To a suspension of NaH (60%, 81 mg) in THF (dry) (10 mL) was added 2-chloroethanesulfonyl chloride (0.085 mL) at 0° C. and the mixture was stirred for 10 min at the same temperature. A solution of 3-(4-(4-ethylphenoxy)phenyl)pyridin-2-amine (117 mg) in THF (dry) (10 mL) was added at 0° C. and the mixture was stirred at room temperature under nitrogen for 4 hr. The mixture was quenched with water at 0° C. Water, EtOAc and THF were added and the mixture was extracted. Silica-gel was added to the organic phase and the volatiles were removed in vacuo. The mixture supported on silica-gel was purified by column chromatography (silica gel, eluted with MeOH in EtOAc) and concentrated in vacuo to give 9-[4-(4-ethylphenoxy)phenyl]-3,4-dihydropyrido[2,1-c][1,2,4]thiadiazine 2,2-dioxide as a white solid. Platinum(IV) oxide (20 mg) was added to a solution of 9-[4-(4-ethylphenoxy)phenyl]-3,4-dihydropyrido[2,1-c][1,2,4]thiadiazine 2,2-dioxide (153 mg) in THF (dry) (20 mL) and MeOH (20 mL). The mixture was stirred at room temperature under hydrogen for 3 hr. Activated carbon was added and the insoluble solid was removed by filtration through silica gel/Celite pad (eluted with EtOAc). Platinum(IV) oxide (20 mg) was added and the mixture was stirred at room temperature under hydrogen overnight. Activated carbon was added and the insoluble solid was removed by filtration through silica gel/Celite pad (eluted with EtOAc) and the filtrate was concentrated in vacuo. The residue was crystallized from THF/IPE to give the title compound (46.7 mg) as colorless crystals.
