Acetic Acid → 2,2-Dimethyl-5-(1-methylethylidene)-1,3-dioxane-4,6-dione

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Reaction Steps

Meldrum's acid (100.0 g) was charged to a dry, nitrogen flushed reactor. Acetone (632.1 mL) was then charged to the reactor and the mixture was agitated for about 5 minutes at 20° C.-25° C. until a solution was obtained. Acetic acid (0.791 mL) was then charged to the reactor, followed by 1.215 mL of morpholine, and the solution was agitated at 20° C.-25° C. for about 48 hours. An aliquot (˜0.2 mL) was withdrawn for analysis of the conversion, which may be monitored by either GC or 1H-NMR. If the ratio of the area % of 2,2-dimethyl-5-(propan-2-ylidene)-1,3-dioxane-4,6-dione to Meldrum's acid is ≧80:20, proceed to the next step; if it is not, the batch should be aged for an additional 3 hours before repeating the check. The acetone was distilled at about 40° C. and 150-200 mmHg. After approximately two-thirds of the reaction volume was distilled out, 563 mL of methylcyclohexane was charged and the distillation continued until the acetone stopped distilling over. A total of 645 mL (508 g) of distillate was collected for this run. MTBE (500 mL) was charged to the batch at 40° C. and the batch was cooled to 20° C.-25° C. The solution was observed to make sure a cloudy solution was obtained (no solids). If there is solid present, additional MTBE may be charged to effect dissolution. The batch was quickly washed with two 50 g portions of 5 wt. % NaOH solution (prepared from 5 g of NaOH and 95 mL of water). The MTBE was distilled out at 40° C.-45° C. and 150-200 mmHg. A total of 400 mL (300 g) distillate was collected for this run. As distillation proceeds, a white slurry formed. The internal temperature was ramped to 0° C.-5° C. over 1 hour and then held at this temperature for at least 1 hour. The slurry was filtered, the cake was washed with two 100 mL portions of cold (˜0° C.-5° C.) methylcyclohexane, and the solid was dried at 20° C.-35° C. and 25-50 mmHg for no less than 4 hours. 2,2-Dimethyl-5-(propan-2-ylidene)-1,3-dioxane-4,6-dione was obtained as a white solid (93.7 g, 70.4% yield, 96.0 wt. % purity by assay).

Provenance & Evidence