3.3. Representative Procedure under Microwave Conditions. Method 2
A solution of the anthranilic acid (1.0 mmol) in the orthoester (0.45 mL, 2.0–2.7 equivalents) was prepared in a 5-mL microwave tube and stirred for 30 s prior to irradiation at the "high absorption" setting. The reaction was performed under N2 at 100 °C (400 W) for 0.75–3 h. Upon cooling, the crude product crystallized from the reaction mixture and was purified by trituration from 5% ether in pentane.
The following compounds were prepared:
2-Methyl-4H-benzo[d][1,3]
oxazin-4-one (
11a): 130 mg (81%, method 1) and 132 mg (82%, method 2) as white crystals, m.p. 79–80 °C (ref. [
8] 80–81 °C); IR (thin film): 1700, 1624 cm
−1;
1H-NMR (400 MHz, CDCl
3): δ 8.29 (dd, 1H,
J = 7.5, 1.6 Hz, ArH), 7.78 (ddd, 1H,
J = 8.4, 7.1, 1.6 Hz, ArH), 7.69 (d, 1H,
J = 8.4 Hz, ArH), 7.48 (ddd, 1H,
J = 8.1, 7.1, 1.2 Hz, ArH), 2.60 (s, 3H, CH
3);
13C-NMR (101 MHz, CDCl
3): δ 164.1, 153.2, 149.4, 134.9, 127.0, 126.5, 126.3, 120.3, 22.2; HRMS (ESI):
m/z [M + H]
+ calcd. for C
9H
7NO
2: 162.0555, found: 162.0553.
2-Ethyl-4H-benzo[d][1,3]
oxazin-4-one (
11b): 140 mg (80%, method 1) and 145 mg (83%, method 2) as white crystals, m.p. 83–84 °C (ref. [
8] m.p. 85–86
oC); IR (thin film): 1750, 1645 cm
−1;
1H-NMR (400 MHz, CDCl
3): δ 8.20 (dd, 1H,
J = 7.9, 1.5 Hz, ArH), 7.80 (ddd, 1H,
J = 8.4, 7.5, 1.5 Hz, ArH), 7.57 (d, 1,
J = 8.4 Hz, ArH), 7.50 (ddd, 1H,
J = 8.2, 7.5, 1.2 Hz, ArH), 2.73 (q, 2H,
J = 7.5 Hz, CH
2CH
3), 1.37 (t, 3H,
J = 7.5 Hz, CH
2CH
3);
13C-NMR (101 MHz, CDCl
3): δ 163.9, 159.9, 146.5, 136.5, 128.4, 128.1, 126.6, 116.9, 28.2, 10.3; HRMS (ESI):
m/z [M + H]
+ calcd. for C
10H
9NO
2: 176.0712, found: 176.0713.
2-Phenyl-4H-benzo[d][1,3]
oxazin-4-one (
11d): 174 mg (78%, method 1) and 179 mg (80%, method 2) as off-white crystals, m.p. 121–122 °C (ref. [
8] m.p. 123 °C); IR (thin film): 1762, 1615 cm
−1;
1H-NMR (400 MHz, CDCl
3): δ 8.34-8.30 (complex, 2H, ArH), 8.25 (dd, 1H,
J = 7.9, 1.5, ArH), 7.84 (ddd, 1H,
J = 8.1, 7.3, 1.5 Hz, ArH), 7.70 (d,
J = 8.1 Hz, ArH), 7.62-7.48 (complex, 4H, ArH);
13C-NMR (101 MHz, CDCl
3): δ 159.6, 157.1, 147.0, 136.6, 132.6, 130.3, 128.8, 128.6, 128.32, 128.26, 127.2, 117.0; HRMS (ESI):
m/z [M + H]
+ calcd. for C
14H
9NO
2: 224.0712, found: 224.0709.
2,6-Dimethyl-4H-benzo[d][1,3]oxazin-4-one (12a): 119 mg (68%, method 2) as off-white crystals, m.p. 122–123 °C; IR (thin film): 1682, 1595 cm−1; 1H-NMR (400 MHz, CDCl3): δ 7.98 (s, 1H, ArH), 7.61 (d, 1H, J = 8.2 Hz, ArH), 7.44 (d, 1H, J = 8.2 Hz, ArH), 2.47 (s, 3H, CH3), 2.45 (s, 3H, CH3); 13C-NMR (101 MHz, CDCl3): δ 159.9, 159.4, 144.3, 138.5, 137.7, 128.0, 126.2, 116.3, 21.3, 21.2; HRMS (ESI): m/z [M + H]+ calcd. for C10H9NO2: 176.0712, found: 176.0709.
2-Ethyl-6-methyl-4H-benzo[d][1,3]oxazin-4-one (12b): 125 mg (66%, method 2) as white crystals, m.p. 103–104 °C; IR (thin film): 1686, 1596 cm−1; 1H-NMR (400 MHz, CDCl3): δ 7.98 (s, 1H, ArH), 7.60 (d, 1H, J = 8.2 Hz, ArH), 7.46 (d, 1H, J = 8.2 Hz, ArH), 2.71 (q, 2H, J = 7.5 Hz, CH2CH3), 2.47 (s, 3H, ArCH3), 1.36 (t, 3H, J = 7.5 Hz, CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 163.1, 160.1, 144.3, 138.4, 137.7, 128.0, 126.4, 116.5, 26.1, 21.2, 10.3; HRMS (ESI): m/z [M + H]+ calcd. for C11H11NO2: 190.0868, found: 190.0865.
6-Methyl-2-phenyl-4H-benzo[d][1,3]oxazin-4-one (12d): 202 mg (85%, method 2) as off-white crystals, m.p. 144–145 °C; IR (thin film): 1752, 1607 cm−1; 1H-NMR (400 MHz, CDCl3): δ 8.29 (d, 2H, J = 8.2 Hz, ArH), 8.04 (s, 1H, ArH), 7.66-7.47 (complex, 5H, ArH), 2.49 (s, 3H, ArCH3); 13C-NMR (101 MHz, CDCl3): δ 159.8, 156.4, 144.8, 138.7, 137.8, 132.4, 130.4, 128.7, 128.19, 128.17, 127.0, 116.7, 21.2; HRMS (ESI): m/z [M + H]+ for C15H11NO2: 238.0868, found: 238.0870.
7-Methoxy-2-methyl-4H-benzo[d][1,3]oxazin-4-one (13a): 166 mg (87%, method 1) and 168 mg (88%, method 2) as light yellow crystals, m.p. 119–120 °C; IR (nujol): 2830, 1747, 1610 cm−1; 1H-NMR (400 MHz, DMSO-d6): δ 8.00 (d, 1H, J = 8.8 Hz, ArH), 7.14 (dd, 1H, J = 8.8, 2.5 Hz, ArH), 7.05 (d, 1H, J = 2.5 Hz, ArH), 3.91 (s, 3H, OCH3), 2.38 (s, 3H, CH3); 13C-NMR (101 MHz, DMSO-d6): δ 166.3, 161.5, 159.2, 149.0, 130.2, 117.1, 109.5, 109.1, 56.5, 21.5; HRMS (ESI): m/z [M + H]+ calcd. for C10H9NO3: 192.0661, found: 192.0659.
2-Ethyl-7-methoxy-4H-benzo[d][1,3]oxazin-4-one (13b): 176 mg (86%, method 1) and 181 mg (88%, method 2) as light yellow crystals, m.p. 89–90 °C; IR (nujol): 2840, 1767, 1644, 1609 cm−1; 1H-NMR (400 MHz, DMSO-d6): δ 7.99 (d, 1H, J = 8.8 Hz, ArH) 7.14 (dd, 1H, J = 8.8, 2.5 Hz, ArH), 7.07 (d, 1H, J = 2.5 Hz, ArH), 3.92 (s, 3H, OCH3), 2.68 (q, 2H, J = 7.5 Hz, CH2CH3), 1.24 (t, 3H, J = 7.5 Hz, CH2CH3); 13C-NMR (101 MHz, DMSO-d6): δ 166.3, 164.9, 159.2, 149.0, 130.1, 117.3, 109.7, 109.1, 56.6, 27.7, 10.2; HRMS (ESI): m/z [M + H]+ calcd. for C11H11NO3: 206.0817, found: 206.0817.
7-Methoxy-2-propyl-4H-benzo[d][1,3]oxazin-4-one (13c): 189 mg (86%, method 1) and 191 mg (87%, method 2) as light yellow crystals, m.p. 77–78 °C; IR (nujol): 2841, 1766, 1643, 1609 cm−1; 1H-NMR (400 MHz, DMSO-d6): δ 8.00 (d, 1H, J = 8.8 Hz, ArH), 7.14 (dd, 1H, J = 8.8, 2.5 Hz, ArH), 7.07 (d, 1H, J = 2.5 Hz, ArH), 3.92 (s, 3H, OCH3), 2.63 (t, 2H, J = 7.4 Hz, CH2CH2CH3), 1.75 (sextet, 2H, J = 7.4 Hz, CH2CH2CH3); 0.98 (t, 3H, J = 7.4 Hz, CH2CH2CH3); 13C-NMR (101 MHz, DMSO-d6): δ 166.3, 163.9, 159.2, 148.9, 130.1, 117.3, 109.7, 109.1, 56.6, 36.2, 19.2, 13.9; HRMS (ESI): m/z [M + H]+ calcd. for C12H13NO3: 220.0974, found: 220.0971.
7-Methoxy-2-phenyl-4H-benzo[d][1,3]oxazin-4-one (13d): 210 mg (83%, method 1) and 215 mg (85%, method 2) as light yellow crystals, m.p. 149–150 °C; IR (nujol): 2842, 1744, 1607 cm−1; 1H-NMR (400 MHz, DMSO-d6): δ 8.17 (d, 2H, J = 8.1 Hz, ArH), 8.03 (d, 1H, J = 9.4 Hz, ArH), 7.67 (d, 1H, J = 7.3 Hz, ArH), 7.59 (t, 2H, J = 8.1 Hz, ArH), 7.15 (m, 2H, ArH), 3.94 (s, 3H, OCH3); 13C-NMR (101 MHz, DMSO-d6): δ 166.4, 158.8, 157.6, 149.2, 133.2, 130.5, 130.3, 129.4, 128.3, 117.6, 109.9, 109.6, 56.6; HRMS (ESI): m/z [M + H]+ calcd. for C15H11NO3: 254.0817, found: 254.0814.
7-Nitro-2-phenyl-4H-benzo[d][1,3]oxazin-4-one (14d): 244 mg (91%, method 2) as light orange crystals, m.p. 175–176 °C; IR (thin film): 1757, 1629, 1608, 1530, 1349 cm−1; 1H-NMR (400 MHz, CDCl3): δ 8.52 (d, 1H, J = 2.2 Hz, ArH), 8.41 (d, 1H, J = 8.6 Hz, ArH), 8.33 (d, 2H, J = 7.4 Hz, ArH), 8.29 (dd, 1H, J = 8.6, 2.2 Hz, ArH), 7.64 (t, 1H, J = 7.4 Hz, ArH), 7.55 (t, 2H, J = 7.4 Hz, ArH); 13C-NMR (101 MHz, CDCl3): δ 159.0, 157.9, 152.9, 148.1, 133.6, 130.4, 129.3, 129.0, 128.7, 122.5, 122.0, 121.3; HRMS (ESI): m/z [M + H]+ calcd. for C14H8N2O4: 269.0562, found: 269.0558.
7-Chloro-2-methyl-4H-benzo[d][1,3]oxazin-4-one (15a): 166 mg (85%, method 2) as white crystals, m.p. 149–150 °C; IR (thin film): 1762, 1696, 1642, 1596 cm−1; 1H-NMR (400 MHz, CDCl3): δ 8.11 (d, 1H, J = 8.4 Hz, ArH), 7.54 (d, 1H, J = 2.0 Hz, ArH), 7.46 (dd, 1H, J = 8.4, 2.0 Hz, ArH), 2.47 (s, 3H CH3); 13C-NMR (101 MHz, CDCl3): δ 161.6, 158.9, 147.5, 142.9, 129.7, 128.8, 126.3, 115.1, 21.4; HRMS (ESI): m/z [M + H]+ calcd. for C9H635ClNO2: 196.0165, found: 196.0166.
7-Chloro-2-phenyl-4H-benzo[d][1,3]oxazin-4-one (15d): 237 mg (92%, method 2) as off-white crystals, m.p. 188–189 °C; IR (thin film): 1760, 1619, 1596 cm−1; 1H-NMR (400 MHz, CDCl3): δ 8.31 (d, 2H, J = 7.4 Hz, ArH), 8.17 (d, 1H, J = 8.4 Hz, ArH), 7.70 (d, 1H, J = 2.0 Hz, ArH), 7.60 (tt, 1H, J = 7.4, 1.4 Hz, ArH), 7.52 (t, 2H, J = 7.4 Hz, ArH), 7.48 (dd, 1H, J = 8.4, 2.0 Hz, ArH); 13C-NMR (101 MHz, CDCl3): δ 158.8, 158.3, 148.1, 143.0, 133.0, 129.9, 129.86, 128.83, 128.79, 128.5, 127.0, 115.4; HRMS (ESI): m/z [M + H]+ calcd. for C14H835ClNO2: 258.0322, found: 258.0317.
(±)-2-Ethoxy-2-phenyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (17d): 232 mg (86%, method 1) as white crystals, m.p. 92–93 °C; IR (thin film): 3254, 1668, 1595 cm−1; 1H-NMR (400 MHz, CDCl3): δ 12.09 (br s, 1H, NH), 8.94 (dd, 1H, J = 8.5, 1.1 Hz), ArH), 8.1 (dd, 1H, J = 8.0, 1.7 Hz, ArH), 8.06 (dd, 2H, J = 7.8, 1.5 Hz, ArH), 7.64-7.49 (complex, 4H, ArH), 7.13 (td, 1H, J = 7.4, 1.2 Hz, ArH), 4.43 (q, 2H, J = 7.1 Hz, OCH2CH3), 1.43 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 168.6, 165.4, 141.9, 134.9, 134.7, 131.9, 130.9, 128.8, 127.4, 122.6, 120.5, 115.5, 61.5, 14.2; HRMS (ESI): m/z [M + H]+ calcd. for C16H15NO2: 254.1181, found: 254.1177.
(±)-2-Ethoxy-2,6-dimethyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (18a): 195 mg (88%, method 1) as white crystals, m.p. 110–111 °C; IR (thin film): 3266, 1677, 1595 cm−1; 1H-NMR (400 MHz, CDCl3): δ 10.97 (br s, 1H, NH), 8.57 (d, 1H, J = 8.6 Hz, ArH), 7.83 (s, 1H, ArH), 7.34 (d, 1H, J = 8.6 Hz, ArH), 4.37 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.33 (s, 3H, ArCH3), 2.22 (s, 3H, CH3), 1.42 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 168.9, 168.4, 139.2, 135.3, 131.9, 130.8, 120.3, 115.0, 61.3, 25.5, 20.7, 14.2; HRMS (ESI): m/z [M + H]+ calcd. for C12H15NO3: 222.1130, found: 222.1128.
(±)2-Ethoxy-2-ethyl-6-methyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (18b): 205 mg (87%, method 1) as white crystals, m.p. 78–79 °C; IR (thin film): 3261, 1677, 1596 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.0 (br s, 1H, NH), 8.62 (d, 1H, J = 8.6 Hz, ArH), 7.83 (s, 1H, ArH), 7.34 (d, 1H, J = 8.6 Hz, ArH), 4.37 (q, 2H, J = 7.0 Hz, OCH2CH3), 2.46 (q, 2H, J = 7.5 Hz, CH2CH3), 2.33 (s, 3H, ArCH3), 1.42 (t, 3H, J = 7.0 Hz, OCH2CH3), 1.27 (t, 3H, J = 7.5 Hz, CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 172.7, 168.4, 139.4, 135.3, 131.7, 130.8, 120.3, 114.9, 61.3, 31.7, 20.7, 14.2, 9.7; HRMS (ESI): m/z [M + H]+ calcd. for C13H17NO3: 236.1287, found: 236.1284.
(±)-2-Ethoxy-6-methyl-2-propyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (18c): 219 mg (88%, method 1) and 222 mg (89%, method 2) as off-white crystals, m.p. 39–40 °C; IR (thin film): 3265, 1682, 1599 cm−1; 1H-NMR (400 MHz, CDCl3): δ 10.98 (br s, 1H, NH), 8.62 (d, 1H, J = 8.6 Hz, ArH), 7.83 (s, 1H, ArH), 7.35 (d, 1H, J = 8.6 Hz, ArH), 4.38 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.41 (q, 2H, J = 7.5 Hz, CH2CH2CH3), 2.33 (s, 3H, ArCH3), 1.78 (sextet, 2H, J = 7.5 Hz, CH2CH2CH3), 1.42 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.01 (t, 3H, J = 7.5 Hz, CH2CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 171.9, 168.4, 139.3, 135.3, 131.7, 130.8, 120.3, 114.9, 61.3, 40.6, 20.7, 19.0, 14.2, 13.8; HRMS (ESI): m/z [M + H]+ calcd. for C14H19NO3: 250.1443, found: 250.1441.
(±)-2-Ethoxy-6-methyl-2-phenyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (18d): 249 mg (88%, method 1) as white crystals, m.p. 117–118 °C; IR (thin film): 3249, 1662, 1602 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.98 (br s, 1H, NH), 8.82 (d, 1H, J = 8.5 Hz, ArH), 8.05 (d, 2H, J = 6.8 Hz, ArH), 7.89 (s, 1H, ArH), 7.58-7.47 (complex, 3H), 7.42 (d, 1H, J = 8.5 Hz, ArH), 4.42 (q, 2H, J = 7.1 Hz, OCH2CH3), 3.36 (s, 3H, ArCH3), 1.44 (q, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 168.9, 165.5, 139.5, 135.4, 135.1, 132.1, 131.8, 131.0, 128.8, 127.3, 120.4, 115.4, 61.5, 20.8, 14.3; HRMS (ESI): m/z [M + H]+ calcd. for C17H17NO3: 284.1287, found: 284.1283.
(±)-2-Ethoxy-2-methyl-7-nitro-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (20a): 212 mg (84%, method 1) and 219 mg (87%, method 2) as light tan crystals, m.p. 108–109 °C; IR (thin film): 3270, 1702, 1604, 1538, 1350 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.16 (br s, 1H, NH), 9.60 (d, 1H, J = 2.4 Hz, ArH), 8.20 (d, 1H, J = 8.8 Hz, ArH), 7.87 (dd, 1H, J = 8.8, 2.4 Hz, ArH), 4.45 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.28 (s, 3H, CH3), 1.46 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 169.2, 166.9, 151.2, 142.2, 131.9, 119.3, 116.4, 115.2, 62.5, 25.5, 14.1; HRMS (ESI): m/z [M + H]+ calcd. for C11H12N2O5: 253.0825, found: 253.0824.
(±)-2-Ethoxy-2-ethyl-7-nitro-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (20b): 229 mg (86%, method 1) and 234 mg (88%, method 2) as light tan crystals, m.p. 74–75 °C; IR (thin film): 3273, 1694, 1600, 1538, 1349 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.18 (br s, 1H, NH), 9.65 (d, 1H, J = 2.4 Hz, ArH), 8.20 (d, 1H, J = 8.8 Hz, ArH), 7.86 (dd, 1H, J = 8.8, 2.4 Hz, ArH), 4.45 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.53 (q, 2H, J = 7.5 Hz, CH2CH3), 1.46 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.30 (t, 3H, J = 7.5 Hz, CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 173.1, 166.9, 151.2, 142.5, 131.9, 119.3, 116.3, 115.3, 62.4, 31.6, 14.1, 9.3; HRMS (ESI): m/z [M + H]+ calcd. for C12H14N2O5: 267.0981, found: 267.0977.
(±)-2-Ethoxy-2-propyl-7-nitro-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (20c): 238 mg (85%, method 1) and 245 mg (88%, method 2) as light tan crystals, m.p. 66–67 °C; IR (thin film): 3270, 1697, 1604, 1538, 1349 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.17 (br s, 1H, NH), 9.65 (d, 1H, J = 2.4 Hz, ArH), 8.20 (d, 1H, J = 8.8 Hz, ArH), 7.86 (dd, 1H, J = 8.8, 2.4 Hz, ArH), 4.45 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.47 (q, 2H, J = 7.4 Hz, CH2CH2CH3), 1.81 (sextet, 2H, J = 7.4 Hz, CH2CH2CH3), 1.46 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.04 (t, 3H, J = 7.4 Hz, CH2CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 172.3, 166.9, 151.2, 142.5, 131.9, 119.3, 116.3, 115.3, 62.4, 40.4, 18.8, 14.1, 13.7; HRMS (ESI): m/z [M + H]+ calcd. for C13H16N2O5: 281.1138, found: 281.1140.
(±)-2-Ethoxy-7-nitro-2-phenyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (20d): 283 mg (90%, method 1) as off-white crystals, m.p. 180–181 °C; IR (thin film): 3257, 1673, 1651, 1600, 1538, 1346 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.62 (br s, 1H, NH), 9.31 (d, 1H, J = 2.4 Hz, ArH), 8.20 (d, 1H, J = 8.8 Hz, ArH), 8.03 (dd, 1H, J = 8.8, 2.4 Hz, ArH), 7.97 (d, 2H, J = 7.4 Hz, ArH, 7.69 (t, 1H, J = 7.4 Hz, ArH), 7.61 (t, 2H, J = 7.4 Hz, ArH), 4.38 (q, 2H, J = 7.1 Hz, OCH2CH3), 1.33 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 166.7, 165.7, 150.6, 141.0, 134.1, 133.1, 132.7, 129.5, 127.7, 1239, 118.2, 116.0, 62.6, 14.3; HRMS (ESI): m/z [M + H]+ calcd. for C16H14N2O5: 315.0981, found: 315.0975.
(±)-7-Chloro-2-ethoxy-2-methyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (21a): 203 mg (84%, method 1) as white crystals, m.p. 75–76 °C; IR (thin film): 3262, 1681, 1578 cm−1; 1H-NMR (400 MHz, CDCl3): δ 10.70 (br s, 1H, NH), 8.43 (d, 1H, J = 2.2 Hz, ArH), 7.92 (d, 1H, J = 8.6 Hz, ArH), 7.23 (dd, 1H, J = 8.6, 2.2 Hz, ArH), 4.83 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.15 (s, 3H, CH3), 1.34 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 169.1, 167.7, 142.4, 140.8, 131.8, 122.6, 120.1, 113.2, 61.6, 25.5, 14.2; HRMS (ESI): m/z [M + H]+ calcd. for C11H1235ClNO3: 242.0584, found: 242.0582.
(±)-7-Chloro-2-ethoxy-2-ethyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (21b): 215 mg (84%, method 1) and 220 mg (86%, method 2) as white crystals, m.p. 69–70 °C; IR (thin film): 3238, 1685, 1581 cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.17 (br s, 1H, NH), 8.86 (d, 1H, J = 2.2 Hz, ArH), 7.96 (d, 1H, J = 8.6 Hz, ArH), 7.04 (dd, 1H, J = 8.6, 2.2 Hz, ArH), 4.38 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.48 (q, 2H, J = 7.5 Hz, CH2CH3), 1.41 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.27 (t, 3H, J = 7.5 Hz, CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 173.0, 167.8, 142.6, 140.9, 131.8, 122.5, 120.2, 113.2, 61.6, 31.7, 14.2, 9.5; HRMS (ESI): m/z [M + H]+ calcd. for C12H1435ClNO3: 256.0741, found: 256.0743.
(±)-7-Chloro-2-ethoxy-2-propyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (21c): 224 mg (83%, method 1) and 227 mg (84%, method 2) as white semisolid, m.p. 25–26 °C; IR (thin film): 3280, 1691, 1581cm−1; 1H-NMR (400 MHz, CDCl3): δ 11.16 (br s, 1H, NH), 8.85 (s, 1H, ArH), 7.96 (d, 1H, J = 8.6 Hz, ArH), 7.04 (dd, 1H, J = 8.6, 2.2 Hz, ArH), 4.38 (q, 2H, J = 7.1 Hz, OCH2CH3), 2.42 (q, 2H, J = 7.4 Hz, CH2CH2CH3), 1.78 (sextet, 2H, J = 7.4 Hz, CH2CH2CH3), 1.42 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.02 (t, 3H, J = 7.4 Hz, CH2CH2CH3); 13C-NMR (101 MHz, CDCl3): δ 172.2, 167.7, 142.5, 140.8, 131.8, 122.5, 120.2, 113.2, 61.6, 40.5, 18.9, 14.2, 13.2; HRMS (ESI): m/z [M + H]+ calcd. for C13H1635ClNO3: 270.0897, found: 270.0893.
(±)-7-Chloro-2-ethoxy-2-phenyl-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (21d): 258 mg (85%, method 1) as white crystals, m.p. 128–129 °C; IR (thin film): 3241, 1673, 1585 cm−1; 1H-NMR (400 MHz, CDCl3): δ 12.13 (br s, 1H, NH), 9.05 (d, 1H, J = 2.1 Hz, ArH), 8.03 (overlapping signals, apparent t, 3H, J ≈ 8.4 Hz, ArH), 7.60-7.49 (complex, 3H, ArH), 7.08 (dd, 1H, J = 8.6, 2.1 Hz, ArH), 4.42 (q, 2H, J = 7.1 Hz, OCH2CH3), 1.43 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 168.1, 165.7, 142.7, 141.0, 134.4, 132.2, 132.0, 128.9, 127.4, 122.8, 120.3, 113.6, 61.8, 14.2; HRMS (ESI): m/z [M + H]+ calcd. for C16H1435ClNO3: 304.0741, found: 304.0737.
(±)-2-Ethoxy-2-methyl-1,2-dihydro-4H-pyrido[2,3-d][1,3]oxazin-4-one (22a): 177 mg (85%, method 1) as white crystals, m.p. 55–56 °C; IR (thin film): 3270, 1680, 1589 cm−1; 1H-NMR (400 MHz, CDCl3): δ 10.79 (br s, 1H, NH), 8.59 (dd, 1H, J = 4.8, 2.0 Hz, PyH), 8.33 (dd, 1H, J = 7.9, 2.0 Hz, PyH), 7.06 (dd, 1H, J = 7.9, 4.8 Hz, PyH), 4.41 (q, 2H, J = 2.1 Hz, OCH2CH3), 2.42 (s, 3H, CH3), 1.42 (t, 3H, J = 7.1 Hz, OCH2CH3); 13C-NMR (101 MHz, CDCl3): δ 169.6, 166.6, 152.9, 152.5, 140.0, 118.0, 111.1, 62.0, 26.0, 14.2; HRMS (ESI): m/z [M + H]+ calcd. for C10H12N2O3: 209.0926, found: 209.0925.