Potassium Carbonate → 4-chloro-N'-hydroxybenzenecarboximidamide

Participants

Reaction Steps

This product was prepared by a modification of the general procedure described in Diana et al. J.Med.Chem. 1995, 38, 1355. A mixture of 4-chlorobenzonitrile (5 g, 36.34 mmol), EtOH (90 mL), hydroxylamine hydrochloride (2.52 g, 36.34 mmol) and K2CO3 (2.51 g, 18.17 mmol) was refluxed for 20 h. The reaction mixture was concentrated, cold water was added, and it was filtered and dried to give 4-chlorobenzoamidoxime as a white solid (3.5 g, 56%). Next, this product (1.7 g, 10 mmol) was taken up in pyridine (34 mL) and treated with ethyl oxalyl chloride (2.22 mL, 20 mmol) at 0° C. The reaction mixture was stirred for 1 h, then poured into pH 7 phosphate buffer, concentrated and partitioned between CHCl3 and water. The organic phase was washed with 10% aqueous NaHCO3 solution, dried over Na2SO4, filtered, concentrated and purified by flash chromatography to give ethyl 3-(4-chlorophenyl)-1,2,4-oxadiazole-5-carboxylate as an amorphous solid (2.14 g, 85%): 1H NMR (300 MHz, CDCl3) δ (TMS) 8.18 (dt, Jt =2.2, Jd =8.6, 2H, arom), 7.56 (dt, Jt =2.2, Jd =8.6, 2H, arom), 4.66 (q, J=7.1, 2H, OCH2), 1.57 (t, J=7.1, 3H, OCH2CH3).

Provenance & Evidence