Telluroxo form

Scheme 6). Similarly, for seleno- and tellurocarboxylic acids, selenol and se-lenoxo, and tellurol and telluroxo forms may co-exist, respectively. Previous studies concerning the tautomerism of thiocarboxylic acids indicate that the thiol form (I) with the s-cis (syn) conformation is the predominant species. 

The syntheses of 2,1,3-benzotelluradiazoles were attempted by reaction of diamine with tellurium dioxide <1998PS221>. However, the reaction of 1,2-phenylenediamine with tellurium dioxide gave benzo-2-telluroxo-l,3-dihydrodiazole 94, which may exist in a polymeric form in the solid state (Equation 39) (Section 6.12.4.1). 

The [2+4] cycloaddition of selenocarbonyl (selenoxo) or tellurocarbonyl (telluroxo) compounds to diene systems remains one of the most widely used reactions for the preparation of various six-membered rings containing selenium or tellurium (see CHEC-II(1996), Section 5.11.7.2.1). The extremely sterically hindered selenal 154 has been isolated in monomeric form in solution and reacts with 2,3-dimethylbutadiene to afford the corresponding dihydro-selenin cycloadduct 155 (Equation 62) C1996AGE660, 1997T12167, 1998PS633>. 

---

See also in sourсe #XX -- [ ]

---