Heterocycles 2,4-disulfide

Aliphatic Mercaptans 3 Heterocyclic Mercaptans 7 Heterocyclic Thioethers 11 Heterocyclic Disulfides 7 Thiophenes 22 Thiazoles 6... 

All three mass spectra of the heterocyclic disulfides 3, j4 and 5 are characterized by intensive molecular ions. The main feature of the fragmentation is the cleavage of the disulfide bond system, giving intensive fragments at m/z 113 (2-methy1-3-fury1thio cation) and m/z... 

The presence of the heterocyclic disulfides in the aroma mixture is easy to understand and can be generally postulated as oxidative decomposition products of the corresponding monomers. Even air oxidation of the monomers may result in dimerization without effort. 

Reduction of heterocyclic disulfides and anodic reactions of sulfhydryl compounds show no special features. Elimination of a sulfhydryl group may be the slow step in some reactions. 

Carboxylic esters, especially lactones, are conveniently obtained via the pyridyl thioesters (18). Some examples are given in Scheme 1. The 2-pyridyl thiol ester method can be further improved if silver ions (AgC104) are used as activators. Corey and Brunelle have also introduced other heterocyclic disulfides, and (19) was found to be superior to other reagents tested for the formation of lactones from w-hydroxyalkanoic acids. 

The Committee evaluated a group of flavouring substances consisting of 51 simple aliphatic and aromatic sulfides and thiols, which included 3 simple sulfides (Nos 1683, 1684 and 1707), 10 acyclic sulfides with oxidized and thiol side-chains (Nos 1668,1675, 1677, 1688-1692, 1703 and 1710), 1 heterocyclic sulfide (No. 1685), 5 thiols (Nos 1659 and 1662-1665), 12 thiols with oxidized side-chains (Nos 1666, 1667, 1669-1674, 1704-1706 and 1708), 3 dithiols (Nos 1660, 1661 and 1709), 7 disulfides (Nos 1693, 1694 and 1696-1700), 2 trisulfides (Nos 1695 and 1701), 2 heterocyclic disulfides (Nos 1686 and 1687) and 6 thioesters and acids (Nos 1676, 1678-1681 and 1702). The evaluations were conducted according to the Procedure for the Safety Evaluation of Flavouring Agents (see Figure 1, Introduction) (Annex 1, reference 131). None of these substances has previously been evaluated. 

The heterocyclic disulfide is expected to undergo reduction to produce a dithiol and oxidation of the cyclic Ihioether. 

Heterocyclic disulfides are five- and six-carbon rings, which may also contain a cyclic thioether bond. The principal metabolic pathways are predicted to be disulfide reduction with ring opening to produce a dithiol and S-oxidation of the cyclic thioether. 

Diethyl trisulfide Heterocyclic disulfides Structural class II 1701 N No safety concern... 

Classification Heterocyclic disulfide Empihcal C10H8N2O2S2 Properties M.w. 252.32... 

Eastman Kodak Co. Thermally developable emulsions and materials containing heterocyclic disulfide compounds... 

N-(2-thiazolyl)dithiocarbamates are prepared by the action of carbon disulfide on 2-aminothiazoles (see Section III.3.C and Ref. 505). When refluxed with secondary amines these heterocyclic dithiocarbamates yield l,T-dialkyl-3-(2-thiazoIyI)thioureas (261) (491). 

The first member of the series. 2-imino-3,4-dimethyl-4-thiazoline (363) is obtained when the di-HBr salt of bis(methylformamidine)disulfide (362i is refluxed for 16 hr in acetone (Scheme 209) (700). The most common preparative methods involve direct heterocyclization by the Hantzsch method (see Chapter II. Section II.4), though the mechanism of this reaction suggests certain limitations according to the respective natures of R2, R3, and in 364 (Scheme 210). 

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

Treatment of the heterocycle, 38 (obtained from ethylene-diamine and carbon disulfide), with nitrous acid affords the N-nitroso compound, 39. Reduction with zinc leads to the corre-... 

Slow evaporation of a solution of 4 in carbon disulfide gives the orange ten-membered heterocycle 6.39 ... 

PAHs Heterocyclic nitrogen and oxygen compounds Aldehydes and ketones Sulfides, disulfides ... 

This silylene formation from 27 under mild conditions permits the synthesis of a variety of interesting carbo- and heterocycles, most of which are new types of compounds. The results are summarized in Schemes 5 and 6. The reactions with benzene and naphthalene represent the first examples of [2+1] cycloadditions of a silylene with aromatic C=C double bonds.59 623 The reactions with carbon disulfide and isocyanide (Scheme 6) are also of great interest because of their unusual reaction patterns.62b... 

A hypothetical structural model developed by Yen (24) represented the organic components of Green River oil shale. The major components were isoprenoids, steroids, terpenoids and cartenoids. The common bridges consisted of disulfide, ether, ester, heterocyclic and alkadiene. Elemental analysis of typical oil shale samples has shown... 

In his approach toward selenium-containing heterocycles with potential biological activity, Abdel-Hafez reacted 2-amino-3-(4,5-dihydro-17/-imidazol-2-yl)-4,5,6,7-tetrahydro-l-benzoselenophene 297 with triethyl orthoformate and benzaldehyde to generate the tricyclic systems 296 and 298, respectively (Scheme 21) <2005RJ0396>. Similarly, reaction with carbon disulfide gave the corresponding thiourea 299. 

There is an enormous literature on thiocarbonyl compounds, due in part to the technical and industrial importance of many of them, including thioamides, thioureas, xanthates, dithiocarbamates and so forth. An excellent, and recent, general review is available.107 There are also specialized reviews germane to the present chapter Griffin, Woods, and Klayman2 discussed the use of thioureas in the synthesis of heterocycles the preparation of thiazoles from thioamides is included in a three-part volume on Thiazoles 108 the use of carbon disulfide in the synthesis of trithiones and related heterocycles has been reviewed by Mayer109 and Huisgen110 has reported numerous examples of 1,3-dipolar cycloadditions in which carbon disulfide was used. 

Phosphorus pentasulfide is used to replace oxygen atoms with sulfur atoms the reaction is commonly carried out in a solvent heated under reflux. Solvents employed include carbon disulfide, aromatic hydrocarbons, and pyridine. If an oxygen atom is part of a heterocycle, then the reagent may replace it with sulfur, as in the formation of 2,1-benzisothiazoles from 2,1-benzisoxazoles.119 Such replacements are, however, not general some prior ring opening appears to be necessary before the reagent can act. For example, under normal conditions furan is not attacked. 

Diathiadiphosphetane disulfides are probably the most studied and the most thermally and hydrolytically stable of all the phosphorus-chalcogen heterocycles. They contain a central four membered P2S2 ring and can be prepared from heating phosphorus pentasulfide with aromatic compounds. The most well-known of these is Lawesson s reagent (43), which is made from anisole and phosphorus pentasulfide,92 and is used extensively in organic synthesis procedures (see Section 5.4.1). Other dithiadiphosphetane disulfides of note are 44 and 45, formed from the reaction of phosphorus pentasulfide with ferrocene or 1 -bromonaphthalene respectively.93... 

Decomposition of highly reactive disulfonium dications in sufficiently nucleophilic medium is accompanied by formation of disulfides. Even hydrolysis of disulfonium dications generated from sterically rigid bis-sulfides often affords some disulfide as a by-product in addition to the monosulfoxide main product. For example, hydrolysis of dication 72 yields sulfoxide 74 and trace amounts of heterocycle 73 (Scheme 28).56... 

As with other haloaromatic systems, Barbier reactions are also suitable for heterocyclic systems. For example, the lithio derivatives formed in situ from iodide 187 upon sonication reacted immediately with electrophiles such as benzaldehyde, hexanal and diphenyl disulfide, to give good yields of 188 <00T3709>. Similar chemistry was also successful with pyrazines, pyrimidines, and pyridazines. 

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