Highly efficient macrocycle and cage formation via hindered urea chemistry

Yang, Yingfeng

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https://hdl.handle.net/2142/113162 Copy

Description

Title

Highly efficient macrocycle and cage formation via hindered urea chemistry

Author(s)

Yang, Yingfeng

Issue Date

2021-07-14

Director of Research (if dissertation) or Advisor (if thesis)

Cheng, Jianjun

Doctoral Committee Chair(s)

Cheng, Jianjun

Committee Member(s)

• Zimmerman, Steven C.
• Chen, Qian
• Evans, Christopher

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Dynamic covalent chemistry
• hindered urea bond
• de-tert-butytlation
• hindered urea macrocycles
• cis-urea preference
• quantitative synthesis
• cyclic peptides
• urea cages
• adsorptive separation

Abstract

Dynamic covalent chemistry (DCC) is a powerful tool that enables the synthesis of novel macrocycles, molecular cages, knots and frameworks, as well as the development of dynamic polymeric materials with unique properties. Hindered urea bond (HUB), a newly developed DCC, has found applications in dynamic materials designs such as self-healing, malleable, shape-memory or environmentally-adaptive materials. However, despite of the intensive research, study of this new, facile dynamic chemistry is still in its infancy. The potential of HUB in the formation of discrete structures in small molecular level is largely overlooked and not demonstrated. What’s more, a turning-off mechanism for HUB was not found which can severally limit the applications of HUB-based materials. Here we report the discovery of acid-assisted de-tert-butylation reaction that can instantly “turn off” the dynamicity of HUB, leading to improved chemical stabilities and mechanical properties of HUB-containing materials. We also demonstrated the use of dynamic HUB for the construction of urea macrocycles with very high efficiency. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C=O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. Building upon the macrocyclization mechanism, we demonstrated that HUB can function as efficient cyclization enabling motif for cyclic peptides. Beyond macrocycles, HUB was also utilized to efficiently construct a series of structures with different topologies as well as urea cages, which were demonstrated to be able to separate important petrochemicals such as pyridine/toluene and benzene/cyclohexane.

Graduation Semester

2021-08

Type of Resource

Thesis

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http://hdl.handle.net/2142/113162

Copyright and License Information

Copyright 2021 Yingfeng Yang

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