C1N2CN3[CH2:10][N:4](C2)CN1C3.[F:11][C:12]1[CH:21]=[CH:20][C:15]([C:16](=[O:19])CBr)=[CH:14][C:13]=1[C:22]([F:25])([F:24])[F:23].C(OCC)(=O)C.C(O)C.[ClH:35]>>[ClH:35].[NH2:4][CH2:10][C:16]([C:15]1[CH:20]=[CH:21][C:12]([F:11])=[C:13]([C:22]([F:25])([F:23])[F:24])[CH:14]=1)=[O:19]Add methenamine (1.10 equiv; 231.55 mmoles; 32.46 g) to a solution of 4-fluoro-3-(trifluoromethyl)phenacyl bromide (60.00 g; 1.00 equiv; 210.50 mmoles) in ethyl acetate (450 mL; 4.60 moles). Stir the mixture at RT overnight. Remove the solvent in vacuo and triturate the solid in methyl tert-butyl ether (MTBE). Filter and dry under reduced pressure. Add ethanol (450 mL; 7.73 moles), followed by hydrogen chloride (150 mL; 8.30 equiv; 1.75 moles) and stir the mixture at RT overnight. Remove the solvent in vacuo and dry the solid in vacuo at 50° C. for a week to obtain 2-Amino-1-(4-fluoro-3-trifluoromethyl-phenyl)-ethanone hydrochloride (54.23 g; 100% yield) as a white solid.
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