Synthesis of propranolol

Propranolol is a β-blocker, one of the most widely used drugs against hypertension and angina. Its 1-amino-2-propanol chain can be built with the Henry reaction: nitromethane adds to 2-(1-naphthyloxy)acetaldehyde to form the nitro alcohol; hydrogenation reduces the nitro group to the amine, and reductive amination with acetone introduces the isopropyl group.

With chiral catalysts, such as Shibasaki’s lanthanum–BINOL complexes, the Henry reaction is enantioselective and gives (S)-propranolol, the active enantiomer, directly.