Ester reduction
Abstract
The reduction of esters into the corresponding primary alcohols requires a powerful hydride (typically, LiAlH4), owing to the reduced electrophilicity of the carbonyl carbon caused by resonance donation from the adjacent oxygen atom.
Keywords
Ester, Reduction, Primary alcohol
Category
Ester
Mechanism
Here, LiAlH4 acts as a hydride donor. The first hydride attacks the electrophilic carbonyl carbon, breaking the C=O bond and transferring the electron pair to the oxygen atom, which becomes an alkoxide coordinated to the metal center. The resulting tetrahedral intermediate then collapses with departure of the alkoxide, generating an aldehyde intermediate. This aldehyde is immediately reduced by a second hydride delivery, breaking the C=O bond and giving a second aluminium alkoxide intermediate. Finally, the metal alkoxide is hydrolyzed during acidic aqueous workup, releasing the primary alcohol and aluminium hydroxide as by-product.
