New Method For Preparation Of 2-iodo-?-acyloxycarbonyl Compounds By N-heterocyclic Carbene Catalysis

?-Acyloxy carbonyl compounds represent basic building blocks in synthetic organic chemistry,which are important structural motifs existing widely in a large number of pharmaceuticals and biologically active compounds.Since the 1970s,the synthesis and research on ?-acyloxycarbonyl compounds have attracted much attention in the chemical field.Traditionally,?-acyloxy carbonyl compounds can be prepared by the substitution of ?-halo carbonyl compounds insertion of ?-diazoketones with alkaline carboxylates and the coupling reaction of ketones with toxic heavy metal oxidants.It was subsequently found that hypervalent iodine compounds as effective oxidants to promote the acyloxylation reaction have been reported.In recent years,ethynylbenziodoxolone(EBX)reagent have attracted a lot of interest because of their mild performance,high selectivity and environmentally friendly nature.Palladium(?)catalyst promotes condensation of an N-aryl imine and an alkynylbenziodoxolone derivative to afford a multisubstituted furan.The reaction of 4-pyridyl imine and Phenyl-EBXs did not afford the desired furan derivative,while 2-iodo-?-acyloxycarbonyl compound was obtained in 22%yield.However,most of these well-established protocols may suffer from certain disadvantages such as the use of a large excess of ketone motifs,harsh reaction conditions,an excess amount of oxidants,toxic metal catalysts,or low yields.Therefore,the development of a simple process,easy operation,mild conditions,and the wide range of substrates methods to access ?-acyloxy carbonyl compounds is still highly desirable in synthetic and pharmaceutical chemistry.In this paper,the catalytic activity and reaction mechanism of the reaction of EBX reagent in the synthesis of 2-iodo-a-acyloxycarbonyl compound with N-heterocyclic carbene as catalyst were studied.The main contents are as follows:Part one:EBX reagents synthesized from phenacetylenes and the N-heterocyclic carbene are subjected to an oxidative rearrangement reaction in the 1,4-dioxaneaqueous solution to synthesis 2-iodo-?-acyloxycarbonyl compounds.Compared with the existing methods,this method is not only suitable for a wide range of substrates,insensitive to air and water,and without transition-metal,Therefore,this transformation is conducive to the production and treatment of drugs.Part two:The EBX reagent and the imidazole N-heterocyclic carbene are oxidized and rearranged under 1,4-dioxane aqueous solution to form the 2-iodo-a-acyloxycarbonyl compound;explore the possible reaction mechanism.