Disulfides with alkenes

Montmorillonite (K-10) impregnated with ZnCl2 works as the catalyst for the trans-addition of dimethyl disulfide to alkenes (Equation (74)).205 Catalysts comprising K-10 impregnated with either CuCl2, FeCl2, or FeCl3 exhibit a comparable activity. 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

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. 

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. 

Photodecomposition of 1,2-benzisothiazole (17) affords the ring-opened disulfide 7.40 If the 3-position is blocked by substitution, then more interesting products may result. Photocycloaddition reactions of 3-phenyl-1,2-benzisothiazole (23) with alkenes afford excellent yields of 2,3-dihydro-1,4-benzothiazepins such as 24.41 With electron-rich alkynes, thiazabicyclohep-tadienes (25) are produced, but no reaction occurs with 2-butyne, 1-phenylpropyne, or dimethyl acetylenedicarboxylate.42 An analogous S—N bond fission occurs with 2-aryl-1,2-benzisothiazolinones.43... 

Oxoesters are oxidized with Mn(OAc)3 to the corresponding radicals that can add intermolecularly or intramolecularly (eq Ib)" to generate alkyl radicals. In the presence of Cu(OAc)2 the latter are rapidly quenched and oxidized to give alkenes. Radical arylation with alkyl iodides can be induced with dibenzoyl peroxide the yield of the reaction can be improved using a catalytic amount of Cu(0Ac)2-H20, which minimizes hydrogen abstraction by the intermediate radical but introduces a competitive electron-transfer oxidation of the intermediate radical. The oxidative addition of disulfides to alkenes (Trost hydroxysulfenylation ) can be promoted by catalytic amounts ofCu(OAc)2. ... 

The less polar nature of disulfides and sulfenamides makes the addition of these reagents to alkenes inefficient. Although thiolates can be generated under reducing conditions,the activation of disulfides and sulfenamides is routinely performed by Lewis acids to enable the introduction of new u bonds other than C—S bonds. As a consequence, the stereospecificity and reactivity observed in the Lewis-acid-promoted addition of disulfides and sulfenamides to alkenes is similar to that of sulfenylation by sulfenyl halides and thi-osulfonium salts. Likewise, the accepted reaction mechanism includes the coordination of Lewis acid, resulting in a thio-sulfonium-like species that can further react with alkene either directly or indirectly by way of dithiosuhonium ions. 

Papadopoulou, M., Spyroudis, S., and Varvoglis, A., l,3-Oxathiole-2-thiones from the reaction of carbon disulfide with zwitterionic iodonium compounds, /. Org. Chem., 50, 1509,1985. Spyroudis, S.P., Photochemical reactions of 2,4-dinitro-6-phenyUodonium phenolate with alkenes, alkynes and aromatic compounds,/. Org. Chem., 51, 3453, 1986. 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

Vinyllithium [917-57-7] can be formed direcdy from vinyl chloride by means of a lithium [7439-93-2] dispersion containing 2 wt % sodium [7440-23-5] at 0—10°C. This compound is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides. It can also be converted to vinylcopper [37616-22-1] or divinylcopper lithium [22903-99-7], which can then be used to introduce a vinyl group stereoselectively into a variety of a, P-unsaturated systems (26), or simply add a vinyl group to other a, P-unsaturated compounds to give y, 5-unsaturated compounds. Vinyllithium reagents can also be converted to secondary alcohols with trialkylb o r ane s. 

Dithiatopazine 73 serves as a sulfur-transfer reagent under thermal conditions. Tlius, heating 73 and diene 130 in toluene at 100°C formed a cyclic disulfide 131 (25%) and a tetrasulfide 132 (28%) with the formation of the alkene 118 (90%). Under similar conditions, the highly strained acetylene 133 was converted to the 1,2-dithiete 134 (65%) and the congested thiophene 135 (12%) (90JA3029). 

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