Chapter 13: Green Catalytic Direct Amide Bond Formation

The amide functionality (–CONHR–) constitutes the backbone of all biologically essential peptides, as well as a wide range of natural products. Hence, they are employed widely in the pharmaceutical industry as a key component of the majority of bioactive compounds. The formation of amide bonds holds a keystone position in organic chemistry. Over the past century, a wide range of methods for accomplishing amide formation have been developed, the vast majority of which are non-atom economic and involve the use high energy activating agents, or other toxic and reactive reagents. Driven by concerns about the associated waste and expense of these processes, it is highly desirable to replace current processes by environmentally benign, catalytic processes of high atom economy. To meet this synthetic challenge, several new catalytic systems have been developed in recent years involving the direct reaction of a carboxylic acid and amine to form an amide with water as the only by-product. In this chapter, state-of-the-art catalytic direct amide formation systems, particularly involving boric acid and boronic acid-based systems are reviewed including some examples of their range of application.