[CH2:1]([O:8][CH2:9][C:10]([F:25])([F:24])[CH2:11][CH2:12]N1C(=O)C2=CC=CC=C2C1=O)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.O.NN.Cl.C(NN)(=O)C1C(=CC=CC=1)C([NH:35]N)=O>C(O)C>[CH2:1]([O:8][CH:9]([NH2:35])[C:10]([F:25])([F:24])[CH2:11][CH3:12])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1The compound N-(4-benzyloxy-3,3-difluorobutyl)-phthalimide (68.5 g, 198.6 mmoles) and hydrazine hydrate (10 g, 200 mmoles) are stirred and heated overnight in ethanol (200 mL) at 90°-100° C. A mixture of concentrated HCl (94 mL) and ethanol (1130 mL) is added, and heating (90°-100° C.) is continued for 1.5 hours. After cooling (ice bath), phthalhydrazide is removed by filtration, and the filtrate is evaporated. The residue is taken up in water and extracted with ether (2×500 mL). After filtration through a membrane filter (Millipore), evaporation of the filtrate yields white crystals. These are dissolved in ethanol, the solution is filtered (Millipore organic) and the filtrate is evaporated to yield a residue which crystallizes on addition of ether: 34 g (68%). Evaporation of the ether extracts yields a partially crystalline material (20 g) consisting of starting material. Repetition of the hydrazine cleavage upon this mixture yields a second crop of 4-benzyloxy-3,3-difluorobutylamine (9.1 g). Total: 43.2 g (86.5%).
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