14.28 : ニトリルからアミンへ: LiAlH_4 の還元

Nitriles react with strong reducing agents like lithium aluminum hydride through a typical nucleophilic acyl substitution to form primary amines.

The reaction requires two equivalents of the reducing agent, which act as a source of hydride ions.

The mechanism begins with a nucleophilic attack by the hydride ion at the nitrile carbon, forming an imine anion.

Next, the imine anion is attacked by another equivalent of the hydride ion, generating a dianion.

Lastly, protonation with water gives a primary amine as the final product.

Unlike lithium aluminum hydride reduction, nitriles react with one equivalent of a milder reducing agent like diisobutylaluminum hydride, followed by hydrolysis to yield an aldehyde.