A solution of azidotrimethylsilane (0.93 mL; 7.1 mmol) and methyl 4-[(trimethylsiloxy)methyl]benzoate (1.35 g; 5.7 mmol) in anhydrous MeCN (3 mL) was added dropwise to a solution of N-(3-oxopropyl)trifluoroacetamide (0.8 g; 4.7 mmol) containing a catalytic amount of anhydrous ferric chloride (38 mg; 0.2 mmol) in anhydrous MeCN (10 mL) cooled to −40° C. The mixture was stirred at −40° C. for 90 min and the reaction quenched with phosphate buffered saline (pH 7.4). The aqueous phase was extracted with DCM. The combined organic layers were washed with brine, dried (MgSO4), filtrated and evaporated. The residue was purified by silica column chromatography (DCM:Hex:EtOAc, 6:3:1) and the methyl 4-[(3-amino-1-azidopropoxy)methyl]benzoate was obtained as a clear viscous liquid, which solidified upon prolonged standing in a yield of 0.95 g (56%). 1H-NMR (500 MHz, CDCl3): δ=2.04-2.14 ppm (m, 2H), 3.40-3.47 ppm (m, 1H), 3.56-3.64 ppm (m, 1H), 3.92 ppm (s, 3H), 4.63 ppm (d, J=12.0 Hz, 1H), 4.66 ppm (dd, J=6.0, 4.5 Hz, 1H), 4.90 ppm (d, J=12.0 Hz, 1H), 6.89 ppm (bs, 1H, NH), 7.41 ppm (d, J=8.5 Hz, 2H), 8.04 ppm (d, J=8.5 Hz, 2H); 13C-NMR (500 MHz, CDCl3): δ=33.94, 35.83, 52.29, 70.66, 90.46, 115.76 ppm (q, J=1146.5 Hz), 127.76, 130.02, 130.14, 141.30, 157.23 (q, J=148.0 Hz), 166.79 ppm. HRMS [+Scan]; calculated m/z for C12H19O3Si 239.1098; observed mass: 239.1095.
