Synthesis of Substituted Pyrroles by using Choline Carboxylate Deep Eutectic Solvent

Pyrroles and their derivatives are the most important group of heterocyclic aromatic components, which exist in many synthetic pharmaceuticals and natural substances[1]. They are the core unit of many complex macrocycles, including the porphyrins of heme, bacteriochlorins, chlorophyll, and porphyrinogens [2]. They have significantbiological properties such as antitumor, antibacterial, antioxidant, and antifungal. Pyrroles also have wide applications in materials science; therefore, several methodshave been developed for the synthesis of the construction of pyrroles. These methods include some useful reactions such as Hantzsch, Knorr, or Paal-Knorr. Deep Eutectic Solvent Choline Carboxylate (DES) was synthesized. DES was characterized by XRD, FT-IR and NMR techniques for their surface area, surface acidity, crystallinity and functionality. The catalytic activity of the DES was determined in synthesis of substituted pyrroles with acetic anhydride. The influential parameters of the reaction such as molar ratio of the reactants, reaction temperature and amount of the DES were optimized. Herein, we wish to report the synthesis of substituted pyrroles using DES as a green and recyclable catalyst between an amine, an aldehyde, a 1,3-dicarbonyl compound, and nitromethane (Scheme 1). The catalyst can be recycled easily and reused several times without significant loss in its activity. The reaction time was decreased from several hours in other methods to some minutes using DES, in the present work.