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reduced pressure. The carbamates 3 were washed with cold water and dried in air. Step 2: TCTas dehydrocyclization reagent: In a 25 mL round
flask, a mixture of a carbamate derivative 3 (1 mmol), TCT (1 mmol), triethylamine (1 mmol) and PEG-400 (0.5 mL) was stirred at room
temperature. The reaction was completed immediately. The mixture was washed with cold water (three times) and dried in air. The
benzoxazine-4-ones 4 may be recrystallized from n-hexane/THF, if needed. Step 2: DCC as dehydrocyclization reagent: In a 25 mL round
flask, a mixture of a carbamate derivative 3 (1 mmol), DCC (1 mmol), triethylamine (1 mmol) and PEG-400 (0.5 mL) was stirred at room
temperature. The reaction was completed immediately. The mixture was poured onto cold water and extracted with CHCl3. The organic layer
was separated, dried over MgSO4, and then, the solvent was removed under reduced pressure. The benzoxazine-4-ones 4 may be recrystallized
from n-hexane/THF, if needed. 2-Ethoxy-(4H)-3,1-benzoxazine-4-one (4a): White solid, mp: 87–89 8C (Lit. 88–90 8C) [6,8]. 2-Ethoxy-6,7-
dimethoxy-(4H)-3,1-benzoxazine-4-one (4b): White solid, mp: 164–166 8C (Lit. 155–156 8C) [5,8a]. IR (KBr): y (cmꢀ1) = 1747 (C O), 1630
(C N). 1H NMR (250 MHz in CDCl3): d 7.37 (s, 1H–Ar), 6.80 (s, 1H–Ar), 4.43 (q, 2H, 3JHH = 6.7 Hz, CH2), 3.95 and 3.90 (2s, 6H, OCH3),
1.41 (t, 3H, 3JHH = 6.7, CH3). 13C NMR (62.5 MHz in CDCl3): d 159.3, 156.7, 154.5, 147.7, 144.8, 107.8, 106.4, 106.3, 65.7, 56.4, 56.2, 14.0.
EI-MS (70 eV): m/z (%) 251 (M+ꢁ, 100). 2-Ethoxy-5-methyl-(4H)-3,1-benzoxazine-4-one (4c): White solid, mp: 102–104 8C (Lit. 104–105 8C)
[5,8a]. 6-Chloro-2-ethoxy-(4H)-3,1-benzoxazine-4-one (4d): white solid, mp: 83–85 8C. IR (KBr): y (cmꢀ1) = 1778 (C O), 1638 (C N). 1H
NMR (250 MHz in CDCl3): d 7.98 (s, 1H–Ar), 7.60 (d, 3JHH = 8.5 Hz, 1H–Ar), 7.31 (d, 3JHH = 8.5 Hz, 1H–Ar), 4.48 (q, 2H, 3JHH = 7.0 Hz,
CH2), 1.43 (t, 3H, 3JHH = 7.0 Hz, CH3). 13C NMR (62.5 MHz in CDCl3): d 158.4, 154.6, 146.8, 136.9, 131.1, 128.0, 126.8, 115.4, 66.3, 14.0.
EI-MS (70 eV): m/z (%) 225 (M+ꢁ, 56), 227 [(M+ꢁ + 2), 18]. 6-Bromo-2-ethoxy-(4H)-3,1-benzoxazine-4-one (4e): White solid, mp: 85–87 8C
(Lit. 87–89 8C) [5]. 7-Chloro-2-ethoxy-(4H)-3,1-benzoxazine-4-one (4f): White solid, mp: 80–82 8C. IR (KBr): y (cmꢀ1) = 1780 (C O), 1622
3
4
3
(C N). 1H NMR (250 MHz in CDCl3): d 7.99 (d, JHH = 8.5 Hz, 1H–Ar), 7.37 (d, JHH = 1.5 Hz, 1H–Ar), 7.26 (dd, JHH = 8.5 Hz,
4JHH = 1.5 Hz, 1H–Ar), 4.49 (q, 2H, 3JHH = 7.2 Hz, CH2), 1.43 (t, 3H, 3JHH = 7.2 Hz, CH3). 13C NMR (62.5 MHz in CDCl3): d 158.7, 155.3,
149.4, 143.1, 130.1, 126.4, 125.1, 112.7, 66.4, 14.0. EI-MS (70 eV): m/z (%) 225 (M+ꢁ, 38), 227 [(M+ꢁ + 2), 13]. 2-Ethoxy-6-(ethyl carbonato)-
(4H)-3,1-benzoxazine-4-one (4g): White solid, mp: 69–71 8C. IR (KBr): y (cmꢀ1) = 1772 (C O), 1732 (C O), 1633 (C N). 1H NMR
(250 MHz in CDCl3): d 8.43 (s, 1H–Ar), 7.72 (d, 3JHH = 7.5 Hz, 1H–Ar), 7.44 (d, 3JHH = 7.5 Hz, 1H–Ar), 4.33-4.22 (m, 4H, 2CH2), 1.45–1.32
(m, 6H, 2CH3). 13C NMR (62.5 MHz in CDCl3): d 158.6, 154.6, 154.5, 140.2, 139.8, 132.5, 126.0 (2C), 118.2, 63.7, 63.5, 14.6, 14.0. EI-MS
(70 eV): m/z (%) 279 (M+ꢁ, 16).