N[C:2](=[CH:6][C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:3]([OH:5])=[O:4].[OH-].[Na+].N([O-])=O.[Na+].F[B-](F)(F)F.[H+].S(=O)(=O)(O)N>O.CC(C)=O.[CH-]1C=CC=C1.[CH-]1C=CC=C1.[Fe+2]>[CH:12]1[C:7]2[CH:6]=[C:2]([C:3]([OH:5])=[O:4])[C:12]3[C:7](=[CH:8][CH:9]=[CH:10][CH:11]=3)[C:8]=2[CH:9]=[CH:10][CH:11]=1
A solution composed of the aminocinnamic acid (3 mmol), NaOH (33 mmol) and NaNO2 in water (10 mL) was added dropwise over 30 min with stirring to 48% fluoroboric acid (43 mmol) at 0-5° C. The mixture was stirred for 1 h, after which sulfamic acid was added until the mixture tested negative to starch-iodide paper. The crude solid was collected by filtration, dissolved in anhydrous acetone (10 mL) and then added dropwise with stirring over a 15 min period to ferrocene (0.056 g, 0.3 mmol) in acetone at rt. After an additional 15 min of stirring, the green reaction mixture was added to water (100 mL). A light-yellow precipitate was collected and the trace amount of ferrocene was removed in vacuo to afford the phenanthrene-9-carboxylic acid.
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