Potassium Iodide → 3-(5-phenylthio-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyhydrocinnamic acid

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Reaction Steps

To a 1 liter, 4 necked, round-bottomed flask equipped with mechanical stirring and a nitrogen atmosphere is charged 100.0 g (0.258 mol) of methyl 3-(5-chloro-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyhydrocinnamate, 350 mL of N,N-dimethylformamide, and 61.9 g (0.773 mol) of 50% aqueous sodium hydroxide solution. The mixture is heated at 75°-80° C. for 3 hours at which point the ester hydrolysis is complete. A catalytic amount of potassium iodide (5.0 g) is added. Thiophenol (32.2 g, 0.258 mol) is then added over a 20 minute period while the temperature remains at 75°-80° C. An additional portion of N,N-dimethylformamide (200 mL) is added during the addition of thiophenol to facilitate stirring. A 25 mL fraction of water/methanol is removed and the solution is refluxed for 48 hours. The reaction mixture is cooled, then partitioned between 1.0 L of 1N hydrochloric acid and 1.0 L of ethyl acetate. The phases are separated and the organic phase is dried over anhydrous magnesium sulfate, and the solvent is then removed under reduced pressure until the total volume is 500 mL. To this is added 200 mL of heptane and the solution is allowed to sit overnight. The resultant crystals are collected by vacuum filtration, washed with 9:1 heptane:ethyl acetate, and dried to afford 83.5 g (72% yield) of the title compound; mp 154°-156° C.

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