Heterocycles Containing Other Elements in the Ring along with Te and N Atoms

Heterocycles Containing Other Elements in the Ring along with Te and N Atoms 

The only known representative of this type of compound, 91, was prepared by 1,3-dipolar addition of mesityl nitrile oxide to telluroketone 85 (93JA7019 94MI1). The reaction proceeds smoothly on heating equimolar amounts of the reactants at 80°C, giving rise to 91 in 70% yield. The heterocycle is a thermally unstable and light-sensitive compound. Thermolysis of a deuterochloroform solution of 91 at 60-90°C in a sealed ampule affords 1,1,3,3-tetramethylindanone and mesityl isonitrile (94M11). 

Sulfur and selenium analogues of 91 are also susceptible of this type of rearrangement. Its rate is defined by the strength of the C-chalcogen bonds in 91 and analogues and was found to increase in the order of S Se Te (94MI1). 

The structure of 91 was studied by X-ray (94M11). The five-member heterocycle is planar. The valence angle (79.4°) has the lowest value for all known five-member tellurium-containing heterocycles. 

3-Di(trifluoromethyl)-5-(4-methylphenyl)-A-1,2,4-thiotellurazoline 92 was obtained in 15% yield on heating 2/7-1,3-thiazete with SbaTes (79CC80). In2To3 can be used in this reaction instead of Sb2Tc3, but the yield of 92 decreases. 

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