Sodium benzeneselenolate

ESTERS Sodium benzeneselenolate. ETHERS Boron tribromide-Sodium iodide-15-Crown-5. Boron trifluoride etherate. Ferric chloride-Silica. Lithium iodide. Silicon(IV) chloride-Sodiuiu iodide. Sodium iodide-Pivaloyl chloride. 2,4,4,6-Tetrabromocyclohexadiene. Trichloro(methyl)silane. 

Triphenylbismuth carbonate. ISOXAZOLES Samarium(II) iodide. LACTONES Sodium benzeneselenolate. METHOXYTHIOANISOLES Sodium-Hexamethylphosphoramide. OXAZIRIDINES Iron(II) sulfate. OXETANES Cyanotrimethylsilane. 

The reactions of aryl tellurium bromides with bromomagnesium benzeneselenolate , sodium benzenethiolate, or sodium benzeneselenolate yield aryl phenyl tellurium chalcogen compounds (p. 208). 

A stereoreversed cyclobutanone formation was realized starting from oxaspiropentanes by using the selenoxide function as a leaving group. Treating oxaspiropentanes 94 with sodium benzeneselenolate in ethanol affords j8-hydroxy selenides 95 which, on oxidation with 3-chloro-peroxybenzoic acid at — 78 to — 30 °C, led directly to the corresponding cyclobutanones 96 (Table 3). The stereochemistry in this reaction is opposite to that normally observed in the acid-catalyzed rearrangement of oxaspiropentanes. 

By use of nickel-catalyzed cross-coupling reactions, a variety of vinylic selenides can be synthesized from vinylic bromides and sodium benzeneselenolate (Scheme 15.77) [158]. 

Fragmentations of heterocycles have played an important role in the preparation of amide derivatives. Moderate to good yields of a-hydroxy-amides were obtained on reaction of a-hydroxy-acid aceto-nides with primary amines.N-Alkyl-2-methyl-2-oxazolinium salts (obtained by mixing alkyl halides and 2-methyl-2-oxazoline in dichloromethane) were found to react with sodium benzeneselenolate to yield -(2-phenylselenoethyl)-t -alkylacetamides, which after oxidation to ] -vinyl analogues with sodium metaperiodate in methanol, gave secondary amides on sequential treatment with mercuric acetate in aqueous tetrahydrofuran and sodium borohydride/3M... 

Nitrophenyl Phenyl Selenium A three necked, round bottom flask fitted with a reflux condenser and a mechanical stirrer is charged with 162 g (1.03 mol) of benzeneselenol dissolved in 600 ml of absolute ethanol and 10 g (0.26 mol) of sodium borohydride are added to the stirred solution to reduce any diphenyl diselenium. Then, 157.5 g (1.0 mol) of 2-chloronitrobenzene and 56 g (1.0 mol) of potassium hydroxide dissolved in 45 ml of water are added, the mixture is heated gently under reflux for 3 h, and kept at 20° overnight to Crystallize 2-nitrophenyl phenyl selenium. The crystals are filtered, extracted with 500 ml of cold water to remove potassium chloride, washed with small amounts of ethanol, and dried in air yield 160 g (58%) m.p. 90-92°. 

Phenyl trimethylsilyi selenide benzeneselenol. The reaction of this anion, generated in. situ from diphenyl diselenide and sodium in THF, with chloro-trimethylsilane gives phenyl trimethylsilyi selenide in 72% yield..The product is sensitive to oxygen, but is stable under N2 indefinitely. It reacts rapidly with an alcohol to form benzeneselenol in high yield. 

Reduction of diphenyl diselenide by sodium metal in refluxing THF produces copious precipitates of the salt of a benzeneselenolate anion 4 (Scheme 4 a)... 

This naked selenolate is more reactive than the one complexed with borane 1 [1]. For example, in the presence of HMPA, 4 undergoes an SN2-type ester cleavage to produce the corresponding acids and alkyl phenyl selenides (Sect. 3.3) [6 a]. Uncomplexed selenolate 4 can also be prepared by the reduction of benzeneselenol (PhSeH) with sodium hydride (NaH) (Scheme 4b) [6aj. 

Treatment of diphenyl diselenide with tributylphosphine in an alkaline medium generates a benzeneselenolate anion [24], which reacts with various electrophiles, such as halides, epoxides, a, -unsaturated ketones, to generate various selenides [24,25]. The mechanism for the generation of the benzeneselenolate is proposed as shown in Scheme 17 [25]. A selenophosphonium ion and/or a pentavalent phosphorus species are initially formed in the reaction of diphenyl diselenide and tributylphosphine, and then the addition of sodium hydroxide liberates the benzeneselenolate and phosphine oxide. 

The reaction with a, -epoxy carbonyl compounds 12 leads to the corresponding reductive ring-opened products, -hydroxy carbonyl compounds 13, in good yields (Scheme 22). Electrochemically generated benzeneselenolate [21,22] and sodium phenylseleno(triethoxy)borate (1) [35, 36], have been applied for this type of reaction as a nucleophilic selenolate. In the latter case, the reaction mechanism was suggested as shown in Scheme 23 [36]. Reaction of 1 with 12 first produces the ring-opened adduct 14, which is then reacted with an excess amount of 1 to produce the final product 13. This method is important as a simple synthetic procedure to aldols and -hydroxy esters that are rather difficult to obtain by other methods. The reactions have been extended to the reduction of more functionalized a, -epoxy carbonyl compounds [37] and have been successfully applied for the synthesis of several natural products [38]. 

A few examples of the reduction of aliphatic diazo compounds to hydrazines exist," but this is not a generally applicable method for the synthesis of alkylhydrazines. On the other hand, arylhydrazines can be prepared by reduction of aromatic diazonium salts.The most commonly used reagents for this conversion are sulfur dioxide (or sodium sulfite) and tin(II) chloride, these being used to reduce arenediazo-nium chlorides in aqueous solution. Several other reagents, including sodium amalgam and triphenylphosphine, have been used for specific reductions of this type. Arenediazonium tetrafluoro-borates have been reduced to the correspwnding hydrazinium salts (3) by benzeneselenol in dichloro-... 

Phenyl Phenylseleno Tellurium 0.79 g (5 mmol) of benzeneselenol are dissolved in 5ml of anhydrous tetrahydrofuran. Under nitrogen, 2.6 ml of 2 molar ethyl magnesium bromide (5.2 mmol) in diethyl ether are added, the mixture is heated under reflux for 2 h, cooled to 0°, and a solution of phenyl tellurium bromide, prepared from 1.02 g (2.5 mmol) of diphenyl ditellurium and 0.40 g (2.5 mmol) of bromine in tetrahydro-furan/benzene, is added. The reaction mixture is then warmed to 20°. stirred at 20" for 30 min, then 40 ml of low-boiling petroleum ether followed by aqueous ammonium chloride solution are added. The organic layer is separated, washed with saturated aqueous sodium chloride, dried with anhydrous magnesium sulfate, filtered, and evaporated. The residue (1.38g) is plaeed on a eolumn containing 120g of silica gel G, the product (Rf 0.60) is eluted with petroleum ether, the eluate is evaporated, and reddish needles are obtained yield 1.13 g (63%) m.p, 48° (petroleum ether). 

A mild and convenient method has been attained by using the imidazolide (8 equation 6) or triazolide (9 equation 7) of carboxylic acids as a key intermediate. Treatment of an imidazolide of carboxylic acid with 1.2 equiv. of benzeneselenol and 0.02 equiv. of sodium phenoxide provided the selenol ester in a quantitative yield. In the case of the triazolide of carboxylic acids, the reaction proceeded in the absence of base.2 ... 

Benzeneselenol, a representative selenol, is a colorless liquid of greater acidity than benzenefhiol [pK = 5.9 (PhSeH) 6.5 (PhSH)]. Benzeneselenol is usually synfhesized by the reaction of phenylmagnesium bromide with metallic selenium then quenching wifh aqueous hydrochloric acid [10]. Similar hydrolysis of the sodium phenylseleno(triethoxy)borate complex prepared by fhe reduction of diphenyl diselenide wifh sodium borohydride is a convenient alternative [11]. 

Phenyl trimefhylsilyl selenide is also a useful precursor of benzeneselenol, which is formed on treatment of fhe former wifh methanol [12]. Phenyl trimefhylsilyl selenide is conveniently prepared by fhe reduction of diphenyl diselenide with sodium in THF and then silylation of the fhus formed PhSeNa with trimefhylsilyl chloride. It can also be prepared by silylation of PhSeLi, which can be prepared in situ from metallic selenium and phenyllifhium in THF (Scheme 15.4). 

Because of its acidity benzeneselenol gives phenylselenolate ions in fhe presence of bases such as MeLi (in EtgO) [13] and NaH (in THF) [14]. Sodium selenolate prepared by NaBH4 reduction of (PhSe)2 is believed to be a complex with triethyl borate... 

The preparation of /3-selenocarbonyI compounds by addition of sodium ben-zeneselenolate to enones gives low yields of the adducts, whereas the yields are much better using the air-sensitive benzeneselenol. Benzeneselenol is conveniently prepared in situ by sodium borohydride reduction of diphenyl diselenide. ... 

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