N[C:2]1[CH:9]=[C:8]([CH3:10])[CH:7]=[CH:6][C:3]=1[C:4]#[N:5].N([O-])=O.[Na+].[S:15](=[O:18])(O)[O-:16].[Na+].O.[ClH:21]>S([O-])([O-])(=O)=O.[Cu+2]>[C:4]([C:3]1[CH:6]=[CH:7][C:8]([CH3:10])=[CH:9][C:2]=1[S:15]([Cl:21])(=[O:18])=[O:16])#[N:5]To a solution of 2-amino-4-methylbenzonitrile (2.65 g, 20 mmol), as prepared in the preceding step, in 30% aqueous HCl (7 mL) was added 40% aqueous sodium nitrite (6 mL) at 0°-5° C. After 15 minute, to the diazo solution were added 30% HCl (15 mL), copper sulfate (100 mg) and 40% aqueous sodium bisulfite (15 mL) at 5°-10° C. The mixture was stirred for 30 minute, then additional water (50 mL) was added. The mixture was extracted into dichloromethane (3×50 mL), and the dichloromethane solution was washed with brine (50 mL) and dried over Na2SO4. After removing the solvent in vacuo, the residue was purified by flash column chromatography (2:1 dichloromethane/hexane) to give the title compound as a white solid (2.1 g, 52%). 1H-NMR (300 MHz, CDCl3) δ 8.03 (s, 1H), 7.87 (d, J=7.8 Hz, 1H), 7.66 (d, J=7.8 Hz, 1H), 2.59 (s, 3H).
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