Ester reduction into aldehyde
Abstract
The reduction of an ester to an aldehyde is most commonly achieved using DIBAL-H (diisobutylaluminum hydride) under carefully controlled conditions, typically at −78 °C. The selectivity of this transformation relies on the formation of a stable, aluminum-coordinated intermediate that prevents over-reduction.
Keywords
Ester, Reduction, Aldehyde
Category
Ester
Mechanism
First, a hydride from DIBAL-H attacks the electrophilic carbonyl carbon of the ester. This breaks the 𝜋 bond of the C=O group and transfers the electron density onto the oxygen atom, generating a tetrahedral alkoxide intermediate coordinated to the aluminum center. At low temperature and with controlled stoichiometry (typically one equivalent of DIBAL-H), this tetrahedral intermediate does not collapse immediately and no second hydride transfer occurs. Upon aqueous acidic workup, the intermediate collapses: the alkoxy group is eliminated, and the aluminum–oxygen bonds are cleaved, releasing the corresponding aldehyde.
