Macrocycles, adducts and monomeric boron compounds derived from 2,6-dimethanolpyridine and arylboronic acids

Abstract The reaction of 2,6-dimethanolpyridine with arylboronic acids at room temperature led to the formation of tetrameric compounds 1a – 1e in good yields. Since the tetrameric derivatives were insoluble in common organic solvents, their characterization was based on IR, mass spectrometry, as well as 13 C and 11 B NMR, in the solid state. Macrocyclic compounds 1a – 1e can be hydrolyzed upon heating in DMSO to give adducts 2a – 2e , which are only held by a coordination bond between the nitrogen and boron atoms, as demonstrated by 1 H, 13 C and 11 B NMR, in solution. Moreover, the presence of an additional carbon atom in the aliphatic chain of the ligand, as in the case of 2,6(β-diethanolamine)pyridine, leads exclusively to the formation of the monomeric specie 4 , as established by X-ray diffraction analysis.