J. Boudreau et al. / Tetrahedron Letters 47 (2006) 1695–1698
1697
Organometallic Compounds; VCH: Weinheim, Germany,
1996; Vol. 2; (f) Papadogianakis, G.; Sheldon, R. A. New
J. Chem. 1996, 20, 175.
to the hydroxyl groups, the reactions are sluggish and
very poor results were obtained at room temperature
(Table 1, entries 7–10). Better results were obtained by
increasing the reaction temperature to 40 °C. However,
the yields are still low ranging from 20% to 39%.
Remarkably, the oxidation performed using higher cat-
alyst/substrate ratio, and longer reaction time led to full
conversion of the alcohols (Table 1, entries 9 and 10).
2. (a) Sheldon, R. A.; Kochi, J. K. In Metal-Catalyzed
Oxidations of Organic Compounds; Academic Press: New
York, 1981; (b) Ley, S. V.; Norman, J.; Griffith, W. P.;
Marsden, P. Synthesis 1994, 639; (c) Hudlicky, M.
Oxidations in Organic Chemistry; ACS: Washington,
DC, 1990; (d) Cainelli, G.; Cardillo, G. Chromium
Oxidations in Organic Chemistry; Springer: Berlin, 1984.
3. (a) Muzart, J. Chem. Rev. 1992, 92, 113; (b) Sheldon, R.
A.; Arends, I. W. C. E.; Dijksman, A. Catal. Today 2000,
57, 157; (c) Almeida, M. L. S.; Beller, M.; Wang, G.-Z.;
Ba¨ckvall, J. E. Chem. Eur. J. 1996, 2, 1533; (d) Muzart, J.;
Nait Ajjou, A.; A¨ıt-Mohand, S. Tetrahedron Lett. 1994,
35, 1989; (e) Cecchetto, A.; Fontana, F.; Minisci, F.;
Recupero, F. Tetrahedron Lett. 2001, 42, 6651; (f)
Betzemeier, B.; Cavazzini, M.; Quici, S.; Knochel, P.
Tetrahedron Lett. 2000, 41, 4343; (g) Sato, K.; Aoki, M.;
Takagi, J.; Noyori, R. J. Am. Chem. Soc. 1997, 119,
12386.
4. (a) Nait Ajjou, A.; Pinet, J.-L. Can. J. Chem. 2005, 83,
702; (b) Nait Ajjou, A.; Ferguson, G. Tetrahedron Lett.
2003, 44, 9139; (c) Nait Ajjou, A. Tetrahedron Lett. 2001,
42, 13; (d) ten Brink, G.-J.; Arends, I. W. C. E.; Sheldon,
R. A. Science 2000, 287, 1636; (e) ten Brink, G.-J.; Arends,
I. W. C. E.; Sheldon, R. A. Adv. Synth. Catal. 2002, 344,
355; (f) Sloboda-Rozner, D.; Alsters, P.; Neumann, R. J.
Am. Chem. Soc. 2003, 125, 5280; (g) Liu, R.; Dong, C.;
Liang, X.; Wang, X.; Hu, X. J. Org. Chem. 2005, 70, 729;
(h) Uozumi, Y.; Nakao, R. Angew. Chem., Int. Ed. 2003,
42, 194.
To further explore the efficiency of our catalytic system,
the oxidation of hereroaromatic alcohols was extended
to 2-thienyl and 2-furyl-1-alkanols (Table 1, entries
11–15). While 2-thienyl alcohols are fully converted at
room temperature, 2-furyl analogs are moderately trans-
formed to the corresponding ketones. Fortunately,
excellent yields were achieved at 40 °C (Table 1, entries
14 and 15).
To evaluate the synthetic potential of CuCl2/BQC/
TBHP system, a range of 2-pyrrolyl and indolyl-1-alka-
nols were investigated. Excellent yields were reached in
all the cases at 40 °C (Table 1, entries 16–20). These
results indicate the significant synthetic utility of our
system since the oxidations of 2-pyrrolyl alcohols were
performed with free (NH)-pyrroles, and there was no
need to introduce protecting groups. Furthermore, 2-
ketopyrroles,6e,f and 2-ketoindoles6f–h,13 are known
for their biological properties. These latter compounds
are generally prepared by the oxidation of the corre-
sponding alcohols using stoichiometric amounts of
PDC.13
5. (a) Katritzky, A. R.; Rees, C. W.; Scriven, E. F. V.
Comprehensive Heterocyclic Chemistry II; Pergamon:
Oxford, 1996; (b) Joule, J. A.; Mills, K. Heterocyclic
Chemistry; Blackwell Science: Oxford, 2000.
In a similar manner, this system allows the synthesis
of bis heteroaromatic ketones in very high yields demon-
strating its broad synthetic scope. Thus, ketones
containing 2-thienyl moieties coupled with 2-pyridyl,
2-imidazolyl, or 2-thiazolyl group were successfully
prepared (Table 1, entries 21–23).
´
6. (a) Richard, F.; Carreyre, H.; Perot, G. J. Catal. 1996,
159, 427; (b) Choudary, B. M.; Sateesh, M.; Lakshmi
Kantam, M.; Ranganath, K. V. S.; Raghavan, K. V.
Catal. Lett. 2001, 76, 231; (c) Isaev, Y.; Fripiat, J. J. J.
Catal. 1999, 182, 257; (d) Viaud, M. C.; Jamoneau, P.;
Baudin, M.-L.; Savelon, L.; Guillaumet, G. Tetrahedron
1997, 53, 5159; (e) Yadav, J. S.; Reddy, B. V. S.; Kondaji,
G.; Srinivasa Rao, R.; Praveen Kumar, S. Tetrahedron
Lett. 2002, 43, 8133; (f) Katritzky, A. R.; Suzuki, K.;
Singh, S. K.; He, H.-Y. J. Org. Chem. 2003, 68, 5720; (g)
Yeung, K.-S.; Farkas, M. E.; Qiu, Z.; Yang, Z. Tetra-
hedron. Lett. 2002, 43, 5793; (h) Cruz, R. P. A.; Ottoni, O.;
Abella, C. A. M.; Aquino, L. B. Tetrahedron. Lett. 2001,
42, 1467; (i) Chatani, N.; Fukuyama, T.; Tatamidani, H.;
Kakiuchi, F.; Murai, S. J. Org. Chem. 2000, 65, 4039.
7. (a) Chinchilla, R.; Najera, C.; Yus, M. Chem. Rev. 2004,
104, 2667; (b) Marcantonio, K. M.; Frey, L. F.; Murry, J.
A.; Chen, C.-Y. Tetrahedron Lett. 2002, 43, 8845; (c) Frey,
L. F.; Marcantonio, K. M.; Chen, C.-Y.; Wallace, D. J.;
Murry, J. A.; Tan, L.; Chen, W.; Dolling, U. H.;
Grabowski, E. J. J. Tetrahedron 2003, 59, 6363; (d) Chen,
C.-Y.; Reamer, R. A.; Chilenski, J. R.; McWilliams, C. J.
Org. Lett. 2003, 5, 5039.
In conclusion, the catalytic system composed of CuCl2
and 2,20-biquinoline-4,40-dicarboxylic acid dipotassium
salt (BQC), was found to be highly efficient for the selec-
tive oxidation of secondary 1-heteroaromatic-1-alkanols
to the corresponding heteroaromatic ketones, with
aqueous tert-butyl hydroperoxide. The catalytic system
is compatible with various heterocycles such as 2-, 3-,
and 4-pyridines, thiophens, furans, pyrroles, indoles,
imidazoles, and thiazoles.
Acknowledgements
We are grateful to NSERC of Canada and to FESR for
financial support of this research.
8. Kernag, C. A.; Bobbitt, J. M.; McGrath, D. V. Tetra-
hedron. Lett. 1999, 40, 1635, and references cited therein.
9. (a) Nait Ajjou, A.; Muzart, J.; Savelon, L.; Guillaumet, G.
Synthesis 1994, 359; (b) Liu, R.; Liang, X.; Dong, C.; Hu,
X. J. Am. Chem. Soc. 2004, 126, 4112; (c) Ansari, I. A.;
References and notes
1. (a) Cornils, B. Org. Proc. Res. Dev. 1998, 2, 121; (b) Nait
Ajjou, A.; Howard, A. J. Am. Chem. Soc. 1998, 120, 1466;
´
Gree, R. J. Org. Lett. 2002, 4, 1507; (d) Marko, I. E.;
´
Giles, P. R.; Tsukazaki, M.; Chelle-Regnaut, I.; Gautier,
´
´
(c) Ungvary, F. Coord. Chem. Rev. 1997, 160, 123; (d) Joo,
A.; Brown, S. M.; Urch, C. J. J. Org. Chem. 1999, 64,
2433; (e) Miller, R. A.; Hoerrner, R. S. Org. Lett. 2003, 5,
285.
´
´
F.; Katho, A. J. Mol. Catal. 1997, 116, 3; (e) Cornils, B.;
Herrmann, A. W. In Applied Homogeneous Catalysis with