Synthesis of 4-Phenyl-6-methynl-5-ethoxycarbonyl-3,4-dihydropyrimidin-2( H)-ketone Using H_6P_2W_(18)O_(62)/SiO_2 as Catalyst

Phosphotungstic acids with Dawson structure( H6P2W18O62) supported on SiO2 were prepared by sol-gel method. The properties of the catalyst were characterized by means of TGA,FTIR,SEM and XRD. The results show that H6P2W18O62 had been well dispersed into the SiO2 support,and the immobilized catalyst exhibited high catalytic activity in the Biginelli reaction for the synthesis of 4-phenyl-6-methyl-5-ethoxycarbonyl-3,4-dihydropyrimidin-2( H)-ketone. The optimized conditions were as follows: fixed benzaldehyde consumption was 0. 04 mol,n( benzaldehyde) ∶ n( ethylacetoacetate) ∶ n( urea) =1∶1. 5∶1.5,the mass ratio of the catalyst to total reactant was 2.0%,the reaction temperature was 80 ℃,and the reaction time was 75 min. The yield of the product could reach 82. 3% under the optimum conditions. It also maintained satisfactory catalytic activity for the synthesis of Biginelli compound after 10 rounds of recycling,and the yield was still above 57. 2%.