Hydrochloric Acid → 6-tert-butoxycarbonyl-2-methoxy-7,8-dihydro-5H-1,6-naphthyridine-5-carboxylic acid

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Reaction Steps

2N Aqueous lithium hydroxide solution (61.8 mL, 123.61 mmol) was added to a solution of 5-ethyl 6-tert-butyl 2-methoxy-7,8-dihydro-1,6-naphthyridine-5,6(5H)-dicarboxylate (6.93 g, 20.60 mmol) in a mixed solvent of EtOH (30 mL) and THF (30 mL) at room temperature, and the mixture was stirred at room temperature for 1.5 hr. The reaction mixture was poured into ice-cooled water, and the pH of the mixture was adjusted to 4 with 6N hydrochloric acid. Then, the mixture was extracted with a mixed solvent of mixed ethyl acetate/THF (3:1) (×3). The organic layer was washed with water and brine, and dried over magnesium sulfate, and the solvent was evaporated under reduced pressure to give 6-(tert-butoxycarbonyl)-2-methoxy-5,6,7,8-tetrahydro-1,6-naphthyridine-5-carboxylic acid (6.37 g, 20.66 mmol, 100%) as a colorless amorphous solid.

Provenance & Evidence