Rotaxanes with dynamic mechanical chirality: Systematic studies on synthesis, enantiomer separation, racemization, and chiral-prochiral interconversion

Fumitaka Ishiwari; Toshikazu Takata

doi:10.3389/fchem.2022.1025977

Rotaxanes with dynamic mechanical chirality: Systematic studies on synthesis, enantiomer separation, racemization, and chiral-prochiral interconversion

Front Chem. 2022 Oct 28:10:1025977. doi: 10.3389/fchem.2022.1025977. eCollection 2022.

Authors

Fumitaka Ishiwari¹, Toshikazu Takata^{1

2

3}

Affiliations

¹ Department of Chemical Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Japan.
² School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, Japan.
³ Graduate School of Advanced Science and Engineering, Hiroshima University, Hiroshima, Japan.

Abstract

Dynamic mechanical chirality of [2]rotaxane consisting of a C _s symmetric wheel and a C _2v symmetric axle is discussed via the synthesis, enantiomer separation, racemization, and chiral-prochiral interconversion. This [2]rotaxane is achiral and/or prochiral when its wheel locates at the center of the axle, but becomes chiral when the wheel moves from the center of the axle. These were proved by the experiments on the enantiomer separation and racemization. The racemization energy of the isolated single enantiomers was controlled by the bulkiness of the central substituents on the axle. Furthermore, the chiral-prochiral interconversion was achieved by relative positional control of the components. The present systematic studies will provide new insight into mechanically chiral interlocked compounds as well as the utility as dynamic chiral sources.

Keywords: chiral-prochiral interconversion; dynamic mechanical chirality; enantiomer separation; mechanical chirality; prochiral; racemization; rotaxane.