NOVELTY - t-Butyl-N,N-bis(2-chloroethyl)carbamate (B) and tetrahydrofuran are added to reaction solution containing 6-chloro-2,3-dihydro-1H-indol-2-one. Obtained solution is heated, stirred, cooled and purified to obtain tert-butyl 6-chloro-2-oxo-1,2-dihydrospiro(indole-3,4'-piperidine)-1'-carboxylate (G). Compound (G) is dissolved in dichloromethane, and added to solution of hydrochloric acid in diethyl ether. Precipitated solid is stirred, filtered and dried to obtain 6-chloro-1,2-dihydrospiro(indole-3,4'-piperidine)-2-one hydrochloride (H) as pharmaceutical intermediate.    USE - Preparation of pharmaceutical intermediate (claimed).    ADVANTAGE - The method efficiently provides pharmaceutical intermediate with high cleanliness and reduced amount of byproducts, without affecting the environment.    DETAILED DESCRIPTION - Bis(2-chloroethyl)amine hydrochloride (A) and triethylamine are dissolved in dichloromethane, and di-t-butyl ester is added, such that the molar ratio of compound (A) and di-t-butyl ester is 0.8-1.2:1. The resultant mixture is cooled to -5 degrees C to 5 degrees C, stirred, diluted with dichloromethane, washed with water, and then with dilute hydrochloric acid and brine. The obtained organic phase is dried, filtered, and spin dried to obtain t-butyl N,N-bis(2-chloroethyl)carbamate (B). Diethyl malonate is added slowly to a solution of sodium hydride in dimethyl sulfoxide, and solution of 4-chloro-1-fluoro-2-nitrobenzene (C) is added, such that the molar ratio of diethyl malonate and solution of compound (C) is 0.3-0.6:1. The obtained mixture is then warmed at 20-30 degrees C, and extracted with ethyl acetate after adding water. The resultant mixture is washed with water, brine, and the organic phase is dried, filtered, spin dried to obtain 1,3-diethyl 2-(4-chloro-2-nitrophenyl)propanedioate (D). The compound (D) is added to 30-70% sulfuric acid, heated at 100-160 degrees C for 5-15 hours, cooled to -5 degrees C to 5 degrees C, and obtained white solid precipitate is filtered, washed with water and dried to obtain 2-(4-chloro-2-nitrophenyl)acetic acid (E). The compound (E) is dissolved in ethanol, and 30-70% sulfuric acid and zinc powder are added. The reaction mixture is stirred for 1-3 days, diluted with ethanol, filtered, concentrated, and water is added. The precipitated white solid is filtered, dried and recrystallized from ethanol to obtain 6-chloro-2,3-dihydro-1H-indol-2-one (F). n-Butyllithium is added to diisopropylamine in tetrahydrofuran at -78 degrees C under nitrogen atmosphere, stirred for 10-50 minutes, and the reaction solution is added to compound (F), and incubated for 0.5-2 hours. The compound (B) and tetrahydrofuran are added to the reaction solution, such that molar ratio of compound (B) with respect to compound (F) is 0.8-1.2:1. The obtained reaction solution is heated at 60-100 degrees C, stirred for 5-15 hours, cooled to room temperature, and purified to obtain tert-butyl 6-chloro-2-oxo-1,2-dihydrospiro(indole-3,4'-piperidine)-1'-carboxylate (G). The obtained compound (G) is dissolved in dichloromethane at -5 degrees C to 5 degrees C, and added to solution of hydrochloric acid in diethyl ether. The precipitated solid is stirred, filtered and dried to obtain 6-chloro-1,2-dihydrospiro(indole-3,4'-piperidine)-2-one hydrochloride (H).