A Chiral Interlocking Auxiliary Strategy for the Synthesis of Mechanically Planar Chiral Rotaxanes

We have serendipitously discovered a combination of reaction partners that function as a “chiral interlocking auxiliary” to both orientate a macrocycle and, effectively, load it onto a new axle. We demonstrate the potential of this finding through the synthesis of a number of targets in high enantiopurity, without separation of stereoisomers, including examples whose axles lack any functional groups that would allow their direct synthesis by other means, so called “impossible” rotaxanes. Intriguingly, by varying the order of bond forming steps, we can effectively choose which end of an axle the macrocycle is loaded onto, allowing the synthesis of both hands of a single target using the same reactions and building blocks.