A chiral auxiliary approach to the synthesis of mechanically planar-chiral rotaxanes

Abstract

Rotaxanes are a class of compounds composed of two or more mechanically interlocked molecules. Mechanically planar chiral rotaxanes are a novel class of compound in that their chirality is due to the isomerism of a mechanical bond, as opposed to the covalent bonding of the individual components. We know of no method to synthesise enantiomerically pure samples of the mechanical isomers of a mechanically planar chiral rotaxane without resorting to advanced purification techniques. The lack of ready availability of these materials has hampered the full investigation of their properties and applications. Of particular interest are their properties as chiral reaction-spaces, such as ligands, organo-catalysts, and chiral resolution agents. This thesis addresses these issues by developing a chiral-auxiliary approach toward the synthesis of mechanically planar chiral rotaxanes whereby an intermediate pair of diastereomeric rotaxanes are synthesised and separated using reliable and scalable standard laboratory techniques. Cleavage of the chiral auxiliary allows for the synthesis of enantiopure mechanically planar chiral rotaxanes. Tuning the structure of the mechanically interlocked components as well as the reaction conditions allows for control over the diastereoselectivity during the mechanical bond forming step.