Tellurium Oxides as Catalysts for Organic Reactions

Diaryl Tellurium Oxides as Catalysts for Organic Reactions 

Several substituted diphenyl tellurium oxides were investigated as catalysts for the aldol condensation between benzaldehyde and tetralone. High catalytic activity is associated with electron-donating substituents in the phenyl rings. Methyl phenyl tellurium oxide had very low catalytic activity  

The smooth condensation of 2,2 -diacetylbiphenyl to dibenzotropone in the presence of bis[4-methoxyphenyl] tellurium oxide is remarkable in view of previous unsuccessful attempts to effect this cyclization with conventional aldol catalysts. Diaryl telluroxides are poor catalysts for aldol condensations involving acidic methylene groups, because formation of tellurium ylides removes the catalyst.  

Diaryl tellurium oxides were found to be effective catalysts for the preparation of benzylidenearenesulfonimides from benzaldehydes and arenesulfonamides.  

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