On-Water Synthesis of 2-Substituted Quinolines from 2-Aminochalcones Using Benzylamine as the Nucleophilic Catalyst.

On-water synthesis of 2-substituted quinolines from 2-aminochalcone derivatives was developed using benzylamine as the nucleophilic catalyst. Various 2-aminochalcones could be applied to this protocol, and the desired 2-substituted quinoline products were isolated in excellent yields by simple filtration. Furthermore, we elucidated the role of benzylamine in this transformation and provided the detailed reaction mechanism. This protocol has several additional advantages, such as simple operation, broad substrate scope, good functional group tolerance, easy product isolation, recycling of the catalyst, and gram-scale synthesis.