- Reductive opening of 1H,3H-benzo[de]isochromene: Synthesis of 1,8-difunctionalised naphthalenes
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The lithiation of 1H,3H-benzo[de]isochromene (6) with lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5% molar) in THF at -50°C gives dianionic intermediate 7, which by reaction with different electrophiles {H2O, D2O, tBuCHO, PhCHO, Me 2CO, (CH3CH2)2CO, [CH 3(CH2)4]2CO, (CH2) 5CO, (CH2)7CO, (-)-menthone} at the same temperature followed by hydrolysis leads to functionalised alcohols 8. If after addition of a carbonyl compound as the first electrophile [tBuCHO, (CH2)5CO, (-)-menthone], the resulting dialcoholate 9 is allowed to react at 0°C, a second lithiation takes place to give intermediate 10 which by reaction with a second electrophile [H2O, tBuCHO, (CH2)5CO, CO2], yields, after hydrolysis, 1,8-difunctionalised naphthalenes 11. Cyclization under acidic conditions of diols 8e-i gives oxygen-containing eight-membered heterocycles, which are homologous to the starting material 6.
- Foubelo, Francisco,Moreno, Benjamín,Yus, Miguel
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- Cyclic acetals as precursors of substituted isochromans and naphthoxepines
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The reaction of 6,8-dioxabenzocycloheptenes 3 or 8,10-dioxacycloocta[de]naphthalenes 5 [easily prepared from the dibenzylic diols 1 and 4, respectively, and a carbonyl compound] with an excess of lithium and a catalytic amount of DTBB (2.5 mol %) in THF a
- Garcia, Daniel,Foubelo, Francisco,Yus, Miguel
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p. 507 - 519
(2008/09/18)
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