6-nitro-4-propargyl-2H-1,4-benzoxazin-3(4H)-one → 6-amino-4-propargyl-2H-1,4-benzoxazin-3(4H)-one

To a slurry of 5.1 g (91 mmol) of iron powder in 42.5 ml of 5% aqueous acetic acid was added dropwise a solution of 4 g of 6-nitro-4-propargyl-2H-1,4-benzoxazin-3(4H)-one dissolved in 42.5 ml of glacial acetic acid and 42.5 ml of EtOAc. The reaction mixture was heated to gentle reflux for 1 hour then cooled to room temperature. The iron was removed by suction filtration. EtOAc (50 ml) was added to the filtrate and the layers were separated. The aqueous phase was extracted with EtOAc (2×50 ml) and the organic layers were combined, washed with saturated aqueous sodium bicarbonate solution (100 ml), and dried (MgSO4). The solvent was removed in vacuo to yield a thin brown oil which was taken up in 50 ml of water and reextracted with EtOAc (3×50 ml). The organic layers were combined, washed with water (2×50 ml) and then dried (MgSO4). The solvent was removed in vacuo to yield 2.55 g (75% yield) of 6-amino-4-propargyl-2H-1,4-benzoxazin-3(4H)-one as a dark brown solid, m.p. 136°-140° C.

1. temperatureThe reaction mixture was heated
2. temperatureto gentle reflux for 1 hour
3. customThe iron was removed by suction filtration
4. additionEtOAc (50 ml) was added to the filtrate
5. customthe layers were separated
6. extractionThe aqueous phase was extracted with EtOAc (2×50 ml)
7. washwashed with saturated aqueous sodium bicarbonate solution (100 ml)
8. dry with materialdried (MgSO4)
9. customThe solvent was removed in vacuo
10. customto yield a thin brown oil which
11. washwashed with water (2×50 ml)
12. dry with materialdried (MgSO4)
13. customThe solvent was removed in vacuo

ORD record

ord-581e264791344e0d8d3bbf0d65469328

Source dataset

uspto-grants-1993_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05238908