O[C:2]1[C:6]2[CH2:7][CH2:8][CH2:9][CH2:10][C:5]=2[S:4][N:3]=1.Cl.[NH+]1C=CC=CC=1.P(=O)(O)(O)O.P(Cl)(Cl)([Cl:25])=O>>[Cl:25][C:2]1[C:6]2[CH2:7][CH2:8][CH2:9][CH2:10][C:5]=2[S:4][N:3]=1A mixture of 3-hydroxy-4,5,6,7-tetrahydro-1,2-benzisothiazole 22a (4.74 g), pyridinium hydrochloride (12.7 g), phosphoric acid (2.1 g) and phosphorus oxychloride (25 mL) was stirred at 90 ° C. for 5 h. The reaction mixture was evaporated and ethyl acetate (130 mL) was added to the residue. A saturated solution of sodium hydrogencarbonate (130 mL) was added and after 10 min of stirring the phases were separated. The aqueous phase was extracted with ethyl acetate (2 x 150 mL) and the combined organic phases were dried and evaporated to give an oil. Column chromatography on silica gel (eluent: toluene-ethyl acetate 1:1) gave the title compound as a yellow oil (2.8 g).
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