Carbon catalyst derived from Himalayan pine for the C-N coupling of organic molecules leading to pyrrole formation

Abstract

Carbon catalyst consisting of a hybrid structure made up of amorphous carbon and nanographite was prepared from the leaves of Pinus Roxburghii. The catalyst was prepared through sodium hydroxide and hydrochloric acid treatment of the dried pine leaves; and further functionalized with sulfuric acid treatment to incorporate the acidic functionalities. The synthesized catalyst was characterized by FTIR, XRD, TEM and XPS spectroscopic techniques and used as a heterogeneous catalyst for C-N coupling reaction leading to pyrrole formation through the nucleophilic attack of nitrogen atom in amines or imines on the dicarbonyl compounds. The optimized method was explored on various 2,4- and 2,5- dicarbonyl compounds and it was found to afford the five member pyrrole nucleus is good to excellent yields. The scope of the reaction was demonstrated by synthesizing thirteen pyrrole derivatives that are well characterized by IR, NMR and mass spectrometry. The mechanism of the reaction was proposed and acidic sites present on the catalyst surface are believed to be the active sites in the conversion.