To a suspension of sodium hydride (97%, 0.024 g, 1.0 mmol) in 1-methyl-2-pyrrolidinone (2 mL) was added 2-oxoindoline-6-carbonitrile (0.119 g, 0.75 mmol). The formed mixture was stirred for 5 min at room temperature and tert-butyl 4-[(6-chloropyridin-3-yl)sulfonyl]piperazine-1-carboxylate (0.181 g, 0.5 mmol) was added. The resulting reaction mixture was set under an N2 atmosphere and stirred for 1 h at 90° C. Methanol (0.5 mL) was added to the mixture and the solvents were removed in vacuo. The crude product was dissolved in methanol (5 mL) and HCl in diethyl ether (4 M, 2.5 mL, 10 mmol) was added followed by reflux for 3 h. From the cooled solution the formed yellow precipitate was collected by filtration and dried to give 0.209 g (92% yield) of the title compound: 1H NMR (DMSO-d6, 400 MHz) δ 11.08 (s, 1H), 9.10 (br s, 2H), 8.67 (s, 1H), 7.89 (s, 2H), 7.78 (d, J=8.0 Hz, 1H), 7.44 (dd, J=8.0, 1.2 Hz, 1H), 7.28 (d, J=1.2 Hz, 1H) 3.31 (br s, 4H), 3.25 (br s, 4H); MS (EI) m/z 384 (M++1).
