β-Hydroxyesters via Crossed Aldol Addition: Reformatsky Reaction

Reformatsky reaction involves the oxidative addition of zinc to the carbonyl oxygen of alpha-bromoester to form a zinc enolate, as depicted in Figure 1. The zinc enolate formed is also referred to as the Reformatsky reagent.

Figure 1. The formation of the Reformatsky reagent

Subsequently, as shown in Figure 2, the zinc enolate attacks the carbonyl group of the aldehyde or ketone to form zinc alkoxide.

Figure 2. The reaction between the zinc enolate and carbonyl group

The zinc oxide gets further protonated to yield the β hydroxyester as the final product. This is illustrated in Figure 3.

Figure 3. The formation of the beta-hydroxyester

Here, the reaction of zinc enolate with the ester does not occur.