ALKENES reactions, carbon disulfide

The meso-ionic 1,3-oxazol-S-ones show an incredible array of cycloaddition reactions. Reference has already been made to the cycloaddition reactions of the derivative 50, which are interpreted as involving cycloaddition to the valence tautomer 51. In addition, an extremely comprehensive study of the 1,3-dipolar cycloaddition reactions of meso-ionic l,3-oxazol-5-ones (66) has been undertaken by Huisgen and his co-workers. The 1,3-dipolarophiles that have been examined include alkenes, alkynes, aldehydes, a-keto esters, a-diketones, thiobenzophenone, thiono esters, carbon oxysulfide, carbon disulfide, nitriles, nitro-, nitroso-, and azo-compounds, and cyclopropane and cyclobutene derivatives. In these reactions the l,3-oxazol-5-ones (66)... 

The second, even more convenient, method to determine double-bond positions in unsaturated hydrocarbons is the use of dimethyldisulfide derivatives (Francis and Veland, 1981 Carlson et al, 1989 Howard, 1993). In this approach, alkenes are dissolved in a carbon disulfide and iodine solution and kept overnight. The reaction yields a derivative with methyl sulfide substituents on each of the carbons that comprised the double bond. If the double bonds are separated by four or more methylene groups, the reaction proceeds... 

Reaction of a four-carbon unit with sulfur sources such as hydrogen sulfide, carbon disulfide, and elemental sulfur is one of the traditional thiophene syntheses that belong to this category (Equation 18). A wide variety of hydrocarbons, for example, alkanes, alkenes, dienes, alkynes, and diynes, serve as four-carbon units. Another practical method is the sulfuration of 1,4-dicarbonyl compounds (Paal synthesis). The method has become very popular with development of sulfuration reagents such as Lawesson s reagent. The reaction of a,/3-unsaturated nitriles with elemental sulfur in basic media, Gewald synthesis, is also useful for the preparation of 2-aminothiophenes which are important compounds in dyestuff and pharmaceutical industries. 

Addition of anionic nucleophiles to alkenes and to heteronuclear double bond systems (C=0, C=S) also lies within the scope of this Section. Chloride and cyanide ions are effieient initiators of the polymerization and copolymerization of acrylonitrile in dipolar non-HBD solvents, as reported by Parker [6], Even some 1,3-dipolar cycloaddition reactions leading to heterocyclic compounds are often better carried out in dipolar non-HBD solvents in order to increase rates and yields [311], The rate of alkaline hydrolysis of ethyl and 4-nitrophenyl acetate in dimethyl sulfoxide/water mixtures increases with increasing dimethyl sulfoxide concentration due to the increased activity of the hydroxide ion. This is presumably caused by its reduced solvation in the dipolar non-HBD solvent [312, 313]. Dimethyl sulfoxide greatly accelerates the formation of oximes from carbonyl compounds and hydroxylamine, as shown for substituted 9-oxofluorenes [314]. Nucleophilic attack on carbon disulfide by cyanide ion is possible only in A,A-dimethylformamide [315]. The fluoride ion, dissolved as tetraalkylammo-nium fluoride in dipolar difluoromethane, even reacts with carbon dioxide to yield the fluorocarbonate ion, F-C02 [840]. 

Corey and Winter converted 1,2-diol into a cyclic thionocarbonate 4.23 on heating with thiocarbonyldiimidazole (4.22) in toluene or xylene. Thionocarbonates 4.23 can also be prepared by the reaction of diol with n-butyllithium, followed by the reaction with carbon disulfide and methyl iodide. Desulfurization-decarboxylation is carried out by heating the cyclic thionocarbonate 4.23 with trimethylphosphite, and alkene is produced (Scheme 4.17). 

Williams carried out a Julia coupling similar to the Keck example. With the removal of the acetal functionality, the coupling step of the Julia reaction was efficient, but the usual reductive elimination procedure failed. As an alternative to the acetylation and reductive elimination procedure, the P-sulfo-nyl xanthate was formed by quenching the addition reaction with carbon disulfide and methyl iodide. Reductive elimination was then carried out with tri-n-butyltin hydride to yield the desired ( )-alkene (399) in an 85 15 ratio with the (Z)-alkene in 83% overall yield (equation 91). 

The easily accessible neutral ionic liquid [pmImJBr promoted a one-pot three-component condensation of an amine, carbon disulfide, and an activated alkene/dichloromethane/epoxide to produce the corresponding dithiocarbamates (Scheme 5.60) in high yields at room temperature. The reactions were very fast in ionic liquids relative to those in other reaction media. These reactions did not require any additional catalyst or solvent. The ionic liquid was recovered and recycled for subsequent reactions. 

Similar to the method described above, a bromo substituent in the alkene moiety leads to the 5,6-unsaturated system. Thus, the reaction of 1 -bromo-2-phenylvinylsulfonamide and carbon disulfide in dimethylformamide/aqueous sodium hydroxide gives the sodium salt of 5-phenyl-1,4,2-dithiazine-3-thiol 1,1-dioxide (5).8... 

This reagent can also be used for the oxidation of methylated aryl derivatives to the corresponding aryl aldehyde, in what has become known as the Etard reaction. Tillotson and Houston found that the Etard reaction is catalyzed by small amounts of alkene, added to or present in the reaction medium. The reaction involves addition of chromyl chloride to a carbon disulfide or carbon tetrachloride solution of the arene. A dark brown, insoluble, and explosive intermediate usually precipitates. Dilute sulfurous acid is added to decompose the precipitate to the aldehyde. Toluene is converted to benzaldehyde and ethylbenzene was oxidized to phenylacetaldehyde with this reagent. 

For example, the reaction of coal with an alkyl chloride in the presence of aluminum chloride (in a solvent such as carbon disulfide) can increase the solubility of the coal from ca. 11% pyridine-soluble material in the original coal to as much as 39% pyridine-soluble material (Schlosberg et al., 1978). Alternatively, the reaction of coal with an alkene (cetene) or with alcohols (dodecanol/ cetanol) in the presence of aluminum chloride renders more than 50% of the coal soluble in quinoline (Sharma and Mishra, 1992). 

Scheme 8.69. The Chugaev reaction. The salt of an alcohol is allowed to react with carbon disulfide, producing the sodium salt of a dithiocarbonate derivative, which, on Sn2 reaction with methyl iodide (CH3I), produces the corresponding xanthate ester. Heating the xanthate (pyrolysis) results in loss of carbon oxysulfide (COS), methane thiol (thiomethane), and the corresponding alkene.

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