1-Hydroxybenzotriazole → 5-(4-(3-Bromobenzyl)-5-methyloxazol-2-yl)-3-(4-(trifluoromethoxy)phenyl)-1,2,4-oxadiazole

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A solution of 4-(3-bromobenzyl)-5-methyloxazole-2-carboxylic acid (300 mg, 1.0 mmol), EDC.HCl (191 mg, 1.0 mmol) and HOBT (135 mg, 1.0 mmol) in DMF (10 mL) was stirred at RT for 2 h, and then N-hydroxy-4-(trifluoromethoxy)benzimidamide (220 mg, 1.0 mmol) was added. The mixture was stirred at 70° C. overnight, cooled to RT, treated with H2O (50 mL) and extracted with EtOAc (3×20 mL). The combined organic layers were washed with H2O (10 mL) and brine (10 mL), dried over Na2SO4, filtered, concentrated and purified by silica gel column chromatography (EtOAc:Petroleum ether=1:5) to afford 5-(4-(3-bromobenzyl)-5-methyloxazol-2-yl)-3-(4-(trifluoromethoxy)phenyl)-1,2,4-oxadiazole as a yellow oil (19 mg, 7%). MS (ES+) C20H13BrF3N3O3 requires 479, 481, found: 480, 482 [M+2+H]+(1:1). 1H NMR (500 MHz, CDCl3) δ 8.24 (d, J=8.5 Hz, 2H), 7.41-7.34 (m, 4H), 7.22-7.19 (m, 2H), 3.94 (s, 2H), 2.44 (s, 3H).

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