Sodium phenyl selenide

Formation of CK-configurated cyclobutanones has also been observed with 2-methylcyclopen-tanone and 2-methylcyclohexanone/8 However, stereoreversed eyclobutanone formation can be achieved by opening the intermediate oxaspiropentane with sodium phenyl selenide, oxidation of the resulting / -hydroxy selenide with 3-chloroperoxybenzoic acid and subsequent rearrangement in the presence of pyridine/18 Thus, from one oxaspiropentane 8, either stereoisomeric eyclobutanone cis- or lrans-9 was produced. The stereoreversed eyclobutanone formation proceeds from a stereohomogenous / -hydroxy selenoxide and is thought to be conformationally controlled. 

Phenyl methyl selenide, C6H5.Se.CH3,2 is a pale yellow oil, B.pt. 200° to 201° C., obtained by the action of methyl iodide on sodium phenyl selenide. 

EPOXIDES Alumina. Bisfbenzonltrile)-dichloropalladium(H). Copper(II) sulfate-Pyridine. Diborane. Diphenyl d isu Ifide-Tri-n-bu t y Iphosphine. Organo-cuprates. Sodium cyanoborohydride. Sodium phenyl selenide. Trimethyl-sllyl phenyl sclcnidc. Trimethylsilyl trifluoromethanesulfonate. Triphenyl-phospliine-Thiocyanogen. 

The Sn2 cleavage of esters and lactones is achieved with sodium phenyl selenide generated by the reaction between sodium hydride and benzene selenol, instead of the more usual sodium borohydride reduction of diphenyldiselenide. When generated under the former conditions the phenyl selenide anion is a potent nucleophile and good yields of seleno-acids are obtained from a wide range of esters and lactones (Scheme 3). ... 

The 7 a-bromo steroid (9) can also be treated with sodium phenyl selenolate (41). The resultant 7 P-phenyl selenide (13) can be oxidized and the corresponding phenyl selenoxide elirninated to form the 7-dehydtocholesteryl ester (11). 

The submitter has synthesized nine alkyl phenyl selenides in yields of 85-95% by treating alcohol solutions of the sodium salt (the selenophenol is dissolved in the calculated amount of 50% aqueous sodium hydroxide diluted with alcohol) with the appropriate alkyl halide or sulfate. 

Phenyl selenide, CeHg.SeH.1—This selenide may be obtained as follows (1) Selenium tetrachloride is allowed to react with benzene in the presence of aluminium chloride. (2) Magnesium phenyl bromide in ether solution is treated with finely divided selenium and the addition product treated with cold hydrochloric acid. The ether layer is then removed, the extracted solution treated with more ether and the extracts combined, then shaken with one equivalent of sodium hydroxide, calculated on the basis of the total amount of selenium used, and dissolved in water to make a 25 per cent, solution. The ether solution is then dried with calcium chloride, the ether removed and the residue distilled, diphenyl diselenide and diphenyl selenide, B.pt. 303° C., being obtained. The sodium hydroxide solution on acidification with a slight excess of concentrated hydrochloric acid, followed by three more extractions with ether, gives on removal of the solvent almost pure phenyl selenide, B.pt. 182° C. The product melts at 60° C., and is insoluble in water, but dissolves in alcohol mercuric chloride gives a white precipitate.2... 

Phenyl ethyl selenide, C6H5.Se.C2H5.3—Phenyl selenide (10 grams) is dissolved in one equivalent of sodium hydroxide in the minimum of water, 50 c.c. of absolute alcohol then added, followed by 20 grams of ethyl bromide. The mixture is heated under reflux for fifteen minutes, then diluted with four times its volume of cold water, extracted three times with ether, the extract washed with water, dried over calcium chloride and distilled. Rectification of the oil obtained gives a 72 per cent, yield of the required selenide, boiling at 214° to 216° C. Treatment with bromacetic acid converts the selenide into phenyl-selenoglycollic acid.4... 

Diphenyl-EGaAS -dithia-O-selenapentalene has been prepared by two different methods (a) reaction of phosphorus pentaselenide with2-phenyl-(5-phenyl-l,2-dithiol-3-ylidene)ethanal86 and (b) reaction of sodium hydrogen selenide with the Vilsmeier salt (70).49... 

Starting with picrotoxinin (1) Yoshikoshi developed an improved synthesis of ( )-picrotin (2). Epoxidation of picrotoxinin (1) with peracid at room temperature led to a 5 2 mixture of the epimeric epoxides. Regioselective cleavage of the epoxide was achieved with sodium phenylselenyl triethoxy boronate. Radical reduction of the phenyl selenides 414 with stannane completed this three-step sequence to picrotin (2) in 87% overall yield. 

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. 

Reactions with Nucleophiles. The epoxide is, by far, the more reactive site and a wide variety of nucleophiles have been used (eq 2) to open the ring at C-3 such as HCl (96%), HOAc (>50%), H2S (65% as cyclized product 3-thietanol), HCN (66%), ethanol (90%), t-butanol (86%), phenyl or benzyl thiol (99% or 93%, respectively), and phenyl selenide (generated in situ from the diselenide and sodium hydroxymethyl sulfite) (>55%). If desired, the epoxide is easily formed from the chlorohydrin by treatment with excess KOH or Et3N. 

Diphenyl selenide is oxidized with peroxyacetic acid at room temperature to diphenyl selenoxide hydrate, C6H5Se(OH)2, in 43% yield after 2 h [1198]. Benzyl phenyl selenide is oxidized to benzyl phenyl selenoxide by sodium periodate in aqueous methanol at 0 °C in 95% yield and by iodobenzene dichloride in aqueous pyridine at -40 °C in 85% yield [773]. 

On p-hydroxyalkyl phenyl selenides, die oxidation-elimination is best achieved with an excess of 30% aqueous hydrogen peroxide according to die original description of Sharpless (Scheme 174, c and d). Although l-(l -hycyclohexyl phenyl selenide p uces under these conditions a hydroperoxide (Scheme 174, a), the sired elimination reaction has been successfully achieved with sodium periodate in ethanol (Scheme 174, b). 

The method used to prepare phenyl selenide can have a pronounced effect on the selectivity of the reagent. It was observed that Michael addition or acetate displacement could be selectively achieved by changing the method of preparation of phenyl selenide. In the illustrated case, the reagent prepared using sodium hydride gave the conjugate addition product (eq 46). 

Phenyl hydrogen selenide, generated from diphenyl diselenide and sodium borohydride in ethanol, promotes the /V-bcnzylation of cyclohex-2-enylamine (equation 54)164. 

Phenyl -tolyl selenide in aqueous suspension is boiled with potassium permanganate for several hours. The manganese mud is dissolved and the 4-carboxydiphenyl selenoxide precipitated by passing in sulphur dioxide. After filtration the precipitate is macerated with dilute sodium carbonate solution, the products of oxidation being separated in this manner into phenyl p-tolyl selenoxide and 4-carboxydiphenyl selenoxide. Addition of dilute sulphuric acid to the sodium carbonate extract causes the separation of 4-carboxydiphenyl selenoxide, which is crystallised from alcohol. The product is a microcrystalline powder, melting with decomposition at 253° to 255° C. Attempts to resolve it into optically active forms have failed the l-menthylamine salt melts at 220° to 222° C. with decomposition, and the d-a-phenyl-ethylamine salt forms feathery needles, M.pt. 194° to 195° C. with decomposition.3... 

Treatment of the hydronitrates in aqueous solution with sodium carbonate causes evolution of carbon dioxide. Evaporation to dryness, followed by extraction with alcohol or benzene, then yields oils which are probably the selenoxides. These oils with concentrated hydrochloric acid are converted into white solids, crystallisable from benzene, xylene, alcohol or dry ether. These solids are the dichlorides of the original selenides, and when prepared by this method their melting-points are as follows Phenyl methyl selenium dichloride, M.pt. 122° C. phenyl ethyl selenium dichloride, M.pt. 64° to 65° C. diphenyl selenium dichloride, M.pt. 142° C. 

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