Study On The Synthesis Of The UV-absorber P-methoxy-2-ethylhexyl Cinnamate By Microwave-assisted

Microwaves are electromagnetic waves with wavelengths ranging from 100cm to 1mm, or frequencies between 300MHz and 300GHz. Microwave can rapidly heat the reactants in a very short time, and activate some reactions whether they can occur or not under normal conditions. The UV-absorber p-methoxy-2-ethylhexyl cinnamate (OMC for short) has good UV absorption and oil-solubility, and is widely used as sunscreen additive. The UV absorbers OMC and its two important intermediates were synthesized including acrylic acid 2-ethylhexyl ester and p-bromo-anisole by microwave-assisted. The results were better than the procedure of traditional heating conditions. The structures were identified by 1H-NMR and GC-MS.P-Bromo-anisole was prepared from phenol by etherification and bromization. The optimized conditions of etherification were: the molar ratio of phenol to dimethyl sulfate was 1:1.3. They reacted for 4 hours under 9.0-9.3 pH. The purity of anisole was 99%, and the yield was 90.3%; the optimized conditions of bromization were: the molar ratio between anisole and bromine was 1:1.3. They reacted at 70℃for 6 hours using cyclohexane as solvent under traditional heating conditions. The purity and yield were 95% and 88% respectively.Acrylic acid 2-ethylhexyl ester was synthesized by acrylic acid and 2-ethyl hexanol. The optimized conditions under traditional heating procedure were: the molar ratio between acrylic acid and 2-ethyl hexanol was 1:1.1. They reacted at 110℃for 3 hours using p-toluenesulfonic acid as catalyst and toluene as solvent. The yield was 74.6%; the optimized conditions under microwave heating procedure were: the molar ratio between acrylic acid and 2-ethyl hexanol was 1:1.2. They reacted at 455w for 40 minutes using p-toluenesulfonic acid as catalyst and toluene as solvent. The yield was 90.1%.The UVB-absorber OMC was synthesized by Heck coupling reaction of p-bromo-anisole and acrylic acid 2-ethylhexyl ester. The optimized conditions of traditional heating procedure were: the molar ratio between p-bromo-anisole and acrylic acid 2-ethylhexyl was 1:1.1. They reacted at 180℃for 2 hours in closed tube protected by nitrogen. 5% palladium /carbon were used as the catalyst. And DMF was used as solvent. The purity was 98% and the yield was 85%. The optimized conditions of microwave heating procedure were: the molar ratio between p-bromo-anisole and acrylic acid 2-ethylhexyl was 1:1.2. They reacted at 455W for 1 hour in closed tube protected by nitrogen. 5% palladium /carbon were used as the catalyst, and DMF was used as solvent. The purity was 98% and the yield was 89%.