Semi-and non-stabilized telluronium ylides

In sharp contrast to the olefmation reaction employing stabilized telluronium ylides, semi-and non-stabilized ylides react with carbonyl compounds to give epoxides (like non-stabilized sulphonium and selenonium ylides). 

Moderate to good yields of a,j8-unsaturated epoxides are obtained, allowing aromatic and aliphatic aldehydes to react with dialkyltelluronium allylide (the dusobutyl derivatives are the reagents of choice).  

Ar= Ph and (methyl, alkoxy, halo, nitro) derivatives, 3-pyridyl, 1-naphthyl, 4-cyclohexenyl, cyclohexyl (55-94 %) 

The moderate c/x-selectivity, observed for aromatic and aliphatic aldehydes, decreases if an NOj group or ort/to-substituents are linked to the aromatic ring. 

Reaction of telluronium allylides with aldehydes (typical procedure)  

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