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Please login to access the full content or check if you have access via Method 7: Titanacyclobutanes from Tebbe's Reagent

DOI: 10.1055/sos-SD-002-00576

Mikami, K.; Matsumoto, Y.; Shiono, T.Science of Synthesis, (20032549.

Titanocene metallacyclobutanes are of interest for the methylenation of carbonyl compounds and the ring-opening metathesis polymerization of cyclic alkenes.[‌337‌] The substitution reactions of titanocene metallacyclobutanes proceed by an initial rate-determining cleavage to a methylidene alkenetitanocene complex, which can then rapidly react with the substrate. Ligand-exchange reactions of titanacyclobutane with alkenes or alkynes afford other titanacyclobutanes or titanacyclobutenes, respectively. Complex 212 reacts with allyl chloride to give the but-3-enyl complex 214, and with benzyl chloride to give 215 (Scheme 105). The formation of these products is explained if titaniumcarbene complex 213 is postulated as the intermediate.[‌1‌] Titanacyclobutenes 216 react with a variety of heteroatom multiple bonds. The aldehyde or ketone carbonyl oxygen coordinates to the titanium center in a pre-equilibrium step before ring expansion to the product metallaoxacyclohexanes 217 (Scheme 105).[‌338‌]

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