A mixture of N,N-dimethyl-3-hydroxy-3-(2-thienyl)propylamine (185 g, 1 mole), potassium hydroxide (112 g, 2 moles) and 1-fluoronaphthalene (146 g, 1 mole) in dimethylsulfoxide (1000 ml) is stirred at 110° C. for 2 hours. After cooling down to 20° C., the mixture is filtered, diluted with water (3 l), monopotassium D-tartrate (188 g, 1 mole) is added, and the mixture is stirred at 80° C. for 0.5 hour. After cooling down, the precipitated product is sucked off, washed with water and dried. Yield: 328 g (85%).
