Issue 24, 2023
From the journal:

Polymer Chemistry

Tetrazine-norbornene versus azide-norbornene ligation: evaluating the toolbox for polymer–polymer coupling†‡

Steffen A. Busche,a   Stefan Peplau,a   Luc Zuhse,a   Désirée Steimer,a   Dennis D. Augusta  and  Hans G. Börner ORCID logo *a  

* Corresponding authors

a Humboldt-Universität zu Berlin, Department of Chemistry, Laboratory of Organic Synthesis of Functional Systems, Brook-Taylor-Str. 2, 12489 Berlin, Germany
E-mail: h.boerner@hu-berlin.de

Abstract

The selective ligation chemistry of the stable norbornene (Nb) with an asymmetric tetrazine (Tz), accessible in a one-pot reaction is adapted to the ligation of polymer segments yielding block copolymers. The Tz/Nb inverse electron-demand Diels–Alder reaction (IEDDA) is compared with the more classical azide (Az)-norbornene Huisgen 1,3-cycloaddition (CA) to ligate end-functionalized polymers. An endo/exo-norbornene end-functionalized polystyrene (PS1.5k-Nb) and polyethylene glycols with either tetrazine or aryl azido functionalities (PEG3k/5k-Tz, PEG3k/5k-Az) are synthesized. While the Tz/Nb IEDDA proceeds cleanly and leads to full conversion in stochiometric mixtures, the Az/Nb CA requires less effort but suffers from slower coupling kinetics and some side reactions. The coupling of PS1.5k-Nb with PEG3k/5k-Az requires 1H-NMR analysis to follow the kinetics and the products suffer from incomplete conversion as well as slight decomposition of the Az-moieties. In contrast, the ligation of PS1.5k-Nb with PEG3k/5k-Tz is robust. The reaction, which is conveniently monitored by UV/Vis spectroscopy, yields the desired PS-block-PEG in high yields and may offer potential for easy scale-up.

Graphical abstract: Tetrazine-norbornene versus azide-norbornene ligation: evaluating the toolbox for polymer–polymer coupling

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Article information

DOI
https://doi.org/10.1039/D3PY00320E
Article type
Paper
Submitted
24 Mar 2023
Accepted
24 May 2023
First published
26 May 2023
This article is Open Access
Creative Commons BY-NC license

Polym. Chem., 2023,14, 2888-2892

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Tetrazine-norbornene versus azide-norbornene ligation: evaluating the toolbox for polymer–polymer coupling

S. A. Busche, S. Peplau, L. Zuhse, D. Steimer, D. D. August and H. G. Börner, Polym. Chem., 2023, 14, 2888 DOI: 10.1039/D3PY00320E

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