To a solution of 2-(methylthio)propanoic acid (0.36 g, 3.00 mmol) in DCM (3 mL) was added oxalyl dichloride (0.29 ml, 3.31 mmol) followed by one drop of DMF. The reaction mixture was stirred for 30 min before all of the solvent was evaporated. The resulting residue was dissolved in DCM (2 mL) and the solution was added to a pre-stirred solution of 3-chloro-N-(prop-2-yn-1-yl)-1-(pyridin-3-yl)-1H-pyrazol-4-amine (0.35 g, 1.50 mmol) and N-ethyl-N-isopropylpropan-2-amine (0.57 ml, 3.31 mmol) in DCM (5.5 mL). The reaction mixture was stirred at ambient temperature for 16 h. The reaction mixture was concentrated and the residue was purified using silica gel chromatography (0-100% EtOAc/hexanes) to afford the title compound as a yellow oil (432 mg, 1.23 mmol, 85%): 1H NMR (400 MHz, CDCl3) δ 8.97 (d, J=2.5 Hz, 1H), 8.66-8.60 (m, 1H), 8.25 (s, 1H), 8.08-8.01 (m, 1H), 7.49-7.42 (m, 1H), 4.86 (s, 1H), 4.29-3.97 (m, 1H), 3.31 (d, J=6.5 Hz, 1H), 2.30-2.24 (m, 1H), 2.09 (s, 3H), 1.46 (d, J=6.9 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 171.30, 148.66, 140.71, 140.18, 135.71, 127.87, 126.35, 124.11, 122.12, 78.53, 72.92, 53.39, 37.97, 16.42, 11.07; ESIMS m/z 335 ([M+H]+).
