Esters are reduced to aldehydes with diisobutylaluminum hydride (DIBAL) at -78°C. A single equivalent must be used to stop the reaction in the aldehyde, avoiding its reduction to alcohol.

dibal-reduction

The DIBAL has the following structure:

dibal-reduction

Reaction Mechanism:

dibal-reduction

Cyclic esters (lactones) reduce with DIBAL to give molecules with aldehyde and alcohol groups.

dibal-reduction