Reaction Steps
A 50 mL round bottom flask equipped with a stirring bar and rubber septum was charged with 3,5-bis(tert-butyldimethylsilyloxy)benzoic acid (0.76 g, 2.0 mmol) and placed under argon. 15 mL dry DCM was added followed by the addition of hydroxybenzotriazole (HOBT; 0.3 g, 2.2 mmol) and N,N′-dicyclohexylcarbodiimide (DCC; 0.45 g, 2.2 mmol) in that order by partial removal of the septum. The resulting slurry was stirred at room temperature for 10 min. Butan-1-amine (0.3 mL, 0.22 g, 3.0 mmol) was then added drop wise and the reaction mixture was stirred overnight. The resulting heterogeneous solution was then filtered over a Buchner funnel and the filtrate was further diluted with DCM and washed with 0.5 M HCl. The aqueous layer was extracted once more with DCM and the combined organics were dried over Na2SO4. The crude reaction mixture was then concentrated on to silica gel via rotary evaporation and subjected to flash chromatography (SiO2, 10% EtOAc-hexanes; Rf=0.3 at 10% EtOAc-hexanes) to afford 13c as a white crystalline solid (0.76 g, 1.8 mmol): mp 114-117° C.; IR (neat) λmax 3294, 2929, 2857, 1632, 1583, 1543, 1438, 1334, 1253, 1163, 1027, 1004, 935, 829, 778, 692, 667, 486 cm−1; 1H NMR (400 MHz, CDCl3) δ 6.81 (d, J=2.1 Hz, 2H), 6.43 (t, J=2.1 Hz, 1H), 6.02 (app s, 1H), 3.41 (q, J=7.1 Hz, 2H), 1.58 (p, J=7.7 Hz, 2H), 1.39 (sex, J=7.2 Hz, 2H), 0.97 (s, 18H), 0.95 (t, J=7.3 Hz, 3H), 0.19 (s, 12H); 13C NMR (100 MHz, CDCl3) δ 167.3, 156.8, 137.1, 114.9, 112.1, 39.9, 31.8, 25.8, 20.3, 18.3, 13.9, −4.3; LRMS (EI) m/z=437.3 [M]+.
