Diels-Alder reaction—IX : The reaction of 1,7-, 2,7-, 2,6-, and 1,6-dihydroxynaphthalene and 6-bromo-2-naphthol with maleic anhydride and the resolution of some derivatives of the adducts

Abstract The Diels-Alder reaction of 1,7-, 2,7-, 2,6-, 1,6-dihydroxynaphthalene and 6-bromo-2-naphthol with maleic anhydride was investigated. All of these 2-naphthol derivatives gave exo - and endo -adducts (II and III) except for the bromo-naphthol, from which only endo -adduct was obtained. The assignment of exo or endo configuration was based on lactone formation on NaBH 4 reduction possible only from the exo isomer, comparison of NMR spectra and in some cases dipole moment measurements. The exo/endo ratios of the formed adducts vary over a wide range. Revolution of methoxy- trans -dicarboxylic acid VIII and IX was accomplished via the cinchonidine salts. The absolute configratuion of the resolved active compounds was determined by applying the octant rule.