Tellurium-containing heterocycles with two heteroatoms

Tellurium-Containing Heterocycles with Two Heteroatoms Igor D. Sadekov and Vladimir I. Minkin... 

Two chapters deal with the increasing influence in heterocyclic chemistry of unusual heteroatoms. Igor D. Sadekov and Vladimir I. Minkin of Rostov University (Russia) survey the chemistry of tellurium-containing heterocycles with two heteroatoms, while Allan Blackman of the University of Otago (New Zealand) summarizes the influence of metals on the reactivity of heterocyclic ligands in his chapter, Reactions of Coordinated Ligands. ... 

Sadekov, I. D., Minkin, V. I., Tellurium-containing Heterocycles with Two Heteroatoms, 58, 47. 

Thus far only eight different types of five-membered heterocycles with two heteroatoms, one of these being tellurium, are known. Of special interest are those containing S,Se, or Te as the second heteroatom in the ring. Such compounds afford electron-donor components of charge-transfer complexes or radical cation salts, exhibiting properties of the so-called organic metals. 

The second method employed for the synthesis of telluraxanthene is similar to that widely used for the preparation of various tricyclic heterocycles containing one or two heteroatoms. It is based on the interaction of 2,2 -dilithiodiphenylmethane with powdered tellurium, by which reaction telluraxanthene 82 has been prepared in 50% yield [81JOM(205)167]. The reaction apparently proceeds through the intermediate bis(telluro-phenolate) 86 which is oxidized to the heterocyclic ditelluride 87. The latter compound eliminates tellurium from its stericaily strained seven-membered ring and converts to telluraxanthene. This mechanistic scheme seems to be corroborated by the observation that the treatment of lithi-oarenes ArLi usually ends in the formation of diarylditellurides Ar2Te2 (74MI1 83MI2). 

There are a number of six-membered heterocycles which contain selenium or tellurium, and two other heteroatoms other than nitrogen, for example, the reaction of formaldehyde and hydrogen selenide gives 1,3,5-oxadiselenane (238) and 1,3,5-dioxaselenane (239 R = Me) <82ZAAC(488)60>. Similarly, acetaldehyde in aqueous acidic solution reacts with hydrogen selenide to afford 2,4,6-trimethyl-1,3,5-dioxaselenane (239 R = Me) <67JCS(B)il7>. 

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