Br[C:2]1[C:11]2[C:6](=[CH:7][C:8]([S:13]([OH:16])(=[O:15])=[O:14])=[CH:9][C:10]=2[OH:12])[CH:5]=[C:4]([S:17]([OH:20])(=[O:19])=[O:18])[CH:3]=1.[CH3:21][N:22](C)C=O>O.[Cu+].[Cu]>[C:21]([C:2]1[C:11]2[C:6](=[CH:7][C:8]([S:13]([OH:16])(=[O:15])=[O:14])=[CH:9][C:10]=2[OH:12])[CH:5]=[C:4]([S:17]([OH:20])(=[O:19])=[O:18])[CH:3]=1)#[N:22]
1-Bromo-8-hydroxynaphthalene-3,6-disulfonic acid (51% strength, 15.0 g, 0.02 mol, prepared as in Example 31, stage 1) was stirred in N,N-dimethylformamide (100 mls). Copper (I) cyamide (2.0 g, 0.022 mol) was added and the mixture boiled under reflux until HPLC analysis indicated complete reaction. In this example 5 hours was required. If necessary further copper cyamide could be added during the reaction. The reaction mixture was cooled down and a small amount of insoluble material removed by filtration. The solvent was removed from the filtrate under vacuum to leave a brown tar. This was slurried in water and a small amount of solid removed by filtration. The filtrate was concentrated to 100 mls and the product precipitated by the addition of solid sodium chloride. The product was recovered by filtration, washed with brine and dried. The dried product (8.9 g) contained 50% sodium chloride. Yield 67%.
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