[I:1][C:2]1[CH:7]=C(N)C=[CH:4][C:3]=1[C:9]1[CH:15]=[CH:14][C:12](N)=[CH:11][C:10]=1[I:16].F[B-](F)(F)F.[H+].N([O-])=[O:24].[Na+].[C:27]([OH:30])(=O)[CH3:28]>>[OH:24][C:12]1[CH:14]=[CH:15][C:9]([C:3]2[CH:4]=[CH:28][C:27]([OH:30])=[CH:7][C:2]=2[I:1])=[C:10]([I:16])[CH:11]=1Glacial acetic acid (200 ml) and 2,2'-diiodobenzidine (20.0 g, 49 mmol) were stirred at room temperature for 20 minutes, and then 100 ml 48% tetrafluoroboric acid was added to the solution. After 30 minutes, the acidic solution was cooled to -5° C., and a sodium nitrite solution (7.2 g NaNO2 in 80 ml water) was slowly added to maintain the temperature below 0° C. The reaction was stirred for 1 hour at 0° C., and the precipitate which formed was filtered and dried for 18 hours under vacuum. The dried product was added over a period of 1 hour to a solution of 2 L water containing 30 ml 85% phosphoric acid at 75° C. Nitrogen was evolved, and heating continued until the evolution of gas was complete (approx. 30 min.). The reaction was cooled to room temperature, the orange product filtered, and recrystallized from 3:1 water:ethanol. A white crystalline product, II, mp 171°-172° C., was collected in 25% yield.
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