SYNTHESIS OF STABLE ATЕ-COMPLEXES OF HETEROAROMATIC BORONIC ACIDS AND 4,6,10-TRIHYDROXY-1,4,6,10-TETRAAZAADAMANTANE

In this article synthesis of stable ate complexes of heteroaromatic boronic acids and 4,6,10-trihydroxy-1,4,6,10-tetraazaadamantane is described. Ate complexes that have betaine structure were prepared by reaction of tris(β-oximinomethyl)amine with 3-pyridinylboronic and 2-thienylboronic acids. Modification of this method consists in usage of alkali metal carbonates as an additional base. This improvement makes it possible to synthesize ate complexes of 3-thienylboronic and 2-furanylboronic acids which are resistant to air-moisture and have improved thermal stability. All substances were synthesized with nearly quantitative yields and characterized by 1H, 13С (DEPT 135) and 11B NMR spectroscopy; elemental analysis and HRMS. According to spectral data, all ate complexes have cage structure and do not have any traces of free heterocyclic boronic acids in NMR spectra. In this article we also demonstrate that such stable ate complexes can be used for covalent immobilization of heterocyclic boronic acids on polymeric matrix. On the first stage polystyrene that contains 4-(benzyloxy)benzyl bromide residues was modified by 4,6,10- tetraazaadamntane fragments. Then, derived material was treated with 3-thienylboronic acid. Novel polymer contains boronic acid in the form of covalently bound ate complex. This polymer has 40% loading according to elemental analysis. We confirmed presence of covalently bound residues of 3-thienylboronic acid and diamantane fragments by comparison of experimental and calculated FTIR spectra. Such polymers can be used for separation of boronic acids from reaction mixtures and in solid phase synthesis.