Aldehydes reaction with Petasis reagent

Dimethyltitanocene (213), called the Petasis reagent, can be used for alkenation of carbonyls (aldehydes, ketones, esters, thioesters and lactones). This reagent is prepared more easily than the Tebbe reagent by the reaction of titanocene dichloride with MeLi. However, this reagent may not be a carbene complex and its reaction may be explained as a nucleophilic attack of the methyl group at the carbonyl [67], Alkenylsilanes are prepared from carbonyl compounds. Tri(trimethylsilyl)titanacyclobutene (216), as a... 

The Petasis reagent (Me2TiCp2, dimethyltitanocene) undergoes similar olefi-nation reactions with ketones and aldehydes. The originally proposed mechanism [3] was very different from that of Tebbe olefmation. However, later experimental data seem to suggest that both Petasis and Tebbe olefmation share the same mechanism, i.e. the carbene mechanism involving a four-membered titanium oxide ring intermediate [6]. 

The Petasis reagent (Me2TiCp2, dimethyltitanocene) undergoes similar olefination reactions with ketones and aldehydes [5]. However, the mechanism is very different. 

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