Tebbe reagent alkene synthesis

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. ... 

Both the Tebbe and Petasis reagents, Cp2CH2ClAlMe2 and Cp2TiMe2, effect the direct conversion of alkenic esters to dihydropyrans. This olefin metathesis has been successfully applied to the synthesis of complex polyether frameworks <96JA1565,96JA10335>. 

In Section 10-2-2, we discussed the synthesis of Tebbe s reagent, a bridged Ti methylidene complex. This reagent converts a C=0 group to an alkene in a manner analogous to that of a phosphorus ylide (Wittig reagent).56 Conversion of a carbonyl to a terminal alkene may seem to be of limited utility until one realizes that, unlike phosphorus ylides that react only with aldehydes and ketones, Tebbe s... 

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