2-Bromotellurenylbenzaldehyde, reaction with ammonia

To date, only the parent benzoisotellurazole 9 has been obtained. For its synthesis, methods similar to those used for the preparation of benzoisothiazole andben-zoisoselenazole were employed. The reaction of 2-bromotellurenylbenzaldehyde with ammonia affords 9 in 74% yield, whereas cyclization of the oxime of o-butyltellurobenzaldehyde catalyzed by PPA gives 9 in 40% yield (78JHC865). In contrast to the reaction of 2-bromoselenenylacetophenone with ammonia, which leads to 3-methylbenzoisoselenazole (73JHC267), 2-bromotellurenylacetophe-none reacts with ammonia to give telluroindoxyl (78JHC865). 

Bromotellurenylbenzaldehyde (or its oxime) serves as the precursors to another tellurium-containing heterocyclic system, namely benzoisotellurazole 34 (78JHC865). The reaction of the aldehyde with ammonia proceeds through the formation of imine 35 followed by its dehydrobromination. The cyclization reaction of oxime 36 is catalyzed by polyphosphorous acid (Scheme 19). 

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