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

摘要

The reaction of 2,6-dimethanolpyridine with arylboronic acids at room temperature led to the formation of tetrameric compounds la-le in good yields. Since the tetrameric derivatives were insoluble in common organic solvents, their characterization was based on IR, mass spectrometry, as well as C-13 and -B-11 NMR, in the solid state. Macrocyclic compounds la-le 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 H-1, C-13 and B-11 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(beta-diethanolamine)pyridine, leads exclusively to the formation of the monomeric specie 4, as established by X-ray diffraction analysis. (c) 2005 Elsevier B.V. All rights reserved.