A. Methyl N,N-dichlorocarbamate. A 2-L, two-necked, round-bottomed flask equipped with a magnetic stirrer, a gas inlet, and a gas outlet is charged with 84 g (1.1 mol) of methyl carbamate, 210 g (2.6 mol) of sodium acetate, 21 g (0.35 mol) of glacial acetic acid, and 400 mL of water and cooled to −10 to −15°C (Note 1). About 175 g (2.5 mol) of chlorine is condensed in a calibrated Schlenk tube (Note 2) cooled with dry ice–methanol. The cooling bath is replaced by an ice–water bath (Note 3) and chlorine is passed slowly (Note 4) (over 2 hr, (Note 5)) at a constant rate into the solution, which is vigorously stirred with a magnetic stirrer. The mixture is transferred to a separatory funnel and the yellow oil which settles is run off. The yellow oil is washed with three subsequent 50-mL portions of a 20% aqueous sodium chloride solution and dried over anhydrous magnesium sulfate. The crude product is then transferred to a distillation apparatus, where it is kept under reduced pressure (11–15 mm) at room temperature for about 20 min. The bath temperature is slowly raised to a maximum of 60°C. The product distills at 43°C (11 mm) to give 102–118 g (63–73%, based on methyl carbamate) of a heavy yellow oil ((Note 6), (Note 7), (Note 8)).

B. N¹,N²-Bis(methoxycarbonyl)sulfur diimide. A 250-mL, three-necked, round-bottomed flask, equipped with a gas outlet stopcock, a thermometer, and a pressure-equalizing dropping funnel and containing a magnetic stirring bar, is purged with dry nitrogen and charged with 53.0 g (0.37 mol) of methyl N,N-dichlorocarbamate and 0.2 mL of pyridine. The dropping funnel is filled with 20.6 g (0.2 mol) of freshly distilled sulfur dichloride (Note 9). The whole apparatus is closed and connected by way of the gas outlet to a paraffin-oil-filled valve (Note 10). About 2 mL of sulfur dichloride is then added dropwise into the stirred flask. When the evolution of chlorine has started (usually after about 5 min) (Note 11), the remainder of the sulfur dichloride is added at such a rate that three to five bubbles of chlorine per second are evolved (Note 12), without allowing the temperature of the reaction mixture to exceed 35°C for more than short intervals. The addition takes 1.5–2 hr. After the addition is completed and the evolution of gas has slowed down significantly, volatile materials are removed by stirring the mixture at 60°C under reduced pressure (11–15 mm) for about 10 min (Note 13). Further removal is accomplished at room temperature at 0.01–0.05 mm for approximately 1 hr. The product (33.0–35.0 g), a moisture-sensitive, viscous, yellow oil, is used directly without further purification (Note 14).

C. Methyl N-(2-methyl-2-butenyl)carbamate. A 250-mL, two-necked flask, equipped with a gas outlet stopcock and a pressure-equalizing dropping funnel, and containing a magnetic stirring bar, is flushed with dry nitrogen and charged with a solution of N¹,N²-bis(methoxycarbonyl)sulfur diimide from Part B in 30 mL of dry chloroform. The solution is cooled with ice water, and 14.1 g (0.20 mol) of 2-methyl-2-butene is slowly dropped in with stirring over 1 hr. After the addition is completed, the reaction mixture is stirred for another 10 hr at room temperature. The funnel is replaced by a distillation unit and most of the solvent is removed (11–15 mm, bath temperature 30°C). To the residue are added 240 mL of a 10% solution of potassium hydroxide in methanol and about 10 mL of water. The mixture is stirred for 3 hr at room temperature, and any precipitate is filtered off (Note 15). The residue is washed with 50 mL of methanol, and the filtrate, a red solution, is concentrated at 40°C (11–15 mm). The residue is taken up in 450 mL of ether and washed with four 100-mL portions of water. The ethereal layer is dried with anhydrous magnesium sulfate and treated with charcoal until the color has changed from red to yellow, whereupon the solvent is removed under reduced pressure. The resultant oil is distilled at 70–75°C (3 mm), 62–64°C (0.2 mm) to give the colorless product, yield 10.7–13.7 g (43–52%, based on N,N-dichlorocarbamate) (Note 16) and (Note 17).