Gekruiste aldolreactie met behulp van sterke basen: gerichte aldolreactie

The crossed aldol reaction between an aldehyde and a ketone – both containing an alpha-hydrogen, in aqueous sodium hydroxide forms a mixture of products.

Alternatively, a strong base like lithium diisopropylamide, abbreviated as LDA, minimizes the number of products.

The slow, dropwise addition of a ketone to the LDA solution irreversibly generates a ketone enolate.

Next, with the slow addition of the aldehyde to this solution, the nucleophilic addition of the ketone enolate to the carbonyl group of the aldehyde produces a single crossed aldol product. This is called a directed aldol addition reaction.

In unsymmetrical ketones, LDA preferentially deprotonates at the less-substituted carbon to form the kinetic enolate.