2-Methyl-[1,4] Benzoxazin-3(4H)-one

Synthesis

1. 125 mM potassium carbonate was added to 100 mL of anhydrous N,N-dimethylformamide (DMF). 2. 50 mM 2-amino-5-nitrophenol was added and stirred at room temperature for 1 hr until completely dissolved. 3. 50 mM 2-bromopropionic acid ethyl ester was added dropwise to the DMF solution in an ice bath under cooled conditions. 4. After the dropwise addition was completed, the reaction mixture was slowly warmed up to room temperature, and then reacted for 12 hrs at 90°C. 5. After the reaction was completed, the reaction mixture was cooled and some of the solvent was removed by distillation under reduced pressure. 6. 300-500 mL of ice water was added to the residue slowly and stirred until a solid precipitate was precipitated. After the reaction was completed, the reaction mixture was cooled and the solvent was removed by distillation under reduced pressure. 6. 300-500 mL of ice water was slowly added to the residue and stirred until a solid precipitate precipitated, and the stirring was continued for half an hour in an ice bath. 7. The precipitate was collected by filtration, and the filter cake was dried in vacuum to give 6.28 g of the intermediate in the form of a brown powder in 77.03% yield. 8. The intermediate was used directly in the subsequent reaction without further purification. 9. The intermediate was used directly in the subsequent reaction without further purification.

References

[1] Tetrahedron Letters, 2010, vol. 51, # 14, p. 1852 - 1855
[2] Chemistry - A European Journal, 2011, vol. 17, # 6, p. 1884 - 1893
[3] Tetrahedron, 2005, vol. 61, # 28, p. 6879 - 6885
[4] Patent: CN107459494, 2017, A. Location in patent: Paragraph 0279; 0281-0283