Synthesis of azacrown macrocycles and related compounds by a crablike cyclization method: A short review

This paper summarizes the application of bis(alpha-chloroamide)s for the pr eparation of azamacrocyclic ligands. Bis(alpha-chloroamide)s look like crab s with two reactive claws so the method is called the crablike cyclization reaction. This cyclization strategy-has been used;to,prepare many different types of macrocyclic compounds over the past 10 years including cyclens, c yclams, perazamacrocycles, diazadithiamacrocycles, and some cage compounds. The method is particularly valuable where no other method will work. In ge neral, the crablike cyclization reaction produces the macrocyclic diamides in 40-70% yields.