Acetic Acid → Ethyl 2,4-dimethyl-1,3-oxazole-5-carboxylate

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Reaction Steps

Prepared as in J. Heterocyclic Chem. 1998, 35, 859. A solution of chloroacetoacetate (20 g, 121 mmol) and acetamide (14.4 g, 240 mmol) in glacial acetic acid (40 mL) was heated to reflux for 72 h. The mixture was cooled to rt and concentrated under vacuum. The resulting material was cooled in an ice bath and made basic (pH 9-10) with 6 N NaOH solution. The aqueous solution was extracted with Et2O (3×100 mL). The combined Et2O layers were dried (Na2SO4), filtered, and concentrated to afford a light brown oil. The crude material was purified by silica gel chromatography, eluting with a gradient of 20 % EtOAc/hexanes to 25 % EtOAc/hexanes to provide the ester (1.8 g, 9 %) as a pale yellow solid. 1H NMR 300 MHz (CDCl3): δ=4.37 (q, J=7.1 Hz, 2 H), 2.49 (s, 3H), 2.43 (s, 3H), 1.38 (t, J=7.1 Hz, 3H). MS (ESI-POS): [M+H]+=191.

Provenance & Evidence