P. J. Stang, Chem. Rev., 2008, 108, 5299; (f) V. V. Zhdankin,
ARKIVOC, 2009, (i), 1.
2 For selected reviews: (a) S. Quideau and L. Pouyse
Proced. Int., 1999, 31, 617; (b) S. Quideau, L. Pouyse
D. Deffieux, Curr. Org. Chem., 2004, 8, 113; (c) S. Quideau,
L. Pouysegu and D. Deffieux, Synlett, 2008, 467;
(d) L. Pouysegu, D. Deffieux and S. Quideau, Tetrahedron, 2010,
66, 2235.
´
gu, Org. Prep.
´
gu and
´
´
3 (a) Y. Kita, H. Tohma, M. Inagaki, K. Hatanaka and T. Yakura,
J. Am. Chem. Soc., 1992, 114, 2175; (b) P. Wipf, Y. Kim and
P. C. Fritch, J. Org. Chem., 1993, 58, 7195; (c) S. Quideau,
M. A. Looney and L. Pouysegu, Org. Lett., 1999, 1, 1651;
(d) J. Liang, J. Chen, F. Du, X. Zeng, L. Li and H. Zhang, Org.
Lett., 2009, 11, 2820; (e) M. Traore, S. Ahmed-Ali, M. Peuchmaur
´
and Y.-S. Wong, Tetrahedron, 2010, 66, 5863; (f) H. Liang and
M. A. Ciufolini, Tetrahedron, 2010, 66, 5884; (g) T. Dohi,
N. Yamaoka and Y. Kita, Tetrahedron, 2010, 66, 5775;
(h) J.-C. Andrez, M.-A. Giroux, J. Lucien and S. Canesi, Org.
Lett., 2010, 12, 4368.
4 (a) L. Pouysegu, A.-V. Avellan and S. Quideau, J. Org. Chem.,
2002, 67, 3425; (b) H. Tohma, Y. Harayama, M. Hashizume,
M. Iwata, Y. Kiyono, M. Egi and Y. Kita, J. Am. Chem. Soc.,
2003, 125, 11235; (c) S. Canesi, D. Bouchu and M. A. Ciufolini,
Angew. Chem., Int. Ed., 2004, 43, 4336; (d) P. Wipf and
S. R. Spencer, J. Am. Chem. Soc., 2005, 127, 225;
(e) L. H. Mejorado and T. R. R. Pettus, J. Am. Chem. Soc.,
2006, 128, 15625; (f) J. Gagnepain, F. Castet and S. Quideau,
Angew. Chem., Int. Ed., 2007, 46, 1533; (g) K. C. Nicolaou,
D. J. Edmonds, A. Li and G. S. Tria, Angew. Chem., Int. Ed.,
2007, 46, 3942; (h) T. Dohi, A. Maruyama, N. Takenaga,
K. Senami, Y. Minamitsuji, H. Fujioka, S. B. Caemmerer and
Y. Kita, Angew. Chem., Int. Ed., 2008, 47, 3787; (i) S. Quideau,
G. Lyvinec, M. Marguerit, K. Bathany, A. Ozanne-Beaudenon,
T. Buffeteau, D. Cavagnat and A. Chenede, Angew. Chem., Int.
Scheme 2 Hypothesized reaction pathway.
1,4-addition with indole, then induces the cyclization of the
generated Michael adduct to provide intermediate I. After
aromatization and protonation of the carbon-silver bond,
4-indole benzofuran 3 is obtained and the silver catalyst is
regenerated.
Ed., 2009, 48, 4605; (j) K. C. Gue
S. Canesi, J. Org. Chem., 2009, 74, 2039; (k) J. T. Hammill,
J. Contreras-Garcıa, A. M. Virshup, D. N. Beratan, W. Yang
and P. Wipf, Tetrahedron, 2010, 66, 5852; (l) K. C. Guerard,
´
rard, C. Sabot, L. Racicot and
´
´
C. Sabot, M.-A. Beaulieu, M.-A. Giroux and S. Canesi, Tetra-
hedron, 2010, 66, 5893; (m) H. Liang and M. A. Ciufolini, Org.
Lett., 2010, 12, 1760.
In conclusion, we have developed an efficient method to
prepare 4-indole benzofurans from 4-alkyl-2-ynylphenols
and indoles via
a hypervalent iodine-induced oxidative
5 (a) R. Imbos, A. J. Minnaard and B. L. Feringa, J. Am. Chem.
Soc., 2002, 124, 184; (b) Y. Hayashi, H. Gotoh, T. Tamura,
H. Yamaguchi, R. Masui and M. Shoji, J. Am. Chem. Soc.,
2005, 127, 16028; (c) Q. Liu and T. Rovis, J. Am. Chem. Soc.,
2006, 128, 2552; (d) N. T. Vo, R. D. M. Pace, F. O’Hara and
M. J. Gaunt, J. Am. Chem. Soc., 2008, 130, 404;
(e) T. A. Wenderski, C. Hoarau, L. Mejorado and T. R.
R. Pettus, Tetrahedron, 2010, 66, 5873.
6 (a) M.-F. Hsieh, P. D. Rao and C.-C. Liao, Chem. Commun., 1999,
1441; (b) I. Kim, K. Kim and J. Choi, J. Org. Chem., 2009, 74,
8492.
7 X. L. Hou, Z. Yang, K. S. Yeung and H. N. C. Wong, in Progress
in Heterocyclic Chemistry, ed. G. W. Gribble and J. A. Joule,
Elsevier, Oxford, 2008, vol. 19, pp. 176–207, and previous volumes
in the series.
dearomatization, a silver-catalyzed cascade Michael addition-
cyclization, and an aromatization. The method provides an
attractive and useful route to introduce functional groups at
the 4-position of benzofurans. The current direction for future
research is aimed at extending the scope and potential
synthesis applications, as well as investigation on the reaction
mechanism.
Financial support from National Natural Science Foundation
of China (21072033) is gratefully acknowledged.
Notes and references
8 For selected reviews, see: (a) Y. Liao, Y. Hu, J. Wu, Q. Zhu,
M. Donovan, R. Fathi and Z. Yang, Curr. Med. Chem., 2003, 10,
2285; (b) G. Zeni and R. C. Larock, Chem. Rev., 2004, 104, 2285;
(c) F. Alonso, I. P. Beletskaya and M. Yus, Chem. Rev., 2004, 104,
3079.
9 (a) S. Pichlmair, M. M. B. Marques, M. P. Green, H. J. Martin and
J. Mulzer, Org. Lett., 2003, 5, 4657; (b) Y. Yuan, H. Men and
C. Lee, J. Am. Chem. Soc., 2004, 126, 14720; (c) K. B. Bahnck and
S. D. Rychnovsky, J. Am. Chem. Soc., 2008, 130, 13177;
(d) T. Magauer, H. J. Martin and J. Mulzer, Angew. Chem., Int.
Ed., 2009, 48, 6032.
z Representative experimental procedure: The mixture of 4-alkyl-2-
ynylphenol 1 (0.5 mmol) with AgOTf (13 mg, 0.05 mmol) in MeOH
(2 mL) was treated with PhI(OAc)2 (177 mg, 0.55 mmol) at 0 1C.
After 2 min, indole 2 (1 mmol) was added. The reaction mixture was
warmed up and allowed to stir at 25 1C. Upon completion by TLC, the
reaction was quenched with saturated NaHCO3, and extracted by
ethyl acetate (100 mL ꢀ 3). The organic layer was dried over
anhydrous Na2SO4, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (15% ethyl acetate
in hexanes) to give the corresponding product 3.
1 For selected reviews: (a) R. M. Moriarty and O. Prakash, Org.
React., 2001, 57, 327; (b) V. V. Zhdankin and P. J. Stang, Chem.
Rev., 2002, 102, 2523; (c) T. Wirth, Top. Curr. Chem., 2003, 224;
(d) M. A. Ciufolini, N. A. Braun, S. Canesi, M. Ousmer, J. Chang
and D. Chai, Synthesis, 2007, 3759; (e) V. V. Zhdankin and
10 (a) T. Yao, X. Zhang and R. C. Larock, J. Am. Chem. Soc., 2004,
126, 11164; (b) T. Yao, X. Zhang and R. C. Larock, J. Org. Chem.,
2005, 70, 7679; (c) N. T. Patil, H. Wu and Y. Yamamoto, J. Org.
Chem., 2005, 70, 4531; (d) W. Li and J. Zhang, Chem. Commun.,
2010, 46, 8839.
c
5628 Chem. Commun., 2011, 47, 5626–5628
This journal is The Royal Society of Chemistry 2011