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Syntheses of Some Cyclopropenes and a Study of the Ir Mode of Rearrangement Using Homogeneous Catalysts Northern Michigan University NMU Commons All NMU Master's Theses Student Works 1973 Syntheses of Some Cyclopropenes and a Study of the ir Mode of Rearrangement Using Homogeneous Catalysts Arudi Lakshminarasimhaiah Ravindra Northern Michigan University Follow this and additional works at: https://commons.nmu.edu/theses Recommended Citation Ravindra, Arudi Lakshminarasimhaiah, "Syntheses of Some Cyclopropenes and a Study of the ir Mode of Rearrangement Using Homogeneous Catalysts" (1973). All NMU Master's Theses. 253. https://commons.nmu.edu/theses/253 This Open Access is brought to you for free and open access by the Student Works at NMU Commons. It has been accepted for inclusion in All NMU Master's Theses by an authorized administrator of NMU Commons. For more information, please contact [email protected],[email protected]. "SYNTHESES OF SOME CYCLOPROPENES AND A STUDY OF THEIR MODE OF REARRANGEMENT USING HOMOGENEOUS CATALYSTS" BY ARUDI LAKSHMINARASIMHAIAH RAVINDRA B.Sc(HONS.), M.Sc., CENTRAL COLLEGE, BANGALORE UNIVERSITY, INDIA. A Thesis Submitted in Partial Fulfillment of the Requirement for the Degree of Master of Arts in Chemistry School of Graduate Studies Northern Michigan University Marquette, Michigan August 1973 ProQuest Number: 10804880 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10804880 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 "SYNTHESES OF SOME CYCLOPROPENES AND A STUDY OF THEIR MODE OF REARRANGEMENT USING HOMOGENEOUS CATALYSTS" by ARUDI LAKSHMINARASIMHAIAH RAVINDRA This thesis is recommended for approval by the students thesis committee: a Chairman Approved by Dean of Graduate Studies Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Arts Northern Michigan University Marquette, Michigan August 1973 ABSTRACT Attempts to synthesize several cyclopropene derivatives are described. The experimental parameters and the optimum reaction conditions are discussed in detail as are the structure and properties of cyclopropene derivatives. Attempts to study the mode of rearrangement of cyclopropene derivatives using homogeneous catalysts are briefly discussed, although the structures of the rearrangement products are not fully understood. ACKNOWLEDGEMENTS The author wishes to thank Dr.Jerome A.Roth for his excellent guidance, both academically and technically, throughout the research and while writing this thesis. Of the many friends and relatives who provided constant en­ couragement, the author is much obliged to Mr.Cliff Schmalzigan and Mr.George Thottakara for their invaluable encouragement throughout the research, especially during moments of frus­ tration, without the help of which this thesis would not have had much physical significance to the author. Finally, the author appreciates the suggestions offered by his thesis committee. iv TABLE OP CONTENTS ABSTRACT ................................ iii ACKNOWLEDGEMENTS ................................ iv LIST OP TABLES ................................ vi LIST OP FIGURES ................................ vii INTRODUCTION 1) Ring strain ......................... 2 2) Mechanism 11 EXPERIMENTAL 1) Experimental conditions .......... 17 2) Experimental procedures: i) Compounds 19 ii) Reactions ...... 22 3) Analyses 34 RESULTS 1) Tricyclopentane system ........ 35 2) Reaction conditions 36 3) Synthetic products .... 38 4) Spectral characteristics .......... 42 5) Rearrangement reactions .......... 45 DISCUSSION .............................. 45 REFERENCE .............................. 51 v LIST OF TABLES TABLE 1 Coupling Constants and s-character. .... 5 TABLE 2 Structural Parameters of Cyclopropene. * 7 TABLE 3 Reactions of Acetylenes with DIazoacetate; ... 15 some reported results. TABLE 4 Starting Materials. 3.9 TABLE 5 Reactions of Some Acetylenes with Diazoacetate. 39 TABLE 6 Reactions Of methyl phenyl propiolate(VIII) ... 39 TABLE 7 Polymerization(Reaction) Times .42 TABLE 8 Infrared Absorptions. J43 TABLE 9 Chemical Shifts Of Cyclopropyl Proton............44 vi LIST OF FIGURES Orbital Overlap in Cyclopropane 3 Dependence of J n on s-character 4 C H Tricyclopentane System 6 Syntheses; first method. 9 Syntheses; second method. 10 Syntheses; third method. 10 Syntheses; fourth method. 10 Mechanism 1. 12 Mechanism 2. 12 Mechanism 3- 13 Attempt to Synthesize the Tricyclopentane System. 35 vii INTRODUCTION The chemistry of cyclopropene and its deriva­ tives is of considerable interest to the theoretical organic chemist as well as the synthetic organic chemist. The interestingly high degree of ,TBaeyer strain" that is incorpo­ rated in the cyclopropene nucleus makes it a suitable subject for theoretical treatments of bonding in organic compounds. Many useful concepts such as aromaticity, bent bonds and hybridi­ zation have been and will continue to be tested on compounds with the cyclopropene structure. The chemistry of cyclopropene and its derivatives is by no means a new subject. The parent hydrocarbon itself has been known for more than four decades. Considering the highly unusual structure of cyclopropene, it is rather astonishing that very little or almost no attention was paid to the chemistry of cyclopropene and its derivatives until the mid-1950Ts. Probably, the four factors which were responsible to a great extent for this remarkable upsurge of activity in the field during the last fifteen years are: a. Tbe developments ,in carbene chemistry provided many new methods for the syntheses of cyclopropene derivatives. b. The application of molecular orbital theory to problems in organic chemistry had become sufficiently common that an attack on the syntheses of cyclopropenyl cations became a challenging goal to the synthetic organic chemist. c. The discovery that natural products, especially certain fatty acids, contain the cyclopropene nucleus(1) attracted the 1 attention of many natural product chemists. d. The interest and the challenge to synthesi e theoretically possible but highly strained compounds contai­ ning fused small rings, like cubane, tetrahedrane, etc.^ made synthetic cyclopropene chemistry a novel field of re­ search in organic chemistry. In order to appreciate the problem, it is necessary to understand the structure and stability of cyclopropene and its derivatives. At this point the structure of cyclopropane shall be .considered. One can extend these di­ scussions to the olefinic derivative, cyclopropene. Ring strain: Steric strain in a molecule exists when bonds are forced to make angles which are abnormal and this results in a higher energy than would be the case in the absence of angle distortions. There are, in general, two kinds of structural features which result in sterically caused ab­ normal bond angles. One of these is found in small-ring compounds, where the angles must be less than those result­ ing from normal orbital overlap. Such a strain is called "small angle strain". The other, called "non-bonded interac­ tions',’ arises when non-bonded atoms are forced into close proximity by the geometry of the molecule(2). To explain the strain in three-membered carbocyclic rings, it is necessary to examine the character of the bonds in the ring. As early as 19^9, the bonds in cyclopropane were discussed in an arti­ cle by Coulson and Moffitt(3). The angles between the lines 2 joining the carbon atoms are 60°. Those bonds of the carbon orbitals cannot be distorted that much from the tetrahedral angle of 109°. The smallest theoretically possible angle between the orbitals of carbon is 90° which is the angle between the pure p orbitals. Consequently, in cyclopropane, the electron density is directed away from the line joining the carbon atoms and the resulting bonds are intermediate in character between«r andbonds, and are called bent or "banana" bonds. Figure.1 shows the direction of orbital overlap. Cyclopropane:0 = 2l' Figure.1 Orbital Overlap in Cyclopropane(the arrows point toward the center of electron density)(4). The most important properties of the three-membered carbocyclic ring result from its tendency to attain the greatest possible overlap of the orbitals with resultant stabilization of the system. This is achiev­ ed by the reduction of the tetrahedral valence angle to 105°3 made possible by a partial change in the state of hybridization where the ring bonds assume higher p-character while the exocyclic bonds consequently acquire a higher 3 s-character. The increased s-character of the exocyclic bonds has been confirmed for many examples (Table 1). The degree of hybridization of a C-H bond can be measured using nuclear magnetic resonance spectroscopy(5)* Natural carbon contains 1.1JS of C 18 isotope which has a nuclear spin J=3g. The coupling of C 18 nuclei, present at the natural concentration in organic compounds, with the protons bonded to them can be measured by high resolu­ tion nuclear magnetic resonance spectroscopy(6). The coupling constant(125 - 250 hz) depends on the disposition of the electrons in the bond, i.e., on the bond order. Using the
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