Oxalyl chloride → 3-[4-(Carbomethoxy)phenyl]-5-(4-phenyl-5-trifluoromethyl-2-thienyl)-1,2,4-oxadiazole

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Reaction Steps

A solution of 408 mg (1.5 mmol) of 4-phenyl-5-trifluoromethyl-thiophene-2-carboxylic acid and 1 mL of oxalyl chloride in 5 mL of CH2Cl2 was treated with 5 drops of DMF. The resulting mixture was stirred at rt for 1 h, then concentrated. The crude acid chloride and 291 mg (1.5 mmol) of 4-(carbomethoxy)benzamidoxime were dissolved in 7 mL of 6:1 v/v xylenes/pyridine. The resulting solution was heated at 140° C. for 1 h, then cooled. The mixture was partitioned between 50 mL of 1:1 EtOAc/ether and 50 mL of 1 N HCl. The organic layer was separated, washed with 3×50 mL of 1 N HCl, 50 mL of sat'd NaHCO3, dried and concentrated. Chromatography on a Biotage 40 M cartridge using hexanes (1L), then 20:1 v/v hexanes/EtOAc (1 L) as the eluant afforded 423 mg (65%) of the title compound: 1H NMR (500 Mhz) δ0 3.97 (s, 3H), 7.48 (app s, 5H), 7.92 (s, 1H), 8.18 (app d, J=8.5, 2H), 8.23 (app d, J=8.5, 2H).

Provenance & Evidence