Microwave-assisted synthesis of isopropyl β-(3,4-dihydroxyphenyl)- α-hydroxypropanoate

Using microwave irradiation heating,isopropyl β-(3,4-dihydroxyphenyl) -α-hydroxypropanoate was synthesised from 3,4-dihydroxybenzaldehyde and acetylglycine through the formation of 2-methyl-4-(3,4-acetoxybenzylene)oxazol- 5-ones,α-acetylamino-β-(3,4-diacetoxyphenyl)acrylic acid,and β-(3,4-dihydroxyphenyl)pyruvic acid followed by clemmensen reduction and esterification. the reaction conditions in terms of operating parameters were optimised by using an orthogonal design of experiment (odoe) approach,including reaction temperature,reaction time,and microwave power level. compared with conventional heating,the reaction time was significantly reduced for all reactions and the product yields were increased (except for the third-step reaction) under microwave heating conditions. the most remarkable microwave enhancement was found in the step of isopropyl β-(3,4-dihydroxyphenyl)- α-hydroxypropanoate production where the reaction time was reduced from 10 hrs (conventional heating) to 25 mins (microwave heating) whilst the yield was increased from 75.6% to 87.1%,respectively. © 2013 qun-zheng zhang et al.