Mechanical bonding activation in rotaxane-based organocatalysts

We report herein the enhanced efficiency as organocatalysts of a series of succinamide-based hydrogen-bonded [2]rotaxanes functionalized with an acyclic secondary amine as the catalytically active site. We also evaluated their catalytic activity, compareds with that of their non-interlocked threads, in an iminium-type process between crotonaldehyde and acetylacetone. The presence of an interlocked polyamide macrocycle notably increased the catalytic activity of the entwined organocatalysts. The mechanized catalysts rapidly form a reactive iminium intermediate with the aldehyde, increasing its population. The hydrogen-bonding interaction established between the macrocycle and the electrophile has been proposed as one of the reasons for the rapid formation and stabilization of this key intermediate.

Automated summary

In this study, a series of succinamide-based hydrogen-bonded [2]rotaxanes with acyclic secondary amine as the catalytically active sites were synthesized and evaluated for their catalytic activity in an iminium-type process. The presence of an interlocked polyamide macrocycle notably increased the catalytic efficiency of the entwined organocatalysts by rapidly forming a reactive iminium intermediate with the aldehyde. The hydrogen-bonding interaction between the macrocycle and the electrophile plays a crucial role in the rapid formation and stabilization of the key intermediate.