Dithiolium salts synthesis

Dithiols, 1,3-dithiolium salts, synthesis and reactivity of 82MI31. 

Tlie interest in the preparation and use of dithiolium salts in connection with the synthesis of TTF derivatives led to the development of a new uses of heteroaromatic cations in organic synthesis. Based on that, a new carbonyl olefination for the synthesis of numerous heterofulvalenes was developed (77S861). For example, 2-dimethoxyphosphinyl-l,3-benzodithiole was deprotonated with butyllithium in THF at -78°C and the resulting phosphonate carbanion reacted with 9-alkyl-acridones to give the dithia-azafulvalenes of type 45 (78BCJ2674) (Scheme 15). 

Another reaction that can be formally grouped with those discussed above is the sulfurization of dithiolium salts with sulfur in pyridine,7 9d 8 9 in which the sulfur also acts as the oxidizing agent. This reaction enjoys a certain importance as a trithione synthesis. Nitro-substituted trithiones such as 94 cannot be obtained by the usual methods, since the nitro groups are reduced under the drastic reaction conditions required. These nitro derivatives can, however, be readily obtained by the method outlined in Scheme 4. 

Judging from these early results, it appears that the reaction of 1,2-dithiolium salts with ammonia offers an elegant synthesis of certain substituted isothiazoles that are difficult to obtain by other methods.98 The reaction of the unsubstituted 1,2-dithiolium salt with NH8, however, does not yield the parent isothiazole system. Moreover, in the case of the 3(5)-methyl salts, the abstraction of a methyl proton activated by the positive charge of the ring successfully competes with this reaction (Section II,B,4).14a... 

This pyrazole synthesis, which undoubtedly profits from the thermodynamic stability of the end products, gives excellent yields (Table VI). Its range of application is limited, however, by the fact that the reaction of 3-substituted unsymmetrical dithiolium salts with substituted hydrazones leads to mixtures of isomers which can be separated only with difficulty. On the other hand, it does permit the preparation of a single 4,5-disubstituted pyrazole from a 3,4-disub-stituted salt and a substituted hydrazine. 

The repetition of the whole transformation, occurring on the remaining isopropyl group in the dithiolium salt 218, affords the bis-dithiolium salt 220, which cyclizes by further reaction with S2CI2 to 3,5-dichloro-bis-dithiolium salt 221 as the key intermediate for the synthesis of bis[l,2]dithiolo[l,4]thiazines 14 and bis[l,2]dithiolopyrroles 124 or 15. 

The final stage of the synthesis of thiophene-functionalized fluorenes 121 involved the condensation of lithio derivatives of compounds 120 with the 1,3-dithiolium salt 119, prepared almost quantitatively from 118 by A-methylation (Scheme 9) <1999J(P2)505>. 

Methylthio-l,2-dithiolium salts are useful intermediates for synthesis and are generally obtained by reaction of methyl iodide or of dimethyl... 

The discovery of the unusually high solid-state electrical conductivity of the charge-transfer complex of TTF with TCNQ has prompted extensive investigations of 1,3-dithiolium salts, an important class of intermediates for the synthesis of tetrathiafulvalene derivatives. 

Dithiolium salts react with the phosphoranes 178. When excess triethylamine is added in the reaction mixture, a TTF derivative is obtained. In a first step, 178 undergoes nucleophilic addition to the 1,3-dithiolium cation. Then triethylamine brings about elimination of triphenylphosphine and formation of TTF (Scheme 31). This synthesis allows the preparation of... 

The treatment of 1,2-dithiolium salts 43 with methylamine gave 3-methyl-aminothiopropenones 44, which were oxidized by iodine to form the TV-methyl-isothiazolium salts 27a,45a, isolated as their perchlorates (73CJC3081). The yields of products were rather poor but the reaction is a very quick synthesis of TV-methyl-isothiazolium salts 27a,45a from the 1,2-dithiolium salts 43 (Scheme 12). 

Martin and Stewart" first described the preparation of the deep-violet complex [Co(SacSac)j] (363 R = Me) from the reaction of C0CI2 with acetylacetone (acacH) and HjS. A similar synthesis d where CFjacac is substituted for acac yields [Co(CFjSacSac)2] (363 R = CFj). The preparation of [Co(PhSacSac)2] via BHi" reduction of the dithiolium salt (3 ) in the presence of C0CI2 has also been reported. ... 

For isomeric thienothiophenes, both general methods of synthesis and original procedures applicable only to the preparation of particular types of compounds have been developed. In recent years, along with conventional methods based on thiophene derivatives as substrates, other approaches using, in particular, cyclopropenethiones, dithiynes and dithiolium salts have been successfully designed. A special section in this review deals with high-temperature synthesis of annulated thienothiophenes and procedures used for the preparation of particular representatives of this class of heterocycles. 

HC104 added dropwise to an ethanolic suspension of 2-piperidino-4-phenyl-1,3-dithiole 4-phenyM,3-dithiolium perchlorate. Y 94%. - This is the last stage of a convenient 4-step synthesis of 1,3-dithiolium salts via phenacyl dithio-carbamates. F. e. s. A. Takamizawa and K. Hirai, Chem. Pharm. Bull. 17, 1924 (1969) reactions of the products with nucleophiles cf. ibid. 17, 1931. 

The well-known synthesis of enamino-thioketones (21) using the reaction of 1,2-dithiolium salts with primary or secondary amines has been the subject of renewed investigation. " Duguay and Quiniou observed that the action of p-methylaniline on unsymmetrical 3,5-diaryI-l,2-dithiolium... 

Further recent papers concerning metal complexes of thio-analogues of j3-diketones deal with the preparation of the cobalt(n) complex of 1,3-diacetylthioacetone, the synthesis and properties of a series of metal complexes of dithioacetylacetone, the synthesis of the nickel(n) complexes of monothio- and dithio-dibenzoylmethane (67) by the nucleophilic cleavage of 1,2-dithiolium salts by hydroxide or mercaptide ions in the presence of nickel(ii) ions, the bromination of the cobalt(m) complex of monothioacetylacetone (68) with iV-bromosuccinimide to yield (69), and the application of monothiodibenzoylmethane as an analytical reagent for quantitative determination of copper. ... 

The synthesis of 1,2-dithiolium salts from /3-diketones has been modified by the use of diacetyl disulphide in place of hydrogen disulphide. Precursors of the general type (30), where Y = O, S, (OEt)a, or N+MCg, and Z = OH, Cl, or OEt, are treated with the diacyl disulphide and a strong acid. This versatile synthesis has been applied to the preparation of a wide range of alkyl- and aryl-substituted dithiolium salts. 

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