Formula C12H16Ti | Molar mass 208.13 g/mol | |
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The Petasis reagent is an organotitanium compound with the formula Cp2Ti(CH3)2. It is an orange-colored solid.
Preparation and use
It prepared by the salt metathesis reaction of methylmagnesium chloride or methyllithium with titanocene dichloride:
Cp2TiCl2 + 2 CH3MgCl → Cp2Ti(CH3)2 + 2 MgCl2The compound is used for transforming carbonyl groups to terminal alkenes. In terms of reactivity, it resembles the Tebbe reagent and 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 is commonly used directly as a solution in toluene THF.
The reaction mechanism is very similar to that of the Tebbe reagent. The active olefinating reagent, Cp2TiCH2, is generated in situ upon heating the solution of Petasis reagent in toluene or THF to 60 °C. With the organic carbonyl, this titanium carbene forms a four membered oxatitanacyclobutane that releases the terminal alkene.