Ethyl 2-methyl-beta-oxobenzenepropanoate → 2-(3-(2,5-Difluorophenyl)-1,2,4-oxadiazol-5-yl)-1-o-tolylethanone

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A solution of ethyl 3-oxo-3-o-tolylpropanoate (0.44 mL; 2.5 mmol) and 2,5-difluoro-N′-hydroxybenzenecarboximidamide (JRD-Fluorochemical, 215 mg; 1.25 mmol) in toluene (1.5 mL) was heated to 120° C. 18 hours. The solvent was removed in vacuo and the residue purified by flash chromatography on a Biotage 25+M column, eluting with petrol containing increasing amounts of EtOAc. The residue was triturated with petrol to give the title compound as an off-white solid which was used directly without any further purification. 1H NMR (CDCl3, 400 MHz) δ 11.62‡ (1H, br s), 7.82-7.74 (1H, m), 7.55-7.12 (6H, m), 5.95‡ (1H, s), 4.68* (2H, s), [2.58, 2.55 and 2.47] (3H, s) (compound isolated as a mixture of keto and enol forms and as a mixture of rotamers, *=keto form, ‡=enol form). LC/MS: 315 (M+H)+. HPLC (Method D) Rt=4.28 min (Purity: 98.4%).

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