Cyanohydrin reaction

In organic chemistry, a cyanohydrin reaction is an organic reaction in which an aldehyde (−CH=O) or ketone (>C=O) reacts with a cyanide anion (N≡C−) or a nitrile (−C≡N) to form a cyanohydrin (>C(OH)C≡N).

With aromatic aldehydes such as benzaldehyde, the benzoin condensation is a competing reaction.

The reaction is used in carbohydrate chemistry as a chain extension method for example that of D-xylose.

The asymmetric cyanohydrin reaction of benzaldehyde with trimethylsilylcyanide is made possible by employment of (R)-Binol[1] at 1–10% catalyst loading.

The chemist Urech in 1872 was the first to synthesize cyanohydrins from ketones with alkali cyanides and acetic acid[2] and therefore this reaction also goes by the name of Urech cyanohydrin method.

Reaction of acetone with sodium cyanide to hydroxyacetonitrile
Reaction of benzoquinone with trimethylsilylcyanide, catalyst KCN is introduced as a 1:1 complex with the Crown ether 18-crown-6
Mechanism of the cyanohydrin reaction
Mechanism of the cyanohydrin reaction
Asymmetric reaction of benzaldehyde with (R)–Binol–lithium(i-propyloxy) gives (S)-acetonitrile with 98% ee
Asymmetric reaction of benzaldehyde with (R)– Binol –lithium(i-propyloxy) gives (S)-acetonitrile with 98% ee