Sodium Hydroxide → 6-fluoro-3,4-dihydro-4-(hydroxymethyl)-2H-benzopyran-4-carboxylic acid

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Reaction Steps

To a solution of 7 g (0.029 mole) Methyl 6-fluoro-3,4-dihydro-4-(hydroxymethyl)-2H-benzopyran-4-carboxylate in 200 mL of McOH was added 7.2 mL of 5N NaOH. The reaction was heated on a steam bath overnight then cooled to room temperature. The MeOH was evaporated and the residue dissolved in water then acidified to pH 4.0 with concentrated HCl. The aqueous was extracted with EtOAc and the EtOAc layer was dried over Na2SO4, filtered and evaporated to give 6 g of crude product. Chromatography on 160 g of silica gel eluting with CH2Cl2 /ether gave 2.7 g of product, m.p. 134°-135° C.

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