Synthesis of sterically encumbered biaryls by [3+3] cyclocondensation reactions and synthesis of arylated pyrazoles, bis(diaryl)sulfones, and bis(alkenyl)pyridines by Pd(0)-catalysed cross-coupling reactions [Elektronische Ressource] / vorgelegt von Ali Asad
99 Pages

Synthesis of sterically encumbered biaryls by [3+3] cyclocondensation reactions and synthesis of arylated pyrazoles, bis(diaryl)sulfones, and bis(alkenyl)pyridines by Pd(0)-catalysed cross-coupling reactions [Elektronische Ressource] / vorgelegt von Ali Asad

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Synthesis of Sterically Encumbered Biaryls by [3+3]
Cyclocondensation Reactions and Synthesis of Arylated Pyrazoles,
Bis(diaryl)sulfones, and Bis(alkenyl)pyridines by Pd(0)-Catalysed
Cross-Coupling Reactions


Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)
der Mathematisch-Naturwissenschaftlichen Fakultät
der Universität Rostock

vorgelegt von
Asad Ali geb. am 20.02.1982 in Takht Bhai Mardan
aus Pakistan

Rostock, June 2010


Dekan : Prof, Dr Hendrick Schubert

1. Gutachter: Prof Dr Andreas Kirschning
University of Hannover, Germany

2. Gutachter: Prof. Dr Peter Langer,
Institut für Chemie, Albert Einstein Str.3a,
8059 Rostock, Germany

Tag der Promotion: 12.10.2010 .


Affectionately dedicated to
My parents, sweet brothers and



Declaration / Erklärung 2
Acknowledgements 7
Abbreviations 8
General Introduction 9
Summary 11


Synthesis of Sterically Encumbered Biaryls by [3+3] Cyclocondensation
Reactions and Synthesis of Arylated Pyrazoles, Bis(diaryl)sulfones, and
Bis(alkenyl)pyridines by Pd(0)-Catalysed Cross-Coupling Reactions

0 General introduction 09
1. Synthesis of sterically encumbered biaryls based on a Cu(I)–catalysed 12
arylation / [3+3] cylocondensation strategy
1.1 Introduction 12
1.2 Results and discussion 13
1.3 Conclusions 18

2. Synthesis of arylated pyrazoles by site-selective Suzuki- 21
Miyaura reactions of tribromopyrazoles
2.1 Introduction to palladium(0)-catalyzed reactions 19
2.2 Introduction to pyrazole syntheses 21
2.3 Results and discussion 21
2.4 Conclusions 26

3. Synthesis of bis(diaryl)sulfones by Suzuki-Miyaura
reactions of 2,4 -bis(trifluorosulfonyloxy)biphenyl sulfone 27
3.1 Introduction 27
3.2 Results and discussion 27
3.3 Conclusions 30

4. First double Heck cross-coupling reactions of dibrominated
pyridines 31
4.1 Introduction 31
4.2 Results and discussion 32
4.3 Conclusions 37

5. Abstract 38

56. Experimental Section 43
6.1 General: Equipment, chemicals and work technique 43
6.2 Procedures and spectroscopic data 46
References 84
Data for x-ray structures 93

By the grace of Allah, the Almighty, the creator of universe, who granted 
Hidayah to the mankind and peace and blessings be upon his prophet, Hazrat 
Muhammad  (Peace  be  upon  Him),  who  exhorted  his  followers  to  seek 
knowledge from cradle to grave, I've been able to complete this academic 
It is my first and foremost obligation to express my sincere gratitude 
from the core of my heart to Professor Dr. Peter Langer my supervisor. His 
proper supervision, experience, time devotion and keen interest enable me to 
accumulate this humble work. 
I ought to submit my thanks to my dear friends, who remembered me in 
their prayers and heart. I wish to acknowledge support and encouragement 
provided by Muhammad Qasim Naeen, Asif Khan, Jamil Ahmad, Amir, Wajid 
Khan, Muhammad Usman and Dr Mukhtar Ullah.    
I am thankful to all my past and present colleagues, Ihsan Ullah Marwat, 
Alina Bunescu, Thomas Rhan, Inam Iqbal, Muhammad Imran, Majid Riahi, 
Rasheed Ahmad, , Olomide, Togam, Muhammad Nawaz, Muhammad Sharif, 
Muhammad  Zeeshan,  Obaid‐Ur‐Rahman,  Javana  Tatar,  Farooq  Ebad,  and 
Mohanad Shkoor for their support encouragement and help to pursue this 
work and all others whom I have missed here do deserve equal credit. 
Thanks  also  go  to  Dr.  Martin  Hein,  Dr  Alexander  Villinger  and  all 
members of technical sections (NMR, IR, MS, EA and X‐Ray etc) of Rostock 
 Finally I express my heartiest gratitude and respect to my mother, father 
sweet brothers, Sisters and all family who encouraged me through‐out my 
studies and supported me what and whenever they could. May God provide me 
the way to fulfill their promises? Special thanks to my dear Atia Shams for her 
prayers and moral support.    

7 Abbreviations

Ar Aromatic
APT Attached Proton Test
ATCC American Type Culture Collection
nBuLi n-Butyl lithium
DEPT Distortion less Enhancement by Polarisation Transfer
EI Electronic Impact
ESI Electro spray Ionization
EtOAc Ethyl acetate
HRMS High Resolution Mass Spectroscopy
IR Infrared Spectroscopy
LDA Lithium Diisopropylamide
MS Mass Spectrometry
Ph Phenyl
NEt Triethylamine 3
NMR Nuclear Magnetic Resonance
HMQC Heteronuclear Multiple Quantum Coherence
HMBC Heteronuclear Multiple Bond Correlation
COSY Correlated Spectroscopy
NOESY Nuclear Over Hauser and Exchange Spectroscopy
MeSiOTf Trimethylsilyl-trifluoromethanesulfonate 3
MeSiCl ethylsilylchloride 3
Mp Melting Point
RCM Ring Closing Metathesis
TBAI Tetra butyl Ammonium Iodide
TFA Trifluoroacetic Acid
TfO Trifluoromethanesulfonic Anhydride 2
THF Tetrahydrofurane
TLC Thin Layer Chromatography
TMS Trimethylsilane
UV Ultraviolet spectroscopy

80. General Introduction and Task of the Thesis

The main focus of chemists is to synthesize both natural products and compounds that do not exist in
nature and to study their physical, chemical and biological properties. This is accompanied by a deep
understanding of the fundamental principles of chemical structure and reactivity and lead to the
development of modern pharmaceutical and chemical industries. Natural products play an important role
in the discovery and development of pharmacologically relevant compounds (drug-like compounds) and
drugs which are actually used in the clinic. In this context, it is important to find new lead structures for
1drug discovery and to develop new synthetic methods or strategies for their assembly. Besides natural
products, synthetic compounds, which do not resemble natural products, also play a key role in
pharmacology. In recent times, the tremendous improvements in synthetic methodology have provided a
convenient access to a great variety of synthetic substances like antibiotic, anti-infective, anti-cancer and
cardio-vascular agents etc.

2 Natural products often represent lead structures in drug discovery. Various natural products have
been reported to show antibiotic activity. Since the discovery of penicillin, a large number of antibiotics
3have been isolated from of microorganisms. Anti-infective compounds are obtained from both animals
and plants. The development of new drugs includes synthetic and semi-synthetic studies, microbial
4transformations, the biological screening and the study of the mechanism of action. The effort to design
better anti-malaria agents for prophylaxis has also led to the discovery of a class of synthetic products,
such as Malarone.

Natural products have provided a great contribution to the chemotherapy of cancer. A number of
5 anticancer drugs are isolated from plants or microorganisms. This includes bleomycin, doxorubicin,
TMmitomycin, paclitaxel (Taxol ); examples of semi-synthetic derivatives of natural products, which are
important anticancer drugs are, Ironotecan (a camptothecin derivative), etoposide or tenoposide (a
podophyllotoxin derivative). Currently, both a semi-synthetic derivative with improved water solubility,
TM TMdocetaxel (Taxotene ) and paclitaxel (Taxol ) are approved and used clinically in the treatment of
ovarian breast cancers. In this context, it is important to note, that the biological activity of synthetically
modified natural products is often better than the activity of the natural products themselves.

9The combination of medicinal chemistry and synthetic chemistry is a good tool for the development
of new drugs. In this context, the generation of compound libraries by combinatorial chemistry and
6 parallel synthesis provides a pool for screening.

Task of my thesis
My own studies, which are outlined in this thesis, are focused on the development of new and reliable
synthetic strategies and their application to the preparation of pharmacologically relevant carba- and

In the first chapter, I had the task to develop a new application of formal [3+3] cyclization reactions
which have been extensively studied before in the group of Prof. Langer. The plan was to develop an
approach to sterically encumbered biaryls by combination of a recently developed Cu-catalyzed
coupling reactions of 1,3-diketones with aryl halides with formal [3+3] cyclizations of 1,3-bis(silyloxy)-

Chapters 2, 3, and 4 of my thesis deal with new synthetic applications of palladium(0)-catalyzed
cross-coupling reactions. In recent years, the group of Prof. Langer has been studying Pd(0)-catalyzed
cross coupling reactions of polyhalogenated arenes and heterocycles. In this context, the issue of site-
selectivity (regioselectivity) plays an important role. I have studied the synthesis of arylated pyrazoles,
bis(diaryl)sulfones, and di(alkenyl)pyridines by Suzuki and Heck reactions of tribrominated pyrazoles,
bis(triflates) of 2’-4-dihydroxy-diphenylsulfone and dibrominated pyridines, respectively.