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Synlett 2008(17): 2633-2636  
DOI: 10.1055/s-0028-1083496
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Synthesis of Triazadibenzo[cd,g]azulenes: How To Connect Four Different Rings in Just One Step?

Martin Matschkea, Rainer Beckert*a, Ernst-Ulrich Würthwein*b, Helmar Görlsc
a Institut für Organische und Makromolekulare Chemie, Friedrich-Schiller-Universität Jena, Humboldtstr. 10, 07743 Jena, Germany
Fax: +49(3641)948212; e-Mail: C6bera@uni-jena.de;
b Organisch-Chemisches Institut, Universität Münster, Corrensstr. 40, 48149 Münster, Germany
Fax: +49(251)8339772; e-Mail: wurthwe@uni-muenster.de;
c Institut für Anorganische und Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessingstr. 8, 07743 Jena, Germany
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Publication History

Received 3 July 2008
Publication Date:
01 October 2008 (online)

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Abstract

Deprotonation at the methyl group of 6-methyl-4H-imid­azo[1,2-a]pyridines yields dimeric triazadibenzo[cd,g]azulenes in just one step. This reaction is interpreted as a cascade reaction involving an anionic electrocyclization reaction, a redox sequence and a subsequent dimerization process. The X-ray structural analysis revealed an anti arrangement of both tetracyclic subunits. By quantum chemical calculations the unexpected ring-closure reaction is interpreted in terms of electronic destabilization of the anionic intermediates 8 by configurational strain enabling the otherwise thermodynamically unfavorable cyclization process.

Key words

electrocyclic reactions - quantum chemical calculations - oxidations - fused ring systems - pyridines

    References and Notes

  • 1a Beckert R. Bauer W. J. Prakt. Chem.  1991,  333:  555 
    Search in Google Scholar
  • 1b Käpplinger C. Beckert R. Günther W. Görls H. Liebigs Ann./Recl.  1997,  617 
  • 1c Käpplinger C. Beckert R. Imhof W. J. Prakt. Chem.  1998,  340:  323 
    Search in Google Scholar
  • 1d Käpplinger C. Beckert R. Darsen A. Günther W. Sulfur Lett.  2001,  281 
  • 2a Brandenburg J. Käpplinger C. Beckert R. Synthesis  1996,  1302 
  • 2b Käpplinger C. Gebauer T. Beckert R. Weiß D. Günther W. Görls H. Friedrich M. Tetrahedron  2004,  60:  3847 
    Search in Google Scholar
  • 3 Stöckner F. Beckert R. Gleich D. Birckner E. Günther W. Görls H. Vaughan G. Eur. J. Org. Chem.  2007,  1237 
    Crossref
  • 4 Matschke M. Blumhoff J. Beckert R. Tetrahedron  2008,  64:  7815 
    CrossrefSearch in Google Scholar
  • 5a Atzrodt J. Brandenburg J. Käpplinger C. Beckert R. Günther W. Görls H. Fabian J. J. Prakt. Chem./Chem.-Ztg.  1997,  339:  729 
    Search in Google Scholar
  • 5b Müller D. Beckert R. Görls H. Synthesis  2001,  601 
  • 5c Beckert R. Hippius C. Gebauer T. Stöckner F. Lüdigk C. Weiß D. Raabe D. Günther W. Görls H. Z. Naturforsch., B  2006,  61:  437 
    Search in Google Scholar
  • 6a Atzrodt J. Beckert R. Görls H. Heterocycles  1999,  51:  763 
    Search in Google Scholar
  • 6b Gebauer T. Beckert R. Weiß D. Knop K. Käpplinger C. Görls H. Chem. Commun.  2004,  1860 
  • 6c Matschke M. Käpplinger C. Beckert R. Tetrahedron  2006,  62:  8586 
    Search in Google Scholar
  • 9a Frisch MJ. Trucks GW. Schlegel HB. Scuseria GE. Robb MA. Cheeseman JR. Montgomery JA. Vreven T. Kudin KN. Burant JC. Millam JM. Iyengar SS. Tomasi J. Barone V. Mennucci B. Cossi M. Scalmani G. Rega N. Petersson GA. Nakatsuji H. Hada M. Ehara M. Toyota K. Fukuda R. Hasegawa J. Ishida M. Nakajima T. Honda Y. Kitao O. Nakai H. Klene M. Li X. Knox JE. Hratchian HP. Cross JB. Bakken V. Adamo C. Jaramillo J. Gomperts R. Stratmann RE. Yazyev O. Austin AJ. Cammi R. Pomelli C. Ochterski JW. Ayala PY. Morokuma K. Voth GA. Salvador P. Dannenberg JJ. Zakrzewski VG. Dapprich S. Daniels AD. Strain MC. Farkas O. Malick DK. Rabuck AD. Raghavachari K. Foresman JB. Ortiz JV. Cui Q. Baboul AG. Clifford S. Cioslowski J. Stefanov BB. Liu G. Liashenko A. Piskorz P. Komaromi I. Martin RL. Fox DJ. Keith T. Al-Laham MA. Peng CY. Nanayakkara A. Challacombe M. Gill PMW. Johnson B. Chen W. Wong MW. Gonzalez C. Pople JA. Gaussian 03, Revision C.02   Gaussian, Inc.; Wallingford CT: 2004. 
  • 9b

    Details of the quantum chemical calculations may be obtained from E.-U. Würthwein upon request.

  • 10 Energies of the DFT-optimized structures were calculated using the SCS-MP2-method. They include DFT zero point correction. See: Grimme S. J. Chem. Phys.  2003,  118:  9095 
    CrossrefSearch in Google Scholar
  • 11 Goumans TPM. Ehlers AW. Lammertsma K. Würthwein E.-U. Grimme S. Chem. Eur. J.  2004,  10:  6468 
    Search in Google Scholar
  • 12 Klötgen S. Fröhlich R. Würthwein E.-U. Tetrahedron  1996,  52:  14801 
    CrossrefSearch in Google Scholar
  • 13 Klötgen S. Würthwein E.-U. Tetrahedron Lett.  1995,  36:  7065 
    CrossrefSearch in Google Scholar
  • 14 Gerdes K. Sagar P. Fröhlich R. Wibbeling B. Würthwein EU. Eur. J. Org. Chem.  2004,  3465 
    Crossref
7

Crystal Data for Compound 10: C44H34N8˙2CHCl3, Mr = 913.53 gmol-¹, blue prism, size 0.04 × 0.04 × 0.04 mm³, triclinic, space group Pi, a = 11.4589 (4), b = 12.5571 (5), c = 15.8154 (9) Å, α = 82.756 (2)˚, β = 68.797 (3)˚, γ = 79.149 (2)˚, V = 2079.51 (16) ų, T = -90 ˚C, Z = 2, ρcalcd. = 1.459 gcm-³, µ(Mo-Kα) = 4.59 cm-¹, F(000) = 940, 14823 reflections in h(-14/14), k(-16/16), l(-16/20), measured in the range 1.95˚≤ Θ ≤27.50˚, completeness Θmax = 99.3%, 9491 independent reflections, Rint = 0.0415, 6118 reflections with Fo >4σ(Fo), 553 parameters, 0 restraints, R1obs = 0.0663, wR² obs = 0.1607, R1all = 0.1129, wR² all = 0.1922, GOOF = 0.983, largest difference peak and hole: 1.255/-0.416 e Å-³. CCDC 686207 (10) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 (1223)336033; or deposit@ccdc.cam.ac.uk].

8

Preparation of 10 Starting from 1 and 2-Amino-6-methylpyridine (6; R = Me); Typical Procedure: A solution of 2-amino-6-methylpyridine (6; 0.216 g, 2.00 mmol) in MeCN (20 mL) was added to a solution of oxalic acid bisimidoylchloride 1 (0.610 g, 2.00 mmol) in MeCN (20 mL). After addition of Et3N (1.4 mL, 10 mmol) the reaction mixture was heated under reflux for about 4-5 h. The purple solution was cooled to r.t., evaporated to dryness and the product was isolated by column chromatography (SiO2, toluene-acetone, 100:1). The bis(2,11,11b-triazadibenzo[cd,g]dihydroazulene) 10 was obtained as dark blue crystalline solid. Selected data for 10: yield: 0.20g, 30%; mp >250 ˚C (dec.). MS (DEI): m/z (%) = 675 (5) [M+], 674 (8) [M+ - 1], 541 (12), 486 (26), 441 (11), 338 (16), 337 (18), 234 (31), 205 (21), 149 (35), 133 (47), 106 (100), 78 (27). ¹H NMR (CDCl3): δ = 2.17 (s, 6 H), 2.25 (s, 6 H), 3.99 (s, 2 H), 6.48 (s, 2 H), 6.65 (d, ³ J = 9.0 Hz, 2 H), 6.83 (d, ³ J = 7.0 Hz, 2 H), 6.87 (d, ³ J = 7.0 Hz, 2 H), 7.05 (m, 2 H), 7.20 (d, ³ J = 9.5 Hz, 4 H), 7.65 (d, ³ J = 8.0 Hz, 4 H), 7.74 (d, ³ J = 8.3 Hz, 2 H). ¹³C NMR (CDCl3): δ = 20.8, 21.2, 41.6, 116.0, 119.9, 120.2, 125.3, 128.5, 129.3, 130.2, 130.4, 132.3, 133.1, 135.6, 139.8, 141.3, 141.7, 142.6, 146.1, 162.3. UV-Vis (CHCl3): λmax (log ε) = 272 (4.4), 457 (3.9), 537 (4.0), 571 (3.9) nm.