3-Chloro-N,N-dimethyl-1-propanamine → 5-(3-dimethylaminopropyl)-3-methylmercapto-5H-dibenzo[a,d]cycloheptene

The Grignard reagent is prepared from dimethylaminopropyl chloride (0.2 mole) and magnesium (0.2 g. atom) in 75 ml. of dry tetrahydrofuran following the method described in U.S. Pat. No. 2,996,503. A 15 ml. portion of this solution is cooled in an ice-bath and stirred while a solution of 4.7 g. (0.0172 mole) of 5-chloro-3-methylmercapto-5H-dibenzo[a,d]cycloheptene in 25 ml. of tetrahydrofuran is added dropwise. The usual precautions, such as careful drying of the apparatus and maintaining a nitrogen atmosphere, are observed. After stirring the mixture for 2 hours at room temperature, the bulk of the solvent is distilled at 30°C. under reduced pressure and the residue dissolved in benzene. The solution is cooled in an ice-bath and the excess Grignard reagent hydrolyzed by the dropwise addition of water. The benzene layer is decanted and the gelatinous precipitate washed with four 25 ml. portions of boiling benzene. After washing with water, the combined benzene solutions are extracted with 50 ml. of 0.5 M. citric acid. The acid extract is rendered alkaline with sodium hydroxide and the oily base extracted into benzene. Evaporation of the washed benzene extract under reduced pressure leaves 5-(3-dimethylaminopropyl)-3-methylmercapto-5H-dibenzo[a,d]cycloheptene as the oily residue weighing, typically, 4.2 g. (75%).