Tebbe reagent enol ether synthesis

The carbonyl group of an ester function can be converted to the corresponding methylene compound using Tebbe s reagent. The reaction can thus be considered as a general method of enol ether synthesis. An example of this reaction is given in Scheme 5. The same conversion can be achieved by reagents prepared from the reduction of 1,1-dibromoalkanes with zinc and TiCU in the presence of TMEDA. °... 

Scheme 21. Titanium-mediated metathesis strategy for the synthesis of cyclic enol ethers and hydroxy olefins, (a) Tebbe reagent (93), THF, reflux, 41% (140), 41% (143) (b) Petasis reagent (110), THF, reflux, 60% (141), 30% (144) (Nicolaou et al.) [34a]...

The enantioselective total synthesis of the cyclooctanoid natural product (+)-epoxydictymene was accomplished in the laboratory of L.A. Paquette. The entire tricyclic framework was constructed by the application of a Claisen rerrangement via a chairlike transition state. The precursor for this / 3,37-sigmatropic rearrangement was obtained by treating a lactone precursor with the solution of the Tebbe reagent in the presence of pyridine. The corresponding enol ether was formed in almost quantitative yield, and immediately after isolation it was treated with triisobutylaluminum to effect the Claisen rearrangement. 

In the synthesis of (-i-)-laurencin, Holmes used Tebbe reagent converted ester to alkene in 71% yield. Nicolaou developed a novel method for direct conversion of olefinic ester to cyclic enol ethers with Tebbe reagent. ... 

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