1,2-Dithiones, synthesis

See also Magnesium-rare earth nitrates, S3mthesis 15 Calcium dithionate, synthesis 50A... 

Barium dithionate, synthesis SOB Europium amalgam, synthesis 18... 

Ferfra S, Ahabchane NH, Mustaphi NEH, Essassi EM, Bellan J, Pierrot M (2001) Synthese de nouveaux macrocycles derives de la quinoxaline-2,3-dithione synthesis of new macrocycles from quinoxaline-2,3-dithione derivative. Phosphorus, Sulfur Silicon Relat Elem 175(1) 169-181. doi 10.1080/10426500108040265... 

Although the synthesis of thiazolidine-2,4-dithione has been reported (357), no examples of a A-2-thiazoline-4-thione bearing a nonprotomeric group at C-2 are known. Some fused compounds are reported in Table 41. 

Imidazole-4,5-dicarboxylic acids, coupling, 5, 403 decarboxylation, 5, 434 1-substituted synthesis, 5, 468 synthesis, 5, 362, 402, 484 Imidazole-4,5-dione, l-alkyl-2-phenyl-synthesis, 5, 129, 479 Imidazole-2,4-diones tautomerism, 5, 370 Imidazole-4,5-diones tautomerism, 5, 370 Imidazole-2,4-dithione, 5,5-diphenyl-tautomerism, 5, 370 Imidazole-2,4-dithiones tautomerism, 5, 370 Imidazolepropanol synthesis, 5, 486 Imidazoles accelerators epoxy resins, 1, 407... 

Indolo[2,3-d][l,3]thiazine-2,4-dithione formation, 4, 299 Indolothiazines synthesis, 4, 519 Indoloyl azides Curtius rearrangement, 4, 288 Indolyl anions acylation, 4, 232 alkylation, 4, 235 Michael-type additions, 4, 236 Indomethacin... 

Lumazine-6,7-dithione, 1,3-dimethyl-synthesis, 3, 292 Lumazines acylation, 3, 290... 

Thiazolidine-2,4-dione, 2-dialkylamino-bisimide synthesis, 5, 129 Thiazolidine-2,4-diones IR spectroscopy, 6, 242 tautomerism, 6, 270 Thiazolidine-2,5-diones synthesis, 5, 138 Thiazolidine-4,5-diones synthesis, 5, 129 6, 316-317 Thiazolidine-2,4-dithiones tautomerism, 6, 270 Thiazolidines "C NMR, 6, 243 conformation, 6, 242, 247 dihydrothiazines from, 2, 93 hydrolysis, 6, 273 IR spectra, 6, 242 ring fission, 5, 80 synthesis, 5, 118 6, 316-321 Thiazolidines, imino-tautomerism, 6, 273 Thiazolidines, methyl-conformation, 6, 242 Thiazolidine-2-thione, 3-acyl-reduction, 1, 469 Thiazolidine-2-thione, 4-alkyl-synthesis, 6, 318... 

The mechanism for the redistribution in oxidation states begins similarly to that of the Paal thiophene synthesis. However, upon formation of dithione 38, nucleophilic addition of one thiocarbonyl into the other produces the intermediate zwitterion 39. A 1,3-tautomerization of hydrogen then gives... 

Numerous examples of the synthesis of tricyclic systems based on indolizine derivative 232 have been reported <2000M959>. The product obtained from the reaction of 232 with carbon disulfide depends on the reaction medium. Thus, in aqueous potassium hydroxide the pyrimidine-dithione 233 is formed, whereas in pyridine the iminothiazine-thione 234 is obtained. In aqueous potassium hydroxide, compound 234 rearranges to 233 (Scheme 12) <2000M959>. 

The synthesis of chloromethylthio heterocycles, e.g., 127 had been described by Goralski and Burk193 in the reaction of benzothiazole-2-thiones, 2-pyridinethiones, and 2-quinolinethiones with chlorobromomethane. In the case of l,3,4-thiadiazole-2,5-dithione, the reaction was made with the preformed alkali metal salt. 

Freund and Wolf10 reported that 2,4-diphenyl-l,2,4-thiadiazolidine-3,5-dithione was formed by heating l,3-diphenyl-2-thiourea with thiophosgene in benzene whereas, a 1,3-thiazetidine was produced at lower temperatures in ether (see Section II). Ohande181 has reported that 3,5-diamino-l,2,4-thiadiazoles are formed by the reaction of thiopseudoureas with carbon disulfide in the presence of bromine. Use has also been made of thioureas in the synthesis of 1,3,4-thiadiazolines (79) via reaction with the halohydrazones 78.185,186 The analogous reaction with solenoureas was recently reported by Bulka and Ehlers187 to yield 1,3,4-selenadiazolines. 

Mesomeric 1,3,5-triazine-dione, -one-thione and -dithione betaines may be synthesized from N,N -disubstituted acetamidines (Scheme 73) (75JHC187). Huffman and Schaefer have reported the synthesis of the triazine 1-oxide (137) in 45% yield from methyl N-cyanoacetimidate and benzamidoxime (equation 70) (63JOC1816). 

Several 1,2-dithiones can be obtained from 1,2-diones by direct sulfurization with P4S[0 or B2S3. The usually heterogeneous reaction can be accelerated by the use of ultrasound.24 Although most dithiones are prone to hydrolysis and decomposition (some cannot be prepared at all under the above conditions), they are most useful intermediates in the synthesis of more complex dithiolenes. 

For example, the julolidine-substituted dithiolene (9) can be obtained18 in low yield by standard procedures the synthesis of the red, crystalline dithione and its conversion to (9) under reducing conditions proceeds in high yield.24 Dithiones are only stable if they are substituted by strongly electron-donating or -withdrawing substituents, and their use is limited to these cases. 

There are two main methods for the synthesis of monothio-/i-diketones, both affording yields in excess of 50%. The first method involves the passage of H,S through a dilute solution of the /5-diketone in ethanol, followed by the rapid passage of HC1 at — 70 °C the conditions are critical.184,183 The second method involves the Claisen-type condensation of ketones with thionic esters, RC(S)OMe, or dithionic esters, RC(S)SMe, in ether in the presence of sodamide.186-188 This method has the advantage that both isomers (46) and (47) can be prepared, whereas the first method yields only isomer (46) when R has a greater electron-withdrawing power than R. 

Thia-3a,6-diaza-2-silapentalene, 2,2-dimethyl-synthesis, 6, 1012 1,3,6-Thiadiazepane-2,7-dithione structure, 6, 904 Thiadiazepines synthesis, 7, 643-646... 

II. SYNTHESIS FROM PREFORMED ALKENEDITHIOLATES, 1,2-DITHIONES, AND THEIR EQUIVALENT... 

Another interesting case of sulfur functionalised NHC complexes comes from Matsumura et fl/. s synthesis of 2,3-disubstituted 6,7-dihydro-5//-2a-thia(2a-S")-2,3,4a,7fl-tetraazacy-clopent[cd]indene-l,4(2H,3//)-dithiones [276,277] (seeFigure4.92). Analogous... 

Increasing the reaction time lead to the formation of the dithione in only very low yield (5 %). Also, the synthesis of 40 has been reported to have been accomplished using the same procedure starting from phthaloyl chloride and 2,5-dimethyl thiophene. Conversion of this to the mono- and di-thiones has been reported to be unsuccessful. 

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