In a 1 L round bottom flask equipped with a magnetic stirrer, addition funnel, powder addition funnel, and nitrogen inlet was added 4-allyl-2-((5-chloro-2-nitrophenyl)diazenyl)-6-methoxyphenol (27.9, 80.2 mmol) from Example 2 and 300 ml absolute ethanol. NaOH (19.3 g, 483 mmol) was dissolved in 140 ml deionized water and approximately one-fourth by volume was added dropwise to the reaction mixture. The reaction mixture was heated to 80° C. and formamidinesulfinic acid (Aldrich, 26.0 g, 241 mmol) was added slowly and concurrently with the remaining sodium hydroxide solution over 30 minutes. The reaction mixture was poured into 3 L deionized water and acidified to pH 4 with 1 N HCl. The yellow solid was dried for 20 hours at 42° C. and then purified by dissolving in hot toluene and then filtering out the dark impurities. The filtrate was concentrated down and purified via recrystallizions in ethanol and diethyl ether to give the pure product (5 g, 20%). 1H NMR (CDCl3) delta: 11.03 (s, 1H, phenol OH), 7.94 (s, 1H, Ar—H benzotriazole ring, 4-position), 7.89 (m, 1H, Ar—H benzotriazole ring, 7-position), 7.80 (s, 1H, Ar—H phenol, 5-position), 7.44 (m, 1H, Ar—H benzotriazole ring, 6-position), 6.81 (s, 1H, Ar—H phenol, 3-position), 6.00 (m, 1H, HC═CH2), 5.16 (m, 2H, HC═CH2), 3.97 (s, 3H, CH3O), 3.43 (d, 2H, Ar—CH2).
