3//-l,2-Dithiole-3-thiones

Carbon disulfide can act as an electrophilic agent with enamines at room temperature. Therefore, treatment of an enamine with both elemental sulfur and carbon disulfide in a polar solvent can result in the formation of a 3H-l,2-dithiole-3-thione (such as 108) and/or a 2H-l,3-dithiole-2-thione (such as 109) (135,139,140). These products are the result of competing... 

From the reactions of sulfur and carbon disulfide with cyclic ketone-derived enamines (570-573) 3H-l,2-dithiole-3-thiones were obtained, whereas the addition of carbon disulfide to other enamines gave a-dithio-pyrones (574), through initial dimerization of the enamine. 

Of greater importance is the reaction of unsaturated compounds with sulfur at 200-250°C, which normally leads to l,2-dithiole-3-thiones (trithiones) but especially with 2-aryIsubstituted 2-butenes and 1- aryl- or 2-aryl-1-butenes, thiophenes are obtained in 15-60% Thus p-methoxy-a-ethylstilbene (50) gives 2-phenyl-3-... 

Amides such as DMF or ureas such as N,N-tetramethylurea react with bis(trimethylsilyl)selenide 604 in the presence of BF3-OEt2 to give selenoamides, for example 617, or selenoureas whereas esters such as n-butyl benzoate react with 604 in the presence of Bp3-Et20 and 2,3-dimethylbutadiene to give 619 via 618 [157]. On heating with P4Sio/sulfur and hexamethyldisiloxane 7 y9-ketoesters such as ethyl acetoacetate are converted to 3H-l,2-dithiole-3-thiones such as 620 in high yields [158] (Scheme 5.51 cf. also Section 8.6). 

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... 

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). 

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... 

Two other N-substituted diisopropylamines (R = CH2CH2C1 and CH2CH2Phth) in the same reaction gave dithiolothiazine 95 which had apparently resulted from the HCl or phthalimide extrusion from 5-mercapto-l,2-dithiole-3-thiones 94 (Scheme 46). 

Structurally similar 5-chloro-l,2-dithiole-3-thiones 97 were obtained upon treatment of N-(2-phthalimidoethyl)-N-alkylisopropylamines with sulfur monochloride and DABCO and a final reaction with tiiethylamine (20030L929). The stability of thiones 97 is explained by the dipole-dipole interaction between the electron-rich l,2-dithiole-3-thione ring and electron-poor phthalimido groups (Scheme 48). 

Bottcher and Liittringhaus thermally decomposed 5-p-methoxy-phenyl-l,2-dithiole-3-thione (165) to obtain a small yield of a compound CioHigOjSj assumed to be 166 [Eq. (46)]. 

Several workers have studied the reactions of l,2-dithiole-3-thiones and related systems with acetylenic esters. The thiones (395), for example, react with DMAD to give 2-thioacylmethylene-l,3-dithioles (396), which may arise through a concerted 1,3-dipolar addition to the S—C=S moiety. These adducts undergo further reaction with DMAD, yielding thiopyran-4-spiro-2 -(l,3-dithioles) (397) (Scheme 62). Similarly, the reaction of 5-phenyl-l,2,4-dithiazole-3-thione (398) with... 

Some years later, the first stable thiocarbonyl ylides 9 and 10 were prepared by the reaction of thiourea with cyano-substituted oxiranes (19,20) or by addition of Rh-di(tosyl)carbenoid to benzo-l,2-dithiole-3-thione (21), respectively. Enhanced stability and the low reactivity of 9 and 10, which enables their isolation in crystalline form, results from the push-pull substitution at the two termini [cf. also (22)]. Another class of stable thiocarbonyl ylides that are also able to afford [3 + 2]-cycloaddition products are the mesoionic 1,3-dithiole-4-ones of type 11 (23,24). 

On the other hand, hydroquinone (3 pmol/L) prevented the staurosporine-induced apoptosis of HL-60 and the IL-3-dependent murine myeloblastic (32D) cell line it also prevented apoptosis of the 32D cells observed in the absence of IL-3. The myeloperoxidase inhibitor indomethacin opposed the effect of hydroquinone on staurosporine-induced apoptosis of HL-60 cells (Hazel et al., 1995, 1996b). Pretreatment of human leukaemia cells ML-1 with buthionine sulfoximine (100 pmol/L for 24 h), in order to decrease their glutathione content, increased the susceptibility of these cells to hydroquinone-induced inhibition of differentiation caused by phorbol acetate pretreatment with l,2-dithiole-3-thione, which induces reduced glutathione synthesis, prevented the differentiation inhibition of hydroquinone. Treatment of DBA/2 mice with 1,2-dithiole-3-thione, which increased the activity of quinone reductase of bone-marrow stromal cells by 50%, decreased the susceptibility of these cells towards hydroquinone (Trush et al., 1996). 

Thermal decomposition of ethyl azidoformate in the presence of 4-phenyl-l,2-dithiole-3-thione leads to 1,2,3-dithiazine (400 Scheme 51) (76CJC3879). 

Thermal decomposition of ethyl azidoformate in the presence of 4-phenyl-l,2-dithiole-3-thione leads to the rare 1,2,3-dithiazine system (254) (76CJC3879). The reaction presumably involves initial attack of the nitrene at S-l, followed by a [1,2] rearrangement of the resulting ylide (Scheme 34). 

Blazy et a/.112,113 showed that addition of triethylsilane to 4- or 5-substituted l,2-dithiole-3-thiones (167) gave compounds 168, methanolysis or pyrolysis of which produced small quantities of substituted thienothiophenes (2) [Eq. (47)]. 

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. 

These spectra were routinely obtained for most of the compounds discussed in forthcoming sections. Specific studies were performed on selected compounds such as (i) (+)-(S )-4,5,6,7-tetrahydroimidazo-9-chloro-5-methyl-6-(3-methyl-but-2-enyl)imidazo [4,5,1 -jk [1,4] benzodiazepin-2(l//)-thione (9-chloro-TIBO)187 and (ii) series of metal chelates derived from l,2-dithiol-3-thion-4,5-dithiolate (dmt)188. The equilibria between 2-ethoxycarbonylthiolane-3-thiones and their (Z)-enethiol tautomers were also studied by these techniques189. It was found that the equilibrium is largely shifted in favor of the enethiols. NMR was also used to study the syn-anti conformational equilibria of seven A-(l-methoxycarbonylethyl)-A4-thiazoline-2-thiones with S conformation of the chiral rotor (43)190. A variety of substituents were used. 

Finally, we turn to sulfur-containing species. Many indane derivatives may be suggested. However, there are only a few for which the enthalpy of formation has been determined phenylene trithiocarbonate (benzo-l,3-dithiole-2-thione) (X = Z = S, Y = CS) (XI), the isomeric benzo-l,2-dithiole-3-thione (X = Y = S, Z = CS) (X) [50],... 

Benzo-l,2-dithiole-3-thione+2C2H6 — oC6H4(CH3)2 + CH3C(S)SSCH3 (21)... 

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). 

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