Benzyl trans-1,3-butadiene-1-carbamate (CAS NO.: 71616-72-3), which is also known as , 1,3-butadienyl-, (E)-, phenyl, could be produced through the following synthetic routes.

A. trans- (CAS NO.:). A 1-l., three-necked, round-bottomed flask is equipped with a mechanical stirrer, a condenser cooled with ice-cold water bearing a calcium chloride drying tube, and a powder funnel. The flask is charged with 206 g. (210 ml., 2.61 moles) of pyridine, and with vigorous stirring 208 g. (2.00 moles) of powdered malonic acid is added in portions. The powder funnel is replaced by a 250-ml., pressure-equalizing dropping funnel containing 126 g. (150 ml., 2.25 moles) of acrolein, which is added, with vigorous stirring, over a 30-minute period. The exothermic reaction begins immediately with evolution of carbon dioxide, and the gently refluxing mixture becomes homogeneous. After 1 hour, as carbon dioxide evolution ceases, the solution is poured onto 1 l. of ice in a 3-l. Erlenmeyer flask, and carefully acidified with 130 ml. of concentrated sulfuric acid. The aqueous layer is extracted with four 250-ml. portions of dichloromethane, and the organic extracts are dried over magnesium sulfate for ca. 10 minutes. The dichloromethane solution is concentrated to ca. 300 ml. on a rotary evaporator with the water bath at 20–30° and allowed to crystallize in a freezer at -10° for several hours. After a first crop, yielding 40–50 g. of product, m.p. 72–73°, is collected, three additional crops are taken following successive concentration of the mother liquor to 150, 70, and 30 ml. Dried under reduced pressure in the presence of phosphorous pentoxide, the four crops of off-white crystals total 82–90 g. (42–46%), m.p. 69–71°.

B. Benzyl trans-1,3-butadiene-1-carbamate. Caution! The following reaction should be carried out in a fume hood to avoid accidental exposure to toxic hydrazoic acid.

A dry, 1-l., three-necked, round-bottomed flask is equipped with a magnetic stirring bar, a thermometer, and a 250-ml., pressure-equalizing dropping funnel bearing a nitrogen inlet. The flask is flushed with nitrogen and charged with 49 g. (0.50 mole) of trans-2,4-pentadienoic acid, 80 g. (0.62 mole) of N,N-diisopropylethylamine, and 300 ml. of acetone. The resulting solution is stirred and cooled to 0° in an ice–salt bath. A solution of 55 g. (0.51 mole) of ethyl chloroformate in 150 ml. of acetone is added over 30 minutes while the temperature is maintained below 0°. Stirring is continued for an additional 30 minutes at 0°, after which a chilled solution of 65 g. (1.0 mole) of sodium azide in 170 ml. of water is added over a 20-minute interval, keeping the temperature below 0°. The contents of the flask are stirred for an additional 10–15 minutes at 0° and poured into a 2-l. separatory funnel containing 500 ml. of ice-water. The acyl azide is isolated by extraction with six 250-ml. portions of toluene. The combined toluene extracts are dried over anhydrous magnesium sulfate for 20 minutes and concentrated to a volume of ca. 300 ml. on a rotary evaporator at a water bath temperature of 40–50°. Caution! The acyl azide is potentially explosive. The solution should not be evaporated to dryness. While the toluene solution is being concentrated, a dry, 2-l., three-necked, round-bottomed flask equipped with a mechanical stirrer, a 500-ml. pressure-equalizing dropping funnel, a simple distillation head, and a heating mantle is charged with 43 g. (0.40 mole) of benzyl alcohol, 250 mg. of 4-tert-butylcatechol, and 200 ml. of toluene. About 30 ml. of toulene is distilled from the flask to remove trace amounts of water, and the distillation head is replaced with a condenser fitted with a nitrogen inlet. The toluene solution is stirred and heated at a rapid reflux under a nitrogen atmosphere as the toluene solution of the acyl azide is added over 30 minutes. The disappearance of the acyl azide and isocyanate is followed by IR analysis. Conversion to the carbamate is complete in 10–30 minutes, after which the solution is cooled rapidly to room temperature by immersing the flask in an ice bath. The toluene is rapidly removed on a rotary evaporator with the water bath at 40–50°, producing a yellow solid residue which is dissolved in 50 ml. of 95% ethanol and allowed to crystallize in a freezer at -25° for several hours. Two crops of pale yellow crystals, m.p. 69–72°, are isolated which total 39–46 g. after drying under reduced pressure. Concentration of the mother liquor affords an oily residue that is placed on a 6 × 80-cm. column packed with 500 g. of silica gel and eluted with 1:9 (v/v) ethyl acetate–hexane. An additional 11–12 g. of crystalline product is obtained from the chromatography, raising the total yield to 50–58 g. (49–57%) of nearly pure benzyl trans-1,3-butadiene-1-carbamate, a pale yellow solid, m.p. 70–73°.