Aliphatic Claisen Rearrangement Promoted by Organoaluminium Reagents

Organoaluminium compounds, R3Al, promote the Claisen rearrangement of allyl vinyl ether derivatives at room temperature under transfer of R or H as a nucleophile to the aldehydic carbon. Treatment of 1-butyl-2-propenyl vinyl ether with a hexane solution of Me3Al (1.0 M, 2.2 equiv) in CH2ClCH2Cl at 25 °C afforded 5-decen-2-ol (91% yield, E⁄Z=47⁄53), which was produced by the [3,3] sigmatropic rearrangement and successive methylation. The rearrangements with alkynylation, alkenylation, and hydrogenation are also achieved. The regular Claisen rearrangement products, or γ,δ-unsaturated aldehydes (ketones), are obtained at 25 °C in good to excellent yields with Et2AlSPh (2.5 equiv) or the combination of Et2AlCl (2.0 equiv) and PPh3 (2.2 equiv).