Rhenium-catalyzed synthesis of stereodefined cyclopentenes from β-ketoesters and aliphatic allenes

(Chemical Equation Presented) Come on allene: Commercially available [Re₂(CO)₁₀] as a catalyst provides five-membered carbocycles in moderate to excellent yields with high stereoselectivity (see scheme). The configuration at each of the three sp³ carbon centers of the ring is defined. The reaction proceeds at the β, γ, and adjacent methylene positions of the allene; previously, similar reactions usually occurred at the α, β, and γ positions of the allene.