Dithiols from disulfides

Dithiolate- or disulfide-bridged analogues of 29 oxidize reversibly to mono- and dications. The Mo—Mo distance (259.9 pm) in [Mo2(/a-SC3H6S)2Cp2] is very similar to that of [29], (R = Me) preliminary magnetic data on the dications, isolated from the reaction of the neutral species with ceric ion, suggest the presence of two unpaired electrons (67). 

Zinc/hydrochloric acid and sodium boron hydride Dithiols from cyclic disulfides s. 56... 

Recently, it has been reported that l,3-dithiole-2-thione (12) reacts with primary amine to give the corresponding thiourea and A-4-thia2oline-2-thione (Scheme 5) (14). 5-Methylenethiazolidine-2-thione (13) obtained from the reaction of propargyl amine and carbon disulfide... 

Sodium or potassium hydrogen sulfite reacts with several thiiranes to give disulfides of /3-mercaptosulfonic acid salts (76EGP122086). Potassium thiocyanate in dimethylformamide or aqueous ethanol isomerizes thiiranes (Scheme 84) (72CJC3930). 1,2-Dithiols are obtained by treatment of thiiranes with NaBH2S3 obtained from sodium borohydride and sulfur (73TL1401). 

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. 

Sulfur has also been added to the condensation product of enamines with cyanoacetic ester (575) and directly to enamines (576). A 2H-l,3-dithiol-2-thione was obtained from morpholinocyclohexene and tetramethylthiuram disulfide (577). 

Bismorpholino disulfide (35) and related compounds are prepared from the corresponding amine (or imide) and disulfur dichloride. An elegant synthesis of the 1,3-dithiole-2-thione (36) from 35 is shown this is an example of two transfer reagents acting in concert.40... 

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... 

A novel synthesis of alkylsulfanylisothiazoles 230 starts with sodium a-cyanoketene dithiolates 227, obtained by the reaction of cyanoacetamides 226 with carbon disulfide in the presence of sodium ethoxide <06SC825>. Treatment of 227 with sulphur and piperidine acetate generates sodium isothiazole-3,5-dithiolates 229. The formation of 229 is assumed to arise from the addition of anionic sulphur to the nitrile group in 227 to give the intermediate 228, which cyclizes upon elimination of anionic sulphur to yield 229. Salts 229 are readily alkylated to furnish 3,5-bis(alkylthio)isothiazole derivatives 230. 

Otto, Sanders, and coworkers have utilized disulfide exchange to generate dynamic libraries of diastereomeric receptors [3]. DCLs made from a racenfic dithiol led to numerous cyclic structures including four cyclic tetramers, with the RR,RR,RR,RR diastereomer being the most stable (along with its all-5 enantiomer). Upon addition of N(CH3)J, the meso-diastereomer shown below was amplified 400-fold (Fig. 5.3). The structure of the diastereomer was confirmed by NMR and re-equilibration... 

Ketene dithiolates (137), readily available from the corresponding substituted acetonitriles and carbon disulfide, serve as versatile starting materials for the synthesis of monocyclic 3-aminothiophenes (Scheme 36). Thus, one sulfur atom was methylated (formation of 138) the other was alkylated... 

Two alternative approaches to the synthesis of the partially unsaturated ring systems are depicted in Schemes 27 and 28. The addition of sulfide ion to the multiple bonds of (208) in the former is facilitated by the activating effect of the sulfinyl or sulfonyl moiety and reaction occurs rapidly, giving yields of 67-84% (79S47). The second approach illustrates the use of an unsaturated dithiolate ion (76JOC1484). The first dianion (209) is generated from electrochemically reduced carbon disulfide and reacts with 1,2-dibromoethane to give the fused compound (210). Hot base-catalyzed hydrolysis cleaves (210) to form a new dianion which, with 1,2-dibromoethane, affords the product. 

Gentle oxidation of thiols generally leads to disulfides. When tetrafluorobenzene-1,4-dithiol is added to dimethyl sulfoxide, it quickly dissolves with warm evolution and a color change of the solution, from which a macrocyclic tetrasulfide 1 precipitates in 95% yield.285... 

Reaction of dibromide 168 with l,T-binaphthalene-2,2 -bis(methylenethiol) 169 gave a mixture containing the disulfide 170 (17% based on 169), dinaphtho[2,l-f l, 2 -rf thiepine 23 (52% based on 169), and the major 171 isolated from reaction between dibromide 168 and dithiol 169 (41% based on 168) (Equation 25) <1995T787>. An efficient synthesis of thiepine 23 by treatment of dibromide 168 with sodium sulfide was also reported <1994JOC1326> (see Section 13.03.9.2). 

In the synthesis of a series of cyclic aromatic disulfide oligomers using oxidative coupling of dithiols with oxygen catalyzed by copper salts and an amine, an effective, easy, and rapid method for the synthesis of macrocyclic aromatic disulfide oligomer from 4,4/-oxybis(benzenethiol) by cyclodepoly-... 

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