Claudie Hubert et al.
COMMUNICATIONS
Org. Lett. 2006, 8, 4819; g) Y. Coquerel, D. Bensa, V.
Moret, J. Rodriguez, Synlett 2006, 2751.
[3] For a recent review on application of electrocyclization
reactions in synthesis, see: a) C. M. Beaudry, J. P. Male-
rich, D. Trauner, Chem. Rev. 2005, 105, 4757; b) J. P. A.
Harrity, O. Provoost, Org. Biomol. Chem. 2005, 2,
1319.
hydes and 1,3-diketones, 4-hydroxycoumarin or 6-
methyl-4-hydroxy-2-pyrone in mild conditions. This
simple procedure using stable, moisture insensitive
and not expensive catalysts should open new opportu-
nities in organic chemistry and applications in synthe-
sis.
[4] For recent reviews, see: a) R. P. Hsung, A. V. Kurdyu-
mov, N. Sydorenko, Eur. J. Org. Chem. 2005, 23; b) Y.
Tang, J. Oppenheimer, Z. Song, L. You, X. Zhang, R. P.
Hsung, Tetrahedron 2006, 62, 10785.
Experimental Section
[5] a) H. C. Shen, J. Wang, K. P. Cole, M. J. McLaughlin,
C. D. Morgan, C. J. Douglas, R. P. Hsung, H. A. Cover-
dale, A. I. Gerasyuto, J. M. Hahn, J. Liu, H. M. Skle-
nicka, L-L. Wei, L. R. Zehnder, C. A. Zificsak, J. Org.
Chem. 2003, 68, 1729; b) K. P. Cole, R. P. Hsung, Chem.
Comun. 2005, 5784; c) G. Cravotto, G. M. Nano, S. Ta-
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[6] a) A. V. Kurdyumov, N. Lin, R. P. Hsung, G. C. Gulli-
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General Procedure for the Synthesis of the 2H-
Pyrans
To previously dried sodium sulfate (150 mg) were succes-
sively added under argon, phosphoric acid 4 or 5 (5 mol%),
dichloromethane or toluene (10 mLmmolÀ1), the diketone
(1 equiv.) and the unsaturated aldehyde (1.5 equivs.). The
solution was stirred at room temperature in dichlorome-
thane or at 608C in toluene until completion by TLC analy-
sis. The solution was then filtered through Celite, and con-
centrated under vacuum. The crude mixture was purified on
silica gel by flash chromatography (eluent: heptane/ethyl
ether, 9/1).
[7] U. K. Tambar, T. Kano, J. F. Zepernick, B. M. Stoltz,
Tetrahedron 2007, 48, 345.
Supporting Information
[8] a) C. Li, E. Lobkovsky, J. A. Porco, J. Am. Chem. Soc.
2000, 122, 10484; b) C. Li, R. P. Johnson, J. A. Porco, J.
Am. Chem. Soc. 2003, 125, 5095.
Experimental details, NMR spectral characterization data
for all compounds are given in the Supporting Information.
[9] M. Shoji, J. Yamaguchi, H. Kakeya, H. Osada, Y. Haya-
shi, Angew. Chem. Int. Ed. 2002, 41, 3192.
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Acknowledgements
The authors thank la RØgion Bretagne for a Ph. D. fellowship
for J. M.
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[15] In toluene at 408C, the yields were comparable but the
reaction times were longer; in CH2Cl2, the yields were
lower.
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of 1k was determined by nOe experiment.
42
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Adv. Synth. Catal. 2008, 350, 40 – 42