2-Bromo-3-phenylpropanoic acid

p-Toluenesulfonic acid (PTSA or pTsOH)

Sodium bicarbonate (NaHCO₃)

Methanol

To a well-stirred mixture of 2-bromo-3-phenylpropanoic acid (10.0 g, 43.65 mmol) in methanol (100 mL) at about 0 ^oC was added p-Toluenesulfonic acid (1.5 g, 8.73 mmol) in portion wise manner. The mixture was then stirred at room temperature for 10-12 min. The reaction mixture was added about 20% sodium bicarbonate solution (50-60 mL). Excess methanol from reaction mixture was evaporated on rota evaporator and remaining reaction mass was extracted in ethyl acetate (100 mL × 2). The combined organic layer dried over sodium sulphate and concentrated under reduced pressure to obtain the product methyl 2-bromo-3-phenylpropanoate (10.2 g, 96 %). All examples gave NMR pure Products (95-98 %).

The reaction seems to be ideal for both large and small scale (10 g- 50mg). Another alcohol (Solvent) like ethanol also works well but taking more time to complete the reaction. 

¹H NMR (500 MHz, CDCl₃): δ = 3.30 (dd, J = 7.1, 14.1 Hz,  1H), 3.53 (dd, J = 8.5, 14.1 Hz, 1H), 3.76 (s, 3H), 4.46 (dd, J = 7.1, 8.5 Hz, 1H), 7.24–7.26  (m, 2H), 7.28–7.31 (m, 1H), 7.33–7.36 (m, 2H); ¹³C-NMR (125 MHz, CDCl₃): δ = 41.1 (CH₂), 45.1 (CH), 52.9 (CH₃), 127.3 (CH), 128.6 (2CH), 129.1 (2CH), 136.7 (C), 169.9 (C) ppm.

C. Vieville, Z. Mouloungui, A. Gaset Ind. Eng. Chem. Res. 1993, 32, 2065

DOI: 10.1021/ie00021a031

N. H. Isaiah, R. Subbarao, J. S. Aggarwal J. Chromatogr., 1969, 43, 519

DOI: 10.1016/S0021-9673(00)99240-9