Yield:34576-91-5 68.7%

Reaction Conditions:

Stage #1: methyl 3-chloro-6-nitrobenzo[b]thiophene-2-carboxylatewith sodium hydroxide;water in ethanol; for 49 h;Heating / reflux;
Stage #2: with hydrogenchloride

Steps:

b (b) 3-CHLORO-6-NITRO-1-BENZOLB] THIOPHENE-2-CARBOXYLIC ACID (V. I. B-026)

2N NaOH 0, N eo Ethanol OZN O C2Nx cl Xo Z 1 : 00 CI CRI Methyl 3-CHLORO-6-NITRO-1-BENZO [B] THIOPHENE-2-CARBOXYLATE (46.2 mg, 0.17 mmol) was dissolved in ethanol (2.0 mL) and aqueous 2N NAOH (0.5 mL) was added. The reaction mixture was heated to reflux for 1.0 hour and then allowed to cool to room temperature and stirred at room temperature for 48 hours. The solvent was evaporated under reduced pressure to afford a white residue which was taken up in water and acidified, then extracted with ethyl acetate, dried and evaporated under reduced pressure to afford a (30.0 mg, 68.7 %) of the desired 3-CHLORO-6-NITRO-1-BENZO [b] THIOPHENE-2-CARBOXYLIC acid as white powder. M. S. m/z 255.71 (M-1) +- 1H NMR (300.13, d6-DMSO) 8 8.14 (1H, m, ArH), 8.35 (1H, m, ArH), 9.20 (1H, m, ArH).

References:

WO2004/58747,2004,A1 Location in patent:Page 42