Synlett 2011(17): 2559-2561  
DOI: 10.1055/s-0030-1289514
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Tandem Route to the Synthesis of Carbazolo[1,2-b]carbazoles

T. Krishna Chaitanya, 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 25 June 2011
Publication Date:
06 October 2011 (online)

Abstract

A simple and facile synthesis of carbazolo[1,2-b]carbazole derivatives via Michael addition of 2-methylindole, condensation of methyl group with the carbonyl, dehydration followed by aromatization by heating in hydrothermal oven is reported.

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A mixture of 2-methylindole (1 mmol), chalcones (1 mmol), 3 Å MS (0.2 g), Pd/C (15 mg, 10%), and AcOH (10 mL) was stirred and loaded under nitrogen atmosphere in an autoclave (25 mL). The autoclave was heated at 180 ˚C for 48 h. After allowing to r.t., the reaction mixture was diluted with EtOAc, filtered through Celite, washed with 5% aq bicarbonate solution and H2O, concentrated in vacuum. In TLC, the products show a characteristic blue fluorescence. The residue is purified by column chromatography to provide the desired carbazolocarbazole. Unreacted starting materials were recovered as nonpolar fractions.
9-Phenyl-2,14-dihydrocarbazolo[1,2- b ]carbazole Yield 43%; mp 176-178 ˚C. IR (KBr): νmax = 3412, 1602, 1466, 1317, 740, 694 cm. ¹H NMR (400 MHz, DMSO-d 6): δ = 11.66 (s, 1 H), 10.82 (s, 1 H), 8.50 (s, 1 H), 8.01 (d, J = 8.0 Hz, 1 H), 7.81 (d, J = 8.0 Hz, 1 H), 7.56-7.64 (m, 4 H), 7.49 (d, J = 7.6 Hz, 2 H), 7.27-7.42 (m, 4 H), 7.17 (t, J = 7.6 Hz, 1 H), 6.76-6.83 (m, 2 H). ¹³C NMR (100 MHz, DMSO-d 6): δ = 142.8, 139.2, 139.1, 138.6, 135.6, 133.2, 133.0, 132.2, 129.7, 127.2, 125.2, 124.6, 123.9, 122.6, 122.2, 122.1, 121.2, 120.0, 119.5, 118.9, 117.5, 116.7, 116.4, 111.8, 111.1, 100.6. MS (pos. Mode): m/z = 382. Anal. Calcd (%) for C28H18N2: C, 87.93; H, 4.74; N, 7.32. Found: C, 87.85; H, 4.81; N, 7.26.