Mechanically Planar Chiral Molecules by a SuFEx-Auxiliary Approach

Abstract

Mechanical chirality, an emerging paradigm in stereochemistry, arises uniquely from the formation of a mechanical bond between achiral and oriented molecular subcomponents, endowing the resulting mechanically interlocked molecules (MIMs) with broad application potential. Despite its potential, it has remained underexplored largely due to the synthetic challenges in producing enantiopure mechanically planar chiral (MPC) molecules, particularly a scalable approach. Here, we introduce the sulfur(VI) fluoride exchange (SuFEx) click reaction into the MIMs field, reporting to employ SuFEx as a metal-free active template method for the synthesis of MPC rotaxanes (up to gram-scale). Subsequently, enantiopure MPC rotaxanes (ee >99%) can be efficiently obtained after the convenient one-step auxiliary elimination by either removal or oxidation of sulfinyl group. Furthermore, the derivative synthesis that can introduce various functional groups either on the macrocycles or on the dumbbells of rotaxanes enables the preparation of a large variety of enantiopure MPC rotaxanes, including higher-order enantiopure MPC [3]rotaxane and enantiopure co-conformationally MPC [3]rotaxane. Notably, using this strategy, enantiopure MPC catenanes can also be obtained by the transformation of rotaxanes, which preserves the enantiopurity and chiroptical properties of parent rotaxanes and provides a new approach to synthesizing enantiopure MPC catenanes.