Iron-catalyzed C—H alkylation and photoredox frontal ring opening metathesis polymerization

Wendell, Chloe Irene

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https://hdl.handle.net/2142/117883 Copy

Description

Title

Iron-catalyzed C—H alkylation and photoredox frontal ring opening metathesis polymerization

Author(s)

Wendell, Chloe Irene

Issue Date

2021-07-07

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

Moore, Jeffrey S.

Doctoral Committee Chair(s)

Moore, Jeffrey S.

Committee Member(s)

• Fout, Alison R.
• van der Donk, Wilfred A.
• Mirica, Liviu M.

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

organic synthesis, carbene chemistry, iron catalysis, frontal polymerization, photoredox, ring opening metathesis

Abstract

Metal alkylidenes are versatile synthetic intermediates which have revolutionized multiple chemical fields. They have been used in the synthesis of countless natural products, drugs, and polymers and have contributed to a different understanding of the chemistry of carbon. This thesis deals with two very different applications of this intermediate. The development of an iron catalyzed metallocarbene C—H insertion method is the subject of the first two chapters. Investigation of a photoinitiated frontal ring opening metathesis polymerization method comprises the last two chapters. Iron metallocarbenes are common intermediates in a wide range of synthetic methods, especially cyclopropanation and insertion into heteroatom-hydrogen bonds. Until 2016, there were no catalytic examples of catalytic iron-carbene C—H insertion. The few stoichiometric examples that existed shed some light on the possible kinetic barriers to developing a catalytic version of this protocol. We optimized an iron (III) phthalocyanine method by enhancing the electrophilicity of the metallocarbene intermediate. This method proved effective for a variety of benzylic C—H bonds, including the benzylic position of δ-tocopherol. Mechanistic investigations demonstrated that the C—H insertion mechanism is stepwise. Activity for tertiary C—H bonds was extensively investigated but proved elusive. Frontal polymerization is a method of polymerizing a resin not by heating the entire mixture, but by heating a small amount, which triggers an autoaccelerated polymerization that travels throughout the resin as a wave, or front. A less common initiation method of frontal polymerization is with light. There are only a handful of photoinitated frontal ring opening metathesis polymerization protocols reported. We have developed a photoinitiated, thermally propagated method with a less active bis(N-heterocyclic carbene) catalyst which we hoped would extend storage lifetime from conventional Grubbs second generation catalyzed systems. We did see a marked increase in storage lifetime when the components were split into two separate solutions and these were thoroughly mixed just before ignition. We established some of the materials properties of the resulting polymer and investigated how the frontal polymerization responded to changes in conditions.

Graduation Semester

2021-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2021 Chloe Wendell

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