Download PDF
Synlett 2003(8): 1210-1212
DOI: 10.1055/s-2003-39915
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Novel Diradical-Mediated Ring Opening Reactions

Georg Rüedi*a, Matthias Nagelb, Hans-Jürgen Hansena
a Organisch-chemisches Institut der Universität, Winterthurerstrasse 190, 8057 Zürich, Switzerland
Fax: +41(1)6356812; e-Mail: georg@access.unizh.ch;
b Swiss Federal Laboratories for Materials Testing and Research (EMPA), Überlandstrasse 138, 8600 Dübendorf, Switzerland
Further Information

Publication History

Received 15 April 2003
Publication Date:
11 June 2003 (online)

    Permissions and Reprints All articles of this category

Abstract

Thermo-isomerization of medium- and large-ring 1-phenylcycloalkanols 1e-i at around 650 °C in a flow reactor system delivers the open-chain phenones 4e-i. A reaction mechanism via an open-chain diradical intermediate, followed by an intramolecular hydrogen transfer is proposed. Thermo-isomerization of α-substituted 1-phenylcyclododecanols 6 proceeds regioselectively under the formation of ω-substituted phenones 7. Furthermore, this novel hydrogen transfer reaction provides a new access to ω-substituted fatty acids.

Key words

thermal ring opening - dynamic gas phase thermo-isomerization - diradical intermediates - radical hydrogen transfer - regioselectivity in homolytic cleavage

    References

  • 1a Nagel M. Hansen H.-J. Fráter G. Synlett  2002,  275 
    Thieme Connect
  • 1b Nagel M. Hansen H.-J. Fráter G. Synlett  2002,  280 
    Thieme Connect
  • For leading references see:
  • 2a Lomas JS. Acc. Chem. Res.  1988,  21:  73 
    Search in Google Scholar
  • 2b Rüchardt C. Beckhaus H.-D. Angew. Chem., Int. Ed. Engl.  1980,  429 
  • 2c Rüchardt C. Beckhaus H.-D. Angew. Chem. Int. Ed. Engl.  1985,  529 
  • 3 Cram DJ. Steinberg H. J. Am. Chem. Soc.  1951,  73:  5691 
    CrossrefSearch in Google Scholar
  • 5a

    Thermo-isomerization reactions were performed in a flow reactor system using a quartz tube (110 cm length, and 3 cm i.d., respectively) heated by a tube furnace (100 cm with 6 different temperature zones, which can be separately adjusted).
  • 5b

    Typical procedure: After evacuation of the apparatus with a high-vacuum oil pump, the starting material (0.5-5 g) was directly distilled through the preheated reactor tube (estimated contact times: about 1-2 s). A flow of nitrogen gas was adjusted from 12 mL/min to 24 mL/min (0.8-2.4 L/h). At the end of the reactor unit the isomerization products were collected in a trap, which was cooled with liquid N2 (90-95% recovery).
  • 5c For details refer to: Nagel M. Fráter G. Hansen H.-J. Chimia  2003,  57:  196 
    Search in Google Scholar
  • 6a Meyers CY. Hou Y. Lutfi HG. Saft HL. J. Org. Chem.  1999,  64:  9444 
    CrossrefSearch in Google Scholar
  • 6b Jacyno JM. Harwood JS. Cutler HG. Deanne M. Tetrahedron  1994,  50:  11585 
    CrossrefSearch in Google Scholar
  • 8 Hungerford NL. Kitching W. J. Chem. Soc., Perkin Trans.1  1998,  11:  1839 
    Search in Google Scholar
  • 9 Dimitrov V. Brabantov S. Simova S. Kostova K. Tetrahedron Lett.  1994,  35:  6713 
    CrossrefSearch in Google Scholar
  • 13a Mori H. Ikoma K. Isoe S. Kitaura K. Katsumura S. J. Org. Chem.  1998,  63:  8704 
    Search in Google Scholar
  • 13b Casanova J. Waegell B. Bull. Soc. Chim. Fr.  1971,  4:  1289 
    Search in Google Scholar
  • 14 Foehlisch B. Joachimi R. Chem. Ber.  1987,  120:  1951 
    Search in Google Scholar
  • 15a Gautier AE. Ph.D. Thesis   ETH Zürich; Switzerland: 1980. 
    Crossref
  • 15b Townsend CA. Scholl T. Arigoni D. J. Chem. Soc., Chem. Commun.  1975,  921 
    Crossref
  • 16 Koch SSC. Chamberlin AR. Synth. Commun.  1989,  19:  829 
    Search in Google Scholar
  • 17a Avery TD. Fallon G. Greatrex BW. Pyke SM. Taylor DK. Tiekink ERT. J. Org. Chem.  2001,  66:  7955 
    Search in Google Scholar
  • 17b Zhang F.-J. Corey EJ. Org. Lett.  2000,  2:  1097 
    Search in Google Scholar
  • 17c Ollis WD. Rey M. Sutherland IO. J. Chem. Soc., Perkin Trans.1  1983,  1009 
4

1-Phenylcycloalkanols 1 were synthesized from the corresponding cycloalkanones by addition of phenyl lithium or phenyl magnesium bromide according to ref. 9.

7

Deuterium content was determined by mass spectroscopy.

10

Deuterium content was determined by 1H NMR spectroscopy, chemical shifts were determined by 2H NMR spectroscopy.

11

2,2,12,12,12-d 5-4g: 1H NMR (300 MHz, CDCl3): δ
(ppm) = 7.95 (dt, J = 7.0 Hz, 1.2 Hz, 2 H), 7.55 (tt, J = 7.3 Hz, 1.3 Hz, 1 H), (tt, J = 7.2 Hz, 1.3 Hz, 2 H), 1.72 (t, J = 7.1 Hz, 2 H), 1.59-1.26 (m, 14 H). 13C NMR (75 MHz, CDCl3): δ (ppm) = 200.47 (C), 137.04 (C), 132.71 (CH), 128.42 (CH), 127.95 (CH), 31.71 (CH2), 29.49 (CH2), 29.37 (CH2), 29.27 (CH2), 29.22 (CH2), 29.21 (CH2), 29.20 (CH2), 24.23 (CH2), 22.42 (CH2). IR (CHCl3): 3063 (vw), 2929 (vs), 2856 (vs), 1679 (s), 1599 (w), 1581 (w), 1467 (w), 1448 (m), 1272 (s)cm-1. MS m/z (rel intensity) 266 (12), 265 (20), 135 (9), 121 (100), 105 (78).

12

Intermolecular processes can be excluded under DGPTI-conditions.