On the Importance of an Acid Additive in the Synthesis of Pyrido[1,2‐
<i>a</i>
]benzimidazoles by Direct Copper‐Catalyzed Amination
作者:Kye‐Simeon Masters、Tom R. M. Rauws、Ashok K. Yadav、Wouter A. Herrebout、Benjamin Van der Veken、Bert U. W. Maes
DOI:10.1002/chem.201100574
日期:2011.5.27
8‐substituted pyrido[1,2‐a]benzimidazoles (4) has been developed by a direct intramolecular CH amination of N‐phenylpyridin‐2‐amines (3). Efficient CH amination of 3 could only be achieved in the presence of catalytic copper and an acid additive. The type of acid (pKa) proved to be crucial for the catalysis. CCl aminations in N‐(2‐chloroaryl)pyridin‐2‐amines allow access to 9‐substituted pyrido[1,2‐a]benzimidazoles
A Direct Intramolecular C−H Amination Reaction Cocatalyzed by Copper(II) and Iron(III) as Part of an Efficient Route for the Synthesis of Pyrido[1,2-<i>a</i>]benzimidazoles from <i>N</i>-Aryl-2-aminopyridines
A novel and efficient synthesis of pyrido[1,2-a]benzimidazoles through direct intramolecular aromatic C-H amination of N-aryl-2-aminopyridines has been developed. The reaction, cocatalyzed by Cu(OAc)(2) and Fe(NO(3))(3)·9H(2)O, is carried out in DMF under a dioxygen atmosphere. Diversified pyrido[1,2-a]benzimidazoles containing various substitution patterns are obtained in moderate to excellent yields
diversified pyrido[1,2-a]benzimidazoles and 1H-benzo[d]imidazoles from N-aryl-2-aminopyridines and N-arylamidines has been developed. The C-H cycloamination reaction was catalyzed by hypervalentiodine(III) speciesgenerated in situ from iodobenzene (catalytic) and peracetic acid (stoichiometric). The reaction proceeded smoothly at ambient temperature to provide the corresponding N-heterocycles in good