Potassium Hydroxide → 3-(5-chloro-1H-indol-1-yl)propanoic acid

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Reaction Steps

Under an N2 atmosphere, crushed KOH was added to a solution of 5-chloro-1H-indole (2.0 g, 13.2 mmol) in DMSO (19 mL, 0.7 M), and the mixture was stirred for 2 h at RT. Methyl 3-bromopropanoate (1.9 mL, 17.2 mmol) was added dropwise, and the reaction was continued to stir at RT overnight. After diluting with H2O, the reaction was cleared with a 4.5 N aqueous KOH solution and washed 3 times with CH2Cl2. The aqueous layer was acidified with a 2N HCl solution to pH 3 and extracted 3 times with CH2Cl2. The organic fractions were combined, dried over MgSO4, filtered, and concentrated. Purification via silica gel chromatography using 0-8% MeOH in CH2Cl2 gave 3-(5-chloro-1H-indol-1-yl)propanoic acid (2 g, 68%). 1H NMR (400 MHz, DMSO-d6) δ 7.58 (d, J=2.0 Hz, 1H), 7.54 (d, J=8.7 Hz, 1H), 7.44 (d, J=3.1 Hz, 1H), 7.13 (dd, J=8.7, 2.1 Hz, 1H), 6.42 (dd, J=3.2, 0.7 Hz, 1H), 4.40 (t, J=6.8 Hz, 2H), 2.75 (t, J=6.8 Hz, 2H). LC/MS (10%-99% CH3CN (0.035% TFA)/H2O (0.05% TFA)), m/z: M+1 obs=224.5; tR=2.74 min.

Provenance & Evidence