Low symmetry and functionalised organic cages prepared using Eglinton and Sonogashira coupling reactions

Abstract

Cages prepared using irreversible reactions in the cage-forming step typically give relatively low yields, but are more robust than cages formed through reversible bond formation reactions. The irreversible reactions are also well-suited to preparing functionalised and/or low symmetry species that are difficult to prepare using self–assembly. In this work, we prepare two hexanitrile-functionalised cages and a hexabromo-functionalised cage using Eglinton coupling reactions, with both hexanitrile-functionalised cages structurally characterised by X-ray crystallography. Yields for the functionalised cages (3–28%) were significantly lower than those previously reported for analogous unfunctionalised cages. We also prepared three cages using Sonogashira coupling reactions, including a tri-nitrile functionalised lower symmetry cage. Unfortunately, these reactions also suffered from low yields (3–11%), with the reaction to give the functionalised cage particularly low-yielding (3%). While the low yields meant we were unable to obtain sufficient amounts of compounds to measure their gas sorption properties, we were able to demonstrate that a hexanitrile cage could be post-synthetically modified to give a hexa-amidinium species.