[CH3:1][S:2]([C:5]1[CH:6]=[C:7]([CH:9]=[CH:10][C:11]=1[O:12][C:13]([F:16])([F:15])[F:14])[NH2:8])(=[O:4])=[O:3].Cl.C1(C)C=CC=CC=1.Cl[C:26](OC(Cl)(Cl)Cl)=[O:27]>C(OCC)(=O)C>[CH3:1][S:2]([C:5]1[CH:6]=[C:7]([N:8]=[C:26]=[O:27])[CH:9]=[CH:10][C:11]=1[O:12][C:13]([F:14])([F:15])[F:16])(=[O:4])=[O:3]
To 3-methylsulfonyl-4-trifluoromethoxyaniline (2.0 mmol, 500 mg) dissolved in ethyl acetate (6 ml) was added 3N HCl in ethyl acetate (5 ml) followed by concentration in vacuo. The residue was treated with toluene (3×5 mL) and each time concentrated in vacuo. To the residue was added toluene (10 mL) and trichloromethyl chloroformate (6 mmol, 0.73 mL), and under a N2-atmosphere the suspension was gently refluxed for 2 hours at 120° C. Additional trichloromethyl chloroformate (6 mmol, 0.73 mL) was added and refluxing was continued overnight. The reaction mixture was concentrated in vacuo to afford 3-methylsulfonyl-4-trifluoromethoxyphenyl isocyanate.
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