Sodium hydrogen selenide

A more general synthesis of selenophene derivatives, starting from diacetylenes and sodium hydrogen selenide, was investigated by Curtis.48 In the synthesis of new tetraphenylporphyrin molecules containing heteroatoms other than nitrogen, Ulman et al.49 used in principle the method of Curtis for the synthesis of the starting material (17). 

The introduction of selenium in the (4 +1) sense was achieved by the use of aqueous sodium hydrogen selenide in several instances where the appropriate di(halomethyl) precursors were readily available. Thus, the dichlorides (254c) and (287) and the dibromides (288) and (289) were converted to the five-membered cyclic selenides (290), (291), (292) and (293) by reaction with aqueous sodium hydrogen selenide high dilution conditions were used to minimize the formation of the dimeric diselenides (294)-(297) (Scheme 99) (77H(6)1349, 77CC163). 

Phenylselenoacetamide, CgH5.CH2.CSe.NH2,1 occurs in almost quantitative yield when phenylaeetonitrile reacts at 80° C. with alcoholic hydrogen selenide, saturated at -10° C., containing sodium hydrogen selenide. The compound separates as glistening white crystals, M.pt. 92° to 92 5° C. 

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],... 

Reaction of 37 with sodium hydrogen selenide affords selenetane 15, selenolane 38, and diselenide 42 (Equation 12). The ratio of the products was dependent on the reaction temperature <2000CAR107>. 

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... 

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... 

Sodium selenides.—The monoselenide, Na2Se, is formed by the action of selenium on a solution of excess of sodium in liquid ammonia, and separates out.6 It can also be produced by the interaction of selenium and sodium hyposulphite, Na2S204.6 It melts above 875° C., and on exposure to air its solution in water acquires a reddish colour, and deposits selenium. In solution it is extensively hydrolyzed, and under these conditions may be regarded as a mixture of sodium hydrogen selenide, NaSeH, and sodium hydroxide. Four hydrates are known, with 4, 9, 10, and 16 molecules of water respectively.7 For the heat of formation of the anhydrous compound Fabre8 gives 59 7 Cal., and for the heat of solution at 14° C., 18-6 Cal. He has also investigated the heat of solution of the hydrates. 

In aprotic solvents, such as dichloromethane and THF, potassium boro-hydride [10], lithium borohydride [8b], lithium triethylborohydride [8a, 11], and diisobutylaluminum hydride (DIBALH) [11] have been used instead of NaBH4. NaBH4 also reduces elemental selenium in alcohol or water to sodium hydrogen selenide or sodium diselenide (Na2Se2) depending on the stoichiometry of the reactants (Scheme 8) [12]. These anions are useful for the synthesis of selenides or diselenides, respectively, via nucleophilic substitution with various electrophiles. 

Related selenoxopurines have been prepared by replacement of the 6-amino group in selected purines. Thus 9-(/3-D-ribofuranosyl)-6-selenoxo-l,6-dihydropurine (371) was conveniently prepared (56% yield) from adenosine in aqueous pyridine with hydrogen selenide over 5 days at 65 °C. In a similar manner 2-aminoadenosine furnished 6-selenoguanosine (21%) (B-78MI40903, p. 673,75CC319,75JHC493). The latter compound may also be obtained (58% yield) from 2-amino-6-chloro-9-(2,3,5-tri-0-acetyl-/3-D-ribofuranosyl)purine and sodium hydrogen selenide. The method adopted for the preparation of selenoxo derivatives depends on the relative availability of the appropriate chloro or aminopurine. 

Similarly, reaction of 2-methylsulfanylquinazolin-4(3//)-onc with sodium hydrogen selenide affords 2,3-dihydro-2-selenoxoquinazolin-4(l//)-one. ... 

Treating the bromo tosylate 224 and bromo mesylate 225 with sodium hydrogen selenide gave the 1,6-episcleno sugars 129 and 133, respectively (Equation 46) <1996AJC343, 1999AJC885>. 

A practically useful method for synthesis of selenoesters has been developed by Barton et al. A wide range of aliphatic and aromatic selenoesters have been synthesized from the appropriate N -disuh-stituted imidoyl chlorides (58) using sodium hydrogen selenide to introduce seleniumJ Imidoyl chlorides (58) can be obtained by the reaction of amides with phosgene. Representative results are shown in Scheme 17 (formulae 59-61). 

The reaction of an imidoyl chloride with sodium hydrogen selenide gave high yield of the selenoamide (equation 33). ° ... 

Diaminocyclopropeneselones 1 were readily obtained from diaminochlorocyclopro-penylium salts and sodium hydrogen selenide. No other cyclopropeneselone derivative has yet been prepared by this method. 

Treatment of arylbis(dimethylamino)cyclopropenylium chlorides with sodium hydrogen selenide in ethanol resulted in the formation of l-aryl-2-dimethylaminocyclopropeneselones 2. No other examples have been reported. 

Treatment of 2,3-diphenylcyclopropenone with sodium hydrogen selenide in ethanol under a nitrogen atmosphere produced 4,5-diphenyl-3//-l,2-diselenol-3-one in 45% yield. 

The triamino- and 1,2-diamino-3-chlorocyclopropenylium ions 9 were transformed into the 2,3-diaminocyclopropeneselone 10 by reaction with sodium hydrogen selenide, which was prepared from sodium borohydride and selenium (see Section S.A.S.l.). ... 

The reaction can be rationalized as involving an E2 fragmentative attack by the telluride anion at the halogen atom. Sodium hydrogen telluride (method B) requires a shorter reaction time than sodium telluride (method A), the 2-bromoalkyl esters reacting very rapidly. Sodium hydrogen selenide reacts similarly but more slowly. ... 

Dialkylamino-substituted 1,2-diselenolylium cations have been prepared from 1,3-bis(dialkylamino)-l,3-dichloropropenylium chloride by treatment with sodium hydrogen selenide and subsequent oxidation with hydrogen peroxide or w-chloroperbenzoic acid <87BCJ2686>. These salts were also prepared by reaction with sodium diselenide in ethanol <86MCLC333>. 

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