Malonic Acid → 2,2-Dimethyl-1,3-dioxane-4,6-dione

Malonic acid (5.2 g, 0.05 mol) and concentrated sulfuric acid (0.5 ml) were added to acetic anhydride (10 ml), and therein the source compound was dissolved thoroughly while stirring at room temperature. Thereto, 4-ethylcyclohexanone (6.31 g, 0.05 mol) was slowly added dropwise while cooling in an ice bath. The stirring of the admixture was continued in an ice bath, and colorless crystals separated out as the reaction progressed. These crystals were filtered off, washed with distilled water, and dried. Thus, 9.0 g of a meldrum's acid derivative was obtained as colorless crystals (in a 85.1% yield). The thus obtained meldrum's acid derivative (4.25 g, 0.02 mol) and N,N′-1,3-pentadiene-1-yl-5-ylidenedianiline hydrochloride (5.70 g, 0.02 mol) were dissolved in methanol (50 ml), and thereto triethylamine (3.04 g, 0.03 mol) was added. The stirring of the resulting admixture was continued at room temperature to result in deposition of violet crystals. Then, these crystals were filtered off, and washed with methanol. Thus, 5.61 g of violet crystals corresponding to Compound (3-I) was obtained (in a 76.3% yield). These violet crystals (4.40 g, 12.0 mmol) and the Compound (1-I) obtained in the foregoing Synthesis (1.71 g, 6.0 mmol) were dissolved in dimethylformamide (20 ml), and thereto triethylamine (1.82 g, 18 mmol) was added dropwise. The resulting admixture was stirred for 4 hours at 50° C. Thereafter, the reaction solution obtained was admixed with distilled water, and extracted with ethyl acetate. The organic layer thus extracted was purified by column chromatography (dichloromethane/methanol=6/1) on silica gel to give 2.0 g of violet powder corresponding to Compound (3-II) (in a 39.5% yield).