Di-tert-butyl malonate (CAS NO.: ), which is also known as , di-t-butyl ester, could be produced through the following synthetic routes.

A 500-ml. Pyrex heavy-walled narrow-mouthed pressure bottle is charged with 100 ml. of ether, 5 ml. of concentrated sulfuric acid, 50.0 g. (0.48 mole) of malonic acid, and approximately 120 ml. (about 1.5 moles) of isobutylene, which is liquefied by passage into a large test tube immersed in a Dry Ice-acetone bath. The bottle is closed with a rubber stopper which is clamped or wired securely in place and is shaken mechanically at room temperature until the suspended malonic acid dissolves. The bottle is chilled in an ice-salt bath and opened; then the contents are poured into a separatory funnel containing 250 ml. of water, 70 g. of sodium hydroxide, and 250 g. of ice. The mixture is shaken (carefully at first), the layers are separated, and the aqueous portion is extracted with two 75-ml. portions of ether. The organic layers are combined, dried over anhydrous potassium carbonate, and filtered into a dropping funnel attached to the neck of a 125-ml. modified Claisen flask. The flask is immersed in an oil bath at about 100°, and the excess isobutylene and ether are removed by flash distillation effected by allowing the solution to run in slowly from the dropping funnel. The dropping funnel is then removed, and the residue is distilled at reduced pressure. The fraction boiling at 112–115°/31 mm. is collected. The yield of colorless di-tert-butyl malonate is 60.0–62.0 g. (58–60%), n²⁵D 1.4158–1.4161, freezing point -5.9 to -6.1°.