[F:1][C:2]1[CH:7]=[CH:6][C:5]([S:8]([NH:11][C:12]2[S:16][C:15]3[CH2:17][CH2:18][CH2:19][CH2:20][C:14]=3[C:13]=2[C:21]([O:23]CC)=[O:22])(=[O:10])=[O:9])=[CH:4][CH:3]=1.O.[OH-].[Li+]>O1CCOCC1.O>[F:1][C:2]1[CH:3]=[CH:4][C:5]([S:8]([NH:11][C:12]2[S:16][C:15]3[CH2:17][CH2:18][CH2:19][CH2:20][C:14]=3[C:13]=2[C:21]([OH:23])=[O:22])(=[O:9])=[O:10])=[CH:6][CH:7]=1A solution of ethyl 2-(4-fluorobenzenesulphonylamino)-4,5,6,7-tetrahydro-benzo[b]thiophene-3-carboxylate (Intermediate 2, 0.12 g) and lithium hydroxide monohydrate (0.036 g) in a mixture of dioxane and water (2:1, 6 ml) was divided between two 2-5 ml microwave vials and the contents of each vial were stirred and heated in the microwave at 120° C. for 30 minutes. The two batches were combined, diluted with water and extracted with ethyl acetate. The aqueous phase was acidified to pH1 by addition of hydrochloric acid (1M) and the resultant suspension was extracted with ethyl acetate, washed with water, dried (MgSO4) and filtered. The filtrate was evaporated to dryness and the residue was purified by chromatography on silica eluting with a mixture of methanol and DCM (2.5%) to give a solid which was triturated with DCM. The resultant solid was collected by filtration to give 2-(4-fluorobenzenesulphonylamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid (0.024 g) as a light orange solid.
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