A solution of 6-[(2-chloro-α,α,α,6-tetrafluoro-p-tolyl) oxy]-α-methyl-1H-benzotriazole-1-acetaldehyde dimethyl acetal (23.0 g, 0.053 mole) in acetic acid is treated with 54 ml of 2.5N H2 SO4 and stirred at 70° C. for 12 hours. A 15 ml portion of the reaction solution is diluted to a total volume of 100 ml with water, the resulting precipitate is separated, washed with water, treated with a solution of hydroxylamine hydrochloride (1.0 g, 0.014 mole) in pyridine and ethanol, heated at 85° C. for several hours, cooled and concentrated in vacuo to give a solid residue. Recrystallization from aqueous ethanol, ethanol and toluene gives the title compound mp 148°-151° C., identified by elemental and NMR analyses.
