Diorgano thiourea dioxide

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. 

Diorgano Tellurium5 (Thiourea Dioxide Method) A mixture of 2 mmol of the diorgano tellurium dichloride and 10 ml of 2 molar aqueous sodium hydroxide solution is stirred for 15 min at 20°. Then, 0.432 g (4 mmol) thiourea dioxide and 10 m/ petroleum ether (30-60°) are added. The mixture is stirred at 20° until it becomes clear. The phases are separated. The aqueous phase is extracted three times with diethyl ether. The combined organic phases are dried with anhydrous magnesium sulfate, the dried mixture is filtered, and the solvent evaporated from the filtrate. The residue is placed on a silica-gel column. The product is eluted with petroleum ether. 

The reduction of diorgano tellurium dichlorides by thiourea dioxide in aqueous sodium hydroxide solution proceeds via diorgano tellurium oxides or dihydroxides as intermediates (see page 432). 

Diorgano tellurium dihalides react with reducing agents (sodium sulfide, sulfites, hydrazine, thiourea dioxide, sodium borohydride) under mild conditions to give the corresponding diorgano tellurium derivatives in high yields. 

Diorgano tellurium oxides are reduced to diorgano telluriums by hydrazine hydrate sulfur dioxide", phenyl trimethylsilyl selenium, formamide , sodium borohydride, and thiourea dioxide . 

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