tert-Butyl ethyl fumarate (CAS NO.: ), which is also known as (E)-dioic acid, ethyl 1,1-dimethylethyl ester, could be produced through the following synthetic routes.

A 500-mL, one-necked flask equipped with a calcium chloride drying tube is charged with 28.83 g (0.20 mol) of monoethyl fumarate, 200 mL of dry dichloromethane, 44.47 g (0.60 mol) of tert-butyl alcohol, and 2.00 g (0.16 mol) of 4-dimethylaminopyridine. The solution is stirred and cooled in an ice bath to 0°C while 45.59 g (0.22 mol) of is added over a 5-min period. After a further 5 min at 0°C the ice bath is removed and the dark-brown reaction mixture is stirred for 3 hr at room temperature. The dicyclohexylurea that has precipitated is removed by filtration through a fritted Büchner funnel (G3), and the filtrate is washed with two 50-mL portions of 0.5 N hydrochloric acid and two 50-mL portions of saturated sodium bicarbonate solution. During this procedure some additional dicyclohexylurea is precipitated, which is removed by filtration of both layers to facilitate their separation. The organic solution is dried over anhydrous sodium sulfate and concentrated with a rotary evaporator. The concentrate is distilled under reduced pressure, affording, after a small forerun, 30.5–32.5 (76–81%) of tert-butyl ethyl fumarate, bp 105–107°C (12 mm).

Notice: Dicyclohexylcarbodiimide is a potent allergen and should be handled with gloves.