Diaryltellurium oxide

Diaryltellurium oxides, characteristics, 9, 591 Diastereoselective hydroformylation, for natural products and... 

Diaryltellurium oxides 8 and aryltellurinic acid anhydrides 9 are white solids and find use as mild oxidizing agents in organic synthesis. These classes of organic tellurium compounds are quite stable and can be handled with no need for special care. 

Arenetellurinic acid anhydrides 137 present similar reactivity to the diaryltellurium oxides shown in Scheme 71. However, oxidation of the iV)./V-diphenylthiourea 138 with 137 gives the unexpected A,iV-diphenylcarbodimide 139 (Scheme 74).201... 

Ley et al. reported a catalytic method for the conversion of thiocarbonyl compounds to their oxo analogues with diaryltellurium oxide. The teUuride is recycled with a halogenating agent like 1,2-dibromotetrachloroethane, water and base (Scheme 7.91) [362, 363]. 

The transfer of iodine to the organic substrate represents a formal reductive elimination at tellurium(lV) to give tellurium(ll) as well as oxidation of the alkene. In a series of diaryltellurium(lV) diiodides, iodination of organic substrates is accelerated by electron-withdrawing substituents and is slowed by electron-donating substituents, which is consistent with the substituent effects one would expect for... 

Diaryl tellurides undergo facile ligand-transfer oxidations with [bis(acyl-oxy)iodo]arenes in chloroform to give stable diaryltellurium dicarboxylates 12 (Scheme 7) [23]. Similar ligand-transfer oxidations of triarylbismuthanes and triarylstibanes with BAIB in dichloromethane leading to Bi(V) and Sb(V) diacetates 13 and 14 have also been reported [24,25]. The triarylbismuth diacetates were employed for high yield Cu(II)-catalyzed arylations of a series of aryl-amines [24]. 

Diorganotellurium oxides 8 are prepared by oxidation of diorganotellurides. The dialkyl derivatives are prone to air oxidation specially when they are in solution. The diaryl tellurides 3 are more stable being oxidized to the corresponding tellurium oxides 8 by sodium periodate32 or A -chlorosuccinimide followed by alkaline hydrolysis82 (Scheme 14). Alternatively, diaryltellurium dichlorides 6, prepared by electrophilic aromatic substitution (Section 9.13.6.2, Scheme 70), can be hydrolyzed in alkaline medium to the corresponding tellurium oxide 883 (Scheme 14). 

Considering that diaryl teUurides debrominate v/c-dibromides, forming diaryltellurium dibromides (see Section 4.1.12.1), which in turn can be easily hydrolysed to the corresponding telluroxides by aqueous bases, a catalytic procedure has been provided for the oxidation of thiocarbonyl compounds. 

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