Synlett 2010(18): 2808-2812  
DOI: 10.1055/s-0030-1258818
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Copper-Catalyzed Aerobic Oxidative Coupling of Aminocarbazoles and Aminoindoles: Synthesis of Diindolophenazines and Dipyrrolophenazines

Ramu Meesala, Rajagopal Nagarajan*
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Fax: +91(40)23012460; e-Mail: rnsc@uohyd.ernet.in;
Further Information

Publication History

Received 26 July 2010
Publication Date:
08 October 2010 (online)

Abstract

We have developed a simple method for the synthesis of diindolophenazine and dipyrrolophenazine derivatives by the aerobic oxidative coupling of 3-aminocarbazole and 2,3-dimethyl-5-aminoindole derivatives, respectively, in the presence of catalytic CuBr (10 mol%) in DMSO at 80 ˚C while open to air.

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CCDC number of 2d is 760485.

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General Procedure for the Synthesis of 1,9-Dihydrodiindolo[3,2- a :3,2- h ]phenazine (2a) A mixture of 3-aminocarbazole (1.0 mmol) and CuBr (10 mol%) in DMSO was heated at 80 ˚C open to air for 6 h. After completion of the reaction, the reaction mixture was poured on to H2O and extracted with EtOAc (3 × 30 mL). The solvent was dried over anhyd Na2SO4 and evaporated under reduced pressure. The crude material was purified by column chromatography using silica gel (100-200 mesh size) and eluted with a mixture of hexane and EtOAc to obtain the pure product of diindolophenazine. IR (KBr): 3393, 3053, 2926, 2854, 1726, 1601, 1462, 1379, 1265, 1074, 895, 742 cm. ¹H NMR (400 MHz, DMSO-d 6): δ = 12.18 (2 H, s), 9.06 (2 H, d, J = 7.6 Hz), 8.30 (2 H, d, J = 9.2 Hz), 8.23 (2 H, d, J = 8.8 Hz), 7.73 (2 H, d, J = 8.0 Hz), 7.49 (2 H, t, J = 7.2 Hz), 7.43 (2 H, t, J = 7.6 Hz). ¹³C NMR (100 MHz, DMSO-d 6): δ = 139.9, 139.0, 138.9, 138.5, 127.5, 125.2, 123.8, 123.2, 121.0, 120.3, 114.3, 112.4. LC-MS (pos. mode): m/z = 359 [M + H+]. Anal. Calcd for C24H14N4: C, 80.43; H, 3.94; N, 15.63. Found: C, 80.25; H, 3.89; N, 15.77.