Benzeneselenol

Arylthiols (but not alkylthiols) add to terminal alkynes regioselectively to afford a Markovnikov-type adduct 212 in good yield using Pd(OAc)2 as a catalyst[120]. This result is clearly different from the an/i-Markovnikov addition induced by a radical initiator. The hydroselenation of terminal alkynes with benzeneselenol catalyzed by Pd(OAc)2 affords the terminal alkene 213, which undergoes partial isomerization to the internal alkene 214[121]. 

Benzeneselenol (phenylselenol, selenophenol) [645-96-5] M 157.1, b 57-59 /8mm, 71-72 /18mm, 84-86 /25mm, d 1.480, n 1.616. Dissolve in aq N NaOH, acidify with cone HCl and extract with Et20, dry over CaCl2, filter, evap on a steam bath and distil from a Claisen flask or through a short... 

Diphenyl diselenide has been prepared by disproportionation of phenyl selenocyanate in the presence of potassium hydroxide" or ammonia/ and by air oxidation of benzeneselenol. The preparation of benzeneselenol is described in an earlier volume in this series/ In the present procedure phenylselenomagnesium bromide formed from phenylmagnesium bromide and selenium is oxidized directly to diphenyl diselenide with bromine/ Thus the liberation of the malodorous and toxic hydrogen selenide and benzeneselenol is avoided. Benzeneselenenyl chloride has been prepared by thermal elimination of ethyl chloride from ethyl phenyl selenide di-chloride/ by thermal elimination of chlorine from phenylselenium trichloride," and by chlorinolysis of diphenyl diselenide with either sulfuryl chloride " or chlorine. " ... 

The benzeneselenolates of mercury, [Hg(SePh)2] and (Bu4N)[Hg(SePh)3], both adopt simple structures, with mononuclear complex entities which posses near-linear Se—Hg—Se and near trigonal-planar HgSe3 cores, respectively.335... 

Crich and Rumthao reported a new synthesis of carbazomycin B using a benzeneselenol-catalyzed, stannane-mediated addition of an aryl radical to the functionalized iodocarbamate 835, followed by cyclization and dehydrogenative aromatization (622). The iodocarbamate 835 required for the key radical reaction was obtained from the nitrophenol 784 (609) (see Scheme 5.85). lodination of 784, followed by acetylation, afforded 3,4-dimethyl-6-iodo-2-methoxy-5-nitrophenyl acetate 834. Reduction of 834 with iron and ferric chloride in acetic acid, followed by reaction with methyl chloroformate, led to the iodocarbamate 835. Reaction of 835 and diphenyl diselenide in refluxing benzene with tributyltin hydride and azobisisobutyronitrile (AIBN) gave the adduct 836 in 40% yield, along with 8% of the recovered substrate and 12% of the deiodinated carbamate 837. Treatment of 836 with phenylselenenyl bromide in dichloromethane afforded the phenylselenenyltetrahydrocarbazole 838. Oxidative... 

Lithium benzeneselenolate, I.iSeC6Hs. The sclcnolatc is prepared from I.iC6H5 and Se.1... 

CdSe2C36HM), Benzeneselenol, 2,4,6-tris(l,l-dimethylethyl)-, cadmium salt, [137358-89-5], 31 22... 

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. 

In summary, intramolecular radical cyclization reactions onto aromatic rings can provide quick access of otherwise not so easily assembled Ca0. -C.ryi bonds, although the yields are generally low and the process suffers from a lack of regioselectivity. Noticeably, Crich found that a catalytic amount of benzeneselenol, which can also be generated in situ reduction of diphenylselenide with stannane [57]. This method should find synthetic utility in intramolecular radical addition to arenes. 

Addition of 10 mol% of diphenyl diselenide to hydrostannylation reactions involving electron-rich alkenes resulted in a dramatic improvement in yield. For example, reaction of o - [(f-butyl)dimethylsilyl]oxy styrene with PhsSnH (1.1 equiv.) in the presence of PhSeSePh and 2,2/-azobis(2-methylpropanenitrile) (AIBN) afforded 2- [(f-butyl)dimethylsilyl]oxy -2-phenylethyl triphenylstannane in 95% yield after 2 h. This reaction is believed to benefit from the increased rate of H-atom transfer, resulting from the in sz fM-generated polarity-reversal catalyst benzeneselenol.55... 

In the presence of /9-cyclodextrin, that binds to the R group of substituted epoxides, benzeneselenol reacts regio- and stereo-specifically to give an 80% yield of the j3-hydroxy selenide.42 Because the selenol only attacks the least substituted carbon with inversion of configuration, the reaction must occur by an SN2 mechanism. 

Examples of halide reduction chemistry include the BU3 SnH-mediated reduction of iodide (41) en route to clavepictine A and B reported by Momose and coworkers64 (equation 17) as well as the reduction of iodide (42) during Danishefsky s work towards the synthesis of epothilone A (equation 18)73. Herzog and Roewer demonstrated that trimethyltin hydride can be used to effect the reduction of halooligosilanes to the corresponding silane in the presence of a Lewis base such as triphenylphosphine (equation 19)77, while Crich and Mo reported the beneficial effect of catalytic benzeneselenol during the BU3 SnH-mediated reduction and fragmentation of bromo-/) -lactones (43) (equation 20)94. 

Formylphenyl tellurium bromide and benzeneselenol in refluxing pyridine produced 2-formylphenyl phenylseleno tellurium2. 

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°. 

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