University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Winter 1968 SOME REACTIONS OF ARYLLITHIUMS WITH DIARYL SULFOXIDES SANDRA YEAGER BAST Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation BAST, SANDRA YEAGER, "SOME REACTIONS OF ARYLLITHIUMS WITH DIARYL SULFOXIDES" (1968). Doctoral Dissertations. 869. https://scholars.unh.edu/dissertation/869 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. This dissertation has been microfilmed exactly as received 6 8 -14, 97 0 BAST, Sandra Yeager, 1939- SOME REACTIONS OF ARYLLITHIUMS WITH DIARYL SULFOXIDES. University of New Hampshire, Ph. D ., 1968 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SOME REACTIONS OF ARYLLITHIUMS WITH DIARYL SULFOXIDES by SANDRA YEAGER BAST B. A. Thiel College, 1960 M. S. University of New Hampshire, 1963 A THESIS Submitted to the University of New Hampshire In Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Graduate School Department of Chemistry February 1968 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This thesis has been examined and approved. Thesis director, Kenneth K. Andersen Associate Professor of Chemistry » V O l JJ Alexander R. Amell, Prof. of Chemistry Q h j a L G L . ____________ Paul R. Jones, #rof. of Chemistry Robert E. Lyle, Prof. of Chemistry David H. Chittenden, Assistant Prof. of Electrical Engineering h ic u c A . I 11^ t_______________ Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS The author wishes to express her sincere appreciation to Dr. Kenneth K. Andersen for his encouragement and help in the direction of this research. The author also wishes to thank Dr. J. J. Uebel for his assistance with the gas 'ij ‘ chromatographic analyses and interpretation of the nuclear magnetic resonance spectra which was of immeasurable help during the absence of Dr. Andersen. Thanks are expressed to Miss Anne Kohl and to Dr. Charles M. Wheeler, whose friendship and understanding were a constant source of encouragement throughout the author’s stay at the University of New Hampshire. Thanks are also due to Miss Kohl for the typing of this manuscript. Financial assistance for this work from the National Institutes of Health is gratefully acknowledged. The author is' most indebted to her husband, John, whose advice greatly furthered the completion of this work. 111• • • Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Page LIST OF TABLES...................................vi S LIST OF FIGURES................................. vii ABSTRACT...... viii I. INTRODUCTION..................................... 1 II. RESULTS AND DISCUSSION........................... 12 A. Preparation of Symmetrical Diaryl Sulfoxides .. .12 B. The Reaction of jo-Tolyllithium with jo-Tolyl Sulfoxide....................................14 C. The Reaction of Mesityllithium with Mesityl Sulfoxide....................................22 III. EXPERIMENTAL.....................................30 A. Preparation of Symmetrical Diaryl Sulfoxides and Derivatives.............................. 30 1. The Reaction of Grignard Reagents with N,N*-Thionyl di-imidazole................. 30 2. Oxidation of Sulfoxides to Sulfones......... 34 3. Reduction of Sulfoxides to Sulfides......... 35 B. Preparation of m,p’ -Bitolyl................... 35 1. Attempted Preparation by a Diazotization Reaction................................. 35 2. The Reaction of £-Tolylmagnesium Bromide with 3-Methylcyclohexanone................ 36 iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLES OF CONTENTS (continued) Page C. The Reaction of £-Tolyllithium with p-Tolyl Sulfoxide.................................... 37 D. The Reaction of p-Mesityllithium with Mesityl Sulfoxide.................................... 41 E. Gas Chromatographic Analyses.................. 44 1. Purification of m-jp’ -Bitolyl............... 44 2. Product Analysis of the Reaction of p- Tolyllithium with £-Tolyl Sulfoxide......... 45 IV. SUMMARY.......................................... 51 V. BIBLIOGRAPHY..................................... 65 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES Page 1. Substituted Diphenyl Sulfoxides and Derivatives...... 32 2. Determination of Weight Factors for Quantitative Gas Chromatographic Analysis........................49 3. Product Analysis of the Reaction of p-Tolyllithium with £-Tolyl Sulfoxide............ T ............... 50 vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES Page 1. Nuclear Magnetic Resonance Spectrum of ^ 2. Nuclear Magnetic Resonance Spectrum of C20H26SO...... 57 3. Nuclear Magnetic Resonance Spectrum of m,p-Bitolyl....58 4. Nuclear Magnetic Resonance Spectrum of Mesityl Sulfide........................................... 59 5. Infrared Spectrum of C27H32S....................... 60 6. Infrared Spectrum of C20H26S^...................... ^ 7. Infrared Spectrum of m,£! -Bitolyl................... 62 8. Infrared Spectrum of Mesityl Sulfide................ 63 9. Infrared Spectrum of Di(£-trifluoromethyl)biphenyl. .. .64 vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT SOME REACTIONS OF ARYLLITHIUMS WITH ARYL SULFOXIDES by SANDRA YEAGER BAST The mechanism of the reaction of sulfoxides with organolithium reagents is now known with certainty. Various mechanisms have been invoked to explain the products ob­ served depending on whether the sulfoxide is dialkyl, aralkyl or diaryl. Previous work by the author concerning the reaction of phenyllithium with phenyl sulfoxide had indicated that a sulfonium salt and benzyne were intermedi­ ates in the reaction. Other workers had argued in favor of the formation of a tetracovalent intermediate which then collapsed to products. The present work was carried out in an attempt to clarify the mechanism of the reaction of aryllithium reagents with aryl sulfoxides. The same para substituent was used on both the aryl­ lithium reagent and on the diaryl sulfoxide. If the mechanism follows a benzyne pathway, then a 4-substituted benzyne would be expected to be formed and subsequent reaction of Vlll• • • Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. this aryne with excess aryllithium would lead to two isomeric biaryls, £,£* -disubstituted and m,£’ -disubstituted. The m,£’ -isomer could arise only from a 4-substituted benzyne and not from collapse of a tetracovalent intermediate nor by a direct nucleophilic displacement of the aryllithium reagent on an intermediate sulfonium salt nor on the original sulfoxide. Any of these latter mechanisms would give rise to only the £,£' -isomer. Generation of a 4-substituted benzyne was shown to occur in the reaction of £-tolyllithium with £-tolylsulfoxide. The major products were toluene, £- tolyl sulfide (98.97o), £,£’ -bitolyl (48.4-607o) and m,£'- bitolyl (19.7-27.67o) . The formation of m,£'-bitolyl in significant amounts indicates a predominate aryne mechanism and excludes a tetracovalent intermediate or nucleophilic displacement as the only pathway. For reactions in the literature known to proceed through an aryne mechanism, the isomer ratios for substitu­ tion of a given aryne are virtually constant. With 4-methyl- benzyne, meta substitution is favored somewhat over para substitution (58 meta/42 para). The fact that the isomer ratio obtained in this study is 28 meta/72 para certainly does not discredit a benzyne mechanism here as well. It, instead, suggests that although a benzyne mechanism ix Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. predominates (calculated to be greater than 507,) , an alternate mechanism may also be taking place. These alternate possi­ bilities are discussed. When there are no ortho-hydrogens on the sulfoxide or on the lithium reagent, as in the case of mesityl sulfoxide and mesityllithium, an aryne mechanism cannot occur and completely different types of products are obtained. The major products are mesitylene, C20H26SO an°* C27H32S * Gom" plete identification of the last two substances was not achieved, but possible structures are suggested as well as possible mechanisms for their formation. Failure to obtain mesityl sulfide and bimesityl as products serves as evidence against collapse of a tetracovalent intermediate or a nucleo­ philic displacement reaction on mesityl sulfoxide or on an intermediate trimesityl sulfonium salt. A new preparation of symmetrical diaryl sulfoxides has been devised employing the reaction of a Grignard reagent with N,N' -thionyldiimidazole. This method offers a convenient synthesis of symmetrical diaryl sulfoxides, provided the desired