Title: An Aromatic‐Olefin Equilibrium: 1,6‐Methano[10]annulene‐Tricyclo[4.4.l.0<sup>1,6</sup>]undeca‐2,4,7,9‐Tetraene Valence Tautomerism
Abstract: Angewandte Chemie International Edition in EnglishVolume 12, Issue 7 p. 570-572 Communication An Aromatic-Olefin Equilibrium: 1,6-Methano[10]annulene-Tricyclo[4.4.l.01,6]undeca-2,4,7,9-Tetraene Valence Tautomerism† Prof. Dr. Harald Günther, Prof. Dr. Harald Günther Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDipl.-Chem. Hans Schmickler, Dipl.-Chem. Hans Schmickler Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDr. Wolfgang Bremser, Dr. Wolfgang Bremser Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDipl.-Chem. Franz A. Straube, Dipl.-Chem. Franz A. Straube Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorProf. Dr. Emanuel Vogel, Corresponding Author Prof. Dr. Emanuel Vogel Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this author Prof. Dr. Harald Günther, Prof. Dr. Harald Günther Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDipl.-Chem. Hans Schmickler, Dipl.-Chem. Hans Schmickler Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDr. Wolfgang Bremser, Dr. Wolfgang Bremser Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorDipl.-Chem. Franz A. Straube, Dipl.-Chem. Franz A. Straube Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this authorProf. Dr. Emanuel Vogel, Corresponding Author Prof. Dr. Emanuel Vogel Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Institut für Organische Chemie der Universität 5 Köln 41, Zülpicher Strasse 47 (Germany)Search for more papers by this author First published: July 1973 https://doi.org/10.1002/anie.197305701Citations: 29 † Applications of 13C-Resonance Spectroscopy, Part 6.—Part 5: ref. [11]. Generous support of this work by the Deutsche Forschungsgemeinschaft and the Fonds der chemischen Industrie is gratefully acknowledged. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References 1 E. Vogel and H. D. Roth, Angew. Chem. 76, 145 (1964); Angew. Chem. internat. Edit. 3, 228 (1964). 2(a) ESR: F. Gerson, E. Heilbronner, W. A. Böll, and E. Vogel, Helv. Chim. Acta 48, 1494 (1965); (b) electron diffraction: L. K. Montgomery and J. Croetzer personal communication; (c) 1H-NMR: H. Günther, Z. Naturforsch. 20 b, 948 (1965); (d) X-ray structure analysis: M. Dobler and J. D. Dunitz, Helv. Chim. Acta 48, 1429 (1965); (e) photoelectron spectrum: R. Boschi, W. Schmidt, and J.-C. Gfeller, Tetrahedron Lett. 1972, 4107; (f) UV: H.-R. Blattmann, W. A. Böll, E. Heilbronner, G. Hohlneicher, E. Vogel, and J.-P. Weber, Helv. Chim. Acta 49, 2017 (1966); (g) enthalpy of formation: W. Bremser, R. Hagen, E. Heilbronner, and E. Vogel, Helv. Chim. Acta 52, 418 (1969); (h) dipole moments: W. Bremser, H. T. Grunder, E. Heilbronner, and E. Vogel, Helv. Chim. Acta 50, 84 (1967). 3(a) M. Görlitz and H. Günther, Tetrahedron 25, 4467 (1969); (b) E. Ciganek, J. Amer. Chem. Soc. 93, 2207 (1971); E. Vogel, W. Wiedemann, H. D. Roth, J. Eimer, and H. Günther, Liebigs Ann. Chem. 759, 1 (1972), and further literature cited therein. 4 E. Vogel, Pure Appl. Chem. 20, 237 (1969); E. DeCleur, Dissertation, Universität Köln 1969. 5 V. Rautenstrauch, H.-J. Scholl, and E. Vogel, Angew. Chem. 80, 278 (1968); Angew. Chem. internat. Edit. 7, 288 (1968). 6 H. Günther and H. H. Hinrichs, Liebigs Ann. Chem. 706, 1 (1967). 7 There is still some uncertainty as to the correct interpretation of the C-1C-6 distance in solid (4 a) (1.80 Å) found by X-ray structural analysis ( R. Bianchi, A. Mugnoli, and M. Simonetta, Chem. Commun. 1972, 1073). 8 13C-NMR spectroscopy [10] proves superior to 1H-NMR spectroscopy in this case because the C-1,6 and C-11 resonances are more sensitive probes for the valence tautomerism (4) ⇌ (5). The changes in the resonance frequencies due to chemical exchange amount to ca. 2000 Hz (C-1,6) but less than 100 Hz in 1H-NMR spectroscopy (peripheral protons). Moreover, the13C-NMR spectra are not complicated by spin-spin coupling. Previous 1H-NMR spectra accordingly did not lead to clear-cut results. 9 H. Günther, H. Schmickler, H. Königshofen, K. Recker, and E. Vogel, Angew. Chem. 85, 261 (1973); Angew. Chem. internat. Edit. 12, 243 (1973). 10 H. Günther and T. Keller, Chem. Ber. 103, 3231 (1970). 11 H. Günther, H. Schmickler, and G. Jikeli, J. Magn. Resonance, in press. 12 E. Vogel and V. Rautenstrauch, unpublished. 13 Synthesis: E. Vogel and F. A. Straube, to be published. 14 In 11,11-dimethylene-1,6-methano[l0]annulene [13] C-1 and C-6 are deshielded in comparison with (1)(δ =123.2 ppm). Here the introduction of the three-membered ring could effect opening of the angle C-1C-11C-6 and thereby increase the distance between C-1 and C-6. It has not yet been established whether the deshielding is the result of an equilibrium shift or a manifestation [15] of the separation-dependent overlapping of the 2pz orbitals on C-1 and C-6 in the aromatic system which has been detected experimentally[2a,e,f]. A “normal” substituent effect (replacement of the H atoms at C-l1 byCH2CH2) could also be responsible for the deshielding, although the findings for (6) and (7) make this possibility appear rather unlikely. 15 Cf. A. V. Kemp-Jones, A. J. Jones, M. Sakai, C. P. Beeman, and S. Masamune, Can. J. Chem. 51, 767 (1973). 16 In one case we found a barrier Δ G* of 8—9 kcal/mol for the comparable norcaradiene-cycloheptatriene system[3 a]. Here the splitting of the 13C resonances was observed already at ca. −90°C. (H. Günther, W. Peters, and R. Wehner, unpublished). Since no line broadening could be detected for (4 a) ⇌ (5 a), even at –110°C, the known relationship between coalescence temperature and free energy of activation affords Δ G* < 6.6 kcal/mol for a δv value of 2000 Hz[8, 10] for this system. 17 Since this is to our knowledge the first case of valence tautomerism between an aromatic compound and an olefin the energetics of the system (4) ⇌ (5) are of particular interest. A Δ H° value of the order of 0.2 kcal/mol in favor of (4 a) can be estimated from the 13C data of (4 a) ⇌ (5 a). The question whether the dynamic process can also be ascribed to a valence tautomerism of the type (2) ⇌ (3) cannot be answered by 13C-NMR spectroscopy. However, this possibility can be ruled out on the basis of the UV spectra, which exhibit bands characteristic of the delocalized 10π system [2a, f] in all case. (We are grateful to Dr. W. A. Böll for a discussion on this point.) Citing Literature Volume12, Issue7July 1973Pages 570-572 ReferencesRelatedInformation
Publication Year: 1973
Publication Date: 1973-07-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 30
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