Photochemistry of (E,E)-1,5-cyclodienes in protic and aprotic media Citation for published version (APA): Reijnders, P. J. M. (1979). Photochemistry of (E,E)-1,5-cyclodienes in protic and aprotic media. Technische Hogeschool Eindhoven. https://doi.org/10.6100/IR116882 DOI: 10.6100/IR116882 Document status and date: Published: 01/01/1979 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 25. Sep. 2021 PHOTOCHEMISTRY OF (f;,f;)-1,5-CYCLODIENES IN PROTIC AND APROTIC MEDIA PROEFSCHRIFT Ter verkrijging van de graad van Doctor in de Technische Wetenschappen aan de Technische Hogeschool Eindhoven, op gezag van de Rector Magnificus, Prof. Dr. P. v.d. Leeden, voor een commissie aangewezen door het College van Dekanen in het openbaar te verdedigen op vrijdag 4 mei 1979 te 16.00 uur door PETER JOSEPH MICHAËL REIJNDERS Geboren te Tegelen OFFSET KURVER SITTARD B.V. DIT PROEFSCHRIFT IS GOEDGEKEURD DOOR DE PROMOTOREN PROF. DR. H.M. BUCK EN DR. H. CERFONTAIN #aw ~/;e., ~~ ,#a;e ~/~~4~<!,. te;[_ ~t?>U)'U<:.- Die Natur ist aller Meister Meister Johann ~!o'lfgang Goethe Con.ten.ts Chapter 1 General introduction 9 I.1 The photoahemistry of alkenes 9 I.2 The photoahemistry of aayaZia and ayalie mono-enes in protie medfa 10 I.3 The photoahemistry of aeyelie and eyelie 1,5-dienes in protia media 11 Referenees 17 Chapter 11 The photochemistry of (,!?.)-2,6-dimethyl- 2,6-octadiene 19 II.1 Introduetion 19 II.2 Synthesie of (EJ-2,6-dimethyl-2,6- oatadiene 19 II.3 Irradiation of (E)-2,B-dimethyl- 2,6-oetadiene 20 II.4 Disaussion 21 II.5 Experimental part 22 Referenees 24 Chapter 111 The photochemistry of (E ,E)-germacra- 1 ( 10), 4, 7 ( 11 )-trien-8-one 25 III.1 Introduetion 25 III.1.1 Chemistry of (E,E)-germa­ ara-1(10),4,7(11)-trien- 8-one 25 III.1.2 Photoahemistry of enones 26 III.2 Irradiation of germaerone 27 III.3 ExperimentaZ part 29 Referenaes and Notes 32 Chapter IV The photochemistry of rn..!D-germacra- 1 (10) ,4, 7(11)-triene 34 )V.1 Introduation 34 IV.2 Synthesis of (E,EJ-germaarene 35 IV.3 Irradiation of (E,E)-germaarene 36 IV.4 Disaussion 37 IV.S Struature eluaidation of the produats formed by irradiation of (E,E)- germaarene 41 IV.6 Experimental part 44 Referenaes and Notes 48 Chapter V Synthesis of (_g -1, 5-cyclodienes 49 V.1 Introduation 49 V.2 Synthesis of (E,E)-3,3'-polymethyZ- enebis(allylbromides) 51 V.3 Cyalization of (E,E)-3,3 1 -poZy­ methylenebis(allylbromides) 52 V.4 Disaussion 54 V.S Experimental part 56 Referenaes and Notes 63 Chapter VI The photochemistry of (É_"~)-1, 5-cyclo­ dienes 66 VI.1 Introduation 66 VI.2 Irradiation of (E,EJ-1,5-ayalo­ dienes 67 VI.3 Meahanism for the formation of the photoproduats of (E,E)-1,5-ayalo- dodeaadiene 69 VI. 4 General disaussion 71 VI.S Struature eZuaidation of the produats formed by irradiation of (E,E)-1,5- ayalododeaadiene 72 VI.6 Experimental part 73 Referenaes and Notes 75 SuIDIDar")' 76 SaIDenvatting 78 CurriculuID vitae 80 Dankwoord 81 The work described in this thesis was supported by The Netherlands Foundation for Chemical Research (SON) with financial aid from The Netherlands Organization for the Advancement of Pure Research (ZWO). CHAPTER 1 General introduction I.1 The photoahemistry of aZkenes During the last decades photochemistry is receiving much interest, which is strongly stimulated by reasons of energy­ fixation originating from solar energy. In particular, organic molecules containing chromophoric groups are excellent systems for the conversion of light quanta into chemica! bonds. Con­ siderable progress in the understanding of photochemical re actions of alkenes was achieved by the outstanding investigat­ ions of Havinga and SahZatmann 1 of conjugated olefinic systems visualized in the photochemical isomerization of ergosterol into lumisterol and viae versa. The theoretical rationalization of the complementary behaviour under thermal and photochemical circumstances was made fully understandable by Woodward and Hoffmann 2 in their comprehensive study of reactions controlled by orbital symmetry considerations, already mentioned by 3 Oosterhoff • This approach offered the conditions for the synthesis of strained organic molecules by irradiation, from which the stored energy can be liberated only in the presence 4 of metal catalysts under thermal conditions • For compounds which contain only C=C chromophores, the lowest singlet electronic excitation (n + nx) corresponds with 170-180 nm(~ 700 kJ/mol). The triplet excitation energy is considerably lower (~ 350 kJ/mol). In view of the large energy difference (S + T),the intersystem crossing in alkenes is quite unlikely. Merer and Mulliken's 5 calculations have showed that in both singlet and triplet state rotation about the central olefinic bond occurs since there is no effective n- 9 double bond in the TI~-excited state. The energy minimum for this rotation is to be found in the perpendicular conformat­ ion (Fig. I-1). The existence of this relaxed twisted E (kJ /rooie) î 200 îtfi lt Torsionol Angle ---- Fig. I-1 Energy vePsus rotation about the centra! bond in the excited states of ethylene; relaxed twisted state at TI/2 ("phantom") state also explains clearly the photochemical § 6 1 to~ isomerization of olefins • Calculations by Salem et al revealed that in the relaxed twisted state a relatively high charge separation may be present for the initiation of photo­ chemical reactions. I.2 The photoahemiatPy of aayalia and ayalia mono-enes in pPotia media Investigations on alkene photochemistry have been limited mainly to acyclic systems in the presence of sensi­ tizers6 • 8. Beside photoaddition to the sensitizer in certain cases, the only genera! pattern of behaviour to emerge was § to ~ isomerization, a transformation arising from the ortho­ gonal conformation of the triplet state. Other processes which 10 may arise from this peculiar geometry have been discovered by 9 10 Kropp and Marshall , independently. lrradiation of p-menth- 1-ene l in methanol/p-xylene brought forth a mixture of the exocyclic derivative ~and the ethers 1 (Fig. I-2). Further hv + 2 3 Fig. 1-2 Products of irradiation of p-menth-1-ene in methanol 11 17 investigations - on this subject resulted in the following mechanistic picture. After attainment of the n-n~ triplet, rapid relaxation into the orthogonal oriented species occurs after which T +{S~}intersystem crossing to either the f or~­ IS~} manifold can easily be achieved. Although acyclic and cyclic alkenes with a ring larger than cyclohexane are rela- ti ve ly free to adopt an orthogonal triplet geometry and isomerize to a ground state olefin, the incorporation of the double bond in a small ring leads to severe restrictions on the "free rotor effect". The resulting ~-cycloalkene would be extraordinarily strained, and relief of strain via rapid pro­ tonation occurs. This results in exocyclic alkene formation (proton abstraction) or ether forrnation (quenched by methanol). Radical abstraction from the solvent and/or dimerization of the product are the observed processes if an g-species cannot 11 be accommodated • 1.3 The photoahemistry of aayalia and ayalia 1,5-dienee in protia media Photochemical reactions on acyclic 1,5-dienes, mainly 1 1 performed in the vapour phase, led to radical-induced re­ arrangement products 1 8 (Fig. 1-3). Acetone sensitiz.ed irra­ 19 diation gives §to Z isomerization • There are no reports on irradiations of acyclic 1,5-dienes in protic media, however, hv + +. c Hg B Fig. I-3 Vapour phase irradiation of 1 ,5-hexadiene on cyclic 1,5-dienes there is quite some documentation. Re­ search on these compounds is mainly based on compounds con­ taining the c~.~)-1,5-cyclodecadiene skeleton, which are easily accessible as natural products (sesquiterpenes). The interrelation between conformation and product structure in cyclization of these natural products was elucidated by 0 Suther • Depending on the conformation adopted by the 1,5-diene segment a crossed orientation (leading toa chair cyclohexane) or a parallel orientation (leading to a twisted baat cyclohexane) of the double bonds can be discerned.