Reductive opening of 1H,3H-benzo[de]isochromene:: synthesis of 1,8-difunctionalised naphthalenes

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 -50degreesC gives dianionic intermediate 7, which by reaction with different electrophiles {H2O, D2O, (BuCHO)-Bu-t, PhCHO, Me2CO, (CH3CH2)(2)CO, [CH3(CH2)(4)](2)CO, (CH2)(5)CO, (CH2)(7)CO, (-)-menthone} at the same temperature followed by hydrolysis leads to functionalised alcohols 8. If after addition of a carbonyl compound as the first electrophile [(BuCHO)-Bu-t, (CH2)(5)CO, (-)-menthone], the resulting dialcoholate 9 is allowed to react at 0degreesC, a second lithiation takes place to give intermediate 10 which by reaction with a second electrophile [H2O, (BuCHO)-Bu-t, (CH2)(5)CO, 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. (C) 2004 Elsevier Ltd. All rights reserved.