To a stirred solution of 3-phenyl-1H-indole-2-carboxylic acid ethyl ester (3.99 g, 15.0 mmol) in DMF (25 mL) cooled to 0° C. and under a nitrogen atmosphere was added NaH (60% in mineral oil, 720 mg, 18.0 mmol). After stirring for 10 min at RT, the reaction mixture was cooled to 0° C. and 4-methylbenzenesulfonyl chloride (3.44 g, 18.0 mmol) in DMF (15 mL) was added. Stirring was continued for 16 h at RT then the mixture was poured into 1.0M HCl and extracted with EtOAc (×2). The combined organic layers were washed with water, then dried (Na2SO4) and concentrated in vacuo. The resulting residue was purified by column chromatography (Si—PCC, gradient 30-100% DCM in pentane) affording 3-Phenyl-1-(toluene-4-sulfonyl)-1H-indole-2-carboxylic acid ethyl ester as a colourless oil (3.25 g, 52%). 1H NMR (CDCl3, 400 MHz): δ 8.08 (1H, d, J=8.43 Hz), 7.92 (2H, d, J=8.37 Hz), 7.53-7.36 (7H, m), 7.28-7.21 (3H, m), 4.35 (2H, q, J=7.15 Hz), 2.36 (3H, s), 1.25 (3H, t, J=7.14 Hz).
