An Efficient Method for the Synthesis of Indolo[3,2-b]carbazoles from 3,3′-Bis(indolyl)methanes Catalyzed by Molecular Iodine

Abstract

The reaction of 3,3′-bis(indolyl)methanes in the presence of molecular iodine as catalyst in refluxing acetonitrile affords indolo[3,2-b]carbazoles in good yields.

Key words

indolo[3,2-b]carbazoles - 3,3′-bis(indolyl)methanes - iodine - indole

References and Notes

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17

Experimental Procedure: 3,3′-Bis(indolyl)phenylmethane (1a, 1 mmol, 322 mg) was taken up in a round-bottom flask containing MeCN (5 mL). I₂ (2 mol%) was added and the mixture refluxed for 20 min. The obtained solid was filtered, dried, and recrystallized from a mixture of DMF-CHCl₃. The structure of the compound obtained was identified from spectroscopic data and elemental analysis.6,12-Diphenyl-5,11-dihydroindolo[3,2- b ]carbazole (2a)White solid, mp 350 °C. Yield 80% (326 mg). R _f = 0.84 [EtOAc (7%)-PE]. IR (KBr): 3394 (NH stretch), 3062 (w), 3019 (w), 1492 (w), 1456 (s), 745 (s), 702 (m) cm^-1. ¹H NMR (300 MHz, DMSO-d ₆): δ = 6.72-6.77 (t, 2 H, J = 7.41 Hz), 6.87-6.92 (t, 2 H, J = 7.32 Hz), 6.98-7.0 (d, 4 H, J = 7.71 Hz), 7.05-7.08 (d, 2 H, J = 7.83 Hz), 7.14-7.19 (t, 6 H, J = 7.14 Hz), 7.58 (s, 2 H), 9.93 (s, 2 H, NH). ¹³C NMR (75 MHz, DMSO-d ₆): δ = 140.0, 136.51, 134.29, 133.31, 132.44, 130.18, 128.11, 126.93, 124.61, 122.33, 117.64, 114.81, 111.47. MS: m/z = 409.8 [M + H]⁺. Anal. Calcd for C₃₀H₂₀N₂; C, 88.23; H, 4.90; N, 6.86. Found: C, 88.26; H, 4.93; N, 6.82.