Hydrogen-bond-induced selectivity of a head-to-head photo-dimerisation of dialkynylanthracene - access to tetradentate Lewis acids

Using 2-hydroxypropyl-protecting groups, 1,8-dialkynylanthracene photo-dimers were prepared in head-to-head-configuration by UV irradiation on a multi-gram scale. In non-polar solvents, the combination of non-covalent hydrogen bonds and pi-pi-interactions induces the formation of the syn-isomer in up to 85% yield. Instead, more polar solvents or irradiation of unprotected 1,8-diethynylanthracene led to formation of the corresponding anti-isomer in large excess. Cleavage of the protecting groups under basic conditions affords a rigid hydrocarbon skeleton with four directional functions. This was used as a building block for a tetradentate boron Lewis acid. Its applicability as a host for Lewis-base substrates was demonstrated by the formation of adducts with various nitrogen bases. Adduct formation with hydrazine leads to impressive networks between the tetraboron host and the substrate molecules.

Automated summary

In this study, 1,8-dialkynylanthracene photo-dimers were prepared in head-to-head configuration using 2-hydroxypropyl-protecting groups and demonstrated their applicability as a building block for a tetradentate boron Lewis acid. The formation of adducts with various nitrogen bases showed the potential of the compound as a host for Lewis-base substrates, with impressive networks formed between the tetraboron host and the substrate molecules in the case of adduct formation with hydrazine.