Titanacyclobutenes, readily prepared from Cp2TiCH2·Al(CH3)2Cl and alkynes, react with ketones and aldehydes to afford metallacyclic products resulting from insertion into either the titanium-alkyl or the titanium-vinyl bond of the titanacyclobutene. The latter insertion products are thermally unstable, undergoing facile retro [4+2] cycloaddition to afford substituted 1,3-dienes in good yield.