) and dimethyl acetylenedicarboxylate, addition to both sulfur atoms leads to 1,3-dithioles (85) (77SST(4)339, 80H(14)785, 81H(16)156, 81H(16)595). Isothiazol-3-one 1-oxide and the corresponding 1,1-dioxide give normal adducts with cyclopentadiene and anthracene (80MI41700), and saccharin forms simple 1 1 or 1 2 adducts with dimethyl acetylenedicarboxylate (72IJC(B)881). 

Square planar Ni11 complexes (50a) and (50b) of the quinoxaline-2,3-dithiolate ligand are oxidizable in chemically reversible, electrochemically quasi-reversible processes to yield Ni111 species, also featuring the (dxy)1 configuration.198 Interestingly, the difference in protonation state makes for a 0.20V difference in oxidation potential ((50a) +0.12V (50b) +0.32V vs. SCE), consistent with the less basic S-donors in the thione form. 

Examples of reactions involving replacement and cyclization are the long-known preparation of thiophenes (89) from 1,4-diketones, and the formation of l,2-dithiole-3-thione (90) from the salicylate ester analog (91).120 In the latter instance, oxidative cyclization with formation of an S—S bond has occurred this is a common feature of these reactions, particularly if such a link is needed to complete a five-membered ring. Another example of this aspect is afforded by the reaction of the propane-1,3-dione derivatives (92) which yield 3,5-diaryl-1,2-dithiolylium salts (93) when heated with phosphorus pentasulfide in carbon disulfide, followed by perchloric acid.121... 

The synthesis, X-ray structure and solid state NMR of 4,4-dimethyl-l,2-ditellurolane 75 have been reported <98PS(136-8)291>. Chemoselective oxidation of 1,2-dithiole derivatives using dimethyldioxirane to give products such as 76 has been described <00SUL169>. Cycloaddition of dihydroquinoline-fused l,2-dithiole-3-thiones 77 with DMAD gives the spiro 1,3-dithioles 78 <99CHE587>. Dicationic thiatelluroles such as 79 have been prepared <00AG(E)1318>, anti cancer properties have been claimed for the simple dithiolopyrrolones... 

Dithiodimorpholine, 23 642 l,3-Dithiole-2-thiones, thiocrowned and oxothiocrowned, 23 707 Dithiols, one-pot oxidation polymerization of, 23 713... 

The anodic oxidation of l,2-dithiole-3-thiones (R R = H, Ph, respectively) was reported [9,10] to yield disulfide-linked bis(dithiole-3-thione) dication (Scheme 3). 

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... 

LB films prepared from tridecylmethyl-ammonium Au-(dmit)2 and H2dmit = 4,5-dimercapto-l,3-dithiol-2-thione, transferred to hydrophobized glass substrates, and oxidized (by Br2 or electrochemicaily) Absorption spectra and temperature-dependent conductivity measurements... 

Oxo dithioic acids react with a combination of (Me3Si)2S and A-chlorosuccinimide in the presence of imidazole to give oxidative ring closure to the 3//-l,2-dithiole-3-thiones (equation 21)39. 

A better synthesis of a-(l,2-dithiol-3-ylidene)ketones from thio-pyran-4-thiones consists in the reaction with sodium hydroxide in dimethylformamide (DMF), followed by ferricyanide oxidation (Eq. 3).11... 

Aryl-l,2,4-dithiazole-3-thiones react with phenylacetylene giving two compounds, namely, A-(4-aryl-l,3-dithiol-2-ylidene) thiobenz-amide (52) and 2,5-diaryl- 1,6,6a IV-trithia-3-azapentalene, which may also be considered as AT-(5-aryl-l -dithiohS-ylideneJthiobenz-amide (53). This compound is converted into the corresponding benzamide (54) by mercuric acetate oxidation, the opposite reaction being realized with phosphorus pentasulfide.79... 

Pyran-4-thiones (147a) and 4//-thiopyran-4-thiones (147b) react with sodium hydrosulfide or sodium hydroxide respectively to give acyclic products which on oxidation form 3-acylmethylene-l,2-dithioles (11) (Scheme 26) (70JCS(C)2412). 

S c s c c Bis-1,3-dithiol-2-yl f 4,5-dioxo-2-thioxo-l,3-dithiolane f l,3-dithiolane-2-thione 5-oxide f tetrathiafulvalenes (TTl, s)ax... 

Thione groups can often be eliminated by oxidation probably the sulfinic acid is the intermediate. Sometimes the sulfinic acid can be isolated (e.g., 740 741), but more often it spontaneously loses SO2. In this way, thiazoline-2-thiones give thiazoles, l,2-dithiole-3-thiones 742 are converted into 1,2-dithiolylium salts 743, l,3-dithiole-2-thiones 744 into 1,3-dithiolylium salts 745, 1,5-disubstituted imidazole-2-thiones into imidazoles <2003JHC229>, and 3-mercapto-l,2,4-triazoles into the parent triazole <2006S156>. In the pyrazole series, 746 also loses an A-methyl group to yield 747. 

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). ... 

Coupling can also occur via a substituent, as for 1,2-dithiol-3-thiones, which are anodically oxidized to bis(dithiolyium)disulfides [48]. The related a-(l, 2 -dithioT3 -ylidene)acetophenones 16 are analogously oxidized to a di-cation (17) that de-protonates to give the uncharged dimer 18. When, however, the electrolysis was conducted in the presence of an oxidant such as DDQ, or by further oxidizing dimer 18, a new di-cation (19) was formed (Scheme 14) [49]. 

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