Synthesis of Cp-Re complexes via olefinic C-H activation and successive formation of cyclopentadienes

Treatment of an α,β-unsaturated ketimine with an α,β-unsaturated carbonyl compound in the presence of a rhenium complex, Re₂(CO)₁₀, gave a cyclopentadienyl-rhenium complex. This reaction proceeds via rhenium-catalyzed C-H bond activation of an olefinic C-H bond, insertion of an α,β-unsaturated carbonyl compound into a Re-C bond of the alkenylrhenium intermediate, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline to give a cyclopentadiene derivative, followed by the formation of a cyclopentadienyl-rhenium complex from the cyclopentadiene derivative and the rhenium complex.