Synthesis Of Fully Substituted 4-Carbonyl Imidazolium Salts From Enamines Via Iodine-Mediated Oxidative Cyclization

Among numerous nitrogen-containing heterocyclic derivatives,the imidazolium compounds play an important role.Thanks to the special properties of imidazolium compounds,they have broad application prospects in the fields of organic catalysis and material chemistry.This kind of organic salt is an important nitrogen-containing heterocyclic carbene(NHC)precursor and important ionic liquid.Therefore,the research and application of the properties of these compounds,as well as the research of their synthesis methods,have become the research hotspots of organic chemistry in the past ten years.Since there are still some shortcomings in the existing imidazolium salt synthesis method,the research for simple and highly efficient synthetic methods for imidazolium compounds is important for the development of organic catalysis,new drugs and functional materials.In this paper,we have developed a synthetic method for the construction of 4-carbonyl imidazolium salt in good yield with iodine as the substrate/catalyst.The enamines substrate required for the reaction could be obtained by condensation of the corresponding β-dicarbonyl compounds with amines.Under the participation of inorganic base,the enamine compounds obtained by condensation undergoes iodinate,intermolecular quaternization,Aza-Michael addition and subsequent elimination reaction,oxidative cyclization,under the mediation of iodine,successfully constructed 29 new 4-carbonyl imidazolium salt derivatives.This imidazolium compounds synthesis method is simple in operation,has no metal participation,and could be scaled up to a gram scale to facilitate the supply of raw materials required for further research.This reaction has the advantages of wide application range of substrate & functional group compatibility,provides a novel and convenient synthetic route for the construction of imidazolium salt.