Hydrogen Peroxide → 4-[4-(4-Chlorophenylamino)phthalazin-1-yloxymethyl]pyridin-2-yl carboxylic acid methylamide

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Caution—this reaction is potentially explosive and latent violent exotherms have been noted, especially if the reaction is heated and unreacted hydrogen peroxide is present. The product of step 1 above (0.600 g, 1.65 mmol) was dissolved in 16.5 ml of N-methyl-formamide. The reaction was charged with concentrated sulfuric acid (0.264 ml, 4.96 mmol) followed by FeSO4-7H2O (0.115 g, 0.413 mmol). The solution was stirred at ambient temperature for 15 min then 30% wt. hydrogen peroxide/water (0.338 ml, 3.31 mmol) was added (exotherm noted). TLC analysis after 1 h indicates the reaction is 50% done. The reaction was again charged with concentrated sulfuric acid (0.264 ml, 4.96 mmol) followed by FeSO4-7H2O (0.115 g, 0.413 mmol). To the reaction is added 6 aliquots of 30% wt. hydrogen peroxide/water (each aliquot is 0.338 ml, 3.31 mmol) over 3 h. The opaque brown reaction was stirred for 24 h at 30 C. TLC analysis now indicates no starting material is present. The reaction was quenched with saturated potassium carbonate (100 ml) and the solids filtered off washing with water. The aqueous layer was extracted with diethyl ether (3×175 ml), and the combined organics dried (MgSO4) and concentrated to give an orange solid. The crude product was purified by silica gel chromatography (100% dichloromethane→10% acetone/dichloromethane) to give the clean desired compound as a tan solid (64 mg, 0.152 mmol; 9% yield). TLC (10% acetone/dichloromethane): Rf=0.38.

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