New flavins and their application to chemical photocatalysis [Elektronische Ressource] / vorgelegt von Harald Schmaderer

Harald Høffding

Informations

• Publié par: universitat_regensburg
• Publié le: 01 janvier 2009
• Nombre de lectures: 29
• Langue: English
• Poids de l'ouvrage: 6 Mo

Extrait

New Flavins and Their Application
to Chemical Photocatalysis





Dissertation


Zur Erlangung
des Doktorgrades der Naturwissenschaften
(Dr. rer. nat.)
an der Fakultät für Chemie und Pharmazie
der Universität Regensburg





vorgelegt von

Harald Schmaderer

aus Cham


Regensburg – 2009 The experimental work was carried out between November 2005 and
February 2009 at the University of Regensburg, Institute of Organic
Chemistry under the supervision of Prof. Dr. Burkhard König.















The PhD–thesis was submitted on: 23. February 2009
Date of the colloquium: 20. March 2009


Board of Examiners:

Prof. Dr. Rainer Winter (Chairman)
Prof. Dr. Burkhard König (1st Referee)
Prof. Dr. Hans-Achim Wagenknecht (2nd Referee)
Prof. Dr. Alfons Penzkofer (Examiner)

























A good scientist is a person
in whom the childhood quality
of perennial curiosity lingers on.
Once he gets an answer,
he has other questions.

Frederick Seitz
Acknowledgement


I would like to thank Prof. Dr. Burkhard König for the opportunity to work in
his group, for a fascinating and open topic, for always being optimistic and
giving me the freedom to develop my work, and for always saying “yes”
when I asked for “some minutes”.

The DFG Graduate College GRK 640 and the DFG Priority Programme
SPP 1118 supported my work financially. I am very grateful for this and for
the possibility to visit many interesting conferences within the last years.

I am grateful to all staff and co-workers of the König group for very friendly
collaboration and for all christmas parties, skiing trips and coffee breaks.

I would like to thank all members of the Central Analytical Department for
doing their job so sophisticated, engaged and friendly.

Thanks to the „AK König Service Center for computer problems” with Andi
Grauer, Benno Gruber and Alex Riechers, helping me with all the troubles a
PC is able to create.

I really enjoyed the constructive and inspiring meetings of the
photocatalysis subgroup and I appreciate for all the help and ideas.

I owe my thanks to Stephan Fagerer, Adriane Lochner, Karin Lehner, Andi
Hohenleutner, Markus Daerr, Natascha Kuzmanovic, and Susa Schmidbauer
for their engaged work during research internships.

I am very grateful to Dr. Petra Hilgers for helping me with fluorous
chemistry, for proofreading and for sharing her experience with me.

Thanks to Dr. Claudia Wanninger-Weiß for joining me in flavin chemistry,
for funny discussions, for proofreading, and for her kind help.
I owe my thanks to Bianca Attenberger for her engaged final thesis, for
every day questions and for making our lab days more human.

I express my debt gratitude to Dr. Jiří Svoboda for welcoming me so
friendly when I started here, for introducing me to flavin chemistry and of
course for the very fruitful, inspiring, funny, and coffein-saturated working
atmosphere that we had together as the “sehr geehrte Laborkollegen” in the
“yellow lab”.

Thanks to Danny Vomasta for all the badminton matches, to Stefan “Toni”
Stadlbauer for improving my skiing technique, to Michi Egger for the soccer
sessions, and to Robbie Lechner as the second “flavin-man” for all the
discussion about the chemistry our most beloved molecule might perform or
not.

I am very much grateful to the „Zaubermann“ Florian Ilgen for our daily
lunch, for playing “PhD-golf” and for the time we spent together.

I would like to thank my friend Dr. Tilmann Fahlbusch for his support and
for all the discussions we had about chemistry and other important things of
life.


From my entire heart, I would like to thank my parents Inge and Ludwig,
my sister Eva and my brother Jörg. Without their love, support and
encouragement, I would not have made it to this point.


I express my heartfelt gratitude to Lela for walking with me in the same
direction within the last thirteen years, for all our decisions, for her love and
support and for marrying me. I am deeply enjoying every day of our
conjoint live.
Table of contents

Summary 3
Zusammenfassung 4
Chapter 1
Flavin Photocatalysts with Substrate Binding Sites 6
Introduction 6
Templated flavin photoreductions 9
Templated flavin photooxidations 12
Summary and outlook 15
References 16
Chapter 2
Thiourea-Enhanced Flavin Photooxidation of Benzyl Alcohols 20
Introduction 20
Results and discussion 21
Synthesis 21
Photocatalytic Oxidations 28
Conclusion 38
Experimental part 39
References 58
Chapter 3
Photooxidation of Benzyl Alcohols with Immobilized Flavins 64
Introduction 64
Results and discussion 66
Synthesis 66
Photooxidations in aqueous homogeneous solution 68
Photooxidation with silica gel-immobilized flavins 73
Flavin immobilization by entrapment in PE-pellets or glues 78
Conclusion 80
Experimental part 81
References 89
Chapter 4
Synthesis of Rigidified Flavin-Guanidinium Ion Conjugates
and Investigation of Their Photocatalytic Properties 92
1 Introduction 92
Results and discussion 93
Synthesis 93
Structural investigations 94
Preliminary catalytic reactions 96
Conclusion 99
Experimental part 100
References 105
Chapter 5
Synthesis of a Bicyclic Diamine Derived from Kemp´s Acid 108
Introduction 108
Results and discussion 109
Synthesis 109
Crystal structure 110
Two dimensional NMR experiments 111
Experimental part 112
References 115
Chapter 6
Copper-Mediated 3-N-Arylation of Flavins 118
Introduction 118
Results and discussion 119
Copper-mediated flavin 3-N-arylation 119
UV/Vis and fluorescence spectra of 3-N-aryl flavins 124
Summary 127
Experimental part 128
References 135
List of abbreviations 139
Appendix A 142
Appendix B 148
Appendix C 160
Appendix D 170
Appendix E 178
List of publications 188
Curriculum vitae 189

2 Summary

Summary

The presented dissertation comprises the synthesis of substituted flavins
and their application as photocatalysts. Chapter 1 contains a short
introduction into possible redox states of flavins, especially under light
irradiation and previous applications of flavin-based photocatalysts in
particular of our working group are presented. The synthesis of various
flavin-thiourea derivatives is described in chapter 2. These compounds and
mixtures of flavins with thiourea were successfully applied to the
photooxidation of 4-methoxybenzyl alcohol. High conversions were achieved
with such catalytic systems and also the use in preparative experiments.
However, in water as reaction media, the reaction proceeds faster and with
increased efficiency. In contrast to reactions in acetonitrile, also non
activated benzyl alcohols can be oxidized. Chapter 3 contains the
experiments in water and the immobilization of flavins on solid support or in
polyethylene. Simple separation from the reaction mixture and possible
recycling make these catalysts valuable for application, however, showing
the same reactivity compared to homogeneous solution. Templated flavins
were synthesized by fixing the chromophore together with a substrate
binding site on a platform (chapter 4). Such assemblies increase the
probability for a photoinduced electron transfer reaction, therefore
optimizing the reactivity of flavins under light irradiation. A novel synthetic
approach to 3-N-arylation by reaction with phenyl boronic acids is presented
in chapter 5. For the first time, this method enables a direct coupling of
aromatic systems to the 3-N-position of a flavin. Terminatory, chapter 6
contains the synthesis of a new diamin derived from Kemp´s Acid. This
easily accessible rigid platform makes the composition of structurally
defined compositions feasible.


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