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Nickel and Cobalt-Catalyzed Hydrofunctionalization Reaction of Alkene

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Nickel and Cobalt-Catalyzed Hydrofunctionalization Reaction of Alkene 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 iPr nickel. This work has shown that readily accessible ( PDI)CoCl2 reacts with 2 o equivalents NaEt3BH at -78 C in toluene to generate a catalyst that effects highlyselective anti-Markovnikov hydrosilylation of the terminal double bond in alkene, 1,3- and 1,4-dienes. Primary and secondary silanes such as PhSiH3, Ph2SiH2 and PhSi(Me)H2 react with a broad spectrum of dienes without affecting the configuration of the other double bond. A slight modification of the reaction conditions using a less reactive silane (OEt)2Si(Me)H leads to unprecedented and highly selective reduction of the terminal double bond with no contamination from the silane or reduction products of ii 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) iii 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. iv 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 v 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. vi 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 vii 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 . viii Raya, B.; Biswas, S.; RajanBabu, T. V. “Selective Cobalt-Catalyzed Reduction of Terminal Alkenes and Alkynes using (EtO)2Si(Me)H.”ACS Catal.; 2016, 6, 6318-6323. 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 ix Table of Contents Abstract ............................................................................................................................... ii Dedication ........................................................................................................................... v Acknowledgement .............................................................................................................. vi Vita ................................................................................................................................... viii Publication ........................................................................................................................ viii Fields of Study ..................................................................................................................
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