864274-04-4

c) Synthesis of 2-methylbenzo[d]oxazole-6-carbaldehyde; To a solution of (2-methylbenzo[d]oxazol-6-yl)methanol (12.5 g, 76 mmol) in dichloromethane (200 mL) was added pyridinium chlorochromate (20 g, 93 mmol, 1.2 equiv.) and the reaction mixture was stirred for 1 h at room temperature. Diatomaceous earth (10 g) and activated carbon (2 g) were added to decolorize the mixture, which was filtered after continued stirring for 15 min. After evaporation of the solvent, the crude product was purified by column chromatography (eluent ratio 1:10 ethyl acetate:dichloromethane) to give 8.2 g (66% yield) of pure 2-methylbenzo[d]oxazole-6-carboxaldehyde.1H-NMR (CDCl3): δ 2.73 (s, 3H), 7.79 (d, 1H, J = 8.1 Hz), 7.88 (dd, 1H, J = 8.1 Hz, J' = 1.2 Hz), 8.03 (d, 1H, J = 1.2 Hz), 10.09 (s, 1H).LC-MS (m/z): 162.2 (MH+). Retention time (Rt): 1.47 min.

[1] Patent: WO2005/82901, 2005, A1. Location in patent: Page/Page column 33; 61-62
[2] Patent: WO2007/103755, 2007, A2. Location in patent: Page/Page column 81; 83