Application
Benzyl-N-vinyl carbamate (Z-vinylamine; Benzyl vinylcarbamate) is a valuable synthetic intermediate. This compound undergoes alkylation readily on the carbon R to the nitrogen, a property that has been used in the synthesis of a-lactam antibiotics. Z-vinylamine can be readily polymerized into polyvinyl amine derivatives[1].
Preparation
A 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 ℃.
Synthesis
General procedure for the synthesis of O-benzyl-N-vinyl carbamates from acryloyl azide and benzyl alcohol: Preparation of (phenylmethoxy)-N-vinyl carboxamide. Benzyl alcohol (76.5 ml, 792 mmol), hydroquinone (3.05 g, 27.7 mmol) and pyridine (3 ml, 27.7 mmol) were added to a 500 ml single-necked flask and the mixture was stirred at 100 °C. Subsequently, a toluene solution of 1-aza-1-diaza-1,3-dien-2-one (200 mL) was slowly added dropwise. After the dropwise addition was completed, the reaction mixture was continued to be stirred at 110°C for 30 minutes and then at room temperature for 12 hours. After completion of the reaction, the reaction mixture was concentrated by reduced pressure distillation (0.4 mmHg) to give the crude product. Further purification afforded the intermediate O-benzyl-N-vinylcarbamate (phenylmethoxy)-N-vinylcarboxamide (43.1 g, 45% yield) as a colorless oil (boiling point 110-115 °C), which solidified after standing at room temperature. The molecular weight of the product was confirmed to be 178 (M* + H) by electrospray mass spectrometry (M.S.).
