Methanol → 4-Oxo-4,5-dihydrothieno[3,2-c]quinoline-7-carboxylic acid

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Reaction Steps

Methyl 4-oxo-4,5-dihydrothieno[3,2-c]quinoline-7-carboxylate (1.0 eq, 618 mg, 2.38 mmol) was suspended in 10 ml of a mixture of MeOH, THF, and water (1:1:1, v:v:v). LiOH (2.0 eq, 114 mg, 4.76 mmol) was added and the mixture was stirred at room temperature for 2 hours. An additional amount of LiOH (114 mg) was added and the mixture was stirred for an hour. LiOH (50 mg) was added and the mixture stirred for an additional 2 hours. Water was added and the solution filtered through a pad of celite. The pad of celite was thoroughly washed with aqueous 1 N NaOH. The solution was acidified with 6 N aqueous HCl to induce precipitation of the expected material. Filtration and drying afforded 4-oxo-4,5-dihydrothieno[3,2-c]quinoline-7-carboxylic acid as a yellow solid (562 mg, 96% yield). LCMS (ES): 95% pure, m/z 246 [M+1]+; 1H NMR (DMSO-d6, 400 MHz) δ 7.61 (d, J=5.2, 1H), 7.73 (dd, J=1.6, J=8.0, 1H), 7.88 (d, J=5.6, 1H), 7.92 (d, J=8.4, 1H), 8.02 (d, J=1.6, 1H), 11.92 (s, 1H), 13.21 (br. s, 1H) ppm.

Provenance & Evidence