LETTER
Condensations of Indole with Carbonyl Compounds
339
4
c
1
In summary, we have demonstrated the lanthanide per- Product 3a: solid, mp 125–126 °C. H NMR (CDCl
): d = 5.89 (s,
3
1
H,), 6.66 (d, 2 H, J = 1.8 Hz), 7.01 (t, 2 H, J = 7.4 Hz), 7.17 (t, 3
H, J = 7.8 Hz), 7.28 (s, 2 H, J = 7.3 Hz), 7.37 (m, 6 H), 7.91 (br s, 2
H, NH). MS (EI): m/z (%) = 322 (100) [M ], 245 (50), 204 (25). IR
KBr): 3450, 3020, 1600, 1490, 1220, 1070, 750 cm .
fluorooctanoates [Ln(PFO) ] to be mild and effective
3
catalysts for the condensation of indole with aldehydes
and ketones in EtOH at room temperature to afford bis-
+
–
1
(
indolylmethanes in high yields. RE(PFO) show high
3
catalytic activity as a new type of rare earth catalysts.
They are easy to prepare, stable and storable in air for a
long time without any changes, easily recycled, and re-
used without obvious loss of activity. With the additional
water-repellent and oil-repellent character of the per-
fluorooctyl chains, the catalysts could form the middle
layer between a supernatant liquid such as hexane or
dichloromethane and the lower water layer when extract-
ing. Therefore, the procedure is expected to become a
useful method for the synthesis of bis-indolylmethanes.
Acknowledgment
We thank the Science Foundation of Lab for Advanced Materials
for financial support of this work.
Reference
(1) (a) Sundberg, R. J. The Chemistry of Indoles; Acadmic
Press: New York, 1970. (b) Gribble, G. W. J. Chem. Soc.,
Perkin Trans. 1 2000, 7, 1045.
(
2) (a) Gregorovich, B. V.; Liang, K.; Clugston, M.; Macdonald,
S. Can. J. Chem. 1968, 46, 3291. (b) Roomi, M.;
Macdonald, S. Can. J. Chem. 1970, 48, 139. (c) Auria, M.
Tetrahedron 1991, 47, 9225.
Typical Experimental Procedure
Catalyst Preparation
To a stirring solution of perfluorooctanoic acid (PFOA, 2.5 g, 0.6
(3) (a) Chatterjee, A.; Manna, S.; Benerji, J.; Pascard, C.;
Prange, T.; Shoolery, J. J. Chem. Soc., Perkin Trans. 1 1980,
553. (b) Noland, W. E.; Venkiteswaran, M. R.; Richards, C.
G. J. Org. Chem. 1961, 26, 4241. (c) Babu, G.; Sridhar, N.;
Perumal, P. T. Synth. Commun. 2000, 30, 1609. (d) Wang,
Y. M.; Wen, Z.; Chen, X. M.; Du, D. M.; Matsuura, T.;
Meng, J. B. J. Heterocycl. Chem. 1998, 35, 313. (e) Yadav,
J. S.; Reddy, B. V. S.; Mueth, C. V. S. R.; Kumar, G. M.;
Madan, C. Synthesis 2001, 783.
mmol) in H O (5 mL), La O (0.32 g, 0.1 mmol) was added, and the
2
2
3
mixture was stirred for 12 h under reflux. The aqueous layer was de-
canted and washed with H O to give a gelatin-like solid. The solid
2
was dried in vacuum at r.t. for 2 h to give a white sheet solid.
La(PFO) : mp:138–140 °C. IR (KBr): 3400–3500 (m), 1650 (m),
3
–
1
1
620 (vs), 1200 (vs), 1150 (vs) cm . ICP: found: La = 11%, calcd
for La(PFO) : La = 10.08%. F NMR (500 MHz, DMSO): d =
1
9
3
–
6
6
81.17 (t, 9 F, J = 0.02 Hz), –115.94 (t, 6 F, J = 0.02 Hz), –112.3 (s,
F), –122.74 (s, 12 F, J = 0.13 Hz), –123.51 (s, 6 F), –126.73 (s,
F). Compared to PFOA, a 1 ppm shift showed in –115.94 Hz,
(
4) (a) Ramesh, C.; Banerjee, J.; Pal, R.; Das, B. Adv. Synth.
Catal. 2003, 345, 557. (b) Yadav, J. S.; Reddy, B. V. S.;
Sunitha, S. Adv. Synth. Catal. 2003, 345, 349. (c) Ji, S. J.;
Zhou, M. F.; Gu, D. G.; Jiang, Z. Q.; Loh, T. P. Eur. J. Org.
Chem. 2004, 1584. (d) Bandgar, B. P.; Shaikh, K. A.
Tetrahedron Lett. 2003, 44, 1959. (e) Chakrabarty, M.;
Ghosh, N.; Basak, R.; Harigaya, Y. Tetrahedron Lett. 2002,
which can illustrate coordination of the La ion. EDS (%): C, 7.12;
O, 7.77; F, 68.88; La, 16.23.
General Procedure for Preparation of Bis-indolylmethanes
To a mixture of indole (2 mmol 0.234 g), aldehydes or ketones (1
mmol, 0.1 mL), EtOH (2 mL), lanthanum perfluorooctanoate
43, 4075. (f) Koshima, H.; Matsusaka, W. J. Heterocycl.
Chem. 2002, 39, 1089.
5) (a) Chen, D. P.; Yu, L. B.; Wang, P. G. Tetrahedron Lett.
[
La(PFO) ] (0.01 mmol, 5%mol) was added and stirred at r.t. for the
3
(
(
appropriate time. When the reaction was complete, the solvent was
removed under reduced pressure. CH Cl (10 mL) and sat. aq NaCl
1
996, 37, 4467. (b) Nagarajan, R.; Perumal, P. T.
2
2
Tetrahedron 2002, 58, 1229. (c) Mi, X. L.; Luo, S. Z.; He, J.
Q.; Chen, J. P. Tetrahedron Lett. 2004, 45, 4567.
solution (10 mL) was added to stand for several minutes, the filtrate
was separated and the water layer was extracted with CH Cl
2
2
6) (a) Kobayashi, S.; Sugiura, M.; Kitagawa, H.; Lam, W. W.
Chem. Rev. 2002, 102, 2227. (b) Wang, L. M.; Xia, J. J.;
Tian, H.; Qin, F.; Qian, C.; Sun, J. Synthesis 2003, 8, 1241.
(
3 × 10 mL), the combined organic layer were dried using anhyd
Na SO and filtered, and the solvent was evaporated. The crude
2
4
products were purified by column chromatography and eluted with
EtOAc–petroleum ether mixture to afford the products.
(
c) Wang, L. M.; Qian, C. T.; Tian, H.; Ma, Y. Synth.
Commun. 2003, 33, 1459. (d) Wang, L. M.; Liu, J. J.; Tian,
H.; Qian, C. T. Synth. Commun. 2004, 34, 1349.
7) (a) Iijima, H.; Kato, T. Langmuir 2000, 16, 318. (b) Furó,
I.; Sitnikov, R. Langmuir 1999, 15, 2669. (c) Dvinskikh, S.
V.; Furó, I. Langmuir 2000, 16, 2962.
After adding the CH Cl and sat. aq NaCl solution, the catalyst was
2
2
deposited in the middle of two phases. Since the catalyst is not sol-
uble in either CH Cl or H O, catalyst recovery was accomplished
(
(
2
2
2
simply by filtration and drying in air or under vacuum.
8) (a) Kobayashi, S.; Wakabayashi, T. Tetrahedron Lett. 1998,
39, 5839. (b) Manabe, K.; Mori, Y.; Wakabayashi, T.;
Nagayama, S.; Kobayashi, S. J. Am. Chem. Soc. 2000, 122,
7202.
Synlett 2005, No. 2, 337–339 © Thieme Stuttgart · New York