Stephen Reaction

Overall Reaction:
$$\text{R--C}\equiv\text{N} + \text{SnCl}_2 + 2\text{HCl} \xrightarrow{\text{Dry Ether}} [\text{R--CH=NH}\cdot\text{HCl}] \xrightarrow{\text{H}_3\text{O}^+} \text{R--CHO} + \text{NH}_4\text{Cl}$$

Intermediate:
$$\text{Aldimine Hydrochloride Salt } ([\text{R--CH=NH}_2]^+\text{Cl}^-)$$

Concept: Conversion of a nitrile into an aldehyde by selective reduction using stannous chloride in an acidic medium, forming an intermediate imine salt that readily undergoes acid-catalyzed hydrolysis.