2-Methyl-2-butene → 6-Chloro-5-[4-(hydroxymethyl)phenyl]-1H-indole-3-carboxylic acid

Participants

Reaction Steps

To a solution of 6-chloro-5-(4-hydroxymethyl-phenyl)-1H-indole-3-carbaldehyde (422 mg, 1.48 mmol) in MeCN (18 mL), tert-butanol (18 mL) and 2-methyl-2-butene (12 mL, 110 mmol) at 0° C. was added a solution of sodium chlorite (1.25 g, 14.8 mmol) and sodium phosphate monobasic hydrate (2.04 g, 14.8 mmol) in water (9 mL) dropwise. The ice bath was removed and the solution was stirred at room temperature. After 5 hours, additional 2-methyl-2-butene (3 mL, 27.5 mmol) was added, followed by sodium chlorite (1.25 g, 14.8 mmol) and sodium phosphate monobasic hydrate (2.04 g, 14.8 mmol) in water (9 mL) dropwise. The resulting solution was stirred at room temperature. After 27 hours total reaction time, the solution was concentrated in vacuo to afford a pale yellow solid. Water (5 mL) was added to the solid and the mixture was extracted with EtOAc (2×50 mL). The combined organic layers were concentrated in vacuo and purified by flash chromatography (35-90% EtOAc/heptane, with 0.2% formic acid modifier) to afford a pale yellow solid. The solid was stirred in EtOAc (5 mL) at 55° C. for 6 hours, and the resulting slurry was cooled to room temperature. The precipitate was filtered and washed with EtOAc (1 mL) to afford the title compound (182 mg, 41% yield) as a cream-colored crystalline solid. MS (ES+) 300.0 (M−H)+. 1H NMR (400 MHz, CD3OD) δ 8.00 (s, 1 H) 7.98 (s, 1 H) 7.56 (s, 1 H) 7.40 (m, 4 H) 4.65 (s, 2 H).

Provenance & Evidence