Selectively reductive amination of levulinic acid with aryl amines to N-substituted aryl pyrroles

Synthesizing nitrogen (N)-containing molecules from biomass derivatives is a new strategy for production of this kind of chemicals. Herein, for the first time we present the synthesis of N-substituted aryl pyrroles via reductive amination/cyclization of levulinic acid (LA) with primary aromatic amines and hydrosilanes (e.g., PMHS) over CsF, and a series of N-substituted aryl pyrroles could be obtained in good to excellent yields at 120 °C. The mechanism investigation indicates that the reaction proceeds in two steps: the cyclization between amine and LA occurs first to form intermediate 5-methyl-N-alkyl-1,3-dihydro-2H-pyrrolones and their isomeride (B), and then the chemo- and region-selective reduction of intermediates take place to produce the final products. This approach for synthesis of N-substituted aryl pyrroles can be performed under mild and green conditions, which may have promising applications.