Mesityl oxide → Ethyl 2,6,6-trimethyl-4-oxocyclohex-2-ene-1-carboxylate

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A mixture of 1020 ml (1041 g, 8.00 mol) of ethyl acetoacetate, 960 ml (824 g, 8.40 mol) of mesityl oxide, 1000 ml of heptane, 600 ml of toluene, and 175 g of zinc chloride was heated at reflux in a 5000 ml round bottom flask while stirring. The flask was equipped with a Dean-Stark trap and drying tube. After 24 h, an additional 25 g of zinc chloride was added and refluxing continued for 36 h. After cooling, the reaction mixture was washed with 1500 ml of water, 5% sodium bicarbonate solution (2×1000 ml), and another 1500 ml of water. Removal of solvent by evaporation yielded 979 g of crude product. Distillation of the crude product provided 453.5 g of the desired ester which represents 27.0% yield. Distillation was at 124°-5° C. (3.0 torr).

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