This indicates, not only the hydrogen on aluminium but also the β-hydrogen on isobutyl groups participates in the reduction. But the double bond is intact during the reduction. ... Thus DIBAL-H is the reagent of choice for the reduction of α,β-unsaturated carbonyl compounds to allylic alcohols.

Which groups does DIBAL-H reduce?

What it's used for: DIBAL is a strong, bulky reducing agent. It's most useful for the reduction of esters to aldehydes. Unlike lithium aluminum hydride, it will not reduce the aldehyde further if only one equivalent is added. It will also reduce other carbonyl compounds such as amides, aldehydes, ketones, and nitriles.

What does DIBAL-H not reduce?

H cannot reduce: amides, acids, isocyanides and nitro groups.