Sodium selenide

A -methyl-5//,7//-dibenzo[d,.g][l,5]telluroazocine 65, its thiooxide 67a (X=S, R= Me) (95JA6388). The same type of reaction with benzylamine and sodium selenide gives A-benzyl-5//,7//-dibenzo[d,g][l,5]telluroazocine selenoxide 67b (X = Se, R = CH2Ph). Reaction of the tellurium dibromide 66 with sodium sulfide carried out in the absence of the primary amines affords the eight-member Te,S-containing heterocycle 5//,7//-dibenzo[d,g][l,5]telluroazocine (92CL151). 

Alternatively, raw anode slimes are aerated with hot dilute sulfuric acid to remove copper. Slimes are then mixed thoroughly with sodium carbonate and roasted in the presence of sufficient air. Sodium selenate formed is leached with water. Hydrochloric acid is added to this selenate solution. Treatment with sulfur dioxide precipitates elemental selenium. Alternatively, the selenate solution is evaporated to dryness. Sodium selenate is reduced to sodium selenide by heating with carbon at high temperatures. Sodium selenide is leached with water. Air is blown over the solution. Selenide is oxidized to elemental selenium which precipitates. 

The structure of the sodium selenide crystal may be described as a cubic close-packed array of Se2- ions, with an Na+ ion in every tetrahedral hole. 

Selenium is soluble in sulphuric acid, forming a green solution which, in the case of the metallic form, probably contains a compound of composition S03Se (p. 338), and in the case of the red amorphous variety, a polymeric form of this compound.8 The presence of selenium does not affect the electrical conductivity of sulphuric aeicl. Dilute aqueous potassium hydroxide dissolves the red variety, producing a solution which probably contains polyselenides in the presence of sodium hydrosulphite, however, only sodium selenide, Na2Se, is obtained.9... 

Selenocyanic Acid, HCNSe, may be prepared in solution by decomposing the lead salt (obtained by treating potassium selenocyanate with lead acetate) with hydrogen sulphide.3 It is stable only in neutral or alkaline solution. Selenocyanuric acid has been obtained 4 as a red amorphous powder by the action of cyanuric chloride on sodium selenide and subsequent precipitation by acids. 

In the case of the benzyl compound, sodium selenide is treated with benzyl chloride ... 

By treating sodium selenide with benzyl chloride. 

This selenide may be obtained as follows (1) Phosphorus pentaselenidc (P2Se5) is treated with alcoholic sodium hydroxide until sodium selenide is produced, air being excluded during the operation. Benzyl chloride is then added and the mixture heated under reflux. Evaporation away of the solvent yields white needles of the selenide, together with yellow scales of the diselenide.8 (2) Potassium selenosulphate is... 

Dibenzyl diselenide, (C6H5.CH2)2Se2.—This compound may be obtained in a variety of ways (1) Sodium selenide is heated for several hours under reflux with benzyl chloride in alcoholic solution.2 (2) A good yield of the diselenide results when a solution of selenium in sodium sulphide or sodium hydroxide is shaken on a machine with benzyl chloride.3 (3) Potassium selenosulphate is shaken with the calculated quantity of benzyl chloride in the cold. (4) An alcohol solution of potassium benzyl selenosulphate is treated with an excess of iodine, and the diselenide remaining in solution is precipitated by the addition of water. The precipitate is collected immediately and recrystallised from alcohol, since the presence of iodine appears to aid decomposition, with deposition of selenium, and it is also necessary to wash the crystals with water to remove any traces of hydriodic acid before drying the product.4 (4) An aqueous solution of potassium benzyl selenosulphate is subjected to electrolysis, using a current of 0 25 to 0 5 ampere, the method of operation being similar to that used for di-p-nitrobenzyl diselenide. 

Although the cyclic selenohydrocarbons having five- or six-membered rings are isolated in good yield by the interaction of alkylene dibromides and sodium selenide, trimethylene dibromide and sodium selenide furnish only a small yield of c cZoselenopropane,... 

When sodium selenide reacts with af-hexamethylene dibromide in alcohol only a small proportion of monomeric ct/cfoselenohexane,... 

It has already been pointed out that this compound may be prepared by hydrolysis of the selenocyanate it may also be obtained by the interaction of sodium selenide and 1-chloroanthraquinone. By the latter process orange-red plates, M.pt. 212° C., result. If 2-chloroanthra-quinone be used in the reaction, 2-anihraquinone selenophenol is obtained as an orange-yellow product, which gives a violet-red solution in sulphuric acid. Concentrated nitric acid causes oxidation to the seleninic acid. 

The analogous reactions with diacetylenes 91 were performed also with sodium sulfide and sodium selenide, their rates progressingly increasing in the order Na2S < Na2Se < Na2Te. 

The synthesis of substituted sclcnolo 2,3-/ ]thiophcncs 208 and selenolo [2,3-b selenophenes 209 via ketene dithioacetals has been published (Scheme 40) [55], The easy access to ketene dithioacetals via carbon disulfide cannot be applied to selenium since the strongly odorous carbon diselenide cannot be readily prepared. The authors [55] overcame this problem using sodium selenide for the synthesis of selenolo[2,3-/ thiophcncs 208, which could be synthesized from methylsulfanylthiophenes 206 and sodium selenide and/or from 5-methylsulfanylselenophenes 207 and thioglycolate. 

Alternatively polymer-bound sodium selenide 6 served as the starting point for an acylat-ing protocol (Scheme 3) [12]. Transformation into selenol ester 9 afforded an active polymer-bound intermediate which was cleaved in the presence of an alkinylcopper species to generate a,/ -alkinyl ketones 10 while the copper selenide can be reacylated using acyl chlorides. 

In five of six nondietary tumor-promotion experiments, sodium selenide significantly reduced the number of mice with tumors induced by 7,12-dimethyl-benzanthracene (DMBA)-croton oil (1). In these experiments, sodium selenide was applied concomitantly along with croton oil to female Swiss albino mice initiated with DMBA. Riley has also observed a reduction in DMBA-phorbol ester carcinogenesis by sodium selenide (2). The effect of selenium-deficient and selenium-adequate diets on DMBA-croton oil and benzopyrene skin carcinogenesis has also been studied. Supplemental dietary selenium inhibited both types of carcinogenesis. 

Sodium selenite and selenodiglutathione have been found to be more effective in inhibiting the growth of Ehrlich ascites tumors than sodium selenide, dimethyl selenide or seleno-DL-cystine. Preincubation of tumor cells with either 1 or 3 ppm Se as GSSeSG, Na SeO or dimethylselenide before reinoculated into mice resulted in a significant increase in survival in mice inoculated with cells pretreated with GSSeSG (69) (Table IV). Vernie et al.,... 

Dimethyl-y-pyrone reacts with sodium selenide (or sodium hydrogen selenide) to give 2,6-dimethyl-4-seleno-y-pyrone (66). This, in turn, reacts with sodium selenide to give 4,6-bis(hydroseleno)-3,5-heptadien-2-one (67), which is readily oxidized by air to 5-methyl-l,2-diselenol-3-yIidene acetone (68).84,85... 

In an extension of their synthesis of 2-nitrothiophenes, Cagniant and co-workers have prepared 2-nitroselenophenes and -tellurophenes by similar procedures.32,33 Thus, the / -chloro-a,/ -unsaturated aldehyde 38 (R = Ph R = H) reacts with bromonitromethane and sodium selenide to form the 2-nitroselenophene 39. Similarly, with sodium telluride and bromonitromethane, chlorovinylaldehydes yield 2-nitrotellurophenes (40). 

Selenium and tellurium can be introduced into organic compounds as the element, as a reduced (-Se2-) species, or as an oxidized (Se02) species. Use of the reduced form is by far the most common and will be discussed first. Unlike in CHEC-II(1996), sodium selenide or telluride can be synthesized, used, and handled quite easily. Air and moisture should be, of course, avoided but these conditions are not the hardest to take care of. 

The first synthesis of (R)-4,5-dihydro-37/-dinaphtho[2,l-f l, 2 -i ]selenepin oxide 110 has been achieved from (R)-(+)-l,l -bi-2-naphthol, which in turn was obtained by resolution of raol,l -bi-2-naphthol. Palladium-catalyzed alkoxy carbonylation of the alcohol 108 gave a dimethyl ester which was then reduced by LiAlfLi, and the resultant diol converted to key intermediate chloride 109. Cyclization with sodium selenide gave a novel enantiomerically pure selenide, which upon oxidation yielded the desired selenoxide 110 <2000SC2975>. 

The chalcogenide 97, 107/,127/-dibenzo[c/][l,5]selenathiocin, has been synthesized by the reaction between bis(2-bromomethylphenyl)sulfide 134 and sodium selenide in a mixture of THF and ethanol at 0°C for 17 h in rather poor yield (25%) <1998T11813>. A new phosphorus-selenium eight-membered heterocycle 136 has been synthesized from the bis-bromide 135 by treatment with sodium selenide in ethanol at room temperature in 81% yield (Scheme 13) <1995H(41)2647>. 

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