p-(Trifluoromethoxy)benzaldehyde → 4-[5-(4-Trifluoromethoxyphenyl)-[1,2,4]oxadiazol-3-yl]phenylamine

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Reaktionsschritte

{4-[5-(4-Trifluoromethoxyphenyl)-[1,2,4]oxadiazol-3-yl]-phenyl}-carbamic acid tert-butyl ester. To a stirred solution of tert-butyl-4-(N-hydroxycarbamimidoyl)-phenylcarbamate (Ace Synthesis) (500 mg; 1.99 mmol) dissolved in 2.5 mL of acetic acid was added 4-trifluoromethoxybenzaldehyde (1.7 mL; 11.94 mmol), and the reaction mixture was stirred at room temperature for 4 d. The mixture was diluted with CHCl3 (20 mL) and filtered through a pad of Celite®. The pad was washed with CHCl3 (20 mL). Heptane (20 mL) was then added to the solution and the solution was concentrated under reduced pressure. This procedure was repeated twice. The residue was purified via radial chromatography using a 3:1 hexane/EtOAc solution as the eluent. Two fractions were isolated. The first fraction isolated (Rf=0.42) was shown to be the title compound (127 mg; 15%). 1H NMR (300 MHz, CDCl3) δ 8.26 (d, J=8.9 Hz, 2H), 8.09 (d, J=8.9 Hz, 2H), 7.52 (d, J=8.6 Hz, 2H), 7.39 (d, J=8.3 Hz, 2H), 6.70 (s, 1H), 1.54 (s, 9H); EI/MS 421 [M]+. The second fraction isolated (Rf=0.11) was shown to be the 4,5-dihydro-1,2,4-oxadiazole (96 mg; 11%). 1H NMR (300 MHz, CDCl3) δ 8.40 (d, J=8.9 Hz, 2 H), 8.00 (d, J=8.9 Hz, 2 H), 7.51 (d, J=8.9 Hz, 2 H), 7.22-7.31 (m, 3 H), 6.87 (s, 1 H), 1.54 (s, 9 H); EI/MS 423 [M]+.

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