N([O-])=O.[Na+].N[C:6]1[CH:7]=[CH:8][C:9]([Cl:15])=[C:10]([CH:14]=1)[C:11]([OH:13])=[O:12].Cl.[K].[C-:18]#[N:19].[K+]>O.[O-]S([O-])(=O)=O.[Cu+2]>[Cl:15][C:9]1[CH:8]=[CH:7][C:6]([C:18]#[N:19])=[CH:14][C:10]=1[C:11]([OH:13])=[O:12]
A solution of NaNO2 (2.21 g, 32 mmol) in water (10 mL) was added to a solution of 5-amino-2-chlorobenzoic acid (5.0 g, 29.14 mmol) in water (40 mL) at 0° C., followed addition of by conc. HCl (10 mL) at −5° C. The reaction mixture was stirred at −5° C. for an additional 1 h and then the diazonium solution was added dropwise into a solution of potassium cuprotetracyanide [prepared by dropwise addition of a solution of KCN (10 g, 15.38 mmol) in water (18 mL) to a solution of CuSO4 (7 g, 43.8 mmol) in water (12 mL) at 70° C.] at 50° C. for 1 h. The reaction mixture was acidified with 1.5 N HCl solution and the product was extracted with EtOAc. The combined extracts were washed with water and brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The crude product was purified by column chromatography (silica 60-120 mesh, eluant 1-2% MeOH in CHCl3) to get 2-chloro-5-cyanobenzoic acid (1.8 g, yield 34%). 1H NMR (400 MHz, DMSO-d6) δ 13.92 (br s, 1H), 8.24 (d, J=2.1 Hz, 1H), 8.02-7.99 (d, J=8.4 Hz, 2.1 Hz, 1H), 7.80-7.78 (d, J=8.2 Hz, 1H). MS (ESI) m/z: Calculated for C8H4ClNO2: 180.99. found: 179.6 (M−H)−.
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