Hydroboration-Oxidation (Anti-Markovnikov Hydration)

$$\text{R--C}\equiv\text{CH} \xrightarrow{1) \, \text{R}_2\text{BH / THF} \quad 2) \, \text{H}_2\text{O}_2 / \text{OH}^-} [\text{R--CH=CH--OH}] \xrightarrow{\text{Tautomerism}} \text{R--CH}_2\text{--CHO}$$

Concept: Sterically hindered organoboranes like disiamylborane ($$\text{Sia}_2\text{BH}$$) are used to stop the reaction at the mono-addition stage. Tautomerism of the resulting anti-Markovnikov enol selectively forms an aldehyde.