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On the Importance of an Acid Additive in the Synthesis of Pyrido[1,2‐ a ]benzimidazoles by Direct Copper‐Catalyzed Amination
Author(s) -
Masters KyeSimeon,
Rauws Tom R. M.,
Yadav Ashok K.,
Herrebout Wouter A.,
Van der Veken Benjamin,
Maes Bert U. W.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100574
Subject(s) - amination , intramolecular force , catalysis , chemistry , copper , combinatorial chemistry , modular design , organic chemistry , computer science , operating system
Not just an acid! An expedient and highly modular synthesis of 6‐, 7‐, and 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 (p K a ) 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.