Reaction Steps
To a solution of 34 (1.68 g, 5.16 mmol) in CH2Cl2 (100 mL) and Et3N (3.6 mL) at 0° C. was added dropwise over 5 min methanesulfonyl chloride (2.96 g, 25.8 mmol), and the solution was allowed to warm to rt over 1 h. After stirring overnight under argon, the mixture was cooled to 0° C. and quenched with water (50 mL). The organic layer was isolated and the aqueous layer extracted twice with 20-mL portions of CH2Cl2. The combined organic extracts were concentrated in vacuo at rt. The crude mesylate was dissolved in DMF (100 mL), and to this solution was added sodium azide (1.68 g, 25.8 mmol). After stirring for 8 h at rt, the mixture was partitioned between water (200 mL) and EtOAc (200 mL). The organic layer was isolated and aqueous layer extracted twice with 50-mL portions of EtOAc. The combined organic extacts were washed with saturated aqueous NaCl, dried over Na2SO4, and concentrated. Flash chromatography over silica gel (1/9 EtOAc:hexane) gave pure 35 as a colorless oil (1.57 g, 87%): Rf=0.90 (1/9 EtOAc:hexane); 1H NMR (300 MHz, CDCl3) δ 7.57 (d, J=6.7 Hz, 4H), 7.41 (m, 6H), 5.88 (m, 1H), 5.00 (dd, J=17.0, 1.5 Hz, 1H), 4.92 (dd, J=10.2, 1.5 Hz, 1H), 3.44 (d, J=12.4 Hz, IH), 2.12 (m, 2H), 1.84 (m, 1H), 1.60 (t, J=12.5 Hz, 1H), 1.30 (m, 3H), 0.92 (d, J=6.7 Hz, 3H), 0.89 (d, J=6.7 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 140.7, 135.3, 132.6, 129.9, 128.0, 113.3, 49.2, 38.8, 27.5, 25.9, 23.3, 20.7, 10.5; IR (neat) 3071 (w), 3051 (w), 2995 (w), 2957 (s), 2923 (m), 2866 (m), 2102 (s), 1642 (w), 1473 (w), 1432 (s), 1264 (m), 1188 (w), 1116 (s), 1004 (w), 915 (m), 743 (s), 701 (s) cm−1; MS (FAB) m/e (rel. intensity) 350 (MH+, 18), 323 (32), 322 (100), 321 (27), 320 (16), 315 (42), 306 (42), 252 (17), 251 (23), 237 (18), 236 (73), 223 (26), 208 (17); HRMS (FAB) calcd for C21H28N3Si: 350.2053. found: 350.2040. Anal. Calcd for C21H27N3Si: C, 72.16; H, 7.79; N, 12.02. Found: C, 71.99; H, 7.91; N, 11.60.
