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A Short Synthesis of 1,4-Dimethyltriphenylene

 

作者: M. John Plater,  

 

期刊: Journal of Chemical Research, Synopses  (RSC Available online 1997)
卷期: Volume 0, issue 11  

页码: 390-391

 

ISSN:0308-2342

 

年代: 1997

 

DOI:10.1039/a704351a

 

出版商: RSC

 

数据来源: RSC

 

摘要:

Me O Me HO 1 Me O 2 Me KOH–MeOH heat O Me Me O Me Me 3 O Me Me H H R heat 4 R = H CH2Br CH2Br 6 Me Me 5 NBS–(PhCO)2O2 heat O O 1 2 3 1 2 3 7 O O 8 FVP, 800 °C 390 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 390–391 J. Chem. Research (M), 1997, 2417–2433 A Short Synthesis of 1,4-Dimethyltriphenylene M. John Plater,* Derek M. Schmidt and R. Alan Howie Department of Chemistry, Aberdeen University, Meston Walk, Aberdeen AB24 3UE, UK The title compound was prepared by the interception of 1,3-dimethylcyclopenta[l ]phenanthren-2-one 2 with norbornadiene to give the Diels–Alder adduct 4 followed by flash vacuum pyrolysis.In a preceding paper1 we described our interest in cyclopentafused polycyclic fragments related to the Buckminsterfullerene surface and reported the synthesis and X-ray crystal structure of (1R,11bR)-11b-hydroxy-1,3-dimethyl-2,11b-dihydro- 1H-cyclopenta[l ]phenanthren-2-one 1 which was prepared by the base catalysed condensation of diethyl ketone with phenanthrenequinone.2,3 Although direct methods of dehydration reported previously have been unsuccessful, treatment with KOH in refluxing MeOH eliminates water to generate 1,3-dimethylcyclopenta[l ]phenanthren-2-one 2.This spontaneously forms the dimer 3 which precipitates as a colourless solid. The dimer 3 has been reported previously2,3 and is unusual because there are only two signals for methyl groups in the 1H NMR spectrum. This was rationalised as arising from a degenerate [3,3] Cope rearrangement which occurs rapidly on an NMR timescale at room temperature in solution.The rearrangement interconverts two pairs of methyl groups, so two averaged signals are observed. An energy barrier of 11.4 kcal molµ1 was calculated for the interconversion from low temperature NMR data. The arrangement is illustrated for the cyclopentadienone sub-structures 7 and 8. We expected that dimer 3 might therefore have rather long carbon–carbon bonds holding it together and so performed an X-ray single crystal structure analysis (Fig. 1).4 This shows the expected endo stereochemistry of the [4+2] Diels–Alder dimer. The bonds holding the dimer together [C(15)·C(34) and C(16)·C(32)], of length 1.602(7) and 1.649(6) Å respectively, are indeed long and weak. A typical covalent C·C bond is 1.54 Å long. To date the longest C·C bonds which have been reliably determined by X-ray crystallography are 1.720(4) and 1.710(5) Å.5,6 The distance between the terminal carbons of the alkenes which bond together during the Cope rearrangement7 is 3.178(6) Å.Heating the dimer in norbornadiene gave the cycloadduct 4. The endo stereochemistry was confirmed by the upfield shielding of the bridgehead methylene proton (R=H) which resonates at µ0.46 ppm. Flash vacuum pyrolysis (FVP) through an unpacked quartz tube at 800 °C gave 1,4-dimethyltriphenylene8 via initial decarbonylation followed by a retro Diels–Alder reaction extruding cyclopentadiene.Free radical bromination gave the precursor 6. Ring closure attempts to give a fullerene fragment with two five-membered rings were however unsuccessful. Pyrolysis of precursor 6 gave a complex reaction mixture from which none of the desired cyclised product was isolated. This contrasts with the successful FVP ring closure of two bromomethyl groups on route to sumanene.9 Presumably precursor 6 may eliminate bromine to give a paraquinonedimethane which may not be reactive enough to cyclise.Alternative approaches to cyclopenta-fused polycyclic fragments of the Buckminsterfullerene surface are in progress. Crystal Data for 2.·C38H28O2, Mr=516.6, F(000)= 2176, orthorhombic, a=10.931(3), b=34.917(17), c= 13.754(8) Å, V=5250(4) Å3, space group Pbca, Z=8, *To receive any correspondence. Fig. 1 Perspective view of the dimer 3 showing the atom numbering scheme. Non-hydrogen atoms are shown as 40% probability ellipsoids and hydrogen atoms as spheres of arbitrary radiusJ.CHEM. RESEARCH (S), 1997 391 Dx=1.307 g cm3, m(MoKa)=0.079 mmµ1. The experimental data were collected at 298 K on a Nicolet P3 diffractometer with MoKa radiation (l=0.71069 Å) and refined using Nicolet P3 software. The structure was solved by direct methods and refined by full matrix least squares on F2. Final R indices [Ia2s(I)] R1=0.0756, wR2=0.1252, for all data R1=0.2169 and wR2=0.1933. The estimated standard deviations for the geometrical parameters involving non hydrogen atoms lie within the following ranges: bond lengths 0.004–0.007 Å; bond angles 0.3–0.6°.Techniques used: IR, 1H and 13C NMR, mass spectrometry, X-ray crystallography References: 15 Schemes: 1 Table 1: Crystal data and structure refinement 3 Table 2: Atomic coordinates and Ueq values for 3 Tables 3 and 4: Interatomic distances and angles, and selected dihedral angles Table 5: Anisotropic displacement parameters for 3 Table 6: Hydrogen coordinates and isotropic displacement parameters for 3 Received, 20th June 1997; Accepted, 30th July 1997 Paper E/7/04351A References 1 M.J. Plater, D. M. Schmidt and R. A. Howie, J. Chem. Res., 1997, (S) 140; (M) 0977–0982. 2 D. W. Jones, J. Chem. Soc., Perkin Trans. 1, 1988, 980; D. W. Jones, J. Chem. Soc., Chem. Commun., 1975, 199. 3 B. Fuchs, M. Pasternak and G. Sharf, J. Chem. Soc., Chem. Commum., 1976, 53. 4 For crystal structures of [4+2] cyclopentadienone dimers see J. Beauhaire, A. Chiaroni, J. L. Fourrey and C. Riche, Tetrahedron Lett., 1983, 24, 4417; J. M. M. Smitts, V Parthasarathi, P. T. Beurskens, A. J. H. Klunder and J. H. M. Lange, J. Crystallogr. Spectrosc. Res., 1988, 18, 791; F. Toda, K. Tanaka, D. Marks and I. Goldberg, J. Org. Chem., 1991, 56, 7332. 5 F. Toda, K. Tanaka, Z. Stein and I. Goldberg, Acta Crystallogr., Sect. C, 1996, 52, 177. 6 G. Kaupp and J. Boy, Angew. Chem., Int. Ed. Engl., 1977, 36, 48. 7 For a review on Cope rearrangements see J. March, Advanced Organic Chemistry, Wiley, New York, 4th edn, 1992, p. 1130. 8 J. Fieser, J. Am. Chem. Soc., 1939, 61, 2958; B. Fuchs and G. Scharf, J. Org. Chem., 1981, 46, 5395. 9 G. Mehta, S. R. Shah and K. Ravikumar, J. Chem. Soc., Chem. Commun., 1993, 1006.

 



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