Synthesis Of Benzothiophene Pyranone Derivatives Based On Intramolecular Cross Dehydrogenation Coupling

Heterocyclic skeleton construction is a hotspot in the field of organic synthesis.Intramolecular cross-dehydrogenation coupling reaction is an important means to construct carbon-carbon bonds in heterocyclic skeletons due to its strong reactivity and high atomic economy.Benzothiophenes are a class of aromatic compounds containing hetero atomic sulfur,which are widely used in the fields of synthetic medicine,pesticides,dyes,and new polymer materials.Coumarin and pyrone compounds are a class of conjugated compounds containing a lactone structure,and the molecules composed of related skeletons have strong biological activity and optical activity.In view of the structural characteristics of coumarin and pyrone,chemists often introduce various functional groups on the coumarin and pyrone precursors to expand the application range of coumarin and pyrone.This paper explores a method for the synthesis of benzothiophene coumarin and pyrone under milder conditions.The specific research is as follows:?1?Devised a method for synthesizing benzothieno-coumarin compounds.The reaction conditions were as follows:0.2 mmol of 4-phenylthiocoumarin as the reaction substrate,palladium acetate?10 mol%?as catalyst,silver acetate?0.4mmol?as oxidant,propionic acid?1 mL?as solvent,stirring at 140°C for 24hours.Twelve benzothiophene coumarin derivatives were synthesized by using this reaction condition.The highest yield was 82%.Six compounds were selected to determine the fluorescence properties and the structures of all products were characterized by HRMS,¹H NMR and ¹³C NMR and other methods.The possible mechanism of the reaction is also proposed.This method has the advantages of high yield,less by-products and simple operation.It is of great practical significance for the synthesis of the compounds.?2?Developed a method for synthesizing thienopyran-2-one derivatives.The method uses 0.2 mmol of 6-methyl-4-phenylthiopyran-2-one as the reaction substrate,palladium acetate?10 mol%?as the catalyst,silver acetate?0.4 mmol?as the oxidant,propionic acid?1 mL?was a solvent and stirred under heating at140°C for 24 hours.Using the reaction conditions,six thienopyran-2-one derivatives were synthesized with a maximum yield of 68%.The method is simple and efficient,which provides a new way for the synthesis of thienopyran-2-ones.