Z.-G. Wang et al.
to obtain the corresponding aldehyde. Then the aldehyde reacts
with o-phenylendiamine and dehydrates to form a Schiff base.
During the next steps, ring closure leads to a five-membered
ring followed by dehydrogenation with Ce(IV) and Ce(III) redox
to form benzimidazole.
Acknowledgement
The authors are grateful for the financial support from the Natural
Science Foundation (no. 11076017).
References
Conclusions
[1] A. R. Porcari, R. V. Devivar, L. S. Kucera, J. C. Drach, L. B. Townsend,
J. Med. Chem. 1998, 41, 1252.
[2] M. T. Migawa, J. L. Girardet, J. A. Walker, G. W. Koszalka,
S. D. Chamberlain, J. C. Drach, L. B. Townsend, J. Med. Chem. 1998, 41,
1242.
We have developed an efficient and environmentally friendly
method for the aerobic oxidation of alcohols and one-pot synthesis
of benzimidzoles from alcohols catalyzed by CAN/[Imim-PEG1000
-
[3] I. Tamm, Science 1957, 126, 1235.
TEMPO] with excellent yields. Owing to the high efficiency and
good compatibility, the catalytic system had a good catalytic perfor-
mance to effectively promote the reaction. Moreover, it could be
recycled and reused without significant loss of catalytic activity for
seven runs. This environmentally friendly catalytic system could find
wider applications in various reactions, which is an ongoing project.
[4] K. J. Lee, K. D. Janda, Can. J. Chem. 2001, 79, 1556.
[5] M. P. Singh, S. Sasmal, W. Lu, M. N. Chatterjee, Synthesis 2000, 1380.
[6] I. Bhatnagar, M. V. George, Tetrahedron 1968, 24, 1293.
[7] K. Bahrami, M. M. Khodaei, F. Naali, J. Org. Chem. 2008, 73, 68358.
[8] F. F. Bower, D. Janda, J. Chem. Soc. 1949, 2971.
[9] P. L. Beaulieu, B. Haché, E. von Moos, Synthesis 2003, 1683.
[10] L. H. Du, Y. G. Wang, Synthesis 2007, 675.
[11] R. L. Lombardy, F. A. Tanious, K. Ramachandran, R. R. Tidwell,
W. D. Wilson, J. Med. Chem. 1996, 39, 1452.
[12] F. Patzold, F. T. Zeuner, H. Heyer, H. J. Niclas, Synth. Commun. 1992, 22,
281.
Experimental
[13] K. A. Shaikh, V. A. Patil, Org. Commun. 2012, 5, 12.
[14] Y. Kawashita, N. Nakamichi, H. Kawabata, M. Hayashi, Org. Lett. 2003,
20, 3713.
[15] S. N. Lin, L. H. Yang, Tetrahedron Lett. 2005, 46, 4315.
[16] T. Iwahama, Y. Yoshino, T. Keitoku, S. Sakaguchi, Y. Ishii, J. Org. Chem.
2000, 65, 6502.
[17] R. Lenz, S. V. Ley, J. Chem. Soc. Perkin Trans. 1997, 3291.
[18] I. E. Marko, P. R. Giles, M. Tsukazaki, I. Chelle-Regnaut, C. J. Urch,
S. M. Brown, J. Am. Chem. Soc. 1997, 119, 12661.
[19] M. J. Schultz, C. C. Park, M. S. Sigman, Chem. Commun. 2002, 3034.
[20] B. Z. Zhan, M. A. White, T. K. Sham, J. A. Pincock, R. J. Doucet,
K. V. R. Rao, K. N. Robertson, T. S. Cameron, J. Am. Chem. Soc.
2003, 125, 2195.
General Information
All starting materials were purchased from commercial sources and
used without further treatment. Analytical thin-layer chromatogra-
phy (TLC) was performed on precoated silica plates. Yields of the
products refer to purification by silica gel column chromatography.
1H NMR spectra were recorded using a Bruker Advance III (500 MHz)
spectrometer with tetramethylsilane as an internal standard. High-
performance liquid chromatography experiments were performed
with a liquid chromatograph (Shimadzu LC-20AT, Japan).
[21] H. B. Ji, T. Mizugaki, K. Ebitani, K. Kaneda, Tetrahedron Lett. 2002, 43,
7179.
General Procedure for Oxidation of Alcohols
[22] M. F. Semmelhack, C. R. Schmid, D. A. Cortés, C. S. Chou, J. Am. Chem.
Soc. 1984, 106, 3374.
[23] M. F. Semmelhack, C. R. Schmid, D. A. Cortés, Tetrahedron Lett. 1986, 27,
1119.
[24] R. Sheldon, Chem. Commun. 2001, 2399.
[25] T. Welton, Coord. Chem. Rev. 2004, 248, 2459.
[26] J. S. Wilkes, J. Mol. Catal. A 2004, 214, 11.
[27] R. D. Rogers, K. R. Seddon, Science 2003, 302, 792.
[28] Y. L. Wang, J. Luo, Z. L. Liu, Appl. Organometal. Chem. 2013, 27, 601.
[29] W. Gil, A. M. Trzeciak, J. J. Ziółkowski, Appl. Organometal. Chem. 2006,
20, 766.
[30] J. S. Yadav, B. V. S. Reddy, K. Premalatha, Adv. Synth. Catal. 1998, 345,
948.
To a 10 ml round-bottom flask, (NH4)2Ce(NO3)6 (0.5mmol), Imim-
PEG1000-TEMPO (0.5 mmol) and benzyl alcohol (10 mmol) were suc-
cessively added under constant vigorous stirring. The reaction was
carried out at a temperature of 50°C and monitored using TLC.
Upon completion, the reaction mixture was cooled to room tem-
perature and extracted three times by adding ether. The organic
phase was dried over anhydrous MgSO4 and evaporated under re-
duced pressure to give benzaldehyde (95% yield) with spectral data
consistent with the assigned structures for the products. The next
run was performed under identical reaction conditions.
[31] C. A. Ohlin, Z. Béni, G. Laurenczy, N. Ruiz, A. M. Masdeu-Bultó, Appl.
Organometal. Chem. 2007, 21, 156.
[32] A. Falla, M. Senea, M. Gayeb, G. Gómeza, Y. Fall, Tetrahedron Lett. 2010,
51, 4501.
[33] X. E. Wu, L. Ma, M. X. Ding, L. X. Gao, Synlett 2005, 4, 607.
[34] V. Nair, A. Deepthi, Chem. Rev. 2007, 107, 1862.
[35] A. Dhakshinamoorthy, K. Pitchumani, Catal. Commun. 2009, 10, 872.
[36] L. Wang, H. Jing, X. Bu, T. Chang, L. Jin, Y. Liang, Catal. Commun. 2007, 8,
80.
Typical Procedure for Synthesis of Benzimidazoles
o-Phenylenediamine (1.08g, 10 mmol), benzyl alcohol (1.08g,
10 mmol), (NH4)2Ce(NO3)6 (0.5 mmol) and Imim-PEG1000-TEMPO
(0.5 mmol) were thoroughly mixed in a 10 ml three-necked flask
equipped with a water-cooled condenser and a gas inlet with vigor-
ous stirring at room temperature. Then, the temperature was raised
to 50°C and the reaction monitored usong TLC. Upon completion,
the mixture was extracted with ether three times, and the organic
layer was dried with anhydrous MgSO4 and rotary evaporated un-
der reduced pressure. The residue was purified by column chroma-
tography on a silica gel using petroleum ether–ethyl acetate (7:1) as
eluent to afford the pure product in 93% yield (m.p. 292–294°C).
The next run was performed under identical reaction conditions.
[37] P. Haldar, J. K. Ray, Tetrahedron Lett. 2008, 49, 3659.
[38] H. Z. Zhi, C. X. Lü, Q. Zhang, J. Luo, Chem. Commun. 2009, 2878.
Supporting Information
Additional supporting information may be found in the online
version of this article at the publisher’s web-site.
wileyonlinelibrary.com/journal/aoc
Copyright © 2014 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2015, 29, 109–112