A. Methyl (chlorosulfonyl)carbamate. A dry, two-necked, 500-ml., round-bottomed flask fitted with a magnetic stirring bar, a 125-ml., pressure-equalizing dropping funnel, and a reflux condenser to which is attached a calcium chloride drying tube is charged with a solution of 70.8 g. (43.6 ml., 0.580 mole) of chlorosulfonyl isocyanate (Note 1) in 150 ml. of anhydrous benzene (Note 2). A solution of 16.0 g. (20.2 ml., 0.500 mole) of anhydrous methanol (Note 3) in 25 ml. of anhydrous benzene (Note 2) is placed in the dropping funnel. The flask is immersed in a water bath (Note 4), stirring is begun, and the methanol–benzene solution is added dropwise over 0.5 hour. Cold water is added to the bath as required to maintain a temperature of 25–30°. The reaction mixture is stirred for an additional 0.5 hour before 125 ml. of olefin-free hexane (Note 5) is added from the addition funnel over a 5-minute period while cooling the flask to 0–5° with an ice bath. The moisture-sensitive product is removed by filtration, washed twice with 40 ml. of hexane, and dried under reduced pressure, giving 76–80 g. (88–92%) of methyl (chlorosulfonyl)carbamate as white crystals, m.p. 72–74° (Note 6). This material should be stored in a brown bottle protected from light (Note 7).

B. Inner salt of methyl (carboxysulfamoyl)triethylammonium hydroxide. A two-necked, 500-ml., round-bottomed flask is fitted with a magnetic stirring bar, a 500-ml., pressure-equalizing dropping funnel, and a condenser to which a calcium chloride drying tube is attached. A solution of 23.0 g. (31.8 ml., 0.225 mole) of anhydrous triethylamine (Note 8) in 50 ml. of anhydrous benzene (Note 2) is placed in the flask, stirring is begun, and a solution of 17.4 g. (0.100 mole) of methyl (chlorosulfonyl)carbamate in 225 ml. of dried benzene (Note 9) is added dropwise over 1 hour. During addition the flask is cooled with a water bath maintained at 10–15°. The resulting mixture is stirred at 25–30° for an additional 0.5 hour then filtered to remove triethylamine hydrochloride (13.8 g.). Evaporation of the filtrate under reduced pressure leaves 22–23 g. of light tan needles, m.p. 70–72° (dec.), which is dissolved in 160 ml. of anhydrous tetrahydrofuran (Note 10) at 30°. On cooling, 20.0–20.6 g. (84–86%) of the inner salt of methyl (carboxysulfamoyl)triethylammonium hydroxide precipitates as colorless needles, m.p. 70–72° (dec.) (Note 11).

C. Methyl n-hexylcarbamate. In a dry, 100-ml., round-bottomed flask fitted with a reflux condenser, to which a calcium chloride drying tube is attached, are placed a boiling chip, 14.8 g. (0.0622 mole) of the inner salt of methyl (carboxysulfamoyl)triethylammonium hydroxide, and 6.0 g. (0.058 mole) of freshly distilled 1-hexanol (Note 12). After a mildly exothermic reaction (occasionally there is a 5-minute induction period), the viscous, yellow reaction mixture is heated with an oil bath at 95° for 1 hour. The mixture is cooled to 30°, diluted with 50 ml. of water, and extracted with three 50-ml. portions of dichloromethane. The organic extracts are combined, washed successively with 100 ml. of 5% hydrochloric acid and 50 ml. of water, and dried over anhydrous magnesium sulfate. After filtration, dichloromethane is removed with a rotary evaporator. The residue is triturated with 50 ml. of anhydrous diethyl ether and filtered; the recovered solid is triturated with two further 50-ml. portions of ether. The three ethereal filtrates are combined and concentrated with a rotary evaporator, affording 8.0 g. of crude product. Fractionation of this oil through a short-path distillation apparatus gives 4.8–4.9 g. (51–52%) of methyl n-hexylcarbamate as a colorless oil, b.p. 59–60° (0.08 mm.); n_D20 1.4361 (Note 13).