Synthesis of Ropivacaine under Ultrasound Irradiation

Ropivacaine hydrochloride was synthesized from 2-pipecolic acid by successive reaction with SOCl2 and 2,6-dimethylaniline at 40°C under ultrasonic irradiation to give (S)-N-(2,6-dimethylphenyl)-piperidin-2-carboxamide (4), and 4 was reacted with 1-bromopropane at 50°C for 1 h under ultrasonic irradiation. The effect of reaction solvent, temperature and time under ultrasonic irradiation were investigated. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields. The total yield was 63.1%, [α]25 D= – 6.7°(c = 2, H2O).