benzyl N-ethenylcarbamate

PreparationA 1-L flask was equipped with a variable speed pump, a mechanical stirrer, a temperature controller, a 4" (10 cm) column packed with ceramic saddles, a distillation head, a spiral condenser (cooled with water at 10–15 ℃), and a receiver. The flask was charged with toluene (150–200 mL) and phenothiazine (0.5 g) and the solution was heated to 105–110 ℃. The receiver was charged with benzyl alcohol (86 g, 0.8 mol), phenothiazine (0.05 g), and triethylamine (0.1–0.3 g). This mixture was cooled in ice and stirred. A solution of acryloyl azide (1 mol), prepared as described above, was pumped into the distillation flask over a period of 4–5 h, maintaining the pot temperature at 105–110 ℃ with a heating mantle. The vapor temperature varied, depending on the rate of addition of the azide, but was in the range 80–100 ℃. The distillate was passed directly into the benzyl alcohol mixture. After the addition of acryloyl azide, the distillation continued, generating a further 10–20 mL of toluene. The receiver was then removed from the distillation set-up, and its contents were stirred at 0–5 ℃ for 1– 2 h. The product mixture was then allowed to gradually warm to room temperature and was stirred until HPLC analysis indicated complete reaction. The mixture was then concentrated in vacuo to a weight of 200–250 g. The residue was treated with heptane (300–350 mL) and cooled to 15 ℃ with stirring. A few seed crystals of benzyl N-vinyl carbamate 810 were added, and the mixture was stirred for 2–3 h. The product was collected by filtration, washed with heptane, and dried in vacuo. Yield 115–128 g (65–72%); mp 41–44 ℃.