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Synlett 2007(9): 1399-1402  
DOI: 10.1055/s-2007-980356
LETTER
© Georg Thieme Verlag Stuttgart · New York

Preliminary Studies on the Michael Addition of Quinones to Nitroolefins: (6bR,10aS)-7,8,9,10,10a,11-Hexahydro-6bH-benzo[a]carbazole-5,6-diones, (4aR,11bS)-1,2,3,4,4a,5-Hexahydro-11bH-benzo[b]carbazole-6,11-diones, and 1,2,3,4-Tetrahydro-5H-benzo[b]carbazole-6,11-diones

José C. Barcia, José M. Otero, Juan C. Estévez, Ramón J. Estévez*
Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
Fax: +34(981)591014; e-Mail: qorjec@usc.es;
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Publication History

Received 7 March 2007
Publication Date:
23 May 2007 (online)

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Abstract

We describe herein preliminary results on the novel Michael addition of naphthoquinones to nitroolefins and its application to the first synthesis of the novel (6bR,10aS)-7,8,9,10,10a,11-hexahydro-6bH-benzo[a]carbazole-5,6-diones and (4aR,11bS)-1,2,3,4,4a,5-hexahydro-11bH-benzo[b]carbazole-6,11-diones, together with a novel synthesis of 1,2,3,4-tetrahydro-5H-benzo[b]carbazole-6,11-diones.

Key words

annulations - asymmetric synthesis - cyclization - indoles - Michael additions - quinones

9

All new compounds gave satisfactory analytical and spectroscopic data. Selected physical and spectroscopic data follow.
Compound 6: mp 181-183 °C (MeOH). IR (NaCl): ν = 1673 (C=O), 1644 (C=O), 1540 (NO2), 1367 (NO2) cm-1. 1H NMR (CDCl3): δ = 1.38-1.64 (m, 2 H, CH2), 1.73-2.08 (m, 5 H, 2 × CH2 and CHH), 2.33-2.51 (m, 1 H, CHH), 3.71 (td, J = 11.6, 4.0 Hz, 1 H, CH), 5.40 (td, J = 11.6, 4.0 Hz, 1 H, CHNO2), 7.67 (td, J = 7.6, 1.5 Hz, 1 H, ArH), 7.76 (td, J = 7.6, 1.5 Hz, 1 H, ArH), 8.05 (dd, J = 7.6, 1.5 Hz, 1 H, ArH), 8.11 (dd, J = 7.6, 1.5 Hz, 1 H, ArH) ppm. 13C NMR (CDCl3): δ = 24.2 (CH2), 25.0 (CH2), 28.4 (CH2), 32.1 (CH2), 38.5 (CH), 85.9 (CHNO2), 121.6 (C), 126.2 (CH), 127.0 (CH), 129.0 (C), 132.7 (C), 133.1 (CH), 135.2 (CH), 153.4 (C), 181.0 (C=O), 183.7 (C=O) ppm. MS-FAB: m/z (%) = 302 (12) [MH+], 137 (100).
Compound 8: IR (NaCl): ν = 2935 (NH), 1681 (C=O) cm-1. 1H NMR (DMSO): δ = 1.16-2.27 (m, 8 H, 4 × CH2), 2.50-2.65 (m, 1 H, CH), 3.43-3.59 (m, 1 H, CH), 7.57-7.94 (m, 4 H, 4 × ArH), 9.21 (br s, 1 H, NH) ppm. 13C NMR (DMSO): δ = 24.3 (CH2), 25.3 (CH2), 28.4 (CH2), 30.0 (CH2), 47.5 (CH), 67.7 (CH), 115.7 (C), 124.2 (CH), 127.4 (C), 127.7 (CH), 131.5 (C), 131.6 (CH), 133.9 (CH), 161.1 (C), 171.2 (C=O), 183.6 (C=O) ppm. MS: m/z (%) = 253 (63) [M+], 195 (100).
Compound 9: IR (NaCl): ν = 2931 (NH), 1670 (C=O), 1628 (C=O) cm-1. 1H NMR (acetone): δ = 1.28-1.92 (m, 6 H, 3 × CH2), 2.20-2.31 (m, 1 H, CH), 2.56-2.74 (m, 2 H, CH2), 3.19-3.33 (m, 1 H, CH), 6.65 (br s, 1 H, NH), 7.68 (td, 1 H, J = 7.5, 1.6 Hz, ArH), 7.76 (td, 1 H, J = 7.5, 1.6 Hz, ArH), 7.91-7.99 (m, 2 H, 2 × ArH) ppm. 13C NMR (acetone): δ = 26.3 (CH2), 27.6 (CH2), 30.6 (CH2), 32.7 (CH2), 50.7 (CH), 70.3 (CH), 124.5 (C), 127.0 (CH), 127.1 (CH), 133.6 (CH), 135.8 (C), 135.9 (CH), 136.2 (C), 156.4 (C), 181.5 (C=O), 182.0 (C=O) ppm. MS: m/z (%) = 253 (91) [M+], 224 (100).
Compound 11a: mp 120-122 °C (MeOH). 1H NMR (CDCl3): δ = 1.45-2.18 (m, 6 H, 3 × CH2), 2.28-2.47 (m, 1 H, CHH), 2.53-2.74 (m, 1 H, CHH), 3.59 (dt, J = 13.0, 3.9 Hz, 1 H, CHAr), 3.91 (s, 3 H, OCH3), 3.96 (s, 3 H, OCH3), 5.07-5.16 (m, 1 H, CHNO2), 6.67 (s, 1 H, ArH), 7.43-7.59 (m, 2 H, 2 × ArH), 8.02 (d, J = 8.0 Hz, 1 H, ArH), 8.23 (d, J = 7.3 Hz, 1 H, ArH) ppm. 13C NMR (CDCl3): δ = 19.9 (CH2), 25.1 (CH2), 25.5 (CH2), 30.5 (CH2), 39.0 (CH), 55.6 (OCH3), 62.3 (OCH3), 86.1 (CHNO2), 102.6 (CH), 121.9 (CH), 122.4 (CH), 125.3 (CH), 125.9 (C), 126.5 (CH), 127.9 (C), 128.6 (C), 146.7 (C), 151.9 (C) ppm. MS: m/z (%) = 315 (100) [M+].
Compound 11b: mp 109-110 °C (MeOH). 1H NMR (CDCl3): δ = 1.42-2.14 (m, 6 H, 3 × CH2), 2.28-2.44 (m, 1 H, CHH), 2.50-2.69 (m, 1 H, CHH), 3.53 (dt, J = 13.1, 3.9 Hz, 1 H, CHAr), 3.85 (s, 3 H, OCH3), 3.92 (s, 3 H, OCH3), 3.95 (s, 3 H, OCH3), 5.06-5.13 (m, 1 H, CHNO2), 6.69 (s, 1 H, ArH), 6.84 (d, J = 7.9 Hz, 1 H, ArH), 7.40 (t, J = 7.9 Hz, 1 H, ArH), 7.62 (d, J = 7.9 Hz, 1 H, ArH) ppm. 13C NMR (CDCl3): δ = 19.8 (CH2), 25.0 (CH2), 25.4 (CH2), 30.5 (CH2), 38.9 (CH), 56.3 (OCH3), 56.8 (OCH3), 62.0 (OCH3), 85.9 (CH-NO2), 105.3 (CH), 106.2 (CH), 114.7 (CH), 117.8 (C), 126.6 (CH), 129.3 (C), 130.7 (C), 146.7 (C), 153.4 (C), 157.3 (C) ppm. MS: m/z (%) = 346 (94) [MH+], 299 (100).
Compound 15b: mp 300-301 °C (dec., CHCl3). 1H NMR (DMSO): δ = 1.60-1.82 (m, 4 H, 2 × CH2), 2.49-2.68 (m, 4 H, 2 × CH2), 4.03 (s, 3 H, OCH3), 7.20-7.31 (m, 1 H, ArH), 7.59-7.73 (m, 2 H, 2 × ArH), 11.95 (br s, 1 H, NH) ppm. 13C NMR (DMSO): δ = 21.5 (CH2), 22.0 (CH2), 22.2 (CH2), 22.6 (CH2), 56.0 (OCH3), 117.8 (C), 120.0 (C), 126.5 (CH), 128.8 (C), 130.0 (CH), 130.3 (C), 134.0 (C), 135.7 (CH), 139.2 (C), 158.7 (C), 176.3 (C=O), 181.3 (C=O) ppm. MS: m/z (%) = 281 (100) [M+].