9544
J. S. Yadav et al. / Tetrahedron 61 (2005) 9541–9544
K1
1
; H NMR (200 MHz,
Table 2. Reactivity of 10 mol% Cu(OTf)
condensation of 2-methylindole with cyclopentenone
2
in various solvents for the
a
1064, 937, 964, 746, 701 cm
CDCl ): d 1.25 (t, 3H, JZ7.5 Hz), 1.60–1.80 (m, 1H), 1.98–
3
2
.20 (m, 3H), 2.30–2.50 (m, 3H), 2.95– 3.08 (m, 2H), 4.00
Run
Reaction
medium
Time (h)
Yield (%)
(q, 2H, JZ7.5 Hz), 7.08–7.23 (m, 2H), 7.38 (d, 3H, JZ8.0,
Hz), 7.48 (dd, 3H, JZ8.0, 2.0 Hz), 7.78 (1H, JZ8.0 Hz);
1
2
3
4
5
[bmim]BF
[bmim]PF
4
4.5
5.0
8.5
7.0
8.5
89
83
68
71
65
1
3
C NMR (75 MHz, CDCl ): d 15.3, 25.8, 32.0, 37.4, 38.4,
3
6
CH
CH
CH
3
3
2
CN
OH
41.3, 48.4, 109.9, 115.3, 119.0, 119.7, 121.4, 126.0, 128.5
(3C), 130.6 (2C), 132.1, 136.0, 136.9, 211.3; FABMS m/z
(%): 317 (M 100), 274 (10), 260 (27), 246 (12), 234 (10),
Cl
2
C
a
Reactions were carried out in 1 mmol scale.
217 (15), 204 (11), 154 (10), 136 (12), 107 (15), 95 (10), 69
(
318.1857, found 318.1846.
C
18), 55 (20); HRMS: calcd for C H NO (MCH )
22 24
light and then developed by using iodine mixed with silica
gel 60–120 mesh.
4.2. General procedure for the conjugate addition of
indoles to a,b-unsaturated compounds
Acknowledgements
G. B. thanks to CSIR New Delhi for the award of fellowship.
A mixture of a,b-unsaturated compound (1 mmol), indole
(
1 mmol) and 10 mol% Cu(OTf)2 in 1-butyl-3-methyl
imidazolium tetrafluoroborate (3 mL) was stirred at ambient
temperature for the appropriate time (as shown in the
Table 1). After completion of the reaction, as indicated by
TLC, the reaction mixture was extracted with diethyl ether
References and notes
(
3!10 mL). The combined ether layers were concentrated
in vacuo and the resulting product was directly charged on a
small silica gel column and eluted with a mixture of ethyl
acetate and n-hexane to afford the pure 1,4-adduct. All known
1. Moore, R. E.; Cheuk, C.; Patterson, G. M. L. J. Am. Chem. Soc.
1984, 106, 6456.
2. (a) Harrington, P.; Kerr, M. A. Can. J. Chem. 1998, 76, 1256.
(b) Harrington, P.; Kerr, M. A. Synlett 1996, 1047.
1
compounds were characterized by H NMR, IR, mass spectra
and their spectroscopic data identical to that reported in the
3. (a) Srivastava, N.; Banik, B. K. J. Org. Chem. 2003, 68, 2109.
(b) Bandini, M.; Cozzi, P. G.; Giacomini, M.; Melchiorre, P.;
Selva, S.; Umani-Ronchi, A. J. Org. Chem. 2002, 67, 3700. (c)
Bartoli, G.; Bartolacci, M.; Bosco, M.; Foglia, G.; Giuliani, A.;
Marcantoni, E.; Sambri, L.; Torregiani, E. J. Org. Chem. 2003,
68, 4594. (d) Alam, M. M.; Varala, R.; Adapa, S. R.
Tetrahedron Lett. 2003, 44, 5115. (e) Bandini, M.; Melchiorre,
P.; Melloni, A.; Umani-Ronchi, A. Synthesis 2002, 1110.
4. (a) Bandini, M.; Fagioli, M.; Melchiorre, P.; Melloni, A.;
Umani-Ronchi, A. Tetrahedron Lett. 2003, 44, 5843. (b)
Jensen, K. B.; Thorhauge, J.; Hazell, R. G.; Jørgensen, K. A.
Angew. Chem., Int. Ed. 2001, 40, 160.
2
,3
literature. The new compounds were characterized by H
1
1
NMR, C NMR, IR, mass spectra and HRMS.
3
4.3. Physical and spectroscopic data for all the new
compounds
4
.3.1. Compound 3d. Pale yellow solid, mp 94–96 8C; IR
KBr): n 3344, 3051, 2922, 2853, 1706, 1638, 1443, 1322,
(
K1
206, 1098, 923, 857, 737, 648 cm ; H NMR (200 MHz,
1
1
CDCl ): d 1.40 (t, 3H, JZ7.0 Hz), 2.10 (s, 3H), 2.78–2.90
3
(
m, 4H), 3.05 (t, 2H, JZ7.0 Hz), 6.93–7.18 (m, 3H), 7.40 (d,
H, JZ7.5 Hz), 7.92 (br s, 1H, NH); C NMR (75 MHz,
1
3
1
CDCl ): d 13.8, 19.4, 23.9, 29.9, 44.0, 115.5, 116.3, 119.5,
5. Bergmann, E. D.; Ginsburg, D.; Pappo, R. Org. React. 1953,
10, 179.
3
1
20.5, 121.0, 126.5, 126.8, 135.0, 208.9; EIMS m/z (%): 215
M 29), 187 (26), 158 (93), 130 (100), 103 (20), 89 (14), 77
6. (a) Soriente, A.; Spinella, A.; De Rosa, M.; Giordano, M.;
Scettri, A. Tetrahedron Lett. 1997, 38, 289. (b) Kotsuki, H.;
Arimura, K.; Ohishi, T.; Maruzasa, R. J. Org. Chem. 1999, 64,
3770. (c) Bartoli, G.; Bosco, M.; Bellucci, M. C.; Marcantoni,
E.; Sambri, L.; Torregiani, E. Eur. J. Org. Chem. 1999, 617.
7. (a) Kobayashi, S. Synlett 1994, 689. (b) Kobayashi, S.;
Hachiya, I.; Takahori, T.; Araki, M.; Ishitani, H. Tetrahedron
Lett. 1992, 33, 6815. (c) Mori, Y.; Kakumoto, K.; Manabe, K.;
Kobayashi, S. Tetrahedron Lett. 2000, 41, 3107.
C
(
(
(
18), 63 (12), 51 (28), 43 (31); HRMS: calcd for C H NO
14 18
C
MCH ) 216.1388, found 216.1384.
4
.3.2. Compound 3g. White solid, mp 125–126 8C; IR
KBr): n3367, 3057, 2964, 2847, 1665, 1593, 1491, 1443, 1356,
(
K1
277, 1098, 745, 692 cm ; H NMR (200 MHz, CDCl ): d
1
1
1
2
4
3
.30 (t, 3H, JZ6.0 Hz), 2.78 (q, 2H, JZ7.0 Hz), 3.65–3.86 (m,
H), 5.05 (t, 1H, JZ7.0 Hz), 6.80 (s, 1H), 6.90 (d, 2H, JZ
8. (a) Welton, T. Chem. Rev. 1999, 99, 2071. (b) Wasserscheid,
P.; Keim, W. Angew. Chem., Int. Ed. 2000, 39, 3772.
9. Sheldon, R. Chem. Commun. 2001, 2399.
13
.2 Hz), 7.10–7.55 (m, 9H), 7.92 (d, 3H, JZ8.0 Hz); C NMR
(75 MHz, CDCl ): d 13.7, 23.8, 38.3, 45.1, 117.2, 119.6, 120.5,
3
1
21.3, 126.2, 126.4, 126.7, 127.8 (2C), 128.0 (2C), 128.3 (2C),
10. Gordon, C. M. Appl. Catal. A: Gen. 2001, 222, 101.
11. (a) Yadav, J. S.; Reddy, B. V. S.; Baishya, G. J. Org. Chem.
2003, 68, 7098. (b) Yadav, J. S.; Reddy, B. V. S.; Basak, A. K.;
Narsaiah, A. V. Tetrahedron Lett. 2003, 44, 1047. (c) Yadav,
J. S.; Reddy, B. V. S.; Basak, A. K.; Narsaiah, A. V. Green
Chem. 2003, 1, 60. (d) Yadav, J. S.; Reddy, B. V. S.; Basak,
A. K.; Narsaiah, A. V. Tetrahedron 2004, 60, 2131. (e) Yadav,
J. S.; Reddy, B. V. S.; Reddy, P. S. R.; Basak, A. K.; Narsaiah,
A. V. Adv. Synth. Catal. 2004, 346, 77.
128.5 (2C), 128.9, 133.0, 135.4, 137.0, 144.2, 198.6; FABMS
m/z (%): 353 (M 12), 234 (100), 219 (12), 204 (15), 154 (10),
C
145 (12), 130 (10), 121 (10), 109 (10), 109 (18), 105 (57), 95
(38), 83 (41), 69 (60), 55 (35); HRMS: calcd for
C H NONa (MCNa ) 376.1677, found 376.1678.
C
2
5 23
4
(
.3.3. Compound 3k. White solid, mp 142–143 8C; IR
KBr): n 3387, 3041, 2931, 2861, 1698, 1458, 1339, 1222,