3-Amino-benzo[b]thiophene-2-carboxylic acid ethyl ester

Synthesis

The general procedure for the synthesis of ethyl 3-aminobenzo[B]thiophene-2-acetate from 2-fluorobenzonitrile and ethyl mercaptoacetate is as follows: Method 1: Synthesis of 4-aminobenzothiophene from 3,4-dipyrimidine 1A. Ethyl 3-amino-carboxylate 2-fluorobenzonitrile (8.25 mmol), diisopropylethylamine (8.25 mmol), and ethyl 2-mercaptoacetate (8.25 mmol) were dissolved in anhydrous N,N-dimethylformamide (5 mL) and stirred for 30 min at room temperature. Potassium carbonate (8.25 mmol) was then added and the reaction mixture was heated to 80 °C and maintained for 20 hours. Upon completion of the reaction, the reaction was quenched by the addition of ice water, the precipitate was collected by filtration and washed with water to afford the target product carboxylate as a white solid in 92% yield. LCMS retention time 7.43 min, [M + H]+ 222; 1H-NMR (CDCl3) δ 7.43 (1H, d, J = 8.1 Hz), 7.65 (1H, d, J = 8.1 Hz), 7.49-7.44 (1H, m), 7.39-7.34 (1H, m), 4.36 (2H, q, J = 7.1 Hz), 1.40 (3H, t, J = 7.1 Hz).

References

[1] Patent: WO2012/131297, 2012, A1. Location in patent: Page/Page column 85
[2] Bioorganic and Medicinal Chemistry Letters, 2014, vol. 24, # 15, p. 3291 - 3297
[3] Journal of Heterocyclic Chemistry, 1997, vol. 34, # 4, p. 1163 - 1172