Petasis reagent

The Petasis reagent (not to be confused with the Petasis reaction) is dimethyl titanocene, Cp2TiMe2, readily prepared by the reaction of methylmagnesium chloride or methyllithium with titanocene dichloride. It is used for transforming carbonyl groups to terminal alkenes, much like the Tebbe reagent or Wittig reaction. Unlike the Wittig reaction, the Petasis reagent can react with a wide range of carbonyls, including aldehydes, ketones and esters. The Petasis reagent is also more air stable than the Tebbe reagent, and can be isolated as a pure solid, or used directly as a solution in toluene-THF.

The active olefinating reagent, Cp2TiCH2, is prepared by heating the Petasis reagent in toluene or THF to 60 °C.