ALIPHATIC CLAISEN REARRANGEMENT PROMOTED BY ORGANOALUMINIUM REAGENTS.

Abstract

Organoaluminium compounds, R//3Al, 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 Me//3Al (1. 0 M, 2. 2 equiv) in CH//2ClCH//2Cl at 25 degree C afforded 5-decen-2-ol (91% yield, E/Z equals 47/53), which was produced by the left bracket 3,3 right bracket sigmatropic rearrangement and successive methylation. The rearrangements with alkynylation, alkenylation, and hydrogenation are also achieved. The regular Claisen rearrangement products, of gamma , delta -unsaturated aldehydes (ketones), are obtained at 25 degree C in good to excellent yields with Et//2AlSPh (2. 5 equiv) or the combination of Et//2AlCl (2. 0 euiv) and PPh//3 (2. 2 equiv).