C[O:2][C:3](=[O:12])[C:4]1[CH:9]=[CH:8][C:7](N)=[CH:6][C:5]=1[Cl:11].S(=O)(=O)(O)[OH:14].N([O-])=O.[Na+].NC(N)=O>O.[N+]([O-])([O-])=O.[Cu+2].[N+]([O-])([O-])=O>[Cl:11][C:5]1[CH:6]=[C:7]([OH:14])[CH:8]=[CH:9][C:4]=1[C:3]([OH:2])=[O:12]4-Amino-2-chloro-benzoic acid methyl ester from Example E41b.1 (5.45 g, 29.4 mmol) was treated with a 35% solution of sulphuric acid (120 ml) and the mixture was stirred and heated until dissolution then cooled to 0° C. Sodium nitrite (4.30 g, 62.5 mmol) in water (25 ml) was added dropwise and the mixture was stirred for 15 min at 0° C. Urea was added to destroy the excess nitrite. Cop-per nitrate (200 mg, 0.83 mmol) was added and heated to 90° C. The reaction mixture was cooled to room temperature, extracted into ethyl acetate×3, dried and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (eluant; 30% EtOAc:70% hexane to 50% EtOAc:49% hexane:1% AcOH) to yield the title compound (3.7 g, 73%).
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