| Chroman-4-ones have possessed excellent biological activities and pharmacological properties,which were widely distributed in natural products and drug molecules.In recent years,the synthesis of chroman-4-one derivatives by radical tandem cyclization has attracted extensive attention in domestic and foreign researchers.Among them,transition metal catalysis was widely used in the praparetion of chroman-4-one compounds.This method has high reactivity,good substrate capacity,concise reaction step and high yield,which could effectively construct carbon-carbon and carbon-oxygen bonds.In this paper,two studies were mainly developed towards the synthesis of difluoroacetylated chroman-4-ones catalyzed by copper salt and the praparetion for alkoxylated chroman-4-ones catalyzed by silver salt.The main contents include the following two parts:Firstly,we used o-allyloxybenzaldehyde as starting material and bromodifluoride reagents as the difluoroacetyl source to obtain a variety of difluoroacetylated chroman-4-ones in the presence of cheap and avaliable copper catalyst,which was carried out via radical cascade cyclization to effectively construct carbon-carbon bonds.In the investigation of different o-allyloxybenzaldehyde substrates and bromodifluoride reagents,it was found that this method showed good substrate capacity with excellent yields.In addition,the reaction mechanism indicated that a difluoromethylene radical was involved in this transformation.Secondly,o-allyloxybenzaldehyde was also employed as the starting material and ethanol was acted as the alkoxyl source to produce a series of alkoxylated chroman-4-ones under the cooperation of silver salt and potassium persulfate,constructing carbon-oxygen bonds effectively.This approach has a wide range of substrates and was suitable for a variety of o-allyloxybenzaldehyde compounds.Moreover,this method also exhibited good functional group tolerance with acetone,which could deliver 1,5-dicarbonylchroman-4-ones in high yields. |
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