Syntheses of Furo-, Oxazino- and Pyranocarbazoles
1589
Ethyl 9-methyl-2-oxo-2,11-dihydropyrano[2,3-a]carbazole-3-carboxylate (7b ): Yellow am or-
ph ous powder, m .p. 218–220 °C. Yield 60%. For C19H15NO4 (321.3) calculated: 71.02% C,
4.71% H, 4.36% N; foun d: 71.18% C, 4.68% H, 4.39% N. IR: 3354, 2923, 1730, 1652, 1285.
1H NMR (400 MHz, DMSO-d6): 12.21 b s, 1 H (H-11, deuterium -exch an geable); 8.92 s, 1 H
(H-4); 8.14–8.03 m , 2 H (H-5, H-6); 7.67–7.56 m , 2 H (H-7, H-8); 7.42 s, 1 H (H-10);
4.35–4.27 q, 2 H, J = 7.1 (COOCH2CH3); 2.83 s, 3 H (CH3); 1.37–1.29 t, 3 H, J = 7.1
(COOCH2CH3). 13C NMR (100 MHz, DMSO-d6): 168.0 (COOEt); 154.1 (C-2); 141.2 (C-4);
116.9 (C-3); 134.7, 132.1, 130.8, 129.1, 125.6, 119.9, 1118.7, 116.4, 115.8, 114.4, 108.9,
104.3 (12 arom . C); 60.1 (COOCH2CH3); 19.7 (CH3); 16.1 (COOCH2CH3). MS (EI, 70 eV),
m/z (rel.%): 321 (100) [M+]; 276 (40); 262 (90); 248 (50); 244 (21); 217 (22).
Ethyl 10-methyl-2-oxo-2,11-dihydropyrano[2,3-a]carbazole-3-carboxylate (7c): Yellow am or-
ph ous powder, m .p. 197–199 °C. Yield 52%. For C19H15NO4 (321.3) calculated: 71.02% C,
4.71% H, 4.36% N; foun d: 70.87% C, 4.76% H, 4.31% N. IR: 3231, 2928, 1717, 1611, 1266.
1H NMR (400 MHz, DMSO-d6): 12.24 b s, 1 H (H-11, deuterium -exch an geable); 8.79 s, 1 H
(H-4); 8.01–7.90 m , 2 H (H-6, H-7); 7.58–7.55 m , 1 H (H-8); 7.44–7.40 d, 1 H, J(5,6) = 8.2
(H-5); 7.38–7.34 d, 1 H, J(9,10) = 8.0 (H-9); 4.50–4.43 q, 2 H, J = 7.1 (COOCH2CH3); 2.63 s,
3 H (CH3); 1.49–1.43 t, 3 H, J = 7.1 (COOCH2CH3). 13C NMR (100 MHz, DMSO-d6): 169.3
(COOEt); 154.7 (C-2); 139.9 (C-4); 118.3 (C-3); 136.8, 134.0, 130.9, 130.0, 126.2, 122.4,
121.0, 119.1, 116.0, 114.1, 109.7, 104.9 (12 arom . C); 59.7 (COOCH2CH3); 23.1 (CH3); 16.1
(COOCH2CH3). MS (EI, 70 eV), m/z (rel.%): 321 (100) [M+]; 276 (45); 262 (97); 248 (32); 244
(27); 217 (41); 196 (23).
Ethyl 8-chloro-2-oxo-2,11-dihydropyrano[2,3-a]carbazole-3-carboxylate (7d ): Yellow am or-
ph ous powder, m .p. 256–258 °C. Yield 50%. For C18H12ClNO4 (341.8) calculated: 63.26% C,
3.54% H, 4.10% N; foun d: 63.38% C, 3.50% H, 4.03% N. IR: 3270, 2925, 1729, 1654, 1306.
1H NMR (400 MHz, DMSO-d6): 12.26 b s, 1 H (H-11, deuterium -exch an geable); 8.87 s, 1 H
(H-4); 8.18 s, 1 H (H-7); 7.95–7.90 d, 1 H, J(6,5) = 8.2 (H-6); 7.50–7.45 m , 3 H (H-5, H-9,
H-10); 4.32–4.26 q, 2 H, J = 7.1 (COOCH2CH3); 1.36–1.29 t, 3 H, J = 7.1 (COOCH2CH3).
13C NMR (100 MHz, DMSO-d6): 168.8 (COOEt); 155.9 (C-2); 140.6 (C-4); 116.7 (C-3); 139.5,
137.9, 132.1, 129.4, 126.1, 121.8, 120.1, 118.7, 115.7, 113.6, 111.6, 109.8 (12 arom . C); 59.7
(COOCH2CH3); 14.9 (COOCH2CH3). MS (EI, 70 eV), m/z (rel.%): 341 (100) [M+]; 343 (28);
296 (47); 282 (95); 268 (32); 237 (39).
Ethyl 2-oxo-2,11-dihydropyrano[2,3-a]carbazole-3-carboxylate (7e): Yellow am orph ous pow-
der, m .p. 222–224 °C. Yield 68%. For C18H13NO4 (307.3) calculated: 70.35% C, 4.26% H,
4.56% N; foun d: 70.21% C, 4.30% H, 4.60% N. IR: 3352, 2924, 1746, 1636, 1249. 1H NMR
(400 MHz, DMSO-d6): 12.34 b s, 1 H (H-11, deuterium -exch an geable); 8.94 s, 1 H (H-4);
8.27–8.22 d, 1 H, J(6,5) = 8.3 (H-6); 8.17–8.12 d, 1 H, J(5,6) = 8.3 (H-5); 7.65–7.61 d, 1 H,
J(10,9) = 8.2 (H-10); 7.60–7.47 m ,
3 H (H-7, H-8, H-9); 4.36–4.27 q, 2 H, J = 7.1
(COOCH2CH3); 1.36–1.30 t, 3 H, J = 7.1 (COOCH2CH3). 13C NMR (100 MHz, DMSO-d6):
171.0 (COOEt); 154.1 (C-2); 138.4 (C-4); 116.3 (C-3); 137.9, 135.1, 134.4, 130.3, 127.8,
124.5, 121.3, 119.3, 116.3, 110.6, 107.4, 106.7 (12 arom . C); 59.1 (COOCH2CH3); 16.4
(COOCH2CH3). MS (EI, 70 eV), m/z (rel.%): 307 (100) [M+]; 262 (40); 248 (94); 215 (16); 182
(12).
The authors are grateful to prof. J. S. Yadav, the Director, ISO quality assurance cell, IICT,
Hyderabad and prof. K. V. Ramanathan, the Chairman, NMR research centre, IISc, Bangalore for
providing mass spectral data and NMR spectra, respectively.
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 11, pp. 1579–1590