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Synlett 2002(6): 0923-0926
DOI: 10.1055/s-2002-31915
LETTER
© Georg Thieme Verlag Stuttgart · New York

New Elements in the Reactivity of α-Cyclopropyl Vinyl Radicals

Emily Mainetti, Louis Fensterbank*, Max Malacria*
UMR 7611, Université Pierre et Marie Curie, 4, Place Jussieu, b. 229, 75005 Paris, France
Fax: +33(1)44277360; e-Mail: fensterb@ccr.jussieu.fr; e-Mail: malacria@ccr.jussieu.fr;
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Publikationsverlauf

Received 22 March 2002
Publikationsdatum:
07. Februar 2007 (online)

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Abstract

The reactivity of the α-cyclopropyl vinyl radical has been examined through the use of propargylic bromomethyldime­thylsilyl ethers bearing a cyclopropyl group on the acetylenic moiety. With unsubstituted precursors, allenes can be obtained. With appropriate trapping possibilities (5-exo cyclization or hydrogen transfer), the cyclopropyl moiety on the vinyl radical is retained.

Key words

vinyl radicals - cyclizations - ring opening - hydrogen transfer - cyclopropanes

    References

  • 1 For a leading review on radical clocks, see: Newcomb M. Tetrahedron  1993,  49:  1151 
    CrossrefGoogle Scholar
  • 2 Nonhebel DC. Chem. Soc. Rev.  1993,  347 
    CrossrefGoogle Scholar
  • 3 For a recent contribution, see: Lis L. Koltun ES. Liu H.-W. Kass SR. J. Am. Chem. Soc.  2002,  124:  1276 
    CrossrefGoogle Scholar
  • 4 Kretzschmar I. Levinson JA. Friend CM. J. Am. Chem. Soc.  2000,  122:  12395 
    CrossrefGoogle Scholar
  • 5 Crandall JK. Tindell GL. Manmade A. Tetrahedron Lett.  1982,  23:  3769 
    CrossrefGoogle Scholar
  • 6 Back TG. Muralidharan KR. J. Org. Chem.  1989,  54:  121 
    Google Scholar
  • 7 Fensterbank L. Malacria M. Sieburth SM. Synthesis  1997,  813 
    Artikel in Thieme ConnectGoogle Scholar
  • 8 Corey EJ. Fuchs PL. Tetrahedron Lett.  1972,  3769 
    CrossrefGoogle Scholar
  • 9 Corley EG. Thompson AS. Huntington M. Org. Synth.  2000,  77:  231 
    Google Scholar
  • 10 Journet M. Malacria M. J. Org. Chem.  1992,  57:  3085 
    Google Scholar
  • 11 Militzer H.-C. Schömenauer S. Otte C. Puls C. Hain J. Bräse S. de Meijere A. Synthesis  1993,  998 
    Artikel in Thieme ConnectGoogle Scholar
  • 12 Journet M. Cai D. DiMichele LM. Larsen RD. Tetrahedron Lett.  1998,  39:  6427 
    CrossrefGoogle Scholar
  • For a radical synthesis of allenes based on the β-elimination of vinylsulfoxides, see:
  • 14a Delouvrié B. Lacôte E. Fensterbank L. Malacria M. Tetrahedron Lett.  1999,  40:  3565 
    CrossrefGoogle Scholar
  • 14b

    Mouriès, V.; Delouvrié, B.; Lacôte, E.; Fensterbank, L.; Malacria, M. Eur. J. Org. Chem. 2002, in press.
    CrossrefGoogle Scholar
  • For instance, see:
  • 15a Lee PH. Bang K. Lee K. Lee C.-H. Chang S. Tetrahedron Lett.  2000,  41:  7521 
    Google Scholar
  • 15b Spino C. Fréchette S. Tetrahedron Lett.  2000,  41:  8033 
    Google Scholar
  • 15c Stichler-Bonaparte J. Kruth H. Lunkwitz R. Tschierske C. Liebigs Ann.  1996,  1375 
    Google Scholar
  • 16a The cis relative stereochemistry was assigned by analogy with our previous work, see ref.10 and: Devin P. Fensterbank L. Malacria M. J. Org. Chem.  1998,  63:  6764 
    CrossrefGoogle Scholar
  • 16b

    Spectral data for 13. IR(neat): 3350, 3080, 2950, 1640, 1250 cm-1; 1H NMR (400 MHz, CDCl3) δ 4.40 (m, 1 H, CH-OH), 2.31 (m, 2 H, CH 2 cyclopentenol + CHCH3), 1.76 (d, J = 13.8 Hz, 1 H, CH 2Si), 1.64 (d, J = 13.8 Hz, 1 H, CH 2Si), 1.34 (m, 1 H, CH cyclopropane), 1.26 (m, 1 H, CH 2 cyclopentenol), 1.11 (d, J = 6.6 Hz, 3 H, CH 3 ), 0.70 (m, 2 H, cyclopropane), 0.55 (m, 1 H, cyclopropane), 0.41 (m, 1 H, cyclopropane), 0.04 [9 H, Si(CH 3)3]; 13C NMR (100 MHz, CDCl3) δ 141.2 (C, C=C), 137.1 (C, C=C), 79.9 (CH, CH-OH), 41.9 (CH2, cyclopentenol), 38.6 (CH, cyclopentenol), 23.0 (CH3), 16.4 (CH2, CH2Si), 9.7 (CH, cyclopropane), 5.8 (CH2, cyclopropane), 5.2 (CH2, cyclopropane), -0.4 [3 CH3, Si(CH3)3]. Anal. Calcd. for C13H24OSi: C, 69.58; H, 10.78. Found: C, 69.55; H, 10.89.
    Crossref
  • 17a We thank one of the referees for bringing to our attention that the rate constant of a 5-exo vinyl radical cyclization has been estimated to be: 3.2 ¥ 108 s-1 at 60 °C: Beckwith ALJ. O’Shea DM. Tetrahedron Lett.  1986,  27:  4525 
    CrossrefGoogle Scholar
  • 17b Compared to a value of 2.3 × 105 s-1 (20 °C) for the alkyl analog: Chatgilialoglu C. Ingold KU. Scaiano JC. J. Am. Chem. Soc.  1981,  103:  7739 
    CrossrefGoogle Scholar
  • 17c

    Although the Beckwith system cannot directly be compared to the system studied herein (different substitution pattern), this data could suggest an intrinsic faster cyclization of the vinyl radical, thus contributing significantly to the observed effect.
    Crossref
  • 18 An alkoxy group reduces the activation barrier for the ring opening of cyclopropylcarbinyl radicals, see: Martinez FN. Schlegel HB. Newcomb M. J. Org. Chem.  1998,  63:  3618 
    CrossrefGoogle Scholar
  • 19 Bogen S. Gulea M. Fensterbank L. Malacria M. J. Org. Chem.  1999,  64:  4920 
    CrossrefGoogle Scholar
13

Spectroscopic data for 10. IR(neat): 2960, 1960, 1750, 1450, 1370, 1270 cm-1; 1H NMR (200 MHz, CDCl3) δ 5.21 (m, 1 H, vinyl), 4.48 (t, J = 2.0 Hz, 2 H, CH 2 O), 3.75 (s, 3 H, CO2CH 3 ), 1.97 (quint, J = 7.4 Hz, 2 H, CH 2 CH3), 1.32 (mAB, 2 H, CH 2 Si), 0.97 (t, J = 7.4 Hz, 3 H, CH 3 ), 0.02 (s, 9 H, Si(CH 3 )3); 13C NMR (50 MHz, CDCl3) δ 201.8 (C, C=C=CH), 155.8 (C, C=O), 97.4 (C, C=C=CH), 94.8 (CH, C=C=CH), 70.1 (CH2, CH2O), 54.8 (CH3, CO2 CH3), 22.5 (CH2, CH2CH3), 18.2 (CH2, CH2Si), 13.6 (CH3), -1.3 (3 CH3, Si(CH3)3). Anal. Calcd. for C12H22O3Si: C, 59.46; H, 9.15. Found: C, 59.34; H, 9.35.