Durham E-Theses Some studies of polyuorinated polycyclic polyenes Hughes, Roger R. How to cite: Hughes, Roger R. (1975) Some studies of polyuorinated polycyclic polyenes, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/8213/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk SOME STUDIES OF POLYFLUORINATED POLYCYCLIC POLYENES by Roger R. Hughes, B.Sc. (Van Mildert College) The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged. A thesis submitted to the University of Durham for the Degree of Doctor of Philosophy 1975 ABSTRACT The attempted addition of difluorocarbene, which was generated from hexafluoropropene epoxide, to polyfluorinated cyclic olefins was largely unsuccessful, although perfluorobicyclo[4,l,0]hept-3-ene was isolated from the addition to perfluorocyclohexa-1,4-diene. It seems that difluorocarbene adds to the polyfluorinated cyclic olefins to form cyclopropanes, which readily eliminate difluorocarbene under the reaction conditions required for their formation. The attempted photochemical isomerisations of pplyfluorobicyclo[2,2,2]octa- 2,5-dienes, via the [2TI;+2TI;] ring closures to their corresponding tetracycles, were also unsuccessful. However, on irradiation dimethyl 1,4,5>6,7,7>8,8- octafluorobicycloC2,2,2]octa-2,5-diene-2,3-dicarboxylate formed a tricyclic biradical, which abstracted a hydrogen from the a methylene group of the diethyl ether solvent to give isomers of dimethyl 2-(3'-oxa-2'-pentyl)-l,4,5>6,7,7,8,8- octafluorotricycloC2,2,2,0-^''^]octane-2,3-dicarboxylate. The tricyclic biradical intermediate is similar to that proposed for the photochemical isomerisation of hydrocarbon bicyclo[2,2,2]hepta-2,5-dienes and their analogues. In contrast to their .corresponding hydrocarbon analogues the tricyclic biradical intermediates formed on irradiation of polyfluorobicyclo[2,2,2]octa-2,5-dienes do not appear to form tetracycles. 2 7 Perfluorotricyclo[6,2,2,0 ' ]dodeca-2,6,9-triene reacted as a diene in the Diels-Alder reactions with ethylene, but-2-yne, acetylene dicarboxylic acid dimethyl ester, perfluoroacetonitrile, tetrafluoroethylene and lH,2H-hexafluoro- cyclopentene. As a consequence imposed by the carbocyclic framework of the diene, the addition of lH,2H-hexafluorocyclopentene gave the exo adduct. The 1,4- alkyne adducts were pyrolysed to give 2,3-disubstituted hexafluoronaphthalenes. 2 7 The pyrolysis of perfluorotricycloC6,2,2,0 ' ]dodeca-2,6,9-triene proceeds 2 7 via a 1,3-alkyl migration to give perfluorotricyclo[8,2,0,0 ' ]dodeca-2,6,8-triene which subsequently eliminates tetrafluoroethylene to give perfluoro-l,2-dihydro- 2 7 naphthalene as the major product. The reaction of perfluorotricyclo[6,2,2,0 ' ]- dodeca-2,6,9-triene with lithium methyl in ether proceeded preferentially at the 2 7 diene moiety. The pyrolysis of the monomethyltridecafluorotricyclo[6,2,2,0 ' ]- dodeca-2,6,9-trienes gave monomethylnonafluoro-1,2-dihydronaphthalenes which had the methyl label in the non-aromatic ring. Nucleophilic substitution in perfluoro-1,2-dihydronaphthalene was found to occur only at the vinylic C3 position with sodium borohydride whereas with lithium methyl four monomethyl substitution products were obtained, both the vinylic, the C6 and C? fluorines being replaced. The gas phase photochemical reaction of perfluoro-1,2-dihydronaphthalene produces the perfluoro-1- and -2- methylenindanes possibly via the perfluorovinyl-o-quinodimethane. ACKNOWLEDGEMENTS I would like to thank Dr. W.J. Feast for his advice and help during the supervision of this work and Professor W.K.R. Musgrave for his interest. Assistance from the technical staff is appreciated and in particular, thanks* are due to Mr. D. Hunter for some practical assistance, I am also indebted to Mrs. E. McGauley for the presentation of the typescript and to Miss H. White for considerable help in the final preparation of this thesis. J . MEMORAr>IDUM The work in this thesis was cairried out in the Chemistry Laboratories of the University of Durham between October 1972 and July 1975. This work has not been submitted for any other degree and is the original work of the author except where acknowledged by reference. NOTF.S TO READER In this thesis compounds previously unreported in the literature are designated by large Roman numbers. [(XIX) and (XXI) have been reported but all of their spectral parameters are not available in the literature]. Other compounds are designated by Arabic numerals. The diagrams in the Introduction to all Chapters have unmarked bonds to hydrogen and in all Discussion Sections urmiarked bonds are to fluorine, unless otherwise stated. A reminder of this is given at the beginning of each Discussion. Tliroughout this thesis a number of abbreviations have been used regularly, these are: infrared spectroscopy (i.r.); ultra-violet spectroscopy (u.v.); mass spectroscopy (m.s.); nuclear magnetic resonance spectroscopy (n.m.r.); photoelectron spectroscopy (PES); gas-liquid chromatography (g.l.c); Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO). Generally the percentage composition of product mixtures has been determined from analytical g.l.c. peak areas which were obtained either by calibration or more usually by direct measurement from the gas density balance. 19 Many of the compounds reported in this thesis have very broad F n. m.r. signals that contain many coupling constants, however, in certain cases the actual width of an unresolved resonance has been helpful in ascertaining the presence or absence of large coupling constants and obviously for these systems it is the base line width that is necessgirily quoted. The chemical shift positions are quoted with respect to internal CFCl^ and internal T.M.S., unless otherwise stated and refer to the centres of bands. Integrated intensities are given in parentheses and coupling constants in Hz. The names of the compounds (I) —> (XXXXIV) are to be found in Appendix C, which also contains the infrared spectra. Appendix B contains the mass spectra 19 and structures of compounds in numerical order. The F n.m.r. data and the structures of compounds are generally to be found in Tables in the Discussions with the exceptions being (I), (V) and (Vl) whose structures are to be found 19 on pages 22, 53 and 95 respectively. The F n.m.r. data for the compounds (I) —>(XXXXIV) are to be found on: Page (I) 26 (II) (IV) Table 1 49 (V) 53 54 (VI) 119 (VII) —> (XII) Table 9 lOO 7-^ lOi (XIII) —^(XV) Table lO IO7 (XVI) and (XVII) Table 14 l4l (XVIII) Table 15 l44 (XIX) —(XXI) Table 16 l48 (XXII) Table 15 144 (XXIII) (XXVIII) Table 17 153 —^ 154 (pCX) (XXXVI) Table 21 191 192 (XXXVII) and (XXXVIII) Table 11 113 (XXXIX) -^(XXXXI) Table 23 2O3 (XXXXII) —^ (XXXXIV) Table 22 20i CONTENTS Abstract Acknowledgements Memorandum Notes to reader Page CHAPTER 1. The addition of difluorocarbene to polyfluorinated cyclic olefins INTRODUCTION 1.1 Methods of generating difluorocarbene 1 1.2 Generation of perfluoroalkylcarbenes 3 1.3 The preparation of polyfluorinated cyclopropanes from difluorocarbenes 4 1.4 Structure and reactivity of difluorocarbene 5 1.5 Structure and reactivity of perfluoroalkylcarbenes lO 1.6 Pyrolysis of highly fluorinated cyclopropanes 11 1.7 Cyclopropyl-allyl rearrangements , 13 DISCUSSION ' Experimental 1.8 Preparation of starting materials 24 1.9 Reaction of hexafluoropropene epoxide with polyfluorinated cyclic olefins 24 1.10 Pyrolysis of perfluorobicyclo[4,1,0]hept-3-ene 26 CHAPTER 2. The photochemistry of polyfluorobicyclo[2,2,2]octa- 2,5-dienes INTRODUCTION 2.1 The photochemistry of norbornadienes 27 2.2 Photochemistry of bicyclo[2,2,2]octa-2,5-dienes 33 Page 2.3 Photochemistry of bicyclo[2,2,0]hexa-2,5-dienes 36 2.4 Photochemistry of bicycloC3,2,2]nona-6,8-dienes 37 2.5 The effect of fluorine on the stability of the cyclopropane ring 38 2.6 The interaction of TC orbitals in non-conjugated bicyclic dienes 43 DISCUSSION 2.7 Preparation of starting materials and spectral parameters of the Diels Alder adducts of perfluorocyclohexa-1,3-diene 48 2.8 The photochemistry of polyfluorobicyclo[2,2,2]octa-2,5-dienes 5O EXPERIMENTAL 2.9 Preparation of starting materials 63 2.10 Photochemical reactions 65 2.11 Irradiation of polyfluorinated bicyclo[2,2,2]octa-2,5-diene systems (a) Gas phase irradiation of 1,2,3,4,7>7>8,8-octafluorobicyclo- [2,2,2]octa-2,5-diene (III) ' 65 (b) Gas phase photolysis of perfluoro-2,3-dimethylbicyclo- [2 ,2 ,2]octa-2 ,5-diene 66 (c) Irradiation of dimethyl l,4,5>6,7,7,8,8-octafluorobicyclo- [2,2,2]octa-2,5-diene-2,3-dicarboxylate 66 (d) The photolysis of perfluoro-2,3-dimethylbicyclo[2,2,2]octa- 2,5-diene in CFCl^ 70 CHAPTER 3. Diels-Alder reactions of tetradecafluorotricyclo- p 7 [6,2,2,0"^'