2148
H. Kargar et al. / Bioorg. Med. Chem. Lett. 21 (2011) 2146–2148
-
IO4
Mn
-
IO3
H
H
N
N
+
H2O
R
R
N
N
O
H
H
4
O
Mn
Mn
N
N
N
R
3
R
1
N
H
H
5
O
H
N
R
Mn
N
H
H
2
Scheme 2.
12. (a) Grimmett, M. R. In Comprehensive Heterocyclic Chemistry; Potts, K. T., Ed.;
Pergamon: Oxford, 1984; Vol. 4, p 345; (b) Lambardino, J. G.; Wiseman, E. H. J.
Med. Chem. 1974, 17, 1182; (c) Kim, H. G.; Lee, J. K.; Lee, J. T.; Lee, C. S. Bull.
Korean Chem. Soc. 2000, 21, 345.
Table 5
Comparison of the obtained results in the dehydrogenation of 2-phenylimidazoline
with some of those reported in the literature
13. (a) Levesque, G.; Gressier, J.-C.; Proust, M. Synthesis 1981, 963; (b)
Mohammadpoor-Baltork, I.; Abdollahi-Alibeik, M. Bull. Korean Chem. Soc.
2003, 24, 1354.
14. Dockner, T.; Frank, A. Ger. Offen. 2,729,017, 1979; Chem. Abstr. 1979, 204100.
15. Kyrides, L. P.; Zienty, F. B.; Steahly, G. W.; Morrill, H. L. J. Org. Chem. 1947, 12,
577.
16. Klem, R. E.; Skinner, H. F.; Walba, H.; Isensee, R. W. J. Heterocycl. Chem. 1970, 7,
403.
17. Amemiya, Y.; Miller, D. D.; Hsu, F. L. Synth. Commun. 1990, 20, 2483.
18. Martin, P. K.; Matthews, H. R.; Rapoport, H.; Thyagarajan, G. J. Org. Chem. 1968,
33, 3758.
19. Hughey, J. L., IV; Knapp, S.; Schudar, H. Synthesis 1980, 489.
20. Anastassiadou, M.; Baziard-Mouysset, G.; Payard, M. Synthesis 2000, 1814.
21. Mohammadpoor-Baltork, I.; Zolfigol, M. A.; Abdollahi-Alibeik, M. Tetrahedron
Lett. 2004, 45, 8687.
22. Mohammadpoor-Baltork, I.; Abdollahi-Alibeik, M. Can. J. Chem. 2005, 83, 110.
23. Abdollahi-Alibeik, M.; Mohammadpoor-Baltork, I.; Zolfigol, M. A. Bioorg. Med.
Chem. Lett. 2004, 14, 6079.
Entry Reagent
Conditions Time
(h)
Yield
(%)
Ref.
19
20
17
24
25
26
1
2
3
4
5
6
BaMnO4
DMSO
Reflux
120 °C
Reflux
À15 °C
Reflux
120 °C
24
48
40
3 min
16
96
51
75
93
40
84
Pd/C (10%)
TCCA/DBu
KMnO4/dioxane
O2/activated
carbon
24
7
[Mn(TPP)Cl]/
NaIO4
rt
5
84
Present
method
In conclusion, an efficient method has been reported for the
dehydrogenation of imidazolines to imidazoles with NaIO4 using
[Mn(TPP)Cl] as catalyst. In addition, this method offers several
advantages including high yields, easy work-up, applicability for
both 2-aryl and 2-alkylimidazolines, and mild reaction conditions
which make it ideal for the use in the oxidation of 2-imdazolines.
24. Mohammadpoor-Baltork, I.; Zolfigol, M. A.; Abdollahi-Alibeik, M. Synlett 2004,
2803.
25. Campos, M. E.; Jimenez, R.; Martinez, F.; Salgado, H. Heterocycles 1995, 40, 841.
26. Haneda, S.; Okui, A.; Ueba, C.; Hayashi, M. Tetrahedron 2007, 63, 2414.
27. All materials were purchased from Merck. Tetraphenylporphyrins was
prepared and metallated according to reported procedures.28–31 All 2-
substituted imidazolines were synthesized by the reported procedures.13b,32
Acknowledgment
1H NMR spectra were recorded on
a Bruker–Avance AQS 400 MHz. TLC
monitored all reactions and all yields refer to isolated products.
General procedure for dehydrogenation of imidazolines with NaIO4 catalyzed by
[Mn(TPP)Cl]: All of the reactions were carried out at room temperature under
air in a 25 mL flask equipped with a magnetic stirrer bar. A solution of NaIO4
(2 mmol) in H2O (10 mL) was added to a mixture of 2-imidazolines (1 mmol),
[Mn(TPP)Cl] (0.05 mmol) in CH3CN (5 mL). The progress of reaction was
monitored by TLC (eluent: EtOAc/MeOH 4:1). After the reaction was
completed, water (30 mL) was added and the corresponding imidazoles were
extracted with CH2Cl2 (2 Â 20 mL). The imidazole derivatives were obtained
after evaporation of solvent. IR and 1H NMR spectral data confirmed the
identities of the products.
The partial support of this work by Payame Noor University
(PNU) of Ardakan is acknowledged.
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