Reaction Steps
(191) A solution of 2-(oxazol-5-yl)pyridine (116 mg, 0.79 mmol) in anhydrous THF (5 mL) cooled to −75° C. under N2 was treated with n-BuLi (2.5 M in hexanes, 1.1 equiv, 0.87 mmol, 0.35 mL), and stirred for 20 min. ZnCl2 (0.5 M in THF, 2.0 equiv, 1.58 mmol, 3.2 mL) was added at −75° C., and stirred for 45 min at 0° C. Cul (1.0 equiv, 0.79 mmol, 151 mg) was added, and the solution was stirred for 10 min at 0° C. A separate flask was charged with hexanoic acid (2 equiv, 1.58 mmol, 186 mg, 0.20 mL) in anhydrous CH2Cl2 (4.2 mL), and to this solution cooled to 0° C. under N2 was added oxalyl chloride (5 equiv, 8.0 mmol, 1.02 g, 0.70 mL). After stirring at rt for 2 h, the solution was concentrated under reduced pressure and dissolved in anhydrous THF (1.5 mL). The solution of hexanoyl chloride was added and the solution was stirred for 1 h at 0° C. The reaction was diluted with EtOAc (10 mL), and washed with 15% aqueous NH4OH (1×10 mL), H2O (1×10 mL), and saturated aqueous NaCl (1×10 mL). The organic layer was dried (Na2SO4), filtered, and concentrated under reduced pressure. Flash chromatography (SiO2, 2.5 cm×17.5 cm, 20% EtOAc-hexanes) afforded 1-(5-(pyridin-2-yl)oxazol-2-yl)hexan-1-one (191) (50 mg, 0.20 mmol, 25% yield) as a light brown powder: mp 49-50.5° C.; 1H NMR (CDCl3, 250 MHz) d 8.64 (br d, J=3.9 Hz, 1H), 7.85-7.75 (m, 3H), 7.32-7.26 (m, 1H), 3.09 (t, J=7.7 Hz, 2H), 1.82-1.70 (m, 2H), 1.40-1.31 (m, 4H), 0.89 (t, J=6.95 Hz, 3H); 13C NMR (CDCl3, 62.5 MHz) d 181.5, 150.3, 146.2, 143.0, 139.3, 130.0, 119.8, 117.0, 113.3, 32.0, 24.2, 16.6, 15.3, 6.8; IR (KBr) umax 2957, 2872, 1700, 1677, 1603, 1426, 1387 cm−1; MALDI-FTMS (DHB) m/z 245.1284 (C14H16N2O2+H+ requires 245.1284).
