I, 2-Dithiole-3-thione

It has been found that a cycloaddition of compound 305 with DMAD affords exclusively spirane 307, which includes a 1,3-dithiole ring (Scheme 57). The expected [3-1-2] cycloaddition as a first phase giving rise to an intermediate 306, followed by a ring closure, rationalizes the reaction outcome. In comparison to 305, a broad range of I,2-dithiole-3-thiones can be efficiently converted into corresponding 2-(2-thioxoalkylidene)-l,3-dithioles, as exemplified by the reaction of 308 with DMAD. Depending on the reaction conditions and structural properties of the initially formed cycloadduct, such as 309, further transformations ate possible. 

An interesting and reactive class of 4ir thiabutadienes capable of useful participation in normal (HOMOd,ene controlled) Diels-Alder reactions are the stable thioacylketene thioacetals, generated by the photoaddition of olefins to I,2-dithiole-3-thiones [Eq. (10)]. 

Davidson NE, Egner PA, Kensler TW. Transcriptional control of glutathione S-transferase gene expression by the chemoprotective agent 5-(2-pyrazinyl)-4-methyl-i, 2-dithiole-3-thione (oltipraz) in rat liver. Cancer Res 1990 50 2251-2255. 

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. 

Table 8 Comparative yields of 3H-1,2-dithiole-3-thiones 258 from 3-oxoesters 264a and 264f-i using P4S10/HMDO reagent or LR...

It has been indicated <1998CAG1609, 1987CNR4271> that among others the parent l,2-dithiole-3-thione lb, in addition to cyclopentano analogue 386 and 5-/i t/-hutyl-suhstituted l,2-dithiole-3-thione 387, shows promising chemoprotective activity. 

Ethoxy-1,2-dithiolium ions react in a similar way with aqueous sodium sulfide to give the corresponding 1,2-dithiole-3-thione. 5-Phenyl-3-chloro-i,2-dithiolium chloride reacts with A -phenylselenourea to give 5-phenyl-l,2-dithiole-3-selone (34). ... 

Aryl-3-methylthio-l,2-dithiolium ions react with secondary aliphatic amines. As shown in Table I, the following compounds may be obtained in various yields 5-aryl-l,2-dithiole-3-thione (56), by sulfur demethylation methyl 3-aryl-3-(dialkylamino)dithioacrylate (57) and A, A-dialkyl-5-aryl-1,2-dithiol-3-iminium ion (58). 

CNDO/2 calculations involving various parametrization methods and performed either with only s- and p-orbitals of sulfur, or including d-orbitals, have been applied to the 3-mercapto-I,2-dithiolium cation and the modification of electronic spectra on l,2-dithiole-3-thione protonation has been given theoretical interpretation. ... 

The sulfuration of /i-ketoesters with phosphorus pentasulfide alone or in a mixture with elemental sulfur is a general method for the synthesis of l,2-dithiole-3-thiones.4 Functional groups are introduced by means of fi-ketoesters substituted with such groups. In this way l,2-dithiole-3-thiones substituted with chloro, cyano, and ester groups in the 4-position5 5 and ester groups in the 5-position have been prepared56 (Scheme 1). 

The stability constants of Ag(I) complexes with a series of l,2-dithiole-3-thiones have been measured in order to obtain quantitative data concerning the complexing ability of the thiones.96 In most cases kinetic measurements involving rates of methylation provide a better method.97 l,2-Dithiole-3-thiones have been used as analytical reagents for metals without further studies of the structure of the complexes formed (cf. Section V). 

In connection with other 1,2-dithiole derivatives the ESCA spectra of l,2-dithiole-3-thiones and 5-phenyl-l,2-dithiol-3-onehave been discussed.275 In the thiones it was found that thiocarbonyl sulfur had an average binding energy near that of dithiocarboxylate sulfur. This means that a positive charge is present in the ring, i.e., mesoionic forms such as 179 must contribute considerably to the structure. The same is true for the l,2-dithiol-3-one. 

Transformations I.4.I.2.I. By Ring Contraction Formation of l,2-Dithiole-3-thiones... 

Kensler TW, Groopman JD, Roebuck BD, Curphey TJ. Chemoprotection by 1, 2-dithiole-3-thiones. In Fluang MT, Osawa T, Flo CT, Rosen RT, Eds. Food Phytochemicals for Cancer Prevention I Fruits and Vegetables. Washington, DC American Chemical Society, 1994 154-163. 

With the help of TLC on silica gel G, Mayer et al. [54] have investigated many heterocyclic sulphur compounds of the trithione (I) (1,2-dithiol-3-thiones) and dithione (II) (l,2-dithiol-3-ones) types, their anils (III), the l,2-thiazoline-5-thiones (IV) and xanthane hydride (V). Petrol ether-benzene (50 + 50) or carbon disulphide are good solvents. 

Acylthio-l,2-dithiole-3-thiones (48) show normal carbonyl-stretching frequencies in the i.r., indicating that there is no significant interaction between the carbonyl oxygen atom and the adjacent S—S bond. ... 

Potential 2-hydroxy- and 2-mercapto-l,3,4-thiadiazoles have been examined both by infrared and by ultraviolet spectra in the solid state and in solution by Sheinker et They concluded that these compounds exist in the 2-oxo and 2-thione forms, respectively. To 2,5-dimercapto-l,3,4-thiadiazole the 2-mercapto-5-thione structure (155) was given. The structure of this compound has been the subject of some controversy. Stanovnik and TiSler have added some valuable arguments to the discussion. They measured the pKfl values of 155, its iV-methyl, iV -phenyl, and iV -phenyl-/S-methyl derivatives (156), and of the conjugate acids of these and the S-methyl derivative (pKn ) (Table III). In all compounds 156 with R = H, the infrared spectrum showed an absorption band near 2300 cm characteristic of the SH group. They also had pK i values near —1.5, Avhich in connection with the infrared evidence was taken as characteristic of an SH group in this situation. Since the 2,5-dithiol structure is excluded by ultraviolet spectral evidence, the 2-mercapto-5-thione structure (155) seems rather well established. It has previously been shown bj Thorn to predominate in chloroform solution, whereas he concluded that the dithione form (157) should predominate in ethanol solution. However, the pK i value for 155, — 1.36, makes it rather probable that Thorn used the monoanion of 155 instead of the acid itself for spectral comparison, and in that case his conclusions have a very weak foundation. 

The structure of [Mo3S4(dmit)3] (dmit=l,3-dithiole-2-thione-4,5-dithiolate) represents one of the rare examples of M3S4 clusters where each metal atom appears as pentacoordinate instead of its more common type-I structure octahedral environment [39]. Complexes [M3Q4(dmit)3] (M = Mo, W Q = S, Se) degrade in air with an almost quantitative yield and afford a series of M(V) dimers of formula [M202(//-Q)2(dmit)2] where the oxygen atoms are in a syn configuration. 

For some strong electron donor molecules the polarization of the X2 molecule may be sufficient that the X atom not complexed to B serves as an electron donor to a second X2 molecule, i.e., the dihalogen is amphoteric , acting as a Lewis acid to Lewis base B, and as a Lewis base to the second X2 molecule, acting as a Lewis acid. For a 1 1 B X2 X2 ratio, an extended adduct (Fig. 1, mode AA) is formed, as illustrated in Fig. 2c for 4,5-bis(bromomethyl)-l,3-dithiole-2-thione-diiodine diiodine (HAMCAA) [58]. This is often referred to as an extended spoke structure. If the second X2 acts as Lewis acid acceptor at either end of the molecule, then a bridged amphoteric adduct (Fig. 1, mode BA) is formed, as illustrated for (acridine I2)2 I2 (QARGIZ) [31] in Fig. 2d. 

A polymeric structure is also observed in the adduct LE 2I2 (LE = 4,5-6z s(bromomethyl)l,3-dithiole-2-thione). LE-I2- I2 bent-shaped units, which are typical in discrete extended spoke adducts with 1 2 (LE/I2) stoichiometry, are joined head-to-tail by soft-soft I- -I interactions involving the terminal iodide atom of the LE-I2 moiety and the terminal iodide atom of the second coordinated di-iodine molecule.37... 

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