A Rational Design for the Directed Helicity Change of Polyacetylene Using Dynamic Rotaxane Mobility by Means of Through‐Space Chirality Transfer

Abstract

Directed helicity control of a polyacetylene dynamic helix was achieved by hybridization with a rotaxane skeleton placed on the side chain. Rotaxane-tethering phenylacetylene monomers were synthesized in good yields by the ester end-capping of pseudorotaxanes that consisted of optically active crown ethers and sec-ammonium salts with an ethynyl benzoic acid. The monomers were polymerized with [{RhCl(nbd)}(2)] (nbd=norbornadiene) to give the corresponding polyacetylenes in high yields. Polymers with optically active wheel components that are far from the main chain show no Cotton effect, thereby indicating the formation of racemic helices. Our proposal that N-acylative neutralization of the sec-ammonium moieties of the side-chain rotaxane moieties enables asymmetric induction of a one-handed helix as the wheel components approach the main chain is strongly supported by observation of the Cotton effect around the main-chain absorption region. A polyacetylene with a side-chain rotaxane that has a shorter axle component shows a Cotton effect despite the ammonium structure of the side-chain rotaxane moiety, thereby suggesting the importance of proximity between the wheel and the main chain for the formation of a one-handed helix. Through-space chirality induction in the present systems proved to be as powerful as through-bond chirality induction for formation of a one-handed helix, as demonstrated in an experiment using non-rotaxane-based polyacetylene that had an optically active binaphthyl group. The present protocol for controlling the helical structure of polyacetylene therefore provides the basis for the rational design of one-handed helical polyacetylenes.

Helical Polyacetylenes Induced via Noncovalent Chiral Interactions and Their Applications as Chiral Materials

“…7) [64, 65]. 21a existed an almost racemic mixture of both helical conformations because the chiral wheel components were located around the tert -ammonium groups far from the polymer backbone and unable to induce a helix-sense bias (Fig.…”

Practical and Scalable Kinetic Resolution of BINOLs Mediated by a Chiral Counterion

“…Monomethyl BINOL can be alkylated with s = 35, enabling recovery of unreacted substrate 1 in 47 %yield (98:2 e.r. [18] Removal of the Oalkyl groups in 1 or its O-benzylated analogue is easily achieved. [18] Removal of the Oalkyl groups in 1 or its O-benzylated analogue is easily achieved.…”

Chiral Discrimination through 1H NMR and Luminescence Spectroscopy: Dynamic Processes and Solid Strip for Chiral Recognition

“…However,t he two halves of the host that are nonequivalent in the complexa re reversed for each possible orientation of the guest molecule. An exchange equilibrium in ab enzonaphthol [24]crown-8 complex with dipyridinium ionbased guests has been reported previously. [34] The exchange was explained in terms of two possible orientations in which the dipyridinium unit could have alignedi tself with the naphtha or benzo end of the crown ether molecule.…”

“…The syntheses of optically pure crown ether-based hostm olecules (R-H and S-H) and as the achiral host molecule Hw ere achieved by the necessary modification of previously reported procedures. [24] The various guest molecules with different chirality (R-G and S-G) were synthesized by hydrogenation of the corresponding imine product of the Schiff base reaction between the appropriate amine and aldehyde derivatives. These secondary amine derivatives were protonated and eventually isolated as the desired hexafluorophosphate salts to become soluble in dichloromethane.…”

“…Synthesis of R ‐H, S ‐H, and achiral crown ethers : R ‐H, S ‐H, and achiral crown ethers were synthesized according a previous method . The characterization details are provided in the Supporting Information.…”