To a suspension of NaH (60%, 10.5 g) in THF (dry) (200 mL) was added 2-chloroethanesulfonyl chloride (11.0 mL) at 0° C. and the mixture was stirred for 10 min at the same temperature. A solution of 3-[4-(cyclohexyloxy)phenyl]pyridin-2-amine (14.1 g) in THF (dry) (150 mL) was added at 0° C. and the mixture was stirred at room temperature under nitrogen for 14 hr. The mixture was quenched with water at 0° C. carefully. Water and hexane were added to form precipitates which were washed with EtOAc and collected to give 9-[4-(cyclohexyloxy)phenyl]-3,4-dihydropyrido[2,1-c][1,2,4]thiadiazine 2,2-dioxide (17.4 g) as an off-white solid. To 9-[4-(cyclohexyloxy)phenyl]-3,4-dihydropyrido[2,1-c][1,2,4]thiadiazine 2,2-dioxide (16.0 g) was added DMSO (280 mL) under heating with oil bath (ca. 90° C.) After being stirred for 10 min., EtOH (520 mL) was dropwised at 85° C. to form precipitates. The mixture was stirred for further 15 min at same temperature and then cooled to room temperature (the oil bath was removed and stirred for 50 min and stirred for 60 min in water bath). The precipitates were collected, washed with EtOH (40 mL) and dried in air for 2 days to give the title compound (13.1 g) as colorless crystals.
