Diels–Alder and Michael addition reactions of indoles with masked o-benzoquinones: synthesis of highly functionalized hydrocarbazoles and 3-arylindoles

Abstract

Highly functionalized hydrocarbazoles and 3-arylindoles are prepared from commercially available 2-methoxyphenols and indoles.

References

1. R. J. Sundberg, The Chemistry of Indoles, Academic Press, New York, 1971; D. J. Chadwick, in Comprehensive Heterocyclic Chemistry, ed. A. R. Katritzky and C. W. Rees, Pergamon, Oxford, 1984, vol. 4, p. 155; R. A. Jones, in Comprehensive Heterocyclic Chemistry, ed. A. R. Katritzky and C. W. Rees, Pergamon, Oxford, 1984, vol. 4, p. 201; R. J. Sundberg, in Comprehensive Heterocyclic Chemistry, ed. A. R. Katritzky and C. W. Rees, Pergamon, Oxford, 1984, vol. 4, p. 313.
2. J. E. Saxton, The Monoterpenoid Indole Alkaloids, Wiley-Interscience, Chichester, 1994; J. E. Saxton, Nat. Prod. Rep., 1997, 14, 559 and references cited therein..
3. S. C. Benson, C. A. Polabrica and J. K. Snyder, J. Org. Chem., 1987, 52, 4610; M. Takahashi, H. Ishida and M. Kohmoto, Bull. Chem. Soc. Jpn., 1976, 49, 1725.
4. M. S. Raasch, J. Org. Chem., 1980, 45, 856.
5. E. Wenkert, P. D. R. Moeller and S. R. Piettre, J. Am. Chem. Soc., 1988, 110, 7188.
6. A. Gieseler, E. Steckhan, O. Wiest and F. Knoch, J. Org. Chem., 1991, 56, 1405.
7. J. H. Markgraff and D. E. Patterson, J. Heterocycl. Chem., 1996, 33, 109.
8. J.-E. Backvall and N. A. Plobeck, J. Org. Chem., 1990, 55, 4528.
9. D.-S. Hsu, P. D. Rao and C.-C. Liao, Chem. Commun., 1998, 1795; P. D. Rao, C.-H. Chen and C.-C. Liao, Chem. Commun., 1998, 155; P.-Y. Hsu, Y.-C. Lee and C.-C. Liao, Tetrahedron Lett., 1998, 39, 659; W.-C. Liu and C.-C. Liao, Synlett, 1998, 912; P.-Y. Hsiu and C.-C. Liao, Chem. Commun., 1997, 1085; C.-S. Chu, P. D. Rao and C.-C. Liao, Chem. Commun., 1996, 1537 and references cited therein..
10. R. Carlini, K. Higgs, C. Older and S. Randhawa, J. Org. Chem., 1997, 62, 2330; R. S. Coleman and E. B. Grant, J. Am. Chem. Soc., 1995, 117, 10 889; K. S. Feldman and S. M. Ensel, J. Am. Chem. Soc., 1994, 116, 3357; A. S. Mitchell and R. A. Russell, Tetrahedron Lett., 1993, 34, 545; M. G. Banwell and M. P. Collis, J. Chem. Soc., Chem. Commun., 1991, 1343 and references cited therein..
11. C.-H. Chen, P. D. Rao and C.-C. Liao, J. Am. Chem. Soc., 1998, 120, 13 254; P. D. Rao, C.-H. Chen and C.-C. Liao, Chem. Commun., 1999, 713.
12. R. M. Moriarty, C. J. Chany II and J. W. Kosmeder II, in Encyclopedia of Reagents for Organic Synthesis, ed. L. A. Paquette, Wiley, Chichester, 1995, vol. 2, p. 1479.
13. Procedure for Diels–Alder or Michael addition reactions of indoles 3 with 1a–c. To a solution of 2(1.0 mmol) in MeOH (10 ml) at 0 °C was added DAIB (1.0 mmol). After 10 min of stirring, an indole derivative 3(5–20 mmol) was added at that temperature and the flask was rapidly warmed up to room temperature or to that of reflux by either removing the ice bath or transferring the reaction vessel to a preheated (100 °C) oil bath. The reaction mixture was stirred at either temperature for 1 h. Then MeOH was removed and the residue obtained was purified by flash chromatography on silica gel using 20% of ethyl acetate in hexanes as eluent to obtain Diels–Alder adducts or aromatized Michael adducts..
14. Crystal data for 7b: C₂₂H₂₅NO₆, M= 399.43, monoclinic, a= 10.6487(1), b= 22.172(3), c= 8.588(2)Å, β= 95.726(1)°, V= 2017.5(5)ų, T= 293(2) K, space group P2₁/c, Z= 4, µ(Mo-Kα)= 0.096 mm^–1, 3545 reflections measured, 3545 unique (R_int= 0.0000). Final R indices [I > 2σ(I)]R1 = 0.0430, wR2= 0.1261. For 10a: C₁₇H₁₄BrNO₄, M= 376.20, triclinic, a= 9.0176(2), b= 9.4144(2), c= 10.3637(1)Å, α= 90.7060(1), β= 96.9180(1), γ= 117.1930(1)°, V= 774.62(2)ų, T= 293(2) K, space group P1̄, Z= 2, µ(Mo-Kα)= 2.673 mm^–1, 7349 reflections measured, 3317 unique (R_int= 0.0347). Final R indices [I > 2σ(I)]R1 = 0.0349, wR2= 0.0893. CCDC 182/1310. See http://www.rsc.org/suppdata/cc/1999/1441/ for crystallographic data in .cif format..