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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

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Abstract

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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 C[BOND]H amination of N-phenylpyridin-2-amines (3). Efficient C[BOND]H 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. C[BOND]Cl aminations in N-(2-chloroaryl)pyridin-2-amines allow access to 9-substituted pyrido[1,2-a]benzimidazoles.

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