PAPER
One-Pot Synthesis of Diindolylmethane
1781
InCl3-Catalyzed Preparation of DIM 3a; Typical Procedure
To a solution of indole (1a; 351 mg, 3 mmol) and hexamethylene-
tetramine (2; 35 mg, 0.25 mmol) in anhyd i-PrOH (5 mL) was added
anhyd InCl3 (67 mg, 0.3 mmol). The reaction mixture turned turbid
after a few minutes. The reaction mixture was then stirred at r.t. for
8 h. Water (10 mL) was added to the reaction mixture followed by
heating at 80 °C for 30 min. It was then extracted with CHCl3 (3 ×
25 mL). The organic layer was dried over anhyd Na2SO4, and the
solvent removed to give a solid mass. Column chromatography of
the residue over silica gel using increasing concentration of CHCl3
in petroleum ether (bp range 60–80 °C) yielded 3a as white solid
(339 mg, 92%).
13C NMR (75 MHz, CDCl3): d = 21.13 (CH2), 33.18 (2 × C, 2 ×
NCH3), 111.09 (2 × C, C-2, C-2¢), 112.55 (2 × C, C-3, C-3¢), 122.14
(2 × C, C-7, C-7¢), 124.73 (2 × C, C-6, C-6¢), 128.49 (2 × C, C-4, C-
4¢), 129.83 (2 × C, C-3a, C-3a¢), 136.30 (2 × C, C-7a, C-7a¢), 139.98
(2 × C, C-5, C-5¢).
ESI–MS: m/z = 455 [M + Na]+.
Anal. Calcd for C19H16Br2N2: C, 52.81; H, 3.73; N, 6.48. Found: C,
53.12; H, 3.80; N, 6.51.
1,1¢-Dimethyl-5,5¢-dinitro-3,3¢-diindolylmethane (3k)
Mp 218–220 °C.
1H NMR (300 MHz, CDCl3): d = 3.80 (s, 6 H), 4.27 (s, 2 H), 6.99
(s, 2 H), 7.31 (d, J = 9.0 Hz, 2 H), 8.13 (dd, J = 9.0, 2.0 Hz, 2 H),
8.53 (d, J = 2.0 Hz, 2 H).
3,3¢-Diindolylmethane (3a)
Mp 159–161 °C (Lit.11 161–162 °C).
IR (KBr): 3396, 1454, 1343, 741 cm–1.
ESI–MS: m/z = 387 [M + Na]+.
1H NMR (300 MHz, DMSO-d6): d = 4.13 (s, 2 H, CH2), 6.92 (t, J =
7.1 Hz, 2 H, H-6, H-6¢), 7.03 (t, J = 7.1 Hz, 2 H, H-5, H-5¢), 7.13 (br
s, 2 H, H-2, H-2¢), 7.32 (d, J = 8.0 Hz, 2 H, H-7, H-7¢), 7.52 (d, J =
8.0 Hz, 2 H, H-4, H-4¢), 10.73 (s, 2 H, 2 × NH).
13C NMR (75 MHz, CDCl3 + DMSO-d6): d = 26.43 (CH2), 116.52
(2 × C, C-2, C-2¢), 120.04 (2 × C, C-3, C-3¢), 123.65 (2 × C, C-7, C-
7¢), 124.07 (2 × C, C-6, C-6¢), 126.36 (2 × C, C-5, C-5¢), 127.79
(2 × C, C-4, C-4¢), 132.67 (2 × C, C-3a, C-3a¢), 141.84 (2 × C, C-7a,
C-7a¢).
Anal. Calcd for C19H16N4O4: C, 62.63; H, 4.43; N, 15.38. Found: C,
63.01; H, 4.89; N, 15.47.
Acknowledgment
S. D. thankfully acknowledges UGC, New Delhi, India for the fi-
nancial support in the form of a Junior Research Fellowship.
References
ESI–MS: m/z = 269 [M + Na]+.
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Anal. Calcd for C17H14N2: C, 82.90; H, 5.73; N, 11.37. Found: C,
82.65; H, 5.80; N, 11.49.
5,5¢-Dimethoxy-3,3¢-diindolylmethane (3d)
Mp 156–158 °C.
1H NMR (300 MHz, CDCl3): d = 3.81 (s, 6 H), 4.17 (s, 2 H), 6.84
(dd, J = 8.7, 2.1 Hz, 2 H), 6.91 (br s, 2 H), 7.06 (d, J = 2.1 Hz, 2 H),
7.25 (d, J = 2.4 Hz, 2 H), 7.81 (s, 2 H, 2 × NH).
13C NMR (75 MHz, CDCl3 + DMSO-d6): d = 26.53 (CH2), 60.94
(2 × C, 2 × OCH3), 106.01 (2 × C, C-4, C-4¢), 116.40 (2 × C, C-6,
C-6¢), 117.26 (2 × C, C-7, C-7¢), 119.58 (2 × C, C-3, C-3¢), 128.66
(2 × C, C-2, C-2¢), 132.97 (2 × C, C-7a, C-7a¢), 137.11 (2 × C, C-3a,
C-3a¢), 158.46 (2 × C, C-5, C-5¢).
ESI–MS: m/z = 329 [M + Na]+.
Anal. Calcd for C19H18N2O2: C, 74.19; H, 5.92; N, 9.14. Found: C,
74.28; H, 5.97; N, 9.20.
5,5¢-Dimethoxy-1,1¢-dimethyl-3,3¢-diindolylmethane (3e)
Mp 112–114 °C.
1H NMR (300 MHz, CDCl3): d = 3.68 (s, 6 H), 3.82 (s, 6 H), 4.14
(s, 2 H), 6.75 (s, 2 H), 6.89 (dd, J = 8.80, 2.4 Hz, 2 H), 7.07 (d, J =
2.4 Hz, 2 H), 7.19 (d, J = 8.8 Hz, 2 H).
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13C NMR (75 MHz, CDCl3): d = 21.42 (CH2), 33.17 (2 × C, 2 ×
NCH3), 56.44 (2 × C, 2 × OCH3), 101.60 (2 × C, C-4, C-4¢), 110.30
(2 × C, C-6, C-6¢), 112.04 (2 × C, C-7, C-7¢), 114.11 (2 × C, C-3, C-
3¢), 128.06 (2 × C, C-2, C-2¢), 128.56 (2 × C, C-7a, C-7a¢), 133.03
(2 × C, C-3a, C-3a¢), 154.03 (2 × C, C-5, C-5¢).
ESI–MS: m/z = 357 [M + Na]+.
Anal. Calcd for C21H22N2O2: C, 75.42; H, 6.63; N, 8.38. Found: C,
75.79; H, 6.90; N, 8.19.
5,5¢-Bromo-1,1¢-dimethyl-3,3¢-diindolylmethane (3g)
1H NMR (300 MHz, CDCl3): d = 3.68 (s, 6 H), 4.09 (s, 2 H), 6.76
(s, 2 H), 7.15 (d, J = 8.6 Hz, 2 H), 7.28 (dd, J = 8.6, 1.6 Hz, 2 H),
7.69 (d, J = 1.6 Hz, 2 H).
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(9) Miyai, T.; Onishi, Y.; Baba, A. Tetrahedron 1999, 55, 1017.
Synthesis 2005, No. 11, 1779–1782 © Thieme Stuttgart · New York