Disulfides reaction with alkenes

Sulfenamides can be synthesized by a metal-assisted reaction with disulfides and amines (eq 13). Conjugated dienols can be synthesized in a highly chemo-, regio-, and stereoselective manner from vinylic halides and allylic alcohols (eq 14). Silver acetate (or silver carbonate) and a catalytic amount of palladium(II) acetate in DMF are the preferred conditions. The reaction is very attractive because it requires only one functionalized alkene reactant and the addition of the vinylic group only occurs at the terminal carbon of the aUyUc alcohol. 4... 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

Sulfide groups can also be introduced by this methodology (entry 24) [405]. Simpkins and coworkers found that the reaction of acceptor-substituted alkenes 363 with diphenyl disulfide in the presence of 10 mol% of Co(eobe)2 344 and PhSiH3 as the stoichiometric hydrogen source furnished 31-71% of a-(phenylthio) carbonyl compounds 364. The intermediacy of radicals was proven by a 5-exo cyclization occurring in competition to the SH2 reaction at sulfur. 

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). 

Reduction of nitroalkenes Nitroalkenes substituted with at least one aryl group are reduced to alkenes rapidly at room temperature by reaction with NagS 9H2O and thiophenol in DMF. Thiophenol is essential as a proton source for this reduction it is converted into diphenyl disulfide during the reaction. 

Tosylamination ofalkenes, The reaction of diphenyl disulfide with chloramine-T in acetone gives, in 91% yield, an adduct of the composition (C6HsSSC6H5)(NTs)2 shown to have the structure (1) by virtue of subsequent reactions with alkenes. Thus it reacts with cyclohexene to give (2), which was reduced by sodium borohydride to (3), whose structure was established by an independent synthesis. 

The reaction of disulfides and diselenides with chloramine-T affords N-SR or N —SeR species which are able to undergo addition to alkenes, for example, cyclohexene by an ionic mechanism. After reduction of the cyclohexene adducts, traiw-jS-functionalized amines 1 and 2 were obtained in low yield89. 

New and efficient procedures for the direct episulfidation of alkenes have been developed. Addition of triphe-nylmethylthiosulfenyl chloride to cyclopentene leads to the adduct 88, which by reduction of the disulfide with LiAlH4 give episulfide 87 in high yield (Scheme 48) <2000SUL131, 1998JOC8654>. The analogous reaction with norbornene yields the jco-episulfide 89 in a diastereoselective fashion. 

The fundamental addition reaction can be modified by the use of transition metals and different reagents. Alkenes react with diphenyl disulfide in the presence of GaCls to give the product with two phenylthio units, PhS—C—C—SPh). The reaction of an alkyne with diphenyl disulfide and a palladium catalyst leads to the bis-vinyl sulfide, PhS-C=C-SPh. ... 

Mixed bimetallic reagents possess two carbon-metal bonds of different reactivity, and a selective and sequential reaction with two different electrophiles should be possible. Thus, the treatment of the l,l-bimetailic compound 15 with iodine, at — 78"C, affords an intermediate zinc carbenoid 16 that, after hydrolysis, furnishes an unsaturated alkyl iodide in 61% yield [Eq. (15) 8]. The reverse addition sequence [AcOH (1 equiv), —80 to — 40 C iodine (1 equiv)] leads to the desired product, with equally high yield [8]. A range of electrophile couples can be added, and the stannylation of 15 is an especially efficient process [Eq. (16) 8]. A smooth oxidation of the bimetallic functionality by using methyl disulfide, followed by an acidic hydrolysis, produces the aldehyde 17 (53%), whereas the treatment with methyl disulfide, followed by the addition of allyl bromide, furnishes a dienic thioether in 76% yield [Eq. (17) 8]. The addition of allylzinc bromide to 1-octenyllithium produces the lithium-zinc bimetallic reagent 18, which can be treated with an excess of methyl iodide, leading to only the monomethylated product 19. The carbon zinc bond is unreactive toward methyl iodide and, after hydrolysis, the alkene 19... 

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). 

Sulfur compounds. Displacement of allylic carbonates with thiols takes place at room temperature. Linear products also predominate from reaction with secondary carbonates. l,2-Bis(phenylthio)alkanes are formed when 1-alkenes are treated with diphenyl disulfide under catalytic conditions ([Ru] catalyst, toluene, 100°). Various functional groups (ester, silyl, etc.) directly bonded to the double bond are tolerated. 

---