Dimethylaluminum Chloride Catalyzed Ene Reactions of Aldehydes

Abstract

Dimethylaluminum chloride, which is a mild Lewis acid and a proton scavenger, catalyzes the ene reactions of aliphatic and aromatic aldehydes with alkenes containing a disubstituted vinylic carbon. Proton-initiated rearrangements do not occur, since the alcohol-Lewis acid complex formed in the one reaction reacts rapidly to give methane and a nonacidic aluminum alkoxide. Formaldehyde and excess Me2AlCl give good yields of ene adducts with all types of alkenes. With 1 equiv of Me2AlCl, formaldehyde and mono- and 1,2-disubstituted alkenes give γ-chloro alcohols resulting from cis addition of chlorine and hydroxymethyl groups to the double bond. © 1982, American Chemical Society. All rights reserved.