[F:1][C:2]([F:15])([F:14])[S:3]([O:6]S(C(F)(F)F)(=O)=O)(=[O:5])=[O:4].[CH:16]([C:18]1[CH:25]=[CH:24][C:21]([C:22]#[N:23])=[CH:20][C:19]=1O)=[O:17].C(N(CC)C(C)C)(C)C>ClCCl>[F:1][C:2]([F:15])([F:14])[S:3]([O:6][C:25]1[CH:24]=[C:21]([C:22]#[N:23])[CH:20]=[CH:19][C:18]=1[CH:16]=[O:17])(=[O:5])=[O:4]2.4 ml (14.27 mmol) of trifluoromethanesulfonic anhydride are added dropwise to a solution of 2 g (13.59 mmol) of 4-formyl-3-hydroxybenzonitrile and 2.5 ml (14.27 mmol) of N,N-diisopropylethylamine in 37 ml of anhydrous dichloromethane at 0° C. under an argon atmosphere. The reaction mixture is stirred at RT for 1 h, then diluted with 70 ml of dichloromethane and washed successively with 1 M hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution. The organic solution is dried over magnesium sulfate and concentrated. The residue is purified by column chromatography on silica gel (mobile phase: cyclohexane/ethyl acetate 7:1). 2.36 g (62% of theory) of the title compound are obtained as a white solid.
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