Dithiole Derivatives

Experimental details have been published for addition reactions between acetylenes (21 R, R = COgMe, COgEt, or H) and l,2-dithiole-3-thiones (20), and for the conversion of the resulting isothiathiophthens (22) into thiathio-phthens with thioacetamide or thiobenzamide. The similar reaction between l,2-dithiole-3-thiones and benzyne, variously generated, has been described.  

Davy and J. Vialle, Bull. Soc. chim. France, 1975, 1435 H. Davy and J.-M. Decrouen, ibid., 1976, 115. 

The product obtained by the action of thioacetic acid on phenylacetylene has now been shown to be (22 R = Ph, = H, R = Me, R = H), which can be synthesized from 5-methyI-l,2-dithiole-3-thione and phenylacetylene.  

A new route to isothiathiophthens has been reported, involving the reaction of 2-methylthio-l,3-dithiolium salts with enamines, and treatment of the intermediate products (23) with hydrogen sulphide. More complex examples, e.g. (24), have also been prepared. 

A study of the mass spectra of isothiathiophthens shows that these compounds behave quite differently from the thiathiophthens, which characteristically lose hydrogen and substituent groups. The iso-compounds generally fragment by loss of the appropriate acetylene residue.  

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Use of the /3-thiodithiocarbonates (25) and acid results in ring closure to the 1,3-dithiol-2-one (26). Methyl, ethyl and isopropyl groups have been utilized in (25) (76S489), and when R = f-butyl, ring closure occurred in the presence of perchloric acid with extreme ease (74JOC95). Other variations of this synthetic route to 1,3-dithiole derivatives are described in Chapter 4.32. 

Phenyl-l,2,3-thiadiazole (513) as well as the 5-phenyl isomer (514) both lose N2 on photolysis. The 1,3-dithiole derivative shown was formed from both thiadiazoles (58LA(614)4). 

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxides has been examined by Still and coworkers192-194. These authors also report that rearrangement to cyclic sulfenates, with subsequent reaction by homolysis of the S—O bond, appears to be a particularly favorable process. For example, ultraviolet irradiation of a solution of 8-methylthiochroman-4-one 1-oxide (133) in benzene for 24h afforded a single crystalline product which was assigned the disulfide structure 134 (equation 54). More recently, Kobayashi and Mutai195 have also suggested a sulfoxide-sulfenate rearrangement for the photochemical conversion of 2,5-diphenyl-l,4-dithiin 1-oxide (135) to the 1,3-dithiole derivatives 136 and 137 (equation 55). 

Figure 56 Two sets of [ ]carboranophanes (92 and 93) derived from the dithiol derivative of m-carborane. (Adapted from ref. 123.)...

A closely related route to a monocyclic dithiole derivative is shown in Scheme 122.186 The easy replacement of cobalt by sulfur in this type of process has analogy in the synthesis of a variety of condensed heterocycles from rhodacyclopentadienes (see Scheme 127 in Section IV,H,1) and cobaltacyclopentadienes (see Scheme 82 in Section IV,C,1). 

Thiolsulfonate-containing compounds can react with thiols with release of the sulfonate end of the molecule to yield disulfide derivatives. The modification reagent 2-aminoethyl-2 -aminoethanethiolsulfonate, or AEAETS, reacts with a sulfhydryl with release taurine (2-aminoethanesulfonate) to form a 2-aminoethyl-dithiol derivative (Figure 1.94). AEAETS can be used to block cysteine residues in proteins and form derivatives containing positively charged amines. 

Figure 2.2 A number of small thiol-containing molecules have proven useful for modification of gold or metallic surfaces. The dithiol derivatives provide better dative bond stability and can t be displaced easily by competing thiols or oxidation. Most thiol-containing compounds used for surface modification also contain terminal functional groups or reactive groups for coupling affinity ligands.

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... 

Tetrathiafulvalenes can be produced by an oxidative electrodimerization of 1,3-dithiole derivatives (Scheme 125) [235]. 

Oakley and co-workers reported the transformation of l,2,5-thiadiazolo[3,4-/ ]pyrazines into tricyclic rings 55 and 57. Titanocene 55 was prepared by reaction of 5,6-dithiol derivative 54 with Cp2TiCl2 under basic conditions (Scheme 37) <1998JA352>, and 6-amino-5-thiol 56 was condensed with sulfur monochloride to give the 1,2,3-dithiazolidine derivative 57 in excellent yield (Scheme 38) <1999JA969>. 

If the addition is carried out in the normal sense, some dimer of the thioketene CHjC(SiMe3)=C=S (a dithiole derivative) is formed. 

Also significant are the alkene dithiolate derivatives such as (73) and (74), prepared according to equations (67) and (68).544,545... 

In [Fe(NO)(S2CNR2)2] the iron is ligated by four sulfur atoms as well as by the nitrosyl ligand similar Fe(NO)S4 chromophores are found (49) in complexes of dithiolenes (7) and dithiols (8). For both dithiolene and dithiol derivatives, reaction of [FeL2]2 (L = 7 or 8) with NO gas yields the nitrosyl derivatives [Fe(NO)L2] (50), in which the nitrosyl ligand has effected a net oxidation. Certain of the mononegative complexes can be oxidized by iodine to neutral Fe(NO)L2 or reduced with borohydride to dinegative [Fe(NO)L2]2 (50). 

There is a long standing interest in the chemistry and the properties of cyclic compounds containing sulfur atom in modern material chemistry due to their redox chemistry. In particular, the focus has been on dithiole derivatives, e.g., dithiafulvenes and tetrathiafulvalenes, since the finding of metallic conductivity and low temperature superconductivity in radical cation salts. The quite low oxidation potentials of 1,4-dithiin compounds have been reported, recently [109]. On the other hand, thioketene dimers (2,4-bis(alkyli-dene)-l,3-dithietane) have been known for more than 100 years and synthesized by various methods [110-115]. The structure of these dimer compounds is similar to that of the redox-active sulfur compounds therefore, the potential electronic property of the thioketene dimer moiety is considerably attractive with the aim of application to a new and better -donor. 

Phosphonium ylides 66 attack 1,2,4-dithiazole derivatives 65 (Y = 0, S) mainly at the S-S bond to give intermediates 67, which can either afford thiazoline derivatives 68 or react further, with a second ylide molecule 66 at the C=Y bond, to finally yield new thiazole and dithiole derivatives 69 and 70. Compounds 70 are predominant in this mixture (yields > 50%). They are oxidized into known dithiole derivatives 71 (Scheme 8) <1993MI33, 1994PS105, 1995PS63, 1999PS393>. 

Benzo[7]thiete 41 reacts in the ortho-qumoiA isomer 41 with cyclic trithiocarbonates such as l,3-dithiolane-2-thione, (ethylene trithiocarbonate), l,3-dithiole-2-thiones, and adamantanethione <1997LA1603>. In boiling toluene, 1,3 dithiolane and dithiole derivatives formed the spiro compound 42 and 43 in good yield. The related l,3-dithiole-2-thiones reacted chemoselectively at the C=S double bond. The use of adamantanethione yielded the polycyclic adduct 44 in a smooth and quantitative reaction (Scheme 3). 

B. Reaction of Dithiole Derivatives with Reactive Methylene... 

C. Reaction of Active Methylene Compounds with Dithiole Derivatives... 

The reactions of some internal perfluoroolefins (perfluorobut-2-ene, perfluoropent-l-ene, and perfluoropent-2-ene) with an S-KF-sulfolane system lead to a five-membered heterocycle-[l,3]-dithiol derivative (82CL201). Thus the reaction with perfluorobut-2-ene gives perfluoro-2-ethyl-2,4,5-tris(trifluoromethyl)-[l,3]dithiol. 

Various 1,2-dithiole derivatives (3) undergo electron transfer under chemical or electrochemical conditions, forming various types of 1,2-dithiolylium cation (80MI43100,80AHC(27)151). These include monocyclic and highly condensed derivatives. 

The preparation of 1,2-dithiole derivatives by oxidation of suitable dithiols is quite general, and may be applied to the preparation of 1,2-dithiolane (1) (69JOC36), benzo-1,2-dithiole (77c) <78JOC3374) and naphtho[l,8-crf][l,2]dithioIe (26) (65JOC3997) from the... 

Many 1,2-dithiole derivatives have been patented or recommended for use as pickling or corrosion inhibitors or as additives to lubricating oils (B-66MI43100). They are efficient in preventing high-temperature fouling of oil feedstock (78USP4116812). 

Some typical 13C NMR spectral data of 1,3-dithiole derivatives are given in Table 5. 

Table 5 13C NMR Spectral Data of some 1,3-Dithiole Derivatives ...

The reaction of trialkyl- and triaryl-phosphines with 1,3-benzodithiolylium salts leads to formation of phosphonium salts which are deprotonated by treatment with n-butyllithium to produce (69). The similar reaction of trialkyl phosphites in the presence of sodium iodide yields dialkyl phosphonates which can be deprotonated to (70). Both (69) and (70) can react further with ketones to give the 2-alkylidene-l,3-dithiole derivatives (71) (80AHC(27)151>. The ylide (72) has also been prepared (80H(l4)27l>. 

Alkoxy compounds of type (163) can serve as generators of carbenes. Thus, treatment of the methoxy derivative (163) with trichloroacetic acid in benzene produces a carbene which in the presence of aromatic aldehydes, forms the dithiole derivatives (75) (80MI43200). 

The dianion (307), easily prepared from phenols and carbon disulfide in the presence of potassium hydroxide in DMSO, can be alkylated with 1,2-dibromoethane to form the 1,3-dithiole derivatives (308) (65LA(684)37). 

A ring transformation takes place in the reaction of 3-mercapto- or 3-acylthio-3-isothiazo-line-5-thiones (331) with reactive alkynic compounds in boiling acetonitrile this reaction produces the 1,3-dithiole derivatives (332) in good yields (80JCS(P1)2693, 80H(14)785). 

Similarly, reaction of 3-chloroacylthio-3-isothiazoline-5-thiones (333) with reactive alkynic compounds proceeds with formation of the 1,3-dithiole derivatives (334) which contain thiazolone or 5,6-dihydro-l,3-thiazin-4-one rings (81H(16)595). 

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