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Synthesis of imidazoles and benzimidazoles
Recent Literature
The copper-catalyzed reaction between two different isocyanides produces
imidazoles in good yields. The mechanism is discussed.
C. Kanazawa, S. Kamijo, Y. Yamamoto, J. Am. Chem. Soc., 2006, 128, 10662-10663.
A simple and efficient approach allows the preparation of biologically active
2,4(5)-diarylimidazoles by parallel synthesis. The formation of
2-aroyl-4(5)-arylimidazoles as side products strongly depends on the reaction
conditions employed.
V. Zuliani, G. Cocconcelli, M. Fantini, C. Ghiron, M. Rivara, J. Org. Chem., 2007,
72, 4551-4553.
An improved and rapid one-pot synthesis of 2,4,5-triaryl imidazoles in a room
temperature ionic liquid does not need any added catalyst. This one-pot
methodology offers excellent isolated yields, simple work up procedures and
efficient recovery and recycling of the ionic liquid.
S. A. Siddiqui, U. C. Narkhede, S. S. Palimkar, T. Daniel, R. J. Lahoti, K. V.
Srinivasan, Tetrahedron, 2005,
61, 3539-3546.
Fused bicyclic imidazole rings have been prepared in good yields by a
sequence of the van Leusen three-component reaction and the ring-closing
metathesis reaction.
V. Gracias, A. F. Gasiecki, S. W. Djuric, Org. Lett., 2005, 7, 3183-3186.
A set of benzimidazoles, 3H-imidazo[4,5-b]pyridines, purines,
xanthines and benzothiazoles was readily prepared from (hetero)aromatic ortho-diamines or ortho-aminothiophenol and aldehydes using
chlorotrimethylsilane in DMF as a promoter and water-acceptor agent,
followed by oxidation with air oxygen.
S. V. Ryabukhin, A. S. Plaskon, D. M. Volochnyuk, A. A. Tolmachev, Synthesis, 2006, 3715-3726.
A highly efficient and versatile method for the synthesis of a series of 2-substituted
N-H, N-alkyl, and N-aryl benzimidazoles containing a wide range of functional groups
was achieved in one step via the Na2S2O4
reduction of o-nitroanilines in the presence of aldehydes.
D. Yang, D. Fokas, J. Li, L. Yu, C. M. Baldino, Synthesis, 2005,
47-56.
A simple and efficient procedure for the synthesis of substituted benzimidazoles
through a one-pot condensation of o-phenylenediamines with aryl aldehydes
in the presence of H2O2 and HCl in acetonitrile at room
temperature features short reaction time, easy and quick isolation of the
products, and excellent yields.
K. Bahrami, M. M. Khodaei, I. Kavianinia, Synthesis, 2007,
417-427.
Various 2-arylbenzimidazoles were synthesized from phenylenediamines and
aldehydes via a one-step process using hypervalent iodine as oxidant. This
method features mild conditions, short reaction times, high yields, and a simple
procedure.
L-H. Du, Y.-G. Wang, Synthesis, 2007,
675-678.
Addition of oxone to a mixture of a 1,2-phenylenediamine and an
aldehyde in wet DMF results in rapid formation of benzimidazoles under very mild
conditions. Products are isolated in high purity in most cases by simple aqueous
precipitation. The reaction is applicable to a wide range of substrates but does
not allow the conversion of aldehydes that are sensitive to oxone under acidic
reaction conditions.
P. L. Beaulieu, B. Haché, E. von Moos, Synthesis, 2003, 1683-1692.
2-Imidazolines were easily prepared in good yields from the reaction of
aldehydes and ethylenediamine with iodine in the presence of potassium carbonate.
The 2-imidazolines were smoothly oxidized to the corresponding imidazoles in
good yields using (diacetoxyiodo)benzene at room temperature.
M. Ishihara, H. Togo, Synlett,
2006, 227-230.
A number of new reactions of IBX with heteroatom-containing substrates were
discovered and their utility was demonstrated. IBX was used for the generation
of imines from secondary amines in notably high yields, for the oxidative
aromatization of nitrogen heterocycles and for the cleavage of dithianes.
K. C. Nicolaou, C. J. N. Mathison, T. Montagnon, Angew. Chem. Int. Ed., 2003,
42, 4077-4082.
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