Cl[C:2]1[C:3]([N+:19]([O-:21])=[O:20])=[CH:4][C:5]([CH3:18])=[C:6]([C:8]2[CH:13]=[CH:12][C:11]([C:14]([NH:16][CH3:17])=[O:15])=[CH:10][CH:9]=2)[CH:7]=1.[CH2:22](OB(C=C)OCCCC)[CH2:23]CC.C(=O)([O-])[O-].[Na+].[Na+]>C1COCC1.O>[CH3:17][NH:16][C:14]([C:11]1[CH:12]=[CH:13][C:8]([C:6]2[CH:7]=[C:2]([CH:22]=[CH2:23])[C:3]([N+:19]([O-:21])=[O:20])=[CH:4][C:5]=2[CH3:18])=[CH:9][CH:10]=1)=[O:15]To a mixture of 5′-chloro-N,2′-dimethyl-4′-nitrobiphenyl-4-carboxamide (Step 2, 100 mg, 0.33 mmol), vinylboronic acid dibutyl ester (90 mg, 0.5 mmol) and sodium carbonate (245 mg, 2.31 mmol) in THF/H2O (8/2 mL) is added dichlorobis(triphenylphospine) palladium (II) (12 mg, 5% mmol). The reaction tube is sealed, the mixture is purged with N2 for 3 min and then heated at 90° C. under N2 for overnight. The reaction is cooled to room temperature and poured into saturated aqueous ammonia chloride solution. The crude reaction mixture is extracted with ethyl acetate (3×15 mL). The organic extracts are combined, washed with brine and concentrated. The crude product is purified with silica gel column chromatography (30% ethyl acetate in DCM) to afford N,2′-dimethyl-4′-nitro-5′-vinylbiphenyl-4-carboxamide as a yellow solid. The obtained solid is dissolved in methanol (20 mL). To this solution is added Pd/C (10%). The reaction mixture is degassed and purged with H2 for several times and stirred under atmospheric hydrogen overnight. The mixture is filtered and concentrated to afford 4′-amino-5′-ethyl-N,2′-dimethylbiphenyl-4-carboxamide as a yellow solid. ESMS m/z 269.2 (M+H+).
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