In a 50 ml 3 necked round bottom flask there were placed 1 gram (4.56 mmol) of 3-piperazinylbenzo[d]isothiazole; 1.25 grams (5.43 mmol) of 6-chloro-5-(2-chloroethyl)indolin-2-one; 50 mg of potassium iodide; 0.82 gram (5.94 mmol) of potassium carbonate and 3 ml of sulfolane. The contents of the flask were heated to 95° C. to 100° C. The reaction was monitored by HPLC. After completion of the reaction, 50 ml of DM water was added to the reaction mixture and stirred. The product was filtered off and washed with water and dried to obtain 1.41 grams (75%) of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydro-2H-indol-2-one. The crude product was purified by IPA and/or THF. The product matched the spectra of a standard NMR and showed the correct retention time by HPLC with 98.0% assay. The melting point of the compound was found to be 218° C.-220° C., and was found to conform with the melting point of 218°-220° C. as disclosed in U.S. Pat. No. 5,206,366.
