From Diorgano Tellurium Oxides

Diorgano tellurium oxides are reduced by hydrazine hydrate to diorgano tellurium compounds. The diorgano tellurium oxides are obtained as the primary products of the reactions of arenetellurinyl acetate or trifluoroacetates with olefins in chloroform, 1,2-dichloroethane, or acetonitrile as reaction media. When the olefin has a hydroxyl group in a j8-, 7-, or -position to the double bond, the addition of the tellurium compound to the double bond is followed by cyclization forming oxacycloalkane derivatives h 

Irgolic Organo Tellurium Compounds with 2 Te—C Bonds or 1 Te=C Bond 

When the reaction was carried out in chloroform in the presence of ethyl carbamate with boron trifluoride-etherate as catalyst, j8-ethoxycarbonylaminoalkyl phenyl tellurium oxides were formed. These tellurium oxides were not purified but reduced with hydrazine to the corresponding tellurium compounds.  

0 H5C6-CH = CH2 + HsCe-Te BFs- 0(C2Hs)2 H2N-COOC2H5 CHCI3,reflux,20h 0 H5C5-CH-CH2-Te  

Better yields were obtained when benzenetellurinyl trifluoroacetate was used in place of the acetate.  

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Dialkyl, alkyl aryl, and diaryl tellurium dichlorides were reduced by thiourea dioxide in a 2 molar aqueous solution of sodium hydroxide to the corresponding diorgano tellurium compounds4,5. The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

A promising method for the synthesis of unsymmctrical diorgano tellurium compounds uses carboxylic acid derivatives and diaryl ditellurium as starting materials. The carboxylic acid chloride, prepared in quantitative yield from the acid and oxalyl chloride is added slowly to a mixture of a diary] ditellurium and the sodium salt of 2-mercaptopyridine N-oxide in toluene at 35°. Under normal laboratory light the aryl tellurium radicals... 

Diorgano tellurium compounds are easily oxidized by elemental halogens to diorgano tellurium dihalides. Generally, the reactions are carried out with solutions of the reagents in inert organic solvents such as diethyl ether, methanol, acetonitrile, dichloromethane, chloroform, carbon tetrachloride, fluorotrichloromethane, benzene, or toluene. Often, the diorgano tellurium dihalides precipitate quantitatively from the reaction mixture. Soluble products are isolated by evaporation of the solvent or by addition of petroleum ether or hexane. 

Aqueous nitric acid, varying in concentration from dilute to concentrated, oxidized diorgano tellurium compounds to diorgano tellurium hydroxide nitrates3 5. Some of these compounds are reported to explode when heated above their melting points3,4,s. 

When diorgano tellurium dichlorides were ground with a suspension of silver oxide, chloride was precipitated as silver chloride. Extraction of the reaction mixture with hot water and cooling of the extract produced the tellurium oxide as a precipitate14. Alternatively, evaporation of the filtrate from the reaction mixture under vacuum left the product as a white residue15. 

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