Lithium Hydroxide → 1-Hydroxyisoquinoline-6-carboxylic acid

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Reaction Steps

To a mixture of methyl 1-oxo-1,2-dihydroisoquinoline-6-carboxylate (25 g, 0.133 mol), tetrahydrofuran (200 mL) and water (200 mL) was added lithium hydroxide (16.8 g, 0.40 mol) at room temperature, and the mixture was stirred for four hours. Thin layer chromatography (petroleum ether/ethyl acetate=1:1) indicated the reaction was complete. The reaction mixture was extracted with ethyl acetate (100 mL×3) to remove impurities. The aqueous layer was acidified with 4 N aqueous HCl to pH 5 and filtered. The solid was dried in vacuum to give 1-oxo-1,2-dihydroisoquinoline-6-carboxylic acid (11.3 g, 48%) as a light yellow solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 11.48 (s, 1H), 8.24 (d, 2H), 7.93 (d, 1H), 7.22 (d, 1H), 6.68 (d, 1H).

Provenance & Evidence