Scope and diastereoselectivity of the "interrupted" Feist-Bénary reaction.

[reaction: see text] The base-promoted condensation of beta-dicarbonyl compounds with alpha-haloketones, the Feist-Bénary reaction, conveniently produces highly substituted dihydrofurans. We show here that this reaction is quite general with respect to the nature of the beta-dicarbonyl compound, proceeding with beta-ketoesters, beta-oxopropionates, beta-diketones, and beta-dialdehydes. We also show that the diastereoselectivity of this reaction depends on the acidity of the nucleophile.