From vinyl sulfides

Strong bases readily eliminate thiol from vinylic sulfides. 1,2-Bis(alkyl- or arylthio)ethynes for example, react with two equivalents of BuLi or alkali amide to give metallated alkyl- or arylthioacetylenes and thiolates [24] ... 

Table 20. 2-Alkyl(or aryl)sulfanyl-l,l-dichlorocyclopropanes from Vinyl Sulfides and Dichlorocarbene...

Vinylsamarium species are generated from vinyl sulfides and sulfones. Protonation or alkylation may then be performed. Formation of C-disaccharides from a 5i-tethered glycosyl sulfone has been effected with Sml2. Intervention of a glycosyl radical intermediate is implicated. 

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. 

Vinyl chloride reacts with sulfides, thiols, alcohols, and oximes in basic media. Reaction with hydrated sodium sulfide [1313-82-2] in a mixture of dimethyl sulfoxide [67-68-5] (DMSO) and potassium hydroxide [1310-58-3], KOH, yields divinyl sulfide [627-51-0] and sulfur-containing heterocycles (27). Various vinyl sulfides can be obtained by reacting vinyl chloride with thiols in the presence of base (28). Vinyl ethers are produced in similar fashion, from the reaction of vinyl chloride with alcohols in the presence of a strong base (29,30). A variety of pyrroles and indoles have also been prepared by reacting vinyl chloride with different ketoximes or oximes in a mixture of DMSO and KOH (31). 

Intermediate 37 can be transformed into ( )-thienamycin [( )-1)] through a sequence of reactions nearly identical to that presented in Scheme 3 (see 22— 1). Thus, exposure of /(-keto ester 37 to tosyl azide and triethylamine results in the facile formation of pure, crystalline diazo keto ester 4 in 65 % yield from 36 (see Scheme 5). Rhodium(n) acetate catalyzed decomposition of 4, followed by intramolecular insertion of the resultant carbene 3 into the proximal N-H bond, affords [3.2.0] bicyclic keto ester 2. Without purification, 2 is converted into enol phosphate 42 and thence into vinyl sulfide 23 (76% yield from 4).18 Finally, catalytic hydrogenation of 23 proceeds smoothly (90%) to afford ( )-thienamycin... 

VINYL SULFIDES FROM TinOACETALS WITH COPPER(I) TRIFLUOROMETHANESULFONATE (Z)-2-METH0XY-1-PHENYLTHI0-13-BUTADIENE... 

Part C of the present procedure illustrates a mild method for effecting the elimination of thiophenol from thioacetals and thioketals under essentially neutral conditions. The reaction of simple thioacetals and thioketals with bis[copper(I) trifluoro-methanesulfonate] benzene complex in benzene-tetrahydrofuran at room temperature affords vinyl sulfides in high yield (Table I). The reaction presumably occurs by coordination of the thiophilic copper(I) reagent with sulfur, heterolysis to a phenylthio-stabilized... 

Vinyl Sulfides from Thioacetals with Copper Trifluoromethanesulfonate ... 

The second cycloaddition substrate took to form of 91 (Scheme 1.9b), incorporating a vinyl sulfone dipolarophile. Beginning with cyano ketone 84, which was readily prepared from 1,5-dicyanopentane via a previously reported three-step sequence [45], condensation with thiophenol produced vinyl sulfide 85 in 84 % yield. Vinyl sulfide 85 underwent bromination in acetonitrile to afford bromo-vinyl sulfide 86 (86 %), which was then treated with isopropylmagnesium chloride [46] to effect metal-halogen exchange affording an intermediate vinyl magnesium bromide species. Subsequent alkylation with Mel in the presence of catalytic CuCN provided the alkylated vinyl sulfide 87 in 93 % yield. The nitrile within vinyl... 

Triphenylphosphine was obtained from Nakarai Chemicals, Japan. When the reaction is carried out without additional triphenylphosphine, the yield of coupling product may drop to 60-70% and the product is accompanied by the by-products, phenyl vinyl sulfide and 4-viny 1-1 -cyclohexene, derived from 3-hydride elimination. 

The preparation of phenyl vinyl sulfide is described Org. Synth., Coll. Vol. VII 1990, 453. The compound is also available from Aldrich Chemical Company, Inc. 

An explanatory mechanism for the formation of vinyl sulfides is shown in Scheme 24. In route a, (phenylthio)carbene 77 generated from chlorosulfide 75 reacts with the nitrile anion to form (phenylthio)carbanion 79, which then undergoes elimination of cyanide ion to produce vinyl sulfide 76. In route b, 75 reacts first with the nitrile anion 74 to produce P-(phenylthio)nitrile 78 followed by base-catalyzed P-elimination. However, route b is unlikely because 79 cannot be generated from 68 due to a larger pKa value of its ot proton than that of the nitrile. In fact, the reaction of chlorosulfide 75a with lithionitrile 80 gave a different product 81 in 63% yield. 

Similar to 67, the oxanickelacycle 69 prepared from 3-hexyne, Ni(cod)2/bipy, and C02 also acted as a nucleophilic reagent. The reaction of 69 with p-tolyl disulfide took place at the Ni-C bond to give vinyl sulfide 70 in 53% yield after esterification (Scheme 23).37 In the case of 2-bromopropiophenone as an electrophile, the cycloadduct 71 was obtained in 47% yield after acidic workup. 

From the same zirconocene intermediates, Huang and co-workers have prepared vinyl sulfides [24,35] and sulfones [26] through use of the appropriate quenching agents (Scheme 4.6). Treatment of vinyl zirconocenes with an equivalent of a disulfide in THF at 60 °C affords, after work-up and purification, (E)-vinyl sulfides in good isolated yields. Vinyl sulfones, which as a class are generally useful as Michael acceptors and Diels—Alder dienophiles, are obtained in about two hours upon treatment of (fc)-vinyl zirconocenes with various sulfonyl chlorides in THF at 40°C. 

Palladium-catalyzed reactions of arylboronic acids have been utilized to craft precursors for constructing indole rings. Suzuki found that tris(2-ethoxyethenyl)borane (149) and catechol-derived boranes 150 readily couple with o-iodoanilines to yield 151, which easily cyclize to indoles 152 with acid [158]. Kumar and co-workers used this method to prepare 5-(4-pyridinyl)-7-azaindoles from 6-amino-5-iodo-2-methyl-3,4 -bipyridyl [159], A similar scheme with catechol-vinyl sulfide boranes also leads to indoles [160]. A Suzuki protocol has been employed by Sun and co-workers to synthesize a series of 6-aryloxindoles [161]. 

E)-Alkenylsilanes and -sulfides.2 Dibromomethyltrimethylsilane (1), prepared from ClSi(CH3)3 and CH2Br2, is reduced by commercial CrCl2 in THF to a reagent that converts aldehydes into (E)-vinylsilanes. A related reaction provides (E)-vinyl sulfides selectively from C6H5SCHC12. 

Phenyl vinyl sulfide is prepared from thiophenol and 1,2-dibromoethane according to the procedure described by Paquette and Carr see Org. Synth. 1985, 64, 157. An earlier, three-step synthesis employing 2-chloroethanol instead of 1,2-dibromoethane is available.2... 

The preparative oxidation of vinyl sulfides is thought to proceed via an intermediate bridged sulfonium cation that can be attacked by an external nucleophile from the less encumbered side to give two isomers (Scheme 21) [87]. 

There are very few examples of photolysis being used for preparation of a carbonyl ylide. The Dittami protocol follows work completed from his lab with aryl vinyl sulfides. Photolysis, followed by cycloaddition, led to the cycloadduct 305 in excellent yield and stereoselectivity. If the aryl vinyl ether 304 was subjected to irradiation in a mixed solution of toluene-methanol at 366 nm rather than a single solvent of toluene, cyclized product was obtained, but no cycloadduct was formed. If a simple phenyl aryl ether was subjected to the same tandem conditions, the cyclized product was generated, but no cycloadduct was detected. 

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