X. Wang, C. Zhao, L. Gao, Y. Zhou, and L. Xu
Vol 000
Ethyl 4-methyl-1H-imidazole-2-carboxylate V.
A
47.62%, H 4.80%, N 22.21%; found: C 47.43%, H
4.54%, N 22.44%.
solution of ethyl 1-benzyl-4-methyl-1H-imidazole-2-
carboxylate (VIa, 120 g) in methanol (1500 mL) was
hydrogenated in the catalyze of palladium hydroxide on
charcoal (12.0 g, 20%) under 4 atm pressure. After the
starting material disappeared completely, the reaction
mixture was filtered, and the catalyst was washed
thoroughly with methanol. Concentration of the filtrate to
afford the title compound (V, 70.0 g, 93%) as a white
solid. 1H NMR (CDCl3) δ = 6.96 (s, 1H), 4.37 (q,
J = 8 Hz, 2H), 2.29 (s, 3H), 1.32 (t, J = 8 Hz, 3H). 13C
NMR (CDCl3) δ = 159.34, 136.75, 61.61, 14.18.
Elemental analysis: Cal: C 54.54%, H 6.54%, N 18.17%;
found: C 44.32%, H 6.38%, N 18.01%.
Acknowledgments. I would like to thank the financial support
from the program of Joint fund project of Guizhou Provincial
Department of Science and Technology (QianKeHe LH Zi
[2014]7545), meanwhile for the support from the project of
Science and Technology Department of Guizhou Province
(QKHSY[2015]3030), I am also appreciated very much. I
would also like to thank Dr. Jianyong Zhang’s useful
explanation on HPLC and LC/MS spectra data.
REFERENCES AND NOTES
In the same condition, ethyl 1-benzyl-5-methyl-1H-
imidazole-2-carboxylate VIb can also afford the same
compound V in >90% yield.
[1] A. Lemus, R. Lindstrom, A. Vickers, T. Wilson, M. Zapf,
J. Weinhouse, M. I. International patent 158998, 2014.
[2] Albrecht, B. K.; Bellon, S. F.; Gehling, V. S. International
Patent 035062, 2015.
4-Methyl-1H-imidazole-2-carboxylic acid I. A solution
of ethyl 4-methyl-1H-imidazole-2-carboxylate (V, 77 g,
0.5 mol) in absolute methanol (600 mL) was added
250 mL aqueous solution of sodium hydroxide (40%) at
room temperature. The solution was heated to 50°C and
maintained at that temperature for 1 h and then cooled to
room temperature, and the solution was acidified to
pH = 6 with concentrated HCl solution (37%). The
solvent was removed under reduced pressure, and the
residue was purified by chromatography using
dichloromethane/methanol = 10/1 as eluent to give
product (I, 60.2 g, 96%) as a white solid. 1H NMR
(D2O) δ = 6.98 (s, 1H), 2.27 (s, 3H). 13C NMR (D2O):
162.61, 140.88, 132.67, 119.42, 10.02. LC–MS: 127
(M + 1). HPLC purity: >98%. Elemental analysis: Cal: C
[3] Flohr, A. International Patent 078836, 2015.
[4] Ritzen, A.; Kehler, J.; Langgard, M.; Nielsen, J.; Kilburn, J. P.;
Farah, M. M. International Patent 152825, 2009.
[5] Ritzen, A.; Kehler, J.; Langgard, M.; Nielsen, J.; Kilburn, J. P.;
Farah, M. M. US Patent 0016303, 2010.
[6] Galeazzi, E.; Guzman, A.; Nava, J. L.; Liu, Y. Z.; Maddox,
M. L.; Muchowski, J. M. J Org Chem 1995, 60, 1090.
[7] Yoon, U. C.; Chae, E. A.; Cho, D. W.; Park, H. J.; Choi, J. H.
Iridium complex and organic light-emitting diodes. International patent
093176, 2010.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet