2,2-Dimethyl-1,3-dioxane-4,6-dione → 3-(2,2-Dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)amino-4-carbethoxy-pyrazole

Meldrum's acid (15.3 g, 106 mmol) was dissolved in toluene (450 mL), triethyl orthoformate (17.6 mL, 106 mmol) was added, and the mixture was heated under reflux for 2 hr. The reaction mixture was allowed to cool to room temperature, ethyl 3-amino-4-pyrazolecarboxylate (15 g, 96.7 mmol) was added, and the mixture was heated under reflux for 3 hr. The reaction mixture was allowed to cool to room temperature, and stirred at room temperature for 10 hr. The precipitated crystals were collected by filtration, washed with diisopropylether (100 mL), and dried under reduced pressure at 40° C. overnight to give the title compound (26.3 g, 88%).