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I. the Cycloheptatriene-Norcaradiene Equilibrium Problem: Solvolysis of Norcaradienylcarbinyl Derivatives

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I. the Cycloheptatriene-Norcaradiene Equilibrium Problem: Solvolysis of Norcaradienylcarbinyl Derivatives Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1976 I. The cycloheptatriene-norcaradiene equilibrium problem: Solvolysis of norcaradienylcarbinyl derivatives. II. Solvolytic formation of bridgehead olefins. III tudiesS of certain cyclopropyl anions and radicals Shih-Lai Lu Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Lu, Shih-Lai, "I. The cycloheptatriene-norcaradiene equilibrium problem: Solvolysis of norcaradienylcarbinyl derivatives. II. Solvolytic formation of bridgehead olefins. III Studies of certain cyclopropyl anions and radicals " (1976). Retrospective Theses and Dissertations. 6242. https://lib.dr.iastate.edu/rtd/6242 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s}". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NOTE: Some pages may have indistinct print. Filmed as received. Xerox University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106 77-7 LU, Shih-Lai, 1946- I. THE CYCLOHEPTATRIENE-NORCARADIENE EQUILIBRIUM PROBLEM. SOLVOLYSIS OF NORCARADIENYLCARBINYL DERIVATIVES. II. SOLVOLYTIC FORMATION OF BRIDGEHEAD OLEFINS. III. STUDIES OF CERTAIN CYCLOPROPYL ANIONS AND RADICALS. Iowa State University, Ph.D., 1976 Chemistry, organic Xerox UniVGrSity Microfilms, Ann Arbor, Michigan 48106 I. The cycloheptatriene-norcaradiene equilibrium problem. SolYolysis of norcaradienylcarbinyl derivatives. II. Solvolytic formation of bridgehead olefins. III. Studies of certain cyclopropyl anions and radicals. by Shih-Lai Lu A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Department: Chemistry Major: Organic Chemistry Approved: Signature was redacted for privacy. n Charge of Major Work Signature was redacted for privacy. Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1976 il TABLE OF CONTENTS Page ABSTRACT iii PART I: THE CYCLOHEPTATRIENE-NORCARADIENE EQUILIBRIUM PROBLEM. SOLVOLYSIS OF NORCARADIENYLCARBINYL DERIVATIVES 1 INTRODUCTION 2 RESULTS AND DISCUSSION 13 EXPERIMENTAL ^0 PART II: SOLVOLYTIC FORMATION OF BRIDGEHEAD OLEFINS 85 INTRODUCTION 86 RESULTS AND DISCUSSION 112 EXPERIMENTAL 190 PART III: STUDIES OF CERTAIN CYCLOPROPYL ANIONS AND RADICALS 242 INTRODUCTION ^^3 RESULTS AND DISCUSSION 263 EXPERIMENTAL 284 BIBLIOGRAPHY 298 ACKNOWLEDGMENTS 310 ill ABSTRACT The kinetics of solvolysis of the epimeric tricyclo- 0^'^]deca-2,4'-diene-10-carbinyl 3f5-dinitro'benzoates, as well as their monoolefin and saturated derivatives, were determined in aqueous acetone. It was found that the anti series solvolyzed faster than the svn analogs. The rate constants were employed to calculated the equilibrium constant for the monosuhstituted cycloheptatriene-norcaradiene equi­ librium; the estimated energy barrier was ca. 4.5 kcal/mole. The second part concerns the study of the silver-assisted hydrolysis (in aqueous acetone) and buffered acetolysis of some monobromo- and dihalopropellanes. The major products formed upon solvolysis of the 10,10-dibromo[4o3.1]propellanes indicated that the reactions occurred via bridgehead olefins transoid in a 7-membered ring, followed by protonation and rearrangement» The solvolysis of ll,ll-dihalo[4.4.l]pro- pellanes were also shown, via the use of 13^C-labeling at the position, to proceed via the intermediacy of a bridgehead olefin species, contrary to ear-.ier conjecture. The relative difficulty of generating a bridgehead double bond transoid in a 6-membered ring was demonstrated by the minor amount of such products isolated from the hydrolysis of 9,9-dlbromo- [3.3.1]propellane. Comparison of the percentage of products which arose from the bridgehead olefin intermediates with iv that which arose from collaps at the bridge position allowed one to estimate an energy difference "between the two type of bridgehead olefins (i._e. , 7 and 6-membered rings) of ca. 6 kcal/mole. Combination of the rate and product data required that all the anti-lO-bromof^. 3.l]T)ropellanes solvolyze via a "partially-opened" cyclopropyl cation intermediate. Part three describes an investigation of the Grignard reagents derived from the epimeric 10-bromo[4.3.l]propellanes; radical intermediates were indicated. The results revealed that the stereoselective formation of the product arose from reduction of the cyclopropyl radicals anti the the 6-membered ring, regardless of the stereochemistry of the starting bromid bromides or the presence of double bonds in the 6-membered ring. Inversion of svn cyclopropyl radicals to the more stable anti analogs was rationalized by arguing that nonbonding interaction between two hydrogens is worse than that between one hydrogen and one half-filled orbital. 1 PART I; THE CYCLOHEPTATRIENE-NORCARADIENE EQUILIBRIUM PROBLEM. SOLVOLYSIS OF NORCARADIENYLCARBINYL DERIVATIVES 2 INTRODUCTION The Cycloheptatriene-Norcaradiene Equilibrium Problem The first substituted norcaradiene, 1, formed from the thermal decomposition of diazoacetic ester in benzene, was reported in 1888 by Buchner.^ It had been generally accepted that the Buchner esters were mixtures of the basic monocyclic and bicyclic structures until Doering and co­ workers 2 reinvestigated the subject. These authors conclud- ed that the Buchner esters are just the four positionally Isomeric cycloheptatriene esters, with the ester group occupying 1, 2, 3» and 7 of the seven-membered ring 2. A third structure 2 was considered by Doering, i.e., an intermediate structure which would be regarded as a pseu- doaromatlc planar compound, a homobenzene; ^ was proposed on the basis of the heat of hydrogénation of cycloheptatriene. 1 2 The problem associated with the valence-tautomeric equilibrium has received a great deal of attention since Doering's work. Until 196?, many experimental results 3 showed that cycloheptatriene and its simple substitution products exist entirely in the monocyclic form.^ Never­ theless, it was found that the isomerization of 4 to 5 takes place only at high temperature, due to dearomatization of the "benzene ring^'during the process. Conversely, benzocycloheptatrienes 6 and 2 do not isomerize to the nor- caradiene form _8 and respectively.^ 7 8 Vogel and coworkers' discovered a very elegant method of fixing the norcaradiene structure. In compound 10 the carbon atoms 1 and 6 of the norcaradiene are held in posi­ tion by an additional five-membered ring (bracket effect). On the other hand, compounds^' containing a tetramethylene bridge are more stable in the cycloheptatriene form, 11. CO_R 8 11 Gunther, et al.^^ found that 12 was more stable than 13 by 0.2 k.cal/mole and that the barrier for the process 12^ 13 was less than 6.6 kcal/mole on the basis of results obtained from variable temperature cmr experiments. It has 13 been shown by Giinther that compound l4 also exists in valence-tautomeric equilibrium with the norcaradiene form. 12 11 14 The magnitude of the H-H coupling constant between the methylene protons (3-5 Hz for norcaradienes and 7-12 Hz for cycloheptatriene derivatives^' 15-23 ^^C-H coupling 17-23 15-23 constants" and UV data have been used to analyze for the presence of the norcaradiene form. There is no doubt that both compounds with the bicyclic and monocyclic form can exist, but the energy barrier between the two systems may vary considerably.
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