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Synthesis of benzimidazolones

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Intramolecular N-arylations of ureas to form benzimidazol-2-ones occur in the presence of KOH and DMSO at close to ambient temperature. Under these conditions the yields are high and a wide range of functional groups are tolerated.
A. Beyer, C. M. M. Reucher, C. Bolm, Org. Lett., 2011, 13, 2876-2879.


CuI/l-proline catalyzed coupling of aqueous ammonia with 2-iodoacetanilides and 2-iodophenylcarbamates affords aryl amination products at room temperature, which undergo in situ additive cyclization under acidic conditions or heating to give substituted 1H-benzimidazoles and 1,3-dihydrobenzimidazol-2-ones, respectively.
X. Diao, Y. Wang, Y. Jiang, D. Ma, J. Org. Chem., 2009, 74, 7974-7977.


A metal-free synthesis of 1-arylbenzimidazol-2-ones from of N-aryl-2-nitrosoanilines can be carried out under mild conditions using solid carbon dioxide as a source of the key carbonyl moiety. The atom economy of the synthesis of the starting materials makes the entire synthesis of the target compounds environmentally friendly.
E. Łukasik, Z. Wróbel, Synthesis, 2016, 48, 1159-1166.


High-yielding reductive alkylation of electron-deficient o-haloarylamines followed by treatment with inexpensive N-chlorosulfonyl isocyanate afforded primary ureas in good overall yields. A Pd-catalyzed urea cyclization reaction furnished imidazopyridinones and benzoimidazolones in excellent yields.
M. McLaughlin, M. Palucki, I. W. Davies, Org. Lett., 2006, 8, 3311-3314.


2-phenoxycarbonyl-4,5-dichloropyridazin-3(2H)-one is a solid stable carbonyl source that is a recyclable. The reagent enables the synthesis of benzo[d]thiazol-2(3H)-ones, benzo[d]oxazol-2(3H)-ones, and benzo[d]imidazol-2(3H)-ones using in one pot out under neutral or acidic conditions to give the corresponding heterocycles in very good yields.
K. E. Ryu, B. R. Kim, G. H. Sung, H. J. Yoon, Y.-J. Yoon, Synlett, 2015, 26, 1985-1990.


In a direct method for the regioselective construction of benzimidazolones, a single palladium catalyst couples monosubstituted urea substrates with differentially substituted 1,2-dihaloaromatic systems via a cascade of two discrete and highly chemoselective C-N bond-forming processes. The method allows a predictable formation of complex heterocycles from simple, readily available starting materials.
J. B. Ernst, N. E. S. Tay, N. T. Jui, S. L. Buchwald, Org. Lett., 2014, 16, 3844-3845.