Tellurides, carbonylation

Carbonyl Telluride. Littie is known about carbonyl teUuride [65312-92-7] COTe. It is formed in poor yield by passing carbon monoxide over teUurium at a high temperature. It is less stable than the selenide. 

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... 

The regioselective reduction of the C=C bond of a, -unsaturated carbonyl compounds, a very important organic reaction, is achieved by means of hydrogen telluride and phenyl tellurol, under appropriate experimental conditions. 

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. " ... 

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. ... 

The reaction exhibits the following featnres chloroacetates give lower yields than bro-moacetates the E confignration is observed for the formed C=C bond a, -nnsatnrated carbonyl compounds lead only to 1,2-addition prodncts ketones are nnreactive nnder the described conditions a large excess of the bromoacetate and sodium telluride is required to assure high conversions. 

Otherwise, dibromomalonates (and nitriles) react with a-unsaturated carbonyl compounds in the presence of only 1 equiv of dibutyl telluride, giving cyclopropane derivates. 

Cyclopropanation of a,fi-unsaturated carbonyl compounds with dibromomalonates (typical procedure) To a mixture of diethyl dibromomalonate (0.95 g, 3 mmol) and methyl vinyl ketone (0.27 g, 3.1 mmol) is added dibutyl telluride (0.73 g, 3 mmol) under argon and with stirring. The exothermic reaction is completed within 1 h. The mixture is chromatographed on an AI2O3, column (70-230 mesh, elution with EtOAc), giving dibutyltellurium dibromide (1.01 g, 84%) and then l-acetyl-2,2-bis(ethoxycar-bonyl)cyclopropane, which is purified by Kiigelrohr distillation (0.59 g (86%) b.p. 88-90°C/0.08 torr). 

Carboxylic acids are also produced through the detellurative carbonylation of several types of telluride by treatment with carbon monoxide at atmospheric pressure and room temperature in the presence of Pd(ll) salts, in various solvents. ... 

Hydroxyvinyl phenyl tellurides submitted to the carbonylation reaction in non-polar solvents (CH2CI2 or CHCI3) lead to butenoMes in moderate yields. ... 

Die nachstehende Arbeitsvorschrift zeigt die Verwendung von Aluminium-tellurid bei der reduktiven Aminierung von Carbonyl-Verbindungen1. 

Reductions. Hydrogen telluride reduces aldehydes and ketones to alcohols in satisfactory yields. The combination Al2Te2 D20 permits deutcration. H2Te reduces a,/J-cm>ncs and a,/ -cnals to the saturated carbonyl compound.1... 

The ligand-exchange syntheses of the examined type are applied to obtain complexes of metal carbonyls and carbonyl cyclopentadienyls with tellurium-organic ligands (Sec. 2.2.4.7) [265-268], Thus, the complexes 689 were isolated (3.96) from heated or UV-irradiated THF solutions, containing the adducts M(CO)5 THF and diorgano-tellurides [269,270] ... 

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