Conversion Of Propargyl Alcohol And 4-Hydroxycoumarin Compounds Catalyzed By Acid-Functionalized Ionic Liquid

4-Hydroxycoumarin and its derivatives,as important core segment of many natural products,have a variety of biological or pharmaceutical activities,which can be used as drug intermediates and have important applications in agriculture and medicine.Therefore,the construction of 4-hydroxycoumarin and its derivatives skeleton has become a research hotspot.As a common compound,alcohol is widely used in the field of organic synthesis,especially in the formation of C-C bond and C-O bond.As a kind of functional materials,ionic liquids are favored by researchers because of their special design and adjustable performance.By grafting acidic groups onto traditional ionic liquids,a series of acid functionalized ionic liquids with specific functions can be prepared,which have good acidic sites and catalytic performance,and play an important role in the field of catalysis.Based on above,a series of acid functionalized ionic liquids based on imidazole,pyrrolidine and pyridine were designed and synthesized in this paper.These ionic liquids were used as catalysts for the conversion of propargyl alcohol and 4-hydroxycoumarins.Among them,the alkylation reaction of the secondary propargyl alcohol and 4-hydroxyxamin were catalyzed by the pyridine ionic liquid,while the cyclization reaction of the tertiary propargyl alcohol and4-hydroxyxamin by the imidazole proton ionic liquid.And a series of 4-hydroxyxamin derivatives were synthesized,which provided new ideas for the construction of 4-hydroxyxamin derivatives.The specific research contents are as follows:1.A series of 4-hydroxycoumarin derivatives were synthesized by the C3-alkylation of 4-hydroxycoumarin with secondary propargyl alcohol using pyridine sulfonic acid functionalized ionic liquid as catalyst and dimethyl carbonate（DMC）as green solvent.Their structures were characterized by ¹H NMR,¹³C NMR and HRMS.The results showed that the catalytic system had the advantages of high catalytic efficiency,low cost,simple preparation,environmental friendiness,and was suitable for aromatic alcohols and aliphatic alcohols,at the same time,it can achieve gram scale-up,and the yield was close to quantitative.In addition,the catalytic system can synthesize rodenticide as commercial coumatetralyl from 4-hydroxycoumarin and1,2,3,4-tetrahydronaphthalene-1-ol in one step.The control experiments stated that the reaction of secondary propargyl alcohol with 4-hydroxycoumarin might carry out the process of carbocation and ether intermediate,and the ionic liquid catalyst fully showed the synergistic catalysis of cation and anion.2.A series of functionalized pyrano[3,2-c]-coumarin derivatives containing tricyclic segments were successfully synthesized by cyclization of tertiary propargyl alcohol with 4-hydroxycoumarin using imidazole based proton ionic liquids as catalysts.The products were characterized by ¹H NMR,¹³C NMR and SXRD.Besides,the results indicated that the catalytic system had obvious advantages in mild reaction conditions,high efficiency,easy separation,wide range of substrate tolerances,recyclability of catalyst,etc.Meanwhile,the cyclization reaction can achieve gram scale reaction.The process of hydrogen transfer and cyclization after the rearrangement between alkynyl carbocations and allene carbocations which was the possible mechanism.