Research On In-situ Generated Iodine-promoted Synthesis Of Substituted Pyridines And ?-acyloxycarbonyl Compounds

Pyridines and ?-acyloxycarbonyl compounds exit in a substantial number of both naturally occurring and synthetic biologically significant molecules.They are widely used not only in functional materials,pesticides and pharmaceuticals,but also as important intermediates and ligands in organic and pharmaceutical synthesis.Although many methods towards the synthesis of pyridines and ?-acyloxycarbonyl compounds have been reported,it is of great significance to develop a simple,efficient and environmentally friendly approaches.The present dissertation mainly includes two parts: synthesis of pyridines and ?-acyloxycarbonyl compounds.(1)Investigation on pyridines synthesis via NH4I-promoted condensation of 1,3-dicarbonyl compounds with DMSO and NH4 OAc was made.The effect of key factors on the formation of target products was systematically investigated,including reaction temperature,promoters,nitrogen source and solvents,and so on.The experimental results indicated that the condensation reaction of 1,3-dicarbonyl compounds with DMSO and NH4 OAc proceeded smoothly to give the corresponding pyridines in high yields at 115 °C with NH4 I as the promoter,DMSO as the solvent and one-carbon synthon.Compared with the traditional methods,the present synthetic route is simpler and more efficient for the synthesis of pyridines.In addition,the transformation could tolerate a wide range of functional groups.The present work provides a novel and efficient method for the synthesis of pyridines.(2)Study on ?-acyloxycarbonyl compounds synthesis via oxidative decarboxylation coupling reaction of ?-oxo carboxylic acids with carbonyl compounds.Similarly,the effect of various factors on the formation of target products was carefully investigated,including oxidants,catalysts and solvents.The optimized conditions are as follows: TBAI as the catalyst,TBHP as the oxidant,EtOAc as the solvent and reaction for 24 h at 80 °C.Under the optimized conditions,the target products could be obtained in moderate to good yields for a variety of ?-oxo carboxylic acids and carbonyl compounds.The investigation on the reaction mechanism demonstrates that the reaction underges a radical process and the decarboxylation of ?-oxo carboxylic acids is due to the oxidation of TBHP.Compared with the synthesis methods reported in literatures,the present method seems to be simpler and more efficient,and provides a new approach for the decarboxylative functionalization of carboxylic acids.