One‐Pot Synthesis of N‐Alkyl Benzotriazoles via a Brønsted Acid‐Catalyzed Three‐Component Reaction

Abstract

A novel three‐component condensation reaction of benzotriazoles, aldehydes and tertiary anilines efficiently catalyzed by readily available organic acid p‐toluenesulfonic acid (PTSA) has been developed. A series of N‐alkyl benzotriazoles were synthesized in up to 97% yield for 21 examples starting from anilines, benzotriazoles and formaldehyde. This strategy features a simple system, atom economy, environmental friendliness, high efficiency, excellent regioselectivity, good functional group tolerance, easily available starting materials, and cheap catalyst. The mechanistic studies indicated that aza quinone methide was probably involved as an intermediate in this transformation.magnified image

p-Toluenesulfonic acid-promoted organic transformations for the generation of molecular complexity

“…Benzotriazole is a valuable heterocycle and an essential structural component in photosensitive compositions, bioactive molecules, and dyes. Prof. Cui 8 disclosed a unique p -toluenesulfonic acid-catalysed three-component condensation reaction of tertiary anilines, aldehydes, and benzotriazoles where a series of N -alkyl benzotriazole derivatives were formed efficiently (Scheme 5). In an acidic medium, a regioselective Friedel–Crafts-type reaction of formaldehyde with anilines generated an active intermediate known as aza quinone methides A2 , which could react with benzotriazoles and likely result in the formation of a new C–N bond and offer a novel approach for obtaining para -selective C–H aminomethylation of anilines.…”