An effective self-templating ring closure method for mixed donor thiophene-based macrocycles

The synthesis via the Mannich reaction of a series of 14- and 15-membered ring mixed donor thiophene-containing macrocycles is reported. The macrocycles each incorporate two oxygen and two nitrogen donor atoms and were obtained in high yields without any requirement for high dilution techniques or metal ion templates. The compounds can be purified by simple recrystallisation. The crystal structure of the 15-membered ring macrocycle C29H32N2O2S2 (4b) has been determined. The structure shows that the bulky benzyl substituents have a major effect on the macrocyclic ring geometry.