Di-tert-butyl diazomalonate (CAS NO.: ), which is known as dioic acid, diazo-, bis(1,1-dimethylethyl) ester, could be produced through the following synthetic route.

A 500-ml., three-necked, round-bottomed flask equipped with a reflux condenser, a dropping funnel, an argon inlet, and a -coated magnetic stirring bar is charged with 10.8 g. (0.0500 mole) of di-tert-butyl malonate , 9.9 g. (0.0502 mole) of p-toluenesulfonyl azide, 0.5 g. (0.001 mole) of methyltri-n-octylammonium chloride, and 200 ml. of dichloromethane. The solution is stirred vigorously as the flask is flushed with argon for 10 minutes, then 10 ml. (0.1 mole) of aqueous 10 N sodium hydroxide is added in one portion. The mixture is stirred for 2 hours, during which time it changes from colorless to pale yellow. A 200-ml. portion of water is added; the organic layer is separated, washed with three 500-ml. portions of water, and dried with anhydrous magnesium sulfate. After filtration of the drying agent, the solvent is removed on a rotary evaporator using a water bath kept at 30°. The residual yellow-orange liquid is distilled at high vacuum. The temperature of the heating bath is gradually raised to ca. 70° and kept at 70–75° during the distillation. After separation of a small forerun, 7.2–7.6 g. (59–63%) of di-tert-butyl diazomalonate is collected, b.p. 44–45° (0.02 mm.), n_D22 = 1.4568.

Notice: Diazomalonic esters are toxic and potentially explosive. They must be handled with care. This preparation should be carried out in a well-ventilated hood, and the distillation of di-tert-butyl diazomalonate should be conducted behind a safety shield.