Boron Macrocycles Based on Multicomponent Assemblies using (3‐Aminophenyl)boronic Acid and Pentaerythritol as Common Reagents; Molecular Receptors toward Lewis Bases

Four cyclic boronate esters were synthesized by using a multicomponent reaction from (3‐aminophenyl)boronic acid, pentaerythritol, and aldehyde derivatives [isophthalaldehyde ( 1 ), dialdehyde A ( 2 ), (3‐formylphenyl)boronic acid ( 3 ), and (2,4‐difluoro‐3‐formylphenyl)boronic acid ( 4 )]. All four reactions lead to the formation of macrocyclic compounds in good yields of more than 70 %. The cavities of the compounds consist of 29‐, 30‐ and 40‐membered rings, and the macrocyclic structures contain two ( 2 ) and four ( 1 and 3 – 4 ) boron atoms as Lewis acids. Additionally, the molecules contain eight ( 1 ) and six ( 2 – 4 ) donor atoms (N,O) within the macrocyclic structure, thus constituting a ditopic cavity. X‐ray analysis of 2 and 3 revealed the whole conformation within the trigonal planar geometry for the boron atoms and the inclusion of neutral guest molecules, chloroform for 2 and benzene for 3 . Titration of the receptors with triethylamine, pyridine, and tetrabutylammonium fluoride show that the Lewis acids are available for interaction with Lewis bases. The interaction was follow by 11 B NMR and UV/Vis spectroscopy.