Methyl 6-chlorobenzo[b]thiophene-2-carboxylate

Synthesis

5551-11-1

2365-48-2

104795-85-9

1. To a 7 mL solution of DMF containing 600 mg (3.23 mmol) of 4-chloro-2-nitrobenzaldehyde was added 559 mg (4.04 mmol) of potassium carbonate and 294 μL (3.23 mmol) of methyl mercaptoacetate sequentially at 0°C. The reaction mixture was stirred for 30 minutes at 0°C, then warmed to room temperature and stirred for 24 hours. The reaction mixture was stirred at 0°C for 30 minutes, then warmed to room temperature and continued stirring for 24 hours. 2. The reaction mixture was slowly poured into ice water, the precipitate was collected by filtration and dissolved in ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give 630 mg (86% yield) of methyl 6-chlorobenzo[b]thiophene-2-carboxylate as a white solid.1H NMR (CDCl3, 300 MHz): δ 3.95 (s, 3H), 7.88 (dd, J = 8.6, 1.9 Hz, 1H), 7.79 (d, J = 8.6 Hz, 1H), 7.85 (d, J = 8.6 Hz, 1H), 7.79 (d, J = 8.6 Hz, 1H). 7.85 (d, J = 1.9 Hz, 1H), 8.02 (s, 1H). 3. To a 5 mL THF solution of 630 mg (2.78 mmol) methyl 6-chlorobenzo[b]thiophene-2-carboxylate was added 6.95 mL of 1N LiOH solution and stirred for 4 hours at room temperature. Upon completion of the reaction, the pH was adjusted to 2-3 with 1N HCl and subsequently extracted with ethyl acetate. The organic phases were combined, washed with brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give 579 mg (98% yield) of 6-chlorobenzo[b]thiophene-2-carboxylic acid as a white solid.MS (ISP): 211.0 (M-H)-. 4. 139 mg (0.65 mmol) of 6-chlorobenzo[b]thiophene-2-carboxylic acid was converted to 52 mg (0.14 mmol) of (6-chlorobenzo[b]thiophen-2-ylmethyl)-[2-(3,4-dichlorophenyl)ethyl]amine by reference to the method of Example S3 (Steps a to b), the product was a colorless liquid.MS (ISP): 370.0 (M+H )+.

References