Methanethiosulfonic acid 2-carboxyethyl ester

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 3-bromopropionic acid 22 (571 mg, 3.73 mmol) and sodium methanethiosulfonate 21 (511 mg, 3.81 mmol) in DMF (5 mL) was stirred under argon at 70° C. After 2 h, t.1.c. (ethyl acetate:methanol, 4:1) indicated the formation of two products (Rf 0.3, 0.6) and the absence of any starting material (Rf 0.2). The reaction mixture was cooled to room temperature, water (10 mL) was added and the resulting mixture extracted with ether (3×20 mL). The organic extracts were combined, washed with brine (30 mL), dried (MgSO4), filtered and concentrated in vacuo. The residue was purified by flash column chromatography (DCM:ether, 3:1 (acetic acid, 0.6%)) to yield 2-carboxyethyl methanethiosulfonate 16 (438 mg, 64%) as a white crystalline solid; m.p. 44-46° C. (ethyl acetate/petrol) [Lit. 44-48° C. m.p., value obtained from Toronto Research Chemicals Inc. website (www.trc-canada.com), nmr spectra assigned using Chemical Concepts SpecInfo]; νmax (thin film) 1716 (st, C═O), 1312, 1130 (S—SO2)cm−1, δH (400 MHz, CDCl3) 2.94 (2H, t, J1,2 6.7Hz, 2 x H-2), 3.36 (3H, s, CH3), 3.38 (2H, t, 2 x H-1); δC (100.6 MHz, CDCl3) δ0.6 (t, C-1), 34.4 (t, C-2), 50.6 (q, CH3), 176.7 (s, C═O); m/z (ES−) 183 (M-H+, 100%). HRMS (ES−) Calcd. For C4H7O4S2 (M-H−) 182.9786. the resulting mixture extracted with ether (3×20 mL) washed with brine (30 mL) dried (MgSO4) filtered concentrated in vacuo The residue was purified by flash column chromatography (DCM:ether, 3:1 (acetic acid, 0.6%))