Study On Synthesis Of P-methoxy Cinnamate As Sun-screening Agent

P-methoxyl cinnamate can prevent UV280-310 nm, and has hingly absorption rate. It is widely used in sunscreen cosmetics currently. Isooctyl p-methoxy cinnamate is the most common sunscreen agent in the world now, it has excellent UV absorption curve and good solubility of the oil and safety, it is an ideal sunscreen.Ethyl p-methoxy cinnamate was synthesized by Knoevenagel reaction of p-methoxyl benzaldehyde and malonic acid using pyridine and aniline as co-catalyst and toluene as solvent, and then esterification of p-methoxyl cinnamic acid and alcohol using p-toluene sulfonic acid as catalyst. The factors influencing the synthesis were studied and the yield of p-methoxyl cinnamate was 68.6%, the yield and purity of ethyl p-methoxy cinnamate were 96.5% and more than 98.5% respectively. The structure of the synthetic product was confirmed by FT-IR and ¹H NMR,¹³C NMR.Methyl p-methoxy cinnamate was synthesized by Claisen-Schmidt condensation from p-methoxybenzaldehyde and methyl acetate using sodium methoxide as catalyst. The factors influencing the synthesis were studied and the yield and purity of the product were 79.0% and more than 99.0% respectively. Otherwise, The structure of the synthetic product was confirmed by FT-IR and ¹H NMR,¹³C NMR and the melt point was m.p.87-89℃(87-88℃).Isooctyl p-methoxy cinnamate was prepared by transesterification of methyl p-methoxy cinnamate with 2-ethylhexan-1-ol using toluene-p-sulfonic acid as catalyst .The factors influencing the reaction were investigated and the conversion of methyl p-methoxy cinnamate and selectivity of the product were 99.7 % and 98.4 % respectively .The purity of the product was more than 99.0% . Otherwise, The structure of the product was confirmed by FT-IR,¹H NMR,¹³C NMR.(E)-butyl-3-(4-methoxyphenyl) acrylate was synthesized by the transesterification of methyl p-methoxy cinnamate and n-butanol over sodium bisulfate, and the influences of the reaction conditions were examined. The results showed that, under the optimum conditions: the conversion of methyl p-methoxy cinnamate was 88.0 % and the selectivity of the product was nearly 100 %. Otherwise, the structures of the two products were confirmed by FT-IR and ¹H NMR,¹³C NMR.