Synthesis Of N-Substituted Pyrroles Catalyzed By Polymers With Sulfonic Groups

Pyrroles are very important heterocyclic compounds,and their derivatives are widely present in natural products and drug molecules.Pyrrole derivatives participate in the growth,they have the properties of anti-tumor,anti-inflammatory,anti-bacterial,anti-oxidant and anti-fungal properties.Therefore,the synthesis of pyrroles and there is very important.Generally,pyrroles are synthesized by Paal-Knorr reaction.The catalysts for Paal-Knorr reaction are studied extensivelly,such as Bronsted acid,Lewis acid,solid acis and so on.There are drawbacks for those catalysts,such as expensive cost,toxicity,unrecycling and complex process and so on.In the paper,catalysts with the properties of recycling,easy separation and environmentally-benign are studied.The reactions are according to the principles of Green Chemistry.In the paper,poly(2-acrylamido-2-methylpropanesulfonic acid)(PAMPS)is prepared using 2-acrylamido-2-methylpropanesulfonic acid(AMPS)as monomer,N,N'-methylenebisacrylamide(MBA)as cross-linking agent and potassium persulfate as initiator.PAMPS is used as heterogenerous catalyst to synthesize N-substituted pyrroles by the reaction of Paal-Knorr reaction of primary amide and 2,5-hexanedione.The yields of prroles are 87-97%.PAMPS is easily seperated from the reaction mixtures,and recycled.There are sulfonic groups in PAMPS,and H+ionized from PAMPS acts as catalyst.At the same time,PAMPS is superabsorbent resin.Water produced in Paal-Knorr reaction could be absorbed by PAMPS,which contribute to the reaction proceeding in forward.The catalytic effect of PAPS is superior to that of 732 cation exchange resin.Sodium lignosulfonate is waste in paper-making industry.Lignosulfonic acid(LSA)is prepared by ion exchanging using sodium lignosulfonate as raw materials.Ferric lignosulfonate(FLS)is prepared by the reaction of LSA and Fe(OH)3.from paper waste sodium lignosulfonate.LSA and FLS are used as heterogenerous catalysts respectively to synthesize N-substituted pyrroles by the reaction of Paal-Knorr reaction of primary amide and 2,5-hexanedione.The yields of prroles using LSA as catalyst are 52-97%.The yields of prroles using FLS as catalyst are 82-97%.LSA and FLS are easily seperated from the reaction mixtures,and recycled.H+ionized from LSA and Fe3+ ionized from FLS act as catalysts,respectively.Paal-Knorr reaction is nucleophilic reaction.The strongr the nucleophilicity of primary amide is,the quicker the reaction,the higher the yields of N-substituted pyrroles.These three catalysts are all polymer solid catalysts with sulfonic groups.They are heterogenerous catalysts,which are cheap and easy to obtain,environmentally friendly,easily separated from the reaction mixture,recycled.The reaction is easily operated.