32.6 gm (0.2 mol) of 6-hydroxy-3,4-dihydro-carbostyril [see F. F. Mayer et al., Ber. Dtsch. Chem. Ges. 60, 858 (1927)] and 27.6 gm (0.2 mol) of potassium carbonate were stirred for 5 minutes in 600 ml of dimethylsulfoxide which had been dried over a molecular sieve, and then 52.2 gm of 4-phenylsulfinyl-butyl bromide (0.2 mol) (prepared from thiophenol and 1,4-dibromo-butane and subsequent oxidation with hydrogen peroxide in glacial acetic acid analogous to Example 2; oily substance, solidified upon standing in the refrigerator) were added. After stirring it for 15 hours at 25° C., the reaction mixture was poured into 6 liters of water. After stirring the aqueous mixture for 30 minutes more, the precipitated product was suction-filtered off and thoroughly washed with water. After drying, the filter cake was recrystallized from about 600 ml of xylene in the presence of charcoal. White crystals with a melting point of 144.5°-145.5° C. were obtained.
