Sodium hydrogen telluride

Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of tellurium powder with an aqueous ethanol solution of sodium borohydride, is an effective reducing reagent for many functionalities, such as azide, sulfoxide, disulfide, activated C=C bonds, nitroxide, and so forth. Water is a convenient solvent for these transformations.28 A variety of functional groups including aldehydes, ketones, olefins, nitroxides, and azides are also reduced by sodium hypophosphite buffer solution.29... 

When the conditions are controlled properly, Zn can mediate the reduction of the C-C double bond of a, (3-unsaturated carbonyl compounds in the presence of a nickel catalyst in aqueous ammonium chloride (Eq. 10.7). The use of ultrasonication enhances the rate of the reaction.15 Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of... 

Sodium hydrogen telluride is prepared by reduction of tellurium with NaBH4 under several conditions. The original procedure uses ethanol as the solvent, adding, after complete reduction of the tellurium, an appropriate amount of acetic acid (see Section 4.1.2, ref. 10 Section 4.1.7, ref. 29). 

The title reagent (prepared by the reaction of sodium hydrogen telluride with chlorotriph-enylstannane) reacts easily with the more active halides such as benzyl bromides whereas common halides need to be activated by cesium fluoride. 

In addition to the described reduction of double bonds conjugated to a carbonyl group, sodium hydrogen telluride and phenyltellurol reduce double (and triple) bonds conjugated to aromatic systems. " ... 

Hydrogen telluride, sodium hydrogen telluride as well as phenyltelluroP afford the reduction of imines to secondary amines. 

In the reduction of imines and enamines with hydrogen telluride and sodium hydrogen telluride, hydrolysis leading to primary amines and carbonyl compounds is frequently competitive with the reduction. This undesired side reaction is minimized by the addition of triethylamine, in the case of hydrogen telluride. ... 

Control of the pH to within the 6-7 range has been shown to be important in the reduction of imines with sodium hydrogen telluride. At a higher pH (10-11) no reduction occurs. ... 

Good yields of secondary amines are achieved using both the methods in the reactions of aromatic and aliphatic aldehydes as well as of diaUcyl ketones and cycloalkanones with aliphatic and alicyclic amines (and ammonia). Anilines give low yields, but when 2 equiv is used in the sodium hydrogen telluride method, the yields are improved. In the reaction of ammonia with aldehydes, symmetrical secondary amines are obtained, whereas glu-taraldehyde and amines lead to N-substituted piperidines. 

The reducing power of sodium hydrogen telluride towards nitro compounds is dependent on their structure. Unhindered nitrobenzenes are reduced to azoxybenzenes whereas sterically hindered nitrobenzenes are reduced to anilines by simple stirring with 5 mol equiv of the reagent at room temperature for 1 h. 

Under alkahne conditions, sodium hydrogen telluride reduces nitrobenzene to A -phenyl-hydroxylamine. ... 

The reduction of nitro- and dinitroalkanes with sodium hydrogen telluride gives, respectively, diazenes (dimers of nitrosoalkenes) and olefins.- ... 

The reduction of azo compounds to hydrazo compounds is also achieved by means of aryltellurols or sodium hydrogen telluride. The last reagent (generated from NaBH4 and... 

Te catalyst) reduces tertiary amine iV-oxides to the corresponding amines.Azides are reduced to primary amines by sodium hydrogen telluride. ... 

Reductive opening of oxiranes with sodium hydrogen telluride and sodium telluride... 

Sodium hydrogen telluride reacts with epoxides, in accordance with an S 2 displacement, giving rise to telluro-alcohols. These products are useful intermediates since they are easily converted into the corresponding alcohols and ketones by treatment with nickel boride followed by oxidation (reaction (a)) or to alkenes via the corresponding tosylates (reaction b)). ... 

Method Sodium hydrogen telluride furnishes higher yields under milder experi-... 

The reactivity of the tellurolate ion is pecuhar, since the corresponding aryl selenolate gives only the disubstituted o-selenoxylenes, and sodium hydrogen telluride gives only poor yields. 

Sodium hydrogen telluride, sodium 0,0-diethyl phosphorotellurolate, alkali 2-thienyl tellurolates and bis(triphenylstannyl) telluride °/KF reduce a-haloketones to the corresponding ketones. 

The reaction has been suggested as involving a one-electron transfer from sodium hydrogen telluride to the nitro compound followed by the detachment of a nitrite anion from the resulting radical anion. 

Sodium hydrogen telluride efficiently dealkylates quaternary ammonium salts to the corresponding tertiary amines in high yields. ... 

Otherwise, the same products can be obtained by a Knovenagel-type reaction between )3-cyanosulphones and aromatic aldehydes in the presence of sodium telluride (behaving as a base). This result is consistent with the above-formulated desulphonylation of an intermediate a-alkylidene )3-cyanosulphone at the expense of the sodium hydrogen telluride formed during the reaction. 

By treating a quaternary a-nitrosulphone with sodium hydrogen telluride, the sulphonyl group is displaced preferentially to the nitro group, as illustrated in the example. ... 

Common esters such as alkyl and benzyl carboxylates are easily dealkylated by sodium hydrogen telluride, sodium telluride and sodium ditelluride in DMF. In accordance with a typical S 2 displacement at the aUcoxy group carbon, methyl, ethyl and benzyl esters react smoothly. The nucleophilicity of the reagents is enhanced by the polar aprotic solvent, and the reactivity decreases with higher alkoxy chains due to steric hindrance (e.g. 

The allyl group, a less familiar protective group for carboxylic acids, can be easily removed from esters by treatment with sodium hydrogen telluride. In contrast to the preceding methods, ethanol has been employed as the solvent. 

Sodium hydrogen telluride, 282 Tin(II) chloride, 298 By other methods Acetic-formic anhydride, 1 Arene(tricarbonyl)chromium complexes, 19... 

The D-tf//o-inositol-based cyclic sulfate 53 has been reduced with sodium hydrogen telluride to the protected conduritol (Equation 13) <2000EJ01285>. 

Isotellurochromenes 151 can be prepared by a ring-closure reaction of 2-ethynylbenzyl bromides with sodium hydrogen telluride (Equation 60) <1998J(P1)2123>. This reaction provided key synthetic intermediates for the preparation of 2-benzotelluropyrylium salts (see Equation (35), Section 7.11.6.2.1). 

Under appropriate experimental conditions, hydrogen telluride, phenyl tellurol, and sodium hydrogen telluride perform the selective reduction of double bonds of a,/3-unsaturated carbonyl systems.89 90 This reaction with a,j3-unsaturated ketones complements the cerium trichloride/sodium borohydride method, which reduces the carbonyl group, keeping the carbon-carbon double bond intact92 (Scheme 18). 

The reaction of nitroalkanes and dinitroalkanes with sodium hydrogen telluride gives nitrosoalkane dimers and olefins, respectively.96 The reduction of other nitrogenated species such as hydroxylamines, azides, nitroso, azo, and azoxy compounds can also be performed by using tellurium reagents.6,11,12... 

Sodium hydrogen telluride reacts with epoxides 41 by a Sn2 mechanism giving the respective telluroalcohols. These intermediates are easily converted into the corresponding alcohols 42 by treatment with nickel boride.97 In contrast, epoxides suffer deoxygenation when treated with alkali 0,0-dialkyl phosphorotellurolates, to give the corresponding olefins 43 (Scheme 21).98,99... 

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