[N-:1]=[C:2]=[O:3].[F:4][C:5]1[C:6]([Si:14]([CH3:17])([CH3:16])[CH3:15])=[C:7]([CH:11]=[CH:12][CH:13]=1)C(O)=O.C(Cl)(=O)C(Cl)=O.[N-]=[N+]=[N-].[Na+]>C(Cl)Cl.O.CC(C)=O>[F:4][C:5]1[C:6]([Si:14]([CH3:17])([CH3:16])[CH3:15])=[C:7]([N:1]=[C:2]=[O:3])[CH:11]=[CH:12][CH:13]=1Preparation of the Intermediate Isocyanate was carried out via a Curtius rearrangement. See Capson, T. L. et al., Tetrahedron Lett., 25, 3515 (1984) and references herein. To a solution of the compound prepared in (2) (3.03 g, 14.3 mmol) in CH2Cl2 (20 mL) was added oxalylchloride (1.30 mL, 15.0 mmol) and the resulting mixture was stirred 3 h at room temperature. The residue obtained after evaporation of the solvent was diluted with THF (10 mL) and injected with vigorous stirring to a ice-cooled solution of NaN3 (3.70 g, 57 mmol) in H2O (20 mL) and acetone (50 mL). After 15 min at 0° C. and 1 min at room temperature, the solution was extracted with Et2O (4×50 mL) and dried (Na2SO4). The residue obtained after evaporation of solvents was refluxed in toluene for 1 h 30 to provide, upon solvent removal, 2.85 g (79%) of a slightly yellow oil: IR (neat, cm−1) 2269, 1598, 1433, 1252, 1228, 846, 788; 1H NMR (300 MHz, CDCl3) δ 0.38 (d, J=1.9 Hz, 9 H), 6.82 (br t, J=8.3 Hz, 1 H), 6.90 (br d, J=8.2 Hz, 1 H), 7.25 (ddd, J1=J2=8.1 Hz, J3=6.6 Hz, 1 H); 13C NMR (75 MHz, CDCl3) δ 0.4, 112.6 (d, JCF=26 Hz), 120.5, 122.5, 131.5, 139.2, 167.4 (d, JCF=241 Hz).
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