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A 22 L, five neck, round bottom flask was equipped with an overhead stirrer, reflux condenser, addition funnel, thermocouple temperature read out, and a heating mantle. The reactor was purged with nitrogen. Acetonitrile (4700 mL) and 4-chloro-2-hydroxybenzamide (1782 g, 10.4 mol) were charged to the reaction flask and the stirring was started. Pyridine (1133 mL, 14.0 mol) was charged to the reactor. The resulting reaction slurry was cooled to less than 10° C. with an ice bath. Ethyl chloroformate (1091 mL, 1237 g, 11.4 mol) was placed in the addition funnel and charged slowly to the stirred reaction mixture such that the temperature of the reaction mixture did not exceed 15° C. during the addition. The temperature of the reaction mixture was held between 10 and 15° C. for 30 minutes after the ethyl chloroformate addition was complete. The ice bath was removed, and the reaction mixture was warmed to ambient temperature. The reaction mixture was then slowly heated to reflux and held at that temperature for 18 hours Liquid chromatographic analysis of the reaction mixture indicated that the reaction was only 80% complete. Approximately half of the solvent was removed by atmospheric distillation. The reaction mixture was cooled first to ambient temperature and then to <10° C. with an ice bath. Additional pyridine (215 mL, 2.65 mol) was added to the reaction mixture. Ethyl chloroformate (235 g, 2.17 mol) was added slowly via an addition funnel to the cold reaction mixture. The reaction mixture was held between 10 and 15° C. for 30 minutes after the ethyl chloroformate addition was complete. The ice bath was removed, and the reaction mixture was warmed to ambient temperature. The reaction mixture was then slowly heated to reflux and held at that temperature for 18 hours, after which time liquid chromatographic analysis indicated that the reaction was complete. The reaction mixture was cooled first to ambient temperature and then to <10° C. with an ice bath. Water (1600 mL) was added slowly via an addition funnel and the resulting slurry held at <10° C. for 90 minutes. The solid product was collected by vacuum filtration through a large sintered glass funnel. The product filter cake was washed with deionized water and vacuum dried at 50° C. for 18 hours to give 1914 g of 7-chloro-2H-1,3-benzoxazine-2,4 (3H)-dione as a tan solid. The yield was 83%.

1. customA 22 L, five neck, round bottom flask was equipped with an overhead stirrer
2. temperaturereflux
3. additioncondenser, addition funnel
4. customThe reactor was purged with nitrogen
5. customThe resulting reaction slurry
6. temperaturewas cooled to less than 10° C. with an ice bath
7. additioncharged slowly to the stirred reaction mixture such that the temperature of the reaction mixture
8. additiondid not exceed 15° C. during the addition
9. customThe ice bath was removed
10. temperatureThe reaction mixture was then slowly heated
11. temperatureto reflux
12. waitheld at that temperature for 18 hours
13. customApproximately half of the solvent was removed by atmospheric distillation
14. temperatureThe reaction mixture was cooled first to ambient temperature
15. customto <10° C.
16. waitThe reaction mixture was held between 10 and 15° C. for 30 minutes
17. customThe ice bath was removed
18. temperaturethe reaction mixture was warmed to ambient temperature
19. temperatureThe reaction mixture was then slowly heated
20. temperatureto reflux
21. waitheld at that temperature for 18 hours
22. temperatureThe reaction mixture was cooled first to ambient temperature
23. customto <10° C.
24. additionWater (1600 mL) was added slowly via an addition funnel
25. waitthe resulting slurry held at <10° C. for 90 minutes
26. filtrationThe solid product was collected by vacuum filtration through a large sintered glass funnel
27. filtrationThe product filter cake
28. washwas washed with deionized water and vacuum
29. customdried at 50° C. for 18 hours