Hydrogen selenide preparation

The selenoureas needed for condensation can usually be prepared by addition of hydrogen selenide to a solution of the corresponding cyanamides or carbodiimides. They can be less dangerously and quite... 

The advantage of this method is that it avoids the use of hydrogen selenide, necessary for the preparation of selenourea from cyanamide (14). Benzoylselenourea is synthesized by the method of Douglass (24) by the action of potassium selenocyanate On benzoyl chloride in acetone solution. 

Selenium heterocycles receive far less mention in the literature than do such homologs as oxazole, thiazole, or imidazole. In fact, preparative methods of selenium heterocycles are much more limited than for the other series, mainly because of manipulatory difficulties arising from the toxicity of selenium (hydrogen selenide is even more toxic) that can produce severe damage to the skin, lungs, kidneys, and eyes. Another source of difficulty is the reactivity of the heterocycle itself, which can easily undergo fission, depending on the reaction medium and the nature of the substituents. 

Trialkyl- and triarylarsine sulfides have been prepared by several different methods. The reaction of sulfur with a tertiary arsine, with or without a solvent, gives the sulfides in almost quantitative yields. Another method involves the reaction of hydrogen sulfide with a tertiary arsine oxide, hydroxyhahde, or dihaloarsorane. X-ray diffraction studies of triphenylarsine sulfide [3937-40-4], C gH AsS, show the arsenic to be tetrahedral the arsenic—sulfur bond is a tme double bond (137). Triphenylarsine sulfide and trimethylarsine sulfide [38859-90-4], C H AsS, form a number of coordination compounds with salts of transition elements (138,139). Both trialkyl- and triarylarsine selenides have been reported. The trialkyl compounds have been prepared by refluxing trialkylarsines with selenium powder (140). The preparation of triphenylarsine selenide [65374-39-2], C gH AsSe, from dichlorotriphenylarsorane and hydrogen selenide has been reported (141), but other workers could not dupHcate this work (140). 

Cautionl Hydrogen selenide is very toxic. This preparation should be carried out in a well-ventilated hood. The operator should wear rubber gloves. The apparatus should be screened from any bright light. 

The difficulties encountered in the synthesis of 2-alkyl- and 2-aryl-substituted selenazoles lie principally in the preparation of the corresponding selenoamides. In this respect, a method is worthy of note in which the use of selenoamides is dispensed with. For this, a nitrile, a hydrogen selenide, and an a-halogenoketone are reacted together in the presence of a condensation catalyst. Phosphorus oxychloride, alone or mixed with zinc chloride or phosphorus trichloride, is specially suitable. The yields of the corresponding 2-alkylseIenazoles are up to a maximum of 25%,... 

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 selenides prepared by any of these methods can be converted to selenoxides by such oxidants as hydrogen peroxide, sodium metaperiodate, peroxycarboxylic acids, 1-butyl hydroperoxide, or ozone. 

Cyano-substituted selenophenes are valuable precursors of formyl derivatives.89 They are also used as starting materials for the preparation of carboxylic acids and their derivatives.128 By treating the cyano compounds with hydrogen selenide, selenoloamides (101) were obtained. As shown in... 

Primary selenoamides are prepared by reaction of nitriles with appropriate selenating reagent, such as phosphorus (V) selenide (P2Se5), hydrogen selenide (H2Se), Al2Se3, NaSeH, trw(trimethylsilyl)monoselenophosphate or potassium selenobenzoate (Scheme 81).248 252... 

Hydrogen selenide is used in preparation of metal selenides and organosel-nium derivatives. It also is used in doping mix for semiconductor apphcations. 

Hydrogen selenide may be synthesized directly from elements by heating at elevated temperatures. It is prepared by heating hydrogen at 440°C with either selenium metal in a sealed tube or with selenium vapor over pumice stone ... 

The selenides may also be obtained by direct combination of the elements, either by passing selenium vapour over the heated metal in a vacuum or by heating the metal with selenium in a crucible, the reaction being started by means of a magnesium fuse.3 In the case of potassium the reaction is explosive. The compounds may also be obtained by the action of hydrogen selenide on the heated metal,4 on the heated metallic chloride or its vapour, preferably in the presence of nitrogen,5 or by reduction with hydrogen or carbon of an oxysalt such as a selenite.6 Selenides have also been prepared by electrolytic methods.7... 

Zinc sulfide, selenide, and telluride are more pronouncedly covalent than die oxide. They can be prepared from the elements, 01 in the case of first two, by the action of H2S or hydrogen selenide upon zinc solutions. Zinc nitride, ZnjN). prepared from zinc dust and NH3, hydrolyzes readily to NH3 and the oxide. Two zinc phosphides are known Z113P2. formed by heating the elements, yields phosphine with acids ZnP and ZnHP have also been prepared. 

Diselenoacetone,4 (CH3.CSe.CH3)2, is prepared by passing hydrogen selenide into a well-cooled mixture of equal volumes of acetone and concentrated hydrochloric acid. A heavy red oil separates, the yield being 50 per cent, by volume. The product is washed with water and... 

The Selenide [(NHCgHg.CO CSe. —This occurs when malon-anilide (5 mols.) and selenium tetrachloride (4 mols.) react in absolute ether at 27° to 30° C. The product darkens at 217° C. and melts at 222° to 223° C. Malon-m-chloroanilide also occurs during the preparation. Reduction of the selenide by alkali hydrosulphite affords the original anilide and hydrogen selenide, whilst treatment with bromine gives dibromomalonanilide and selenium bromide. 

A convenient route to the 1,3-selenazole nucleus uses a polyfunctional reagent such as the vinylphosphonium salt (110), which with sodium hydrogen selenide gives the ylide (111) (Scheme 33). Cyclization of (111) yields the phosphonium derivative (112). A variety of compounds have been prepared by this method [182-184],... 

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... 

This general reaction can be used for preparing other un-symmetrical thioureas when the desired cyanamides can be obtained. The submitter has also prepared l-methyl-l-(l-naph-thyl)-2-selenourea, m.p. 174-175° with decomposition, and l-ethyl-l-(l-naphthyl)-2-selenourea, m.p. 168-170° with decomposition, by substitution of hydrogen selenide for hydrogen sulfide. 

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