Boron tribromide → 2-(4-chlorophenyl)-6-hydroxy-4-methyl-2H-1,2,4-benzothiadiazine-3(4H)-one 1,1-dioxide

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Reaction Steps

To a solution of 2-(4-chlorophenyl)-6-methoxy-4-methyl-2H-1,2,4-benzothiadiazine-3(4H)-one 1,1-dioxide (21.0 g) in methylene chloride (200 ml) was added boron tribromide (1N solution in methylene chloride, 89.2 ml) at ambient temperature. The mixture was stirred for 8 hours at the same temperature and then poured into ice water. The separated solid was collected by filtration, dried, and recrystallized from ethanol to yield 2-(4-chlorophenyl)-6-hydroxy-4-methyl-2H-1,2,4-benzothiadiazine-3(4H)-one 1,1-dioxide (18.86 g).

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