Asymmetric Hydroamination and Reductive Amination in Total Synthesis

Abstract

Asymmetric hydroamination (AHA) and asymmetric reductive amination (ARA) are one of the most popular strategies for enantioselective synthesis of chiral amines, which are very important from a synthetic and a biological point of view. The addition of the NH bond across an unsaturated CC bond is known as hydroamination. AHA is ideal for industrial processes as it is a 100% atom‐economic reaction and involves readily available substrates. For broadening its scope for a variety of substrates, many metal‐based as well as metal‐free catalytic systems have been developed for asymmetric hydroamination. Along with the synthesis of functionalized chiral amines, AHA has served as a key strategy in the synthesis of the core of various natural products like codeine, pseudodistomin, swainsonine and of drugs like pentazocine. Reductive amination is a widely used efficient synthetic protocol to install an amine group in place of a carbonyl group in an organic compound. The reaction proceeds through the formation of imine and subsequent one‐pot reduction of it to give the product amine. Use of a metal‐chiral ligand combination, chiral Brønsted acid or chiral organocatalyst, or chiral auxiliary in the reaction can give rise to chiral amine products that are often valuable synthetic intermediates en route to many drugs and natural products. Application of these protocols in the total synthesis of drugs and natural products will be discussed along with some experimental procedures.