- C-H functionalization/C-N bond formation: Copper-catalyzed synthesis of benzimidazoles from amidines
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(Chemical Equation Presented) Copper closes the ring: Benzimidazoles are synthesized from amidines through a copper-catalyzed C-H functionalization/ C-N bond-forming process. The method tolerates a broad range of functional groups and provides the benzimidazoles in up to 89% yield. Best results are obtained by using 15 mol% Cu(OAc)2, 2-5 equivalents of HOAc as additive, and oxygen as the stoichiometric reoxidant (see scheme).
- Brasche, Gordon,Buchwald, Stephen L.
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p. 1932 - 1934
(2008/12/22)
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- A versatile method for the synthesis of benzimidazoles from o-nitroanilines and aldehydes in one step via a reductive cyclization
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A highly efficient and versatile method for the synthesis of benzimidazoles was achieved in one step via the Na2S2O4 reduction of o-nitroanilines in the presence of aldehydes. Heating a solution of o-nitroaniline (Ic) and an aldehyde in EtOH or another appropriate solvent, in the presence of aqueous or solid Na2S2O4, provided facile access to a series of 2-substituted N-H benzimidazoles 5a-m containing a wide range of functional groups not always compatible with the existing synthetic methods. This methodology has also been applied to the regioselective synthesis of N-alkyl and N-aryl benzimidazoles 6a-f via the cyclization of the corresponding N-substituted nitroanilines 13a-e, respectively. In addition, the method was applied successfully to the synthesis of other imidazole containing heterocyclic ring systems such as 1H-imidazo[4,5-b]pyridines 14a,b and 1H-imidazo[4,5-f]quinoline 15.
- Yang, Donglai,Fokas, Demosthenes,Li, Jingzhou,Yu, Libing,Baldino, Carmen M.
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