1,8,10-Trisubstituted anthracenyl hydrocarbons: Towards versatile scaffolds for multiple-H-bonded recognition arrays

In this work, we describe the synthesis of 1,8,10-trisubstituted anthracenyl scaffolds that, bearing boronic acid functionalities, can act as multiple H-bonding donor systems. The trisubstituted anthracenyl derivatives are synthesized following two main synthetic pathways. Whereas in the first approach trisubstituted anthracenyl derivatives are prepared through the regioselective addition of the relevant organomagnesium nucleophile to 1,8-dichloroanthraquinone, in the second avenue a triflate-bearing anthracene is prepared by reduction of the anthraquinone into the anthrone precursor and functionalized through metal-catalysed cross-coupling reactions. Complementary studies of the Na₂S₂O₄-mediated reduction of 1,8-dichloroanthraquinone allowed to shed further light on the possible mechanism of formation of the anthrone precursor, suggesting the presence of a cis-diol intermediate undergoing antiperiplanar elimination. Solid-state X-ray diffraction investigations of the bisboronic acids show that the molecules self-assemble into dimers through the formation of four H-bonds established between the anti-syn conformers of the boronic acid moieties. ¹H-NMR titrations between bisboronic acids and tetra H-bond acceptor, diisoquinolino-naphthyridine, showed a significant shift of the -B(OH)₂ proton resonances, suggesting the presence of H-bonding interactions between both molecules.