Insertion of Carbon–Heteroatom Multiple Bonds into Bis(η5-cyclopentadienyl)titanacyclobutenes

Titanacyclobutenes that are readily produced by the reaction of Tebbe reagent with disubstituted acetylenes react with a variety of heteroatom multiple bonds. The reaction with aldehydes and ketones is particularly clean and has been studied mechanistically. The aldehyde or ketone carbonyl oxygen coordinates to the titanium center in a preequilibrium step before ring expansion to the product metallaoxacyclohexenes.