Reaction Steps
To a stirred solution of 1.01 g (5.0 mmol) of 1-chloro-2,6-dinitrobenzene and 0.93 g (5.0 mmol) of 1-tert-butyloxycarbonylpiperazine in acetonitrile (5 mL) was added 1.38 g (10 mmol) of K2CO3. The mixture was heated to reflux for 48 h. The solvent was removed under reduced pressure. The crude product was partitioned between EtOAc (100 mL) and 20 mL of H2O. The organic layer was washed with H2O (2×20 mL), dried over Na2SO4 and concentrated. Column chromatography (silica, 10-20% EtOAc/hexanes) provided 1.31 g (85%) of 4-(2,6-dinitro-phenyl)-piperazine-1-carboxylic acid tert-butyl ester TLC (silica, 20% EtOAc/hexanes): Rf=0.35. 1H NMR (400 MHz, CDCl3): 7.75 (d, J=8.2 Hz, 2H), 7.25 (t, J=8.2 Hz, 1H), 3.30 (m, 4H), 2.95 (m, 2H), 1.44 (s, 9H). B. 1-[4-(2,6-Dinitro-phenyl)-piperazin-1-yl]-3-[5-methanesulfonyl-3-(4-trifluoromethyl-phenyl)-4,5,6,7-tetrahydro-pyrazolo[4,3-c]pyridin-1-yl]-propan-2-ol. 4-(2,6-Dinitro-phenyl)-piperazine-1-carboxylic acid tert-butyl ester (220 mg, 0.63 mmol) was dissolved in 5.0 mL of CH2Cl2 and treated with 3.0 mL of trifluoroacetic acid. The reaction mixture was stirred at 25° C. for 1 h before all volatiles were removed. The solid was treated with CH2Cl2 (20 mL) and aqueous KOH (4 N, 10 mL). The organic layer was separated, dried over Na2SO4, and concentrated. The crude oil (67 mg) was dissolved in absolute EtOH (1.2 mL) and treated with 141 mg (0.35 mmol, 1.3 eq) of 5-methanesulfonyl-1-oxiranylmethyl-3-(4-trifluoromethyl-phenyl)-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine. The reaction mixture was refluxed at 85° C. for 3 h and then the solvent was removed. Column chromatography purification (silica, 10-20% acetone/CH2Cl2) provided 150 mg (85%) of 1-[4-(2,6-dinitro-phenyl)-piperazin-1-yl]-3-[5-methanesulfonyl-3-(4-trifluoromethyl-phenyl)-4,5,6,7-tetrahydro-pyrazolo[4,3-c]pyridin-1-yl]-propan-2-ol. TLC (silica, 10% acetone/CH2Cl2): Rf=0.3. MS (electrospray): exact mass calculated for C27H30F3N7O7S, 653.19; m/z found, 654.2 [M+H]+. 1H NMR (400 MHz, CDCl3): 7.71 (d, J=8.2 Hz, 2H), 7.64 and 7.58 (AB pattern, J=8.4 Hz, 4H), 7.20 (t, J=8.2 Hz, 1H), 4.54 (s, 2H), 4.29-4.12 (m, 2H), 3.66 (t, J=5.3 Hz, 2H), 3.70-2.95 (m, 9H), 2.91 (s, 3H), 2.67-2.32 (m, 4H).
