Synthesis of enones and cyclopropanes from bis oxoalkyl tellurium dichlorides

10 Synthesis of enones and cyclopropanes from bis(oxoalkyl)tellurium dichlorides 

The sequential treatment of bis(2-oxomethyl)tellurium dichlorides with 2 equiv of LDA in THF at -78°C and 2 equiv of an aldehyde, followed by heating at 25°C, affords the enones with E geometry in good yields. The same reaction performed with methyl vinyl ketone gives rise to the cyclopropane.  

These reactions involve the intermediacy of a bis-ylide which undergoes a Wittig-type reaction with aldehydes or a Michael 1,4-addition to the enone. 

Moreover, if R is an aryl or t-butyl group, by warming at room temperature after the treatment with LDA at -78°C, triacyl-substituted cyclopropanes are formed via a Michael addition involving the intermediates bis-ylide and bis-acylethylene.  

By treatment with dialkylcuprates, telluroesters are easily converted into ketones in high yields. 

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