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Synlett 2008(17): 2625-2628  
DOI: 10.1055/s-0028-1083519
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A New One-Pot Procedure for a Ring Contraction Reaction using Iodine/H2O2

Sabrina B. Ferreiraa, Carlos R. Kaisera, Vitor F. Ferreira*b
a Instituto de Química, LABRMN, Universidade Federal do Rio de Janeiro, Ilha do Fundão, 21949-900, Rio de Janeiro, Brazil
b Instituto de Química, Departamento de Química Orgânica, Universidade Federal Fluminense, 24020-141 Niterói, Rio de Janeiro, Brazil
Fax: +55(21)26292362; e-Mail: cegvito@vm.uff.br;
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Publication History

Received 17 March 2008
Publication Date:
01 October 2008 (online)

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Abstract

A new procedure for ring contraction from 1,2-quinones using aqueous H2O2 (30%) and catalytic amount of I2 in acetonitrile is reported.

Key words

ring contractions - quinones - lapachones - iodine - hydrogen peroxide

19

Preparation of 18; Representative Procedure for Ketones 18-27: To a solution of I2 (0.1 mmol, 25.4 mg) and 30% aq H2O2 (4 mmol, 0.45 mL) in MeCN (10 mL),
β-lapachone (1; 1 mmol, 154 mg) was added and the solution was stirred at r.t. for 24 h. The reaction mixture was concentrated under reduced pressure and added to CH2Cl2 (10 mL). The organic phase was separated and washed with aqueous solution of sat. Na2S2O3 (3 × 10 mL), dried over anhyd Na2SO4 and evaporated. The crude product was purified by flash column chromatography on silica gel using hexane-EtOAc as eluent.
2,2-Dimethyl-3,4-dihydro-2 H -indeno[1,2- b ]pyran-5-one (18): yellow solid; mp 54-56 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 1.23 (s, 3 H, Me), 1.46 (s, 3 H, Me), 1.98-2.08 (m, 1 H, H-3a), 2.21-2.29 (m, 2 H, H-3b, H-4a), 2.95-3.04 (m, 1 H, H-4b), 7.82 (m, 2 H, H-9), 8.04 (ddd, J = 0.5, 1.2, 8.3 Hz, 1 H, H-6), 8.22 (ddd, J = 0.5, 1.2, 8.3 Hz, 1 H, H-9). ¹³C NMR (75 MHz, CDCl3): δ = 27.5 (Me), 29.0 (Me), 32.6 (C-3), 36.4 (C-4), 88.2 (C-2), 110.0 (C-4a), 126.5 (C-9), 128.5 (C-9a), 130.1 (C6), 131.4 (C-6a), 134.1 (C-7), 134.9 (C8), 162.4 (C-9b), 187.2 (C=O). Anal. Calcd for C14H14O2: C, 78.48; H, 6.59. Found: C, 78.28; H, 6.82.
5 H -Cyclopenta[2,1- b :3,4- b ′]dipyridin-5-one (22): pale yellow solid; mp 213-215 ºC. ¹H NMR (300 MHz, CDCl3): δ = 7.36 (dd, J = 5.2, 7.3 Hz, 2 H, H-4, H-6), 7.98 (dd, J = 1.9, 7.3 Hz, 2 H, H-3, H-7), 8.78 (dd, J = 1.9, 5.2 Hz, 2 H,
H-2, H-8). ¹³C NMR (75 MHz, CDCl3): δ = 124.6 (C-3,
C-7), 128.9 (C-4, C-6), 131.4 (C-4a, C-5a), 154.7 (C-2, C-8), 163.0 (C-8a, C8b), 188.5 (C=O). Anal. Calcd for C11H6N2O: C, 72.52; H, 3.32; N, 15.38. 8.78. Found: C, 72.45; H, 3.30; N, 15.28.
3-Methoxy-1 H -inden-1-one (25): pale yellow solid; mp 67-69 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 3.98 (s, 3 H, OMe), 5.58 (s, 1 H, H-2), 7.45 (m, 4 H, H-4, H-5, H-6, H-7). ¹³C NMR (75 MHz, CDCl3): δ = 55.5 (OMe), 97.0 (C-2), 122.3 (C-4), 122.5 (C-5), 123.3 (C-3a), 127.0 (C-6), 130.1 (C-7a), 123.2 (C-7), 160.2 (C-3), 190.5 (C=O). Anal. Calcd for C10H8O2: C, 74.99; H, 5.03. Found: C, 75.00; H, 5.00.
2,4-Di- tert -butylcyclopentadienone (27): yellow solid; mp 32-35 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 1.14 (s, 9 H, Me), 1.20 (s, 9 H, 3 × Me), 7.70 (s, 1 H, H-5), 6.40 (s, 1 H, H-3). ¹³C NMR (75 MHz, CDCl3): δ = 27.6 (Me), 28.9 (Me), 32.4 (C-t-B), 33.5 (C-t-Bu), 110.5 (C-5), 135.6 (C-3), 140.0 (C-2), 170.5 (C-4), 190.5 (C=O). Anal. Calcd for C13H20O: C, 80.44; H, 9.82. Found: C, 80.55; H, 9.90.