We know that aldose aldehydes are susceptible to the same nucleophilic addition reactions that we learned in carbonyl chemistry. Let's now learn a reaction that involves the formation of a cyanohydrin. The neat thing about this reaction is that the cyano group can then be reduced and hydrolyzed to form a new, chain-lengthened aldehyde.
The original Kiliani-Fischer synthesis required two additional steps after cyanohydrin addition, and resulted in poor yields. However, an improved reducing agent, (H2, Pd/BaSO4), was developed to form imines instead of amines.
Ready for a practice problem?
Predict the product(s) for the following reaction. Provide the mechanism of the imine hydrolysis step if required.