5-endo-Trigonal cyclization of o-substituted gem-difluorostyrenes: syntheses of 2-fluorinated indoles, benzo[b]furans and benzo[b]thiophenes

Abstract

β,β-Difluorostyrenes bearing tosylamido, hydroxy ormethylsulfinyl groups at the o-position undergo intramol-ecular substitution of the nitrogen, oxygen or sulfur withloss of fluorine via a 5-endo-trigonal process leading to2-fluorinated heterocyclic systems in high yields.

References

1. L. G. Sprague, K. B. Baucom, S. F. Sellers and R. A. DuBoisson, in Chemistry of Organic Fluorine Compounds II, ed. M. Hudlicky and A. E. Pavlath, ACS Monograph 187, American Chemical Society, Washington, DC, 1995, pp. 729–756.
2. M. J. Tozer and T. F. Herpin, Tetrahedron, 1996, 52, 8619.
3. J. R. McCarthy, P. S. Sunkara, D. P. Matthews, A. J. Bitonti, E. T. Jarvi, J. F. Sabol, R. J. Resvick, E. W. Huber, W. A. v. d. Donk, G. Yu and J. Stubbe, in Biomedical Frontiers of Fluorine Chemistry, ed. I. Ojima, J. R. McCarthy and J. T. Welch, ACS Symposium Series 639, American Chemical Society, Washington, DC, 1996, ch. 18; P. Bey, J. R. McCarthy and I. A. McDonald, in Selective Fluorination in Organic and Bioorganic Chemistry, ed. J. T. Welch, ACS Symposium Series 456, American Chemical Society, Washington, DC, 1991, pp. 105–133.
4. J. Ichikawa, N. Yokota, M. Kobayashi and T. Minami, Synlett, 1993, 186.
5. J. Ichikawa, M. Kobayashi, N. Yokota, Y. Noda and T. Minami, Tetrahedron, 1994, 50, 11637; J. Ichikawa, N. Yokota, M. Kobayashi, K. Amano and T. Minami, Synlett, 1996, 243.
6. J. Ichikawa, M. Kobayashi, Y. Noda, N. Yokota, K. Amano and T. Minami, J. Org. Chem., 1996, 61, 2763.
7. o-Substituted β, β-dichloro- and -dibromo-styrenes have recently been reported to undergo intramolecular cyclization via electrophilic carbenoids: M. Topolski, J. Org. Chem., 1995, 60, 5588.
8. (a) J. E. Baldwin, J. Chem. Soc., Chem. Commun., 1976, 734; (b) J. E. Baldwin, J. Cutting, W. Dupont, L. Kruse, L. Silberman and R. C. Thomas, ibid, 1976, 736; (c) J. E. Baldwin, R. C. Thomas, L. I. Kruse and L. Silberman, J. Org. Chem., 1977, 42, 3846.
9. D. Craig and A. M. Smith, Tetrahedron Lett., 1992, 33, 695; P. Auvray, P. Knochel and J. F. Normant, Tetrahedron Lett., 1985, 26, 4455; R. Grigg, J. Kemp, J. F. Malone, S. Rajviroongit and A. Tangthongkum, Tetrahedron, 1988, 44, 5361 For a related example, see: R. D. Chambers and M. P. Greenhall, J. Chem. Soc., Chem. Commun., 1990, 1128.
10. A. D. Jones and D. W. Knight, Chem. Commun., 1996, 915; Y. Landais and D. Planchenault, Synlett, 1995, 1191 and references cited therein B. H. Lipshutz and T. Gross, J. Org. Chem., 1995, 60, 3572 and references cited therein M. Kimura, H. Harayama, S. Tanaka and Y. Tamaru, J. Chem. Soc., Chem. Commun., 1994, 2531.
11. For 5-endo radical cyclizations onto an unsaturated carbon, see T. Gimisis and C. Chatgilialoglu, J. Org. Chem., 1996, 61, 1908; T. Sato, N. Chono, H. Ishibashi and M. Ikeda, J. Chem. Soc., Perkin Trans. 1, 1995, 1115; A. V. R. Rao, A. K. Singh, K. M. Reddy and K. Ravikumar, J. Chem. Soc., Perkin Trans. 1, 1993, 3171 See, also: D. L. J. Clive and W. Yang, Chem. Commun., 1996, 1605 For 5-endo radical cyclizations onto a multiple-bonded, first-row heteroatom, see: Y. Yamamoto, M. Ohno and S. Eguchi, J. Org. Chem., 1996, 61, 9264 and references cited therein.
12. M. J. Silvester, Adv. Heterocycl. Chem., 1994, 59, 1; Aldrichim. Acta, 1991, 24, 31; Organofluorine Chemistry, Principles and Commercial Applications, ed. R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum Press, New York, 1994.
13. J. Ichikawa, T. Minami, T. Sonoda and H. Kobayashi, Tetrahedron Lett., 1992, 33, 3779 see also: J. Ichikawa, M. Fujiwara, H. Nawata, T. Okauchi and T. Minami, Tetrahedron Lett., 1996, 37, 8799.
14. For the synthesis of fluoroindoles, see H. F. Hodson, D. J. Madge, A. N. Z. Slawin, D. A. Widdowson and D. J. Williams, Tetrahedron, 1994, 50, 1899 For the synthesis of fluoropyrroles, see Z.-M. Qiu and D. J. Burton, Tetrahedron Lett., 1995, 36, 5119; J. Leroy and C. Wakselman, Tetrahedron Lett., 1994, 35, 8605 and references cited therein.
15. For the synthesis of fluorobenzo[b]furans, see: D. H. R. Barton, R. H. Hesse, G. P. Jackman and M. M. Pechet, J. Chem. Soc., Perkin Trans. 1, 1977, 2604 For the synthesis of fluorofurans, see A. K. Forrest and P. J. O'Hanlon, Tetrahedron Lett., 1995, 36, 2117; K. Burger and B. Helmreich, J. Chem. Soc., Chem. Commun., 1992, 348; H. L. Sham and D. A. Betebenner, J. Chem. Soc., Chem. Commun., 1991, 1134.
16. R. N. Young, J. Y. Gauthier and W. Coombs, Tetrahedron Lett., 1984, 25, 1753.
17. For the synthesis of fluorobenzo[b]thiophenes, see; P. Nussbaumer, G. Petrenyi and A. Stütz, J. Med. Chem., 1991, 34, 65 For the synthesis of fluorothiophenes, see K. Burger and B. Helmreich, Heterocycles, 1994, 39, 819.