Tandem diaza-Cope rearrangement polymerization: turning intramolecular reaction into powerful polymerization to give enantiopure materials for Zn2+ sensors.

Soon-Hyeok Hwang,Tae-Lim Choi

doi:10.1039/d0sc06138g

Abstract

[3,3]-Sigmatropic rearrangement is a powerful reaction to form C–C bonds stereospecifically; however, owing to intrinsic simultaneous bond formation and breakage, this versatile method has not been utilized in polymerization. Herein, we report a new tandem diaza-Cope rearrangement polymerization (DCRP) that can synthesize polymers with defect-free C–C bond formation from easy and efficient imine formation. A mechanistic investigation by in situ1H NMR experiments suggests that this polymerization proceeds by a rapid DCR process, forming an enantiospecific C–C bond that occurs almost simultaneously with imine formation. This polymerization produces not only highly stable polymers against hydrolysis due to resonance-assisted hydrogen bonds (RAHBs) but also chiral polymers containing enantiopure salen moieties, which lead to high-performance Zn2+-selective turn-on chemosensors with up to 73-fold amplification. We also found that their optical activities and sensing performances are heavily dependent on the reaction temperature, which significantly affects the stereoselectivity of DCR.

Highlights

Pericyclic reaction, the reorganization of p-bonds in a concerted manner, is one of the most widely used transformations in synthetic organic chemistry
A mechanistic investigation by in situ 1H NMR experiments suggests that this polymerization proceeds by a rapid diaza-Cope rearrangement (DCR) process, forming an enantiospecific C–C bond that occurs almost simultaneously with imine formation
This polymerization produces highly stable polymers against hydrolysis due to resonance-assisted hydrogen bonds (RAHBs) and chiral polymers containing enantiopure salen moieties, which lead to high-performance Zn2+-selective turn-on chemosensors with up to 73-fold amplification

Summary

Introduction

Pericyclic reaction, the reorganization of p-bonds in a concerted manner, is one of the most widely used transformations in synthetic organic chemistry. We paid attention to Chin and co-workers' reports of highly versatile diaza-Cope rearrangement (DCR) reactions using chiral diamine and benzaldehydes.[39,40,41,42,43,44,45,46,47] A er efficient imine formation, DCR proceeded rapidly to form C–C bonds stereospeci cally, driven by a strong resonance-assisted hydrogen bond (RAHB), thereby providing access to various enantiopure daughter amines Inspired by this powerful DCR, we envisioned a new polymerization ironically using the intramolecular [3,3]-sigmatropic rearrangement in a tandem process with efficient imine formation. These chiral polymers containing salen side-chains can be applied as powerful turn-on chemosensors showing up to 73-fold ampli cation in uorescence intensity

Results and discussion

Conclusions

Conflicts of interest