The Synthesis Of Coumarin Derivatives By Solid Acid And Base Catalysts

Coumarin derivatives as spicery and chemical or medical intermediatesare very important in industry. In recent years, solid super acids and basesare getting more and more attention in organic synthesis for their highactivity, high selectivity as well as environmentally friendliness. At thesame time, microwave technique has attracted many researchers for itsadvantages, such as lower temperature, shorter reaction time and higheryield. In this paper, the applications of solid acids and solid bases andmicrowave on synthesis of coumarins have been studied. The products arewell characterized by mp analysis, IR and MS. The work is as follows:1.Study of the catalytic synthesis of coumarin using solid bases ascatalyst.(1) The synthesis of coumarin was studied under microwave radicalizationwith KF/Al₂O₃ as catalyst. The results indicate that KF/Al₂O₃ is activeunder microwave. When n (salicylaldehyde): n (acetyl oxide): n (KF/Al₂O₃)was 1: 3: 0.5, microwave Power was 600 w and the time of microwaveradicalization was 8 min, the yield of coumarin was as high as 88.9%.Compared with conventional heating, the reaction rate and the yield wereincreased by 30 times and 14% respectively.(2) The synthesis of coumarins under the normal heated condition withcomplex solid bases KF/K₂CO₃/Al₂O₃ was studied as well. The resultshows that under optimum conditions, the yield of the coumarin were ashigh as 89.8%.2. Study of the catalytic synthesis of 4-methyl coumarin derivativesusing solid acids as catalyst. (1) The synthesis of 4-methyl coumarin derivatives starting fromhydroxybenzene and acetyl ethyl acetate with HPW/C as catalyst wasstudied, especially the synthesis of 7-hydroxy-4-methyl coumarinderivatives with HPW/C. All of the products were well characterized andthe effect of the catalyst on the reaction is also studied.The optimum conditions of synthesis of 7-hydroxy-4-methyl coumarinare as follows: reaction temperature is 100℃, n (resorcin): n (acetyl ethylacetate)=1: 1, the amount of loaded phosphotungsic acid is 22.3%, thecatalyst dosage is 0.15g, the reaction time is 3h. The yield is up to 74.3%based on the conditions. The HPW/C catalyst is active and stable, whichcan be recycled for many times.(2) The synthesis of 7-hydroxy-4-methyl coumarin with exchange resinsupported AlCl₃ as catalyst was systematically. studied. The optimumconditions are as'follows: reaction temperature is 105℃, n (re(?)orcin): n(acetyl ethyl acetate)=1: 1, the catalyst dosage is 0.28g, the reaction timeis 3h. The yield is up to 82.5%. The exchange resin supported AlCl₃ can bemore facilely recycled for the bigger particle than that of HPW/C, whichhas further application in synthesis of 7-hydroxy-4-methyl coumarin thanHPW/C.