Alkylation of enolates
Description: Enolates of carbonyl compounds will react with alkyl halides in SN2 reactions to give alkylation products. [private_ReactionGuide]
Notes: Enolates are excellent nucleophiles and this is an important way of making C–C bonds.
Notes: Example 1 shows a deprotonation and alkylation of a diketone. Note that the central carbon is more acidic due to the fact that the enolate will be doubly stabilized by resonance. Example 2 shows how this process can be repeated to add a second alkyl group. Example 3 shows this process with a beta-keto ester. Example 4 shows how LDA can be used as a base for this process with ketones. LDA is an extremely bulky base which leads to formation of the less-substituted enolate.
Mechanism: Removal of a proton from the ketone with strong base (Step 1, arrows A and B) results in an enolate, which then attacks the alkyl halide in an SN2 reaction (Step 2, arrows C and D) to form the alkylated product.