Synthesis
1. 4-Benzylmorpholine-2-carbonitrile (113.0 g, 0.56 mol) was dissolved in ethanol (1030 mL) and stirred to form a homogeneous solution. 2. Concentrated sulfuric acid (165 mL) was added slowly and in batches with stirring, taking care to control the rate of addition in order to manage the exothermic reaction (the internal temperature was raised from room temperature to 65°C during the reaction). 3. After completion of the addition, the reaction mixture was heated to a reflux condition and maintained for 66 hours. 4. reflux, and the reaction was maintained for 66 h. 4. Upon completion of the reaction, the solution was cooled to room temperature and subsequently concentrated to half the original volume under reduced pressure. 5. The concentrate was carefully alkalinized with aqueous potassium carbonate (taking care to prevent foaming due to carbon dioxide release), and subsequently separated by extraction with ether. 6. The organic phases were combined, dried with anhydrous magnesium sulfate, and filtered to remove the drying agent. 7. The filtrate was evaporated under reduced pressure to remove the solvent. The filtrate was evaporated under reduced pressure to remove the solvent to give an oily crude product.8. The crude product was further dried under high vacuum to remove residual volatiles. The final product was 121.3 g of ethyl N-benzylmorpholine-2-carboxylate in 87% yield.
References
[1] Patent: WO2005/47272, 2005, A1. Location in patent: Page/Page column 49-50
[2] Patent: WO2005/47272, 2005, A1. Location in patent: Page/Page column 50
[3] Patent: WO2005/60949, 2005, A2. Location in patent: Page/Page column 276
[4] Journal of Medicinal Chemistry, 1993, vol. 36, # 6, p. 683 - 689
[5] Tetrahedron Letters, 1991, vol. 32, # 20, p. 2281 - 2284
