Caesium carbonate as a highly efficient catalyst for the synthesis of macrocyclic diamides

In this research work, we report the synthesis of macrocyclic diamides from the reaction of diesters and aliphatic diamines in the presence of caesium carbonate. It has been demonstrated that among the carbonate of alkali metals (Li2CO3, Na2CO3, K2CO3 and CS2CO3), CS2CO3 appear to be the best catalyst for macrocyclization. Diesters with different substitution patterns on the aromatic ring reacted smoothly with diamines under optimal conditions, affording the corresponding macrocycles in high yields. Introducing a rigid group (e.g., sulfone) on the substrate led to somewhat decreased yield. Various substrates proved to be suitable for this macrocyclization reaction, especially, the flexible ones.