Goldberg Active Template Synthesis of a [2]Rotaxane Ligand for Asymmetric Transition-Metal Catalysis.

We report on the active template synthesis of a [2]rotaxane through a Goldberg copper-catalyzed C-N bond forming reaction. A C2-symmetric cyclohexyldiamine macrocycle directs the assembly of the rotaxane, which can subsequently serve as a ligand for enantioselective nickel-catalyzed conjugate addition reactions. Rotaxanes are a previously unexplored ligand architecture for asymmetric catalysis. We find that the rotaxane gives improved enantioselectivity compared to a noninterlocked ligand, at the expense of longer reaction times.