Pyridine → ethyl 1-(4-(1,3,4-oxadiazol-2-yl)phenyl)-3-tert-butyl-1H-pyrazole-5-carboxylate

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Reaction Steps

A mixture of 4-(1,3,4-oxadiazol-2-yl)phenylboronic acid (303 mg, 1.60 mmol) and powdered 4A molecular sieves (300 mg) in CH2Cl2 (6 mL) was heated to reflux for 2 h. Ethyl 3-tert-butyl-1H-pyrazole-5-carboxylate (310 mg, 1.6 mmol), pyridine (0.13 mL, 1.6 mmol) and copper (II) acetate (290 mg, 1.6 mmol) were added and the reaction mixture was refluxed for 24 h. The reaction was filtered and the solid was washed with EtOAc (40 mL) and MeOH (40 mL). The combined filtrate and washings were concentrated in vacuo and partitioned between EtOAc (40 mL) and water (20 mL). The organics were washed with water (20 mL), satd aq NaHCO3 (20 mL), water (20 mL), and brine (20 mL), dried (Na2SO4) and concentrated in vacuo. The oily residue was chromatographed to provide ethyl 1-(4-(1,3,4-oxadiazol-2-yl)phenyl)-3-tert-butyl-1H-pyrazole-5-carboxylate (440 mg, > 100% yield) as a visocus oil contaminated with the starting ester. The mixture was used without further purification.

Provenance & Evidence