G. Laus et al. · Benzoxazolinones
485
J = 7.9 Hz, J = 1.6 Hz, 1H), 7.77 (dd, J = 7.9 Hz, J = 1.5 Hz, gen pressure for 4 h using 5 % Pd/C (450 mg) as catalyst.
1H), 11.44 (s, 1H). – 13C NMR (75 MHz, CDCl3): δ = 112.0, The mixture was filtered and the solvent evaporated. The
114.9, 120.6, 129.6, 140.8, 158.9, 176.9. – IR (neat): ν = brown residue was redissolved in hot ethanol (10 mL), water
2190 m, 2141 m, 1638 s, 1596 m, 1444 m, 1237 s, 1172 s, (30 mL) was added, and the solution was cooled to 0 ◦C. The
1128 s, 835 m, 741 s, 712 s cm−1
.
off-white precipitate was collected by filtration and dried in
vacuum. Yield: 3.6 g (97 %). After treatment with charcoal
and filtration, single crystals were obtained by slow evapo-
ration of a solution in MeOH at r. t. Th◦e crystalline hemihy-
drate lost H2O between 75 and 100 C and was converted
into the anhydrous form (see below). – 1H NMR (300 MHz,
[D6]DMSO): δ = 5.31 (s, 2H), 6.26 (d, J = 7.6 Hz, 1H), 6.37
(d, J = 8.1 Hz, 1H), 6.80 (t, J = 7.9 Hz, 1H), 11.3 (br s,
1H). – 13C NMR (75 MHz, [D6]DMSO): δ = 97.6, 108.9,
124.1, 130.2, 130.6, 132.1, 154.6. – IR (neat): ν = 3368 m,
3292 w, 3183 m, 2814 w, 2740 w, 2665 w, 1744 s, 1650 m,
1510 m, 1475 m, 1409 m, 1288 m, 1201 m, 1137 m, 931 m,
2-Hydroxy-3-nitrobenzoyl azide (3b)
Single crystals were obtained from◦acetone/heptane solu-
tion. Yield: 2.0 g (96 %). M. p. 110 C (dec.). – 1H NMR
(300 MHz, CDCl3): δ = 7.03 (t, J = 8.1 Hz, 1H), 8.10 (dd,
J = 7.9 Hz, J = 1.7 Hz, 1H), 8.22 (dd, J = 8.2 Hz, J = 1.7 Hz,
1H), 11.94 (br s, 1H). – 13C NMR (75 MHz, CDCl3): δ =
117.2, 119.1, 132.9, 136.3, 138.3, 156.3, 175.8. – IR (neat):
ν = 2211 m, 2149 m, 1650 m, 1587 m, 1522 s, 1341 s, 1258 s,
1157 s, 1036 s, 800 s, 746 s, 716 s cm−1
.
866 m, 825 m, 768 m, 727 s, 634 m, 601 m, 576 m cm−1
.
7-Bromobenz[d]oxazolin-2-one (4a)
Anhydrous 7-aminobenz[d]oxazolin-2-one (5)
A solution of azide 3a (9.7 g, 40 mmol) in acetone
(200 mL) was refluxed for 3 d. The solvent was evapo-
rated, tolue◦ne (50 mL) was added, and the mixture was
stirred at 0 C. The crystalline product was collected by fil-
tration, washed with toluene, and dried. Yield: 6.1 g (71 %).
M. p. 244 ◦C. – 1H NMR (300 MHz, [D6]DMSO): δ =
7.07 (d, J = 4.7 Hz, 2H), 7.26 (m, 1H), 11.94 (s, 1H). –
13C NMR (75 MHz, [D6]DMSO): δ = 100.8, 109.2, 124.5,
125.3, 131.4, 141.2, 153.3. – IR (neat): ν = 3084 m, 3010 m,
2880 m, 2795 m, 2722 m, 2666 m, 1717 s, 1617 m, 1480 m,
1450 m, 1399 m, 1301 m, 1264 m, 1209 m, 1159 m, 1129 m,
1048 m, 959 m, 927 m, 866 m, 770 s, 726 s, 593 s, 527
s cm−1. – C7H4BrNO2 (214.02): calcd. C 39.28, H 1.88,
N 6.54; found C 39.28, H 1.77, N 6.40.
Single crystals of the anhydrate 5 were obtained from a
solution of the hemihydrate in MeOH at −20 ◦C. NMR spec-
tra were identical to those of the hemihydrate. M. p. 185 ◦C. –
IR (neat): ν = 3408 w, 3372 w, 3328 w, 3115 w, 2827 w,
2749 w, 2678 w, 1755 m, 1705 m, 1657 m, 1622 m, 1511 m,
1474 m, 1414 m, 1291 m, 1209 m, 1157 m, 1140 m, 936 m,
765 m, 631 s, 584 s cm−1
.
3-(2-Hydroxy-3-nitrophenyl)-8-nitrobenz[e][1,3]oxazine-
2,4-dione (6)
Single crystals of 6 were obtained from the mother liquor
of 4b. M. p. 220 ◦C. – 1H NMR (300 MHz, [D6]DMSO): δ =
7.14 (t, J = 8.1 Hz, 1H), 7.67 (dd, J = 7.8 Hz, J = 1.6 Hz, 1H),
7.68 (t, J = 7.9 Hz, 1H), 8.00 (dd, J = 8.2 Hz, J = 1.5 Hz, 1H),
8.36 (dd, J = 7.8 Hz, J = 1.4 Hz, 1H), 8.56 (dd, J = 8.1 Hz,
J = 1.4 Hz, 1H), 11.1 (br s, 1H). – IR (neat): 1770 m, 1720 s,
7-Nitrobenz[d]oxazolin-2-one (4b)
A solution of azide 3b (10.4 g, 50 mmol) in toluene
(200 mL) was stirred at 60 ◦C for 8 h. The product was
1614 m, 1536 s, 1249 s cm−1
.
collected by filtration and dried ◦to yield 4b as fine yellow
1
needles (5.7 g, 63 %). M. p. 233 C. – H NMR (300 MHz, 2-Hydroxy-N-(2-hydroxy-3-nitrophenyl)-3-nitrobenzamide
[D6]DMSO): δ = 7.34 (dd, J = 8.5 Hz, J = 7.9 Hz, 1H), (7)
7.48 (dd, J = 7.8 Hz, J = 1.0 Hz, 1H), 7.82 (dd, J = 8.6 Hz,
A solution of azide 3b (5.6 g, 27 mmol) in toluene
(30 mL) was stirred at 60 ◦C for 48 h. The major prod-
uct 4b was removed by filtration, and the filtrate was taken
to dryness. The oily residue was stirred with aqueous ace-
tone (30 mL) to give yellow crystals of the benzamide 7.
J = 1.0 Hz, 1H), 12.3 (br s, 1H). – 13C NMR (75 MHz,
[D6]DMSO): δ = 115.9, 116.8, 123.9, 131.3, 133.3, 137.6,
153.6. – IR (neat): ν = 3276 w, 3236 w, 3085 w, 3066 w,
2887 w, 2807 w, 2740 w, 2653 w, 1777 m, 1741 m, 1526 s,
1483 m, 1466 m, 1347 s, 1327 m, 1295 m, 1258 m, 1222 m,
1148 m, 1062 m, 910 m, 868 m, 815 s, 736 s, 636 s,
595 s cm−1. – C7H4N2O4 (180.12): calcd. C 46.68, H 2.24,
N 15.55; found C 46.73, H 2.10, N 15.22.
◦
Yield: 0.60 g (14 %). M. p. 246 C. – 1H NMR (300 MHz,
[D6]DMSO): δ = 7.08 (t, J = 8.1 Hz, 1H), 7.13 (t, J = 7.7 Hz,
1H), 7.81 (d, J = 8.3 Hz, 1H), 8.13 (d, J = 8.5 Hz, 1H),
8.16 (d, J = 9.0 Hz, 1H), 8.33 (d, J = 7.4 Hz, 1H), 11.06 (s,
1H). – 13C NMR (75 MHz, [D6]DMSO): δ = 118.6, 119.3,
120.7, 121.5, 128.3, 129.4, 130.0, 135.0, 137.2, 138.7, 145.2,
1
7-Aminobenz[d]oxazolin-2-one hemihydrate (5 · /2 H O)
2
A solution of the nitro compound 4b (5◦.0 g, 23 mmol) 153.0, 165.6. – IR (neat): ν = 3315 w, 3250 w, 3165 w,
in EtOH (250 mL) was hydrogenated at 60 C/4 bar hydro- 1667 m, 1602 m, 1588 m, 1519 s, 1446 s, 1344 m, 1267 s,
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