4720
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33. Zhang, Z. H.; Yin, L.; Wang, Y. M. Synthesis 1949, 2005, 12.
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of products make this procedure an improved practical alternative
to the conventional acid catalyzed thermal reaction.
35. Hasaninejad, A.; Zare, A.; Sharghi, H.; Niknam, Kh.; Shekouhy, M. Arkivoc 2007,
14, 39.
Acknowledgment
36. Zeng, X. F.; Ji, S. J.; Wang, S. Y. Tetrahedron 2005, 61, 10235.
37. Xiao-Fei, Z.; Shun-Jun, J.; Shun-Yi, W. Tetrahedron 2005, 61, 10235.
38. Yadav, J. S.; Reddy, B. V. S.; Sunitha, S. Adv. Synth. Catal. 2003, 345, 349.
39. Chakraborti, A. K.; Roy, S. R.; Kumar, D.; Chopra, P. Green Chem. 2008, 10, 1111.
40. Chakrabarty, M.; Ghosh, N.; Basak, Y.; Harigaya, N. Tetrahedron Lett. 2002, 43,
4075.
One of the authors, J.D. thanks CSIR, New Delhi, for the award of
Junior Research Fellowship.
Supplementary data
41. Kobayashi, K.; Shirai, Y.; Konishi, H. Heterocycles 2009, 78, 2033.
42. Dydio, P.; Zielin´ ski, T.; Jurczak, J. Chem. Commun. 2009, 30, 4560.
43. Experimental procedure for the preparation of [n-Pr2NH2][HSO4]
& [iso-
Supplementary data associated with this article can be found, in
Pr2NH2][HSO4]: Under vigorous stirring, 0.05 mol sulfuric acid was added
dropwise to an ice cold solution of 0.04 mol of the appropriate dialkylamine in
15 mL of chloroform. Removal of chloroform under reduced pressure gave a
white solid product which was dried in vacuo.
Di-n-propylammonium hydrogensulfate [n-Pr2NH2][HSO4]: 1H NMR (400 MHZ
,
References and notes
DMSO, Me4Si) (dH ppm): 0.095(6H, t, J = 6.8 Hz, 2CH3), 1.602(4H, sextet, J =
7.2 Hz, 2CH2), 2.841 (4H, m, 2CH2), 4.447(2H, s, NH2), 8.297(1H, s, HSO4); 13C
NMR(100 MHz, DMSO-d6) (d ppm): 11.349, 19.413, 48.816; HRMS (ESI): m/z
= 199.0879 ([M]+), calcd for C6H17NO4S: 199.0878 ; The thermal decomposition
point 567 K.
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Diethylammonium hydrogensulfate [Et2NH2][HSO4]: prepared by reported
method.45
44. General
procedure
for
the
synthesis
of
aryl/alkyl(2,20-bis-3-
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methylindolyl)methanes and aryl(bis-3,30indolyl)methanes: A solution of skatole
or indole (2 mmol), aldehyde (1 mmol), IL (10 mol %) and ethanol (1 mL) was
irradiated with microwave (560 W) for varying period of times as indicated in
Table 1 and Table 2. After completion of the reaction as indicated by TLC, the
reaction mixture was poured into ice and stirred for 3–4 min. The solid product
was filtered and recrystallized from pet ether (60–80) and EtOAc mixture
(4:1).46,47
4-nitrophenyl(2,20-bis-3-methylindolyl)methane (2a): Orange solid; IR mmax
(KBr): 3437, 3390, 2916, 1593, 1516, 744 cmꢁ1 1H NMR(300 MHZ, DMSO,
;
Me4Si)(dH ppm): 10.477 (2H, s, NH), 8.215 (2H, d, J = 8.7 Hz, ArH), 7.454–7.389
(4H, m, ArH), 7.29 (2H, d, J = 7.8 Hz, ArH), 7.055–6.940 (4H, m, ArH), 6.215 (1H,
s, CH), 2.140 (6H, s, 2CH3); 13C NMR(75 MHZ, CDCl3, Me4Si) d : 147.77, 147.15,
135.56, 131.73, 129.43, 124.24, 122.33, 119.88, 118.78, 111.08, 109.54, 40.80,
8.74; Anal. Calcd for C25H21N3O2: C, 75.93; H, 5.35; N, 10.63; O, 8.09. Found: C,
75.98; H, 5.29; N, 10.65; O, 8.11. HRMS (ESI): m/z = 395.1636 ([M]+), calcd for
11. Freund, M.; Lebach, G. Chem. Ber. 1903, 36, 308.
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4241; (b) Banerji, J.; Chatterjee, A.; Manna, S.; Pascard, C.; Prange, T.; Shoolery,
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C
25H21N3O2: 395.1634.
45. Weng, J.; Wang, C.; Li, H.; Wang, Y. Green Chem. 2006, 8, 96.
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46. Synthesis of compound 2h: A solution of skatole (2 mmol), acetone (1 mL), IL
(10 mol %) irradiated with microwave (560 W) for 7 min. On cooling to
ambient temperature, the IL is precipitated and filtered
. The filtrate on
17. (a) Roomi, M.; MacDonald, S. Can. J. Chem. 1970, 48, 139; (b) Gregorovich, B.;
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dilution with ice cold water gave the crude product as a precipitate which is
purified by column chromatography in silica gel column and EtOAc: Pet.Ether
(60–80) 1:19 as the eluent.
Dimethyl(2,20-bis-3-methylindolyl)methane (2h): White solid; IR
mmax(KBr): 3441,
1612, 734 cmꢁ1
;
1H NMR (300 MHZ, DMSO, Me4Si)(dH ppm): 12.218 (2H, s,
20. Maiti, A. K.; Bhattacharyya, P. J. Chem. Res. 1997, 11, 424.
21. Banerji, J.; Dutta, U.; Basak, B.; Saha, M.; Budzikiewicz, H.; Chatterjee, A. Indian
J. Chem. 2001, 40B, 981.
22. Yadav, J. S.; Subba Reddy, B. V.; Basi, V.; Murthy, C. V. S. R.; Kumar, G. M.;
Madan, C. Synthesis 2001, 5, 783.
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2008, 9, 1728.
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Synthesis 2008, 4, 617.
NH), 8.820 (2H, d, J = 8.4 Hz, ArH), 7.900 (2H, d, J = 7.2 Hz, ArH), 7.549 (2H, t, J =
7.2 Hz, ArH), 7.128 (2H, t, J = 7.2 Hz, ArH), 2.667 (6H, s, 2CH3), 1.782 (6H, s,
2CH3); 13C NMR (75 MHZ, CDCl3, Me4Si) d: 202.59, 140.73, 135.02, 131.51,
122.62, 122.34, 121.07, 53.53, 28.46, 23.46; Anal. Calcd for C21H22N2: C, 83.40;
H, 7.33; N, 9.26. Found: C, 83.42; H, 7.32; N, 9.24. HRMS (ESI): m/z = 302.1785
([M]+), calcd for C21H22N2: 302.1783.
47. Synthesis of compound 2j: It is carried out as per the general procedure with
0.5 mL of acetaldehyde. The crude product is purified by column
chromatography in silica gel column and EtOAc: pet.ether (60–80) 1:19 as
the eluent.
Methyl(2,2/-bis-3-methylindolyl)methane (2j): Orange solid; IR
mmax(KBr): 3419,
2952, 1610, 742 cmꢁ1 1H NMR (300 MHZ, CDCl3, Me4Si)(dH ppm): 7.758 (2H, s,
;
28. Bartoli, G.; Bosco, M.; Foglia, G.; Giuliani, A.; Marcantoni, E.; Sambri, L. Synthesis
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Lett. 2009, 50, 6060.
NH), 7.541 (3H, d, J = 6.9 Hz, ArH), 7.154–7.137 (5H, m, ArH), 4.758 (1H, q,
J = 7.2 Hz, CH), 2.269 (6H, s, 2CH3), 1.775 (3H, d, J = 7.2 Hz, 1CH3); 13C NMR (75
MHZ, CDCl3, Me4Si) d :135.81, 135.09, 129.50, 121.42, 119.30, 118.30, 110.69,
107.08, 29.38, 19.28, 8.58; Anal. Calcd for C20H20N2 : C, 83.30; H, 6.99; N, 9.71.
Found: C, 83.31; H, 6.97; N, 9.72. HRMS (ESI): m/z = 288.1627([M]+), calcd for
31. Nagawade, R. R.; Shinde, D. B. Acta Chim. Slov. 2006, 53, 210.
32. Sadaphal, S. S.; Sonar, M. N.; Ware, M. N.; Shingare, M. S. Green Chem. Lett. Rev.
2008, 1, 191.
C20H20N2: 288.1626.