G Model
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S.M. Baghbanian et al. / C. R. Chimie xxx (2012) xxx–xxx
5
converted to the corresponding bis(indolyl)methane,
while acetophenone did not give the corresponding
product in water and under solvent-free conditions
(Scheme 3).
128.2 (–C ), 128.7 (–CH ), 130.0 (–CH ), 131.6 (–CH ),
131.9 (–C ), 135.0 (–C ), 142.3 (–C ). MS (EI): m/z 384
[M]+. Anal. calcd. for C25H21ClN2: C, 78.01; H, 5.50; N, 7.28.
Found: C, 77.87; H, 5.45; N, 7.13.
The reaction was clean and the products were obtained
in high yields without the formation of any by-products.
All the BIMs prepared were known compounds and their
structures were confirmed by their physical properties and
1H and 13C NMR spectra and comparison with authentic
samples. The catalyst was simply recovered from the
reaction mixture by treating the precipitate with deionized
water to dissolve the catalyst. Finally, on filtration, water
was evaporated and the organocatalyst dried and reused in
successive reactions. The recycled catalyst was found to be
highly efficient even after four times without significant
loss of catalytic activity.
1,4-bis(di(1H-indol-3-yl)methyl)benzene (Scheme 2, 5)
Pink solid, m.p.: 197–198 8C. IR (KBr): 3405, 3052, 2949,
1612, 1452 and 1259 cmꢀ1. 1H NMR (400 MHz, DMSO-d6):
dH (ppm) 5.84 (s, 2H), 6.95 (s, 4H), 7.05 (t, 4H, J = 7.5 Hz),
7.16 (t, 4H, J = 7.6 Hz), 7.24–7.40 (m, 12H), 7.31 (br s, 4H,
NH). 13C NMR (100.6 MHz, DMSO-d6): dC (ppm) 30.1 (2
CH), 111.5 (–CH ), 118.5 (–C ), 118.9 (–CH ), 119.8 (–
CH ), 121.3 (–CH ), 123.8 (–CH ), 127.2 (–C ), 128.5 (–
CH ), 138.1 (–C ), 143.9 (–C ). MS (EI): m/z 566 [M]+.
Anal. calcd. for C40H30N4: C, 84.78; H, 5.34; N, 9.89. Found:
84.55; H, 5.44; N, 9.78.
3,30-(cyclohexane-1,1-diyl)bis(1H-indole) (Table 2, entry
18) Pink solid, m.p.: 116–118 8C. IR (KBr): 3452, 3035,
3. General procedure
2925, 1608, 1495 and 1229 cmꢀ1 1H NMR (400 MHz,
.
CDCl3): dH (ppm) 1.38–1.95 (m, 6H), 2.48–2.55 (m, 4H),
Method y: A mixture of indole (1.0 mmol), aldehyde or
ketone (0.5 mmol) and p-sulfonic acid calix[4]arene (1 mol
%) were added to 3 ml of water and the mixture was stirred
in around bottomed flask at 80 8C for the appropriate time
(Table 2). The progress of the reaction was monitored by
TLC (n-hexane/acetone 4:1). After completion of the
reaction, the resulting solid (crude product) was filtered
and then recrystallized from ethanol–water to afford pure
product.
6.81 (s, 2H), 7.10–7.61 (m, 8H), 7.75 (br s, NH, 2H). 13C NMR
(100.6 MHz, CDCl3): dC (ppm) 25.9 (2 CH2), 28.4 (CH2), 37.2
(2 CH2), 39.3 (C), 110.1(–CH ), 117.5 (–CH ), 119.2 (–
CH ), 120.4 (–CH ), 121.3 (–C ), 123.8 (–C ), 134.2 (–
CH ), 127.6 (–C ), 138.9 (–C ). MS (EI): m/z 314 [M]+.
Anal. calcd. for C22H22N2: C, 84.04; H, 7.05; N, 8.91. Found:
C, 83.98; H, 7.10; N, 8.83.
4. Conclusions
Method yy: A mixture of indole (1.0 mmol), aldehyde or
ketone (0.5 mmol) and p-sulfonic acid calix[4]arene
(0.5 mol %) under solvent-free conditions was stirred at
room temperature for the appropriate time (Table 2). The
progress of the reaction was monitored by TLC (n-hexane/
acetone 4:1). After completion of the reaction, the mixture
reaction was added water (1 ml) and the solid obtained
was filtered and recrystallized from a mixture of diethyl
ether-ethyl acetate to obtain pure product.
In conclusion, in this study, a simple, efficient, green,
and eco-friendly procedure is described for the chemos-
electivity synthesis of bis(indolyl)methanes in water and
under solvent-free conditions using p-sulfonic acid
calix[4]arene as a reusable organocatalyst. Also, good to
high yields and high chemoselectivity of this protocol
provide a low cost procedure for the synthesis of these
compounds.
The physical data (mp, NMR, IR) of these known
compounds were found to be identical with those reported
in the literature. Spectroscopic data for selected examples
are shown below.
Acknowledgment
This research is supported by the Islamic Azad
University, Ayatollah Amoli Branch.
3,30-(phenyl methylene)bis(1H-indole) (Table 2, entry 1)
Pink solid, m.p.: 123–126 8C. IR (KBr): 3412, 3150, 2966,
1610, 1425 and 1112 cmꢀ1. 1H NMR (400 MHz, CDCl3): dH
(ppm) 5.48 (s, 1H, –CH), 6.65 (s, 2H, –NH–CH ), 7.11 (dd,
2H, J = 7.9 Hz, –CH ), 7.17 (dd, 2H, J = 7.9 Hz, –CH ), 7.21
(m, 1H, –CH ), 7.27 (m, 2H, –CH ), 7.33 (d, 4H, J = 8.0 Hz, –
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Please cite this article in press as: Baghbanian SM, et al. p-sulfonic acid calix[4]arene: An efficient reusable
organocatalyst for the synthesis of bis(indolyl)methanes derivatives in water and under solvent-free conditions. C. R.