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P. T. Parvatkar et al. / Tetrahedron Letters 48 (2007) 7870–7872
2. Cimanga, K.; De Bruyne, T.; Pieters, L.; Claeys, M.;
heated at reflux for 5 h. The mixture was allowed to cool
and poured into water (50 mL). This was then extracted
with CHCl3 (3 · 15 mL) and the combined organic
extracts were washed with aqueous satd Na2CO3 solution
(3 · 15 mL). The combined Na2CO3 washings were acid-
ified with 6 N HCl. The resulting solid was filtered, dried,
redissolved in EtOH (15 mL), H2SO4 (five drops) were
added, and refluxed for 24 h. The reaction mixture was
cooled to room temp and after 6 h, the a,b-unsaturated
ester 2 (1.71 g, 71%) precipitated as a crystalline white
solid and was isolated by filtration. IR (KBr, cmÀ1): m
1524, 1570, 1611, 1701; 1H NMR (CDCl3, 300 MHz) d
(ppm): 1.28 (t, 3H, J = 7.2 Hz, –OCH2CH3), 4.29 (q, 2H,
J = 7.2 Hz, –OCH2CH3), 7.02–7.08 (m, 2H, Ar-H), 7.28–
7.41 (m, 3H, Ar-H), 8.12–8.16 (m, 3H, Ar-H), 8.22 (s, 1H,
@CH); 13C NMR (CDCl3, 75 MHz) d (ppm): 13.99, 61.84,
76.60, 77.03, 77.45, 124.56, 124.66, 129.26, 129.37, 131.00,
131.58, 131.68, 133.01, 133.10, 133.55, 133.58, 137.25;
HRMS m/z: [M+Na]+ calcd for C17H14N2O6, 365.0750;
found, 365.0746.
Vlietinck, A. Tetrahedron Lett. 1996, 37, 1703.
3. Cimanga, K.; De Bruyne, T.; Pieters, L.; Vlietinck, A. J.;
Turger, C. A. J. Nat. Prod. 1997, 60, 688.
4. Peczynska-Czoch, W.; Pognan, F.; Kaczmarek, L.; Bora-
tynski, J. J. Med. Chem. 1994, 37, 3503; Cimanga, K.; De
Bruyne, T.; Lasure, A.; Van Poel, B.; Pieters, L.; Claeys,
M.; Vanden Berghe, D.; Kambu, K.; Tona, L.; Vlietinck,
A. J. Planta Med. 1996, 62, 22; Cimanga, K.; De Bruyne,
T.; Pieters, L.; Totte, J.; Tona, L.; Kambu, K.; Berghe,
D.-V.; Vlietinck, A. J. Phytomed. 1998, 5, 209; Bierer, D.
E.; Fort, D. M.; Mendez, C. D.; Luo, J.; Imbach, P. A.;
Dubenko, L. G.; Jolad, S. D.; Gerber, R. E.; Litvak, J.;
Lu, Q.; Zhang, P.; Reed, M. J.; Waldeck, N.; Bruening, R.
C.; Noamesi, B. K.; Hector, R. F.; Calrson, T. J.; King, S.
R. J. Med. Chem. 1998, 41, 894; Abblordeppey, S. Y.;
Fan, P.; Clark, A. M.; Nimrod, A. Bioorg. Med. Chem.
1999, 7, 343; Arzel, E.; Rocca, P.; Grellier, P.; Labaeid,
M.; Frappier, F.; Gueritte, F.; Gaspard, C.; Marsais, F.;
Godard, A.; Queguiner, G. J. Med. Chem. 2001, 44, 949.
5. Molina, P.; Alajarin, M.; Vidal, A. J. Chem. Soc., Chem.
Commun. 1990, 1277; Molina, P.; Alajarin, M.; Vidal, A.;
Sanchez-Andrada, P. J. Org. Chem. 1992, 57, 929; Chen,
Y. L.; Hung, H. M.; Lu, C. M.; Li, K. C.; Tzeng, C. C.
Bioorg. Med. Chem. 2004, 12, 6539; Sundaram, G. S. M.;
Venkatesh, C.; Syam Kumar, U. K.; Ila, H.; Junjappa, H.
J. Org. Chem. 2004, 69, 5760.
6. Alajarin, M.; Molina, P.; Vidal, A. J. Nat. Prod. 1997, 60,
747.
7. Timari, G.; Soos, T.; Hajos, G. Synlett 1997, 1067.
8. Molina, P.; Fresnsda, P. M.; Delgado, S. Synthesis 1999,
326.
9. Fresneda, P. M.; Molina, P.; Delgado, S. Tetrahedron
Lett. 1999, 40, 7275.
10. Shi, C.; Zhang, Q.; Wang, K. K. J. Org. Chem. 1999, 64,
925.
11. Sundaram, G. S. M.; Venkatesh, C.; Syam Kumar, U. K.;
Ila, H.; Junjappa, H. J. Org. Chem. 2004, 69, 5760.
12. Dhanabal, T.; Sangeetha, R.; Mohan, P. S. Tetrahedron
2006, 62, 6258.
13. Patre, R. E.; Gawas, S.; Sen, S.; Parameswaran, P. S.;
Tilve, S. G. Tetrahedron Lett. 2007, 48, 3517.
14. Experimental procedure for the preparation of a,b-unsatu-
rated ester derivative 2: A mixture of o-nitrobenzaldehyde
(1.06 g, 7.01 mmol), o-nitrophenylacetic acid (1.27 g,
7.01 mmol), Et3N (1.1 mL), and Ac2O (15 mL) were
15. Experimental procedure for the preparation of 6H-indo-
lo[2,3-b]quinoline 3: Ester derivative 2 (0.55 g, 1.61 mmol)
and Fe powder (3.6 g) were added to a mixture of EtOH
(10 mL), acetic acid (10 mL), and H2O (5 mL). To this
mixture five drops of concd HCl were added and the
suspension was heated at 120 ꢁC while stirring for 24h.
The mixture was allowed to cool to room temp and then
filtered through Celite. The filtrate was diluted with water
(50 mL) and then extracted with CHCl3 (3 · 15 mL). The
combined organic extract was washed with 10% aqueous
NaHCO3 (25 mL) and H2O (3 · 15 mL), dried over
anhydrous Na2SO4, and concentrated to dryness to give
a yellow solid. The solid was washed with Et2O and air
dried to give 6H-indolo[2,3-b]quinoline 3 (0.26 g, 74%).
Mp > 300 ꢁC (Lit.16 mp: 346 ꢁC); IR (KBr, cmÀ1): m 1231,
1406, 1460, 1614, 3144; 1H NMR (DMSO-d6, 300 MHz) d
(ppm): 7.27 (tm, 1H, H-9), 7.46–7.57 (m, 3H, H-2, H-7, H-
8), 7.72 (ddd, 1H, J = 8.1, 7.2, 0.9 Hz, H-3), 7.98 (d, 1H,
J = 8.4 Hz, H-9), 8.11 (d, 1H, J = 8.1 Hz, H-1), 8.27 (d,
1H, J = 7.8 Hz, H-10), 9.05 (s, 1H, H-11), 11.70 (s, 1H,
NH); 13C NMR (DMSO-d6, 75 MHz) d (ppm): 111.39 (C-
7), 118.37 (C-10b), 120.14 (C-9), 120.76 (C-11a), 122.29
(C-10), 123.20 (C-2), 124.15 (C-10a), 127.45 (C-1), 128.01
(C-11), 128.67 (C-4), 129.13 (C-8 + C-3), 141.93 (C-6a),
146.79 (C-4a), 153.36 (C-5a).
16. Holt, S. J.; Petrow, V. J. J. Chem. Soc. 1948, 922.