Nickel and Cobalt-Catalyzed Hydrofunctionalization Reaction of Alkene DISSERTATION

347 Pages·2016·12.98 MB·English

Nickel and Cobalt-Catalyzed Hydrofunctionalization Reaction of Alkene

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University

By
Balaram Raya, M. S.
Graduate Program in Chemistry

The Ohio State University
2016

Dissertation Committee:
Professor T. V. RajanBabu, Advisor
Professor Craig Forsyth
Professor Jovica Badjic
Copyrighted by
Balaram Raya
2016
Abstract

Organic reactions catalyzed by metal complexes are an effective way to improve
atom economy and environmental friendliness for many synthetic transformations.
Among the various synthetic transformations, hydrosilylation reaction has huge industrial
applications for manufacturing consumer goods. The alkylsilanes from alkene
hydrosilylation are widely used as raw materials in manufacturing silicon rubbers,
molding implants and adhesive. The hydrosilylation reactions can also produce various
organosilicon reagents, which are used in fine chemical synthesis for stereospecific
oxidation and cross coupling reaction. Over the long decades, numerous reports on metal-
catalyzed hydrosilylations include the use of platinum, palladium, rhodium, ruthenium,
iridium, lanthanides and actinides, early transition metals, iron, cobalt to a limited extent
nickel. This work has shown that readily accessible (iPrPDI)CoCl reacts with 2
2
equivalents NaEt BH at -78 oC in toluene to generate a catalyst that effects
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highlyselective anti-Markovnikov hydrosilylation of the terminal double bond in alkene,
1,3- and 1,4-dienes. Primary and secondary silanes such as PhSiH , Ph SiH and
3 2 2
PhSi(Me)H react with a broad spectrum of dienes without affecting the configuration of
2
the other double bond. A slight modification of the reaction conditions using a less
reactive silane (OEt) Si(Me)H leads to unprecedented and highly selective reduction of
2
the terminal double bond with no contamination from the silane or reduction products of
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the more substituted double bond. The major limitation for cobalt catalyzed
hydrosilylation reaction using redox active PDI ligand is its terminal selectivity.
However, this active catalyst did not work for 1,1-disubstituted alkenes. In this
connection, we also observed efficient cobalt catalyst system for hydrosilylation of 1,1-
disubstituted alkenes using chelating phosphine ligand at room temperature, which is able
to do hydrosilylation for numerous substrates such as alkene, vinyl arene, conjugated
diene, 1,4-skipped diene and 1,1-disubstituted alkenes.
Carbocyclizations of α,ω-π-systems are extremely important and useful reactions for the
synthesis of a variety of carbocyclic and heterocyclic compounds. Although metal
catalyzed cyclization has been long known, controlling the selectivity (chemo- and regio-
) remains an important challenge in this field. Nickel complexes have been known to be
specifically effective for cyclic homo-and co-oligomerization of alkenes, alkynes and
dienes. During the past few years, through an approach that relied mostly on mechanistic
insights and systematic examination of ligand effects, RajanBabu group has discovered a
number of protocols for Ni(II)-catalyzed heterodimerization reactions of vinylarenes,
selected 1,3-dienes and strained olefins. Substitution of one of the phenyl groups of
triphenylphosphine with a 2-benzyloxy-(e.g., L18), 2-benzyloxy-methyl-(L19) or 2-
benzyloxyethyl-(L20) phenyl moiety results in a set of simple ligands, which exhibit
strikingly different behavior in various nickel (II)-catalyzed olefin dimerization reactions
including related cycloisomerization of 1,6-dienes. Nickel(II)-catalyzed
cycloisomerization of 1,6-dienes into methylenecyclopentanes, a reaction mechanistically
related to the other heterodimerization reactions, is also uniquely affected by nickel(II)
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complexes of L18, but not of L19 or L20. In an attempt to prepare authentic samples of
the methylenecyclohexane products, nickel(II) complexes of N-heterocyclic carbene
ligands were examined. In contrast to the phosphine, which gives the
methylenecyclopentanes, methylenecyclohexanes are the major products in the N-
heterocyclic carbine ligated nickel (II)-mediated reaction.
This dissertation discusses the ligand effect on hydrofuctionalization of alkenes using
nickel or cobalt metal complexes.

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This dissertation is dedicated to my parents (Khadga Bd. Raya Chhetri and Indra Kumari
Raya Chhetri) and my family who always supported my academic aspirations

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Acknowledgments

I am grateful to my respectable advisor Prof. T.V RajanBabu, for his invaluable
assistance, guidance, innovative ideas and encouragement throughout my Ph.D. Under
his guidance, I learned how to identify and pursue meaningful goals.
I would like to thank the members of my committee, Professor Craig Forsyth and
Professor Jovica D Badjic for their time and valuable comments, and the faculty of
department of chemistry for constructive suggestions. I am grateful to Professor David J
Hart for his candid feedback and for his mentorship while teaching the graduate organic
course.
I would like to thank my parents, Mr. Khadga Bahadur Raya (Chhetri) and Mrs.
Indra Kumari Raya (Chhetri) for their constant encouragement and financial support.
Specific thanks to my beloved wife Mrs. Sulakshana Ghimire and my son Zenil Jung
Raya for their support and encouragement during my tough time. Sulakshana has
supported me through some of my difficult moments and helped me to enjoy some of the
best moment of my life. I am grateful for my wife and son for their love and kindness. In
addition, I would like to thank my brothers (Junga and Rudra) and sisters (Durga,
Mamata and Sabitra) family for their constant encouragement.
I would acknowledge Dr. Tanya Whitmer, NMR lab manager, Mrs. Rebecca
Patton and Mrs. Jennifer Hambach, office support specialist for their consistent help.
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I am grateful for my colleagues, Dr Souvagya Biswas, Stanley Jing and Dr Vagulejan
Balasanthiran sharing their insights and instruction on cobalt chemistry.
Last but not least, I would like to thank all the past and present RajanBabu group
members specifically Dr. Yam N Timsina, Dr. Kendra Dewese, Krishnaja, Bryan,
Milauni for their help and encouragement.
I am in debated to my father-in-law Narendra Kumar Ghimire and mother-in-law
Sita Devi Chauhan for their words of encouragement during my tough times. I am
grateful for my sister-in-laws (Srijana and Namuna) and their family, brother-in-law
(Anurodh and Anupam) for their love and encouragement.
I would like to acknowledge financial support by National Science Foundation
and National Institute of Health, for supporting our research endeavors. I would also like
to acknowledge The Ohio State University Department of Chemistry and Biochemistry
for giving me the opportunity to enrich my educational goals.
I am deeply thankful for the friends I have made here at The Ohio State
University and Nepalese Community in Columbus
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Vita

November 2000 ............................................. M.Sc. in Chemistry,
Tribhuvan University,
Kathmandu, Nepal
2001-2009 ...................................................... Lecturer
Damak Multiple Campus, Nepal
2009-2011 ...................................................... Teaching and Research Assistant
Western Illinois University, IL
2011-2015 ...................................................... Graduate Teaching Assistant, Department of
Chemistry and Biochemistry, The Ohio
State University
2016 .............................................................. Graduate Research Assistant, Department of
Chemistry and Biochemistry, The Ohio
State University

Publications

Raya, B.; Jing, S.; RajanBabu, T. V. “ Control of Selectivity through Synergy between
Catalysts, Silanes and Reaction Conditions in Cobalt-Catalyzed Hydrosilylation of
Dienes and Terminal Alkenes.” Manuscript Submitted .
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Raya, B.; Biswas, S.; RajanBabu, T. V. “Selective Cobalt-Catalyzed Reduction of
Terminal Alkenes and Alkynes using (EtO) Si(Me)H.”ACS Catal.; 2016, 6, 6318-6323.
2
Biswas, S.; Zhang, A.; Raya, B.; RajanBabu, T. V. “Triarylphosphine Ligands With
Hemilabile Alkoxy Groups: Ligands for Nickel (II)-Catalyzed Olefin Dimerization
Reactions. Hydrovinylation of Vinylarenes, 1,3-Dienes, and Cycloisomerization of 1,6-
Dienes.” Adv. Synth. Catal. 2014, 356, 2281-2292.
Raya, B.; Jing, S.; Balasanthiran, V.; RajanBabu, T. V. “Novel Cobalt-Catalyst for
Hydrosilylation of 1,1-disubstituted Alkenes.” Manuscript in Preparation.
Balaram Raya; “Synthesis of Diol and Triol Substrate to Investigate Selective oxidation
of Alcohols using Hypervalent Iodine Compounds.” MS Dissertation, 2011, Western
Illinois University, Macomb, IL.

Fields of Study

Major Field: Chemistry

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