Interlocking the Catalyst: Thread versus Rotaxane-Mediated Enantiodivergent Michael Addition of Ketones to β-Nitrostyrene.

Fumaramide threads bearing one l-prolinamide fragment have been designed as templates for promoting the efficient formation of novel Leigh's [2]rotaxanes. Both threads and rotaxanes are shown to catalyze the asymmetric addition of ketones to β-nitrostyrene in an enantio- and diastereoselective manner. Interestingly, the enantioselective course of these processes is reversed simply by changing from thread to rotaxane as catalyst. DFT computations have allowed to rationalize the stereodivergence shown by the interlocked and noninterlocked catalysts.