Atom-economic catalytic amide synthesis from amines and carboxylic acids activated in situ with acetylenes
Amide bond formation is one of the most frequently used transformations in organic chemistry. The most desirable amide synthesis, a direct condensation of carboxylic acids with amines, is hindered by the intrinsic acid–base reactivity of the starting materials. The thermal amide bond formation from the ammonium carboxylate salts requires high temperatures, which can be lowered by Lewis acids or boronic acid derivatives. However, even the best known systems are limited to a narrow range of amines and require scavenging the reaction water, for example, by large amounts of molecular sieves.