[4+2] Cycloadditions between 2-pyrones and benzyne. Application to the synthesis of binaphthyls

Article abstract of DOI:10.1016/S0040-4039(97)01176-3

Cycloaddition of benzyne to 2-pyrones affords the corresponding naphthalene derivatives, the intermediate bicyclic adduct not being detected. Benzopyrones do not react with benzyne under similar conditions probably because this would require the fused aromatic ring to lose aromaticity in the Diels-Alder transition state, which is therefore destabilized. 4-Bromo-2-naphthoic acid methyl ester (obtained by cycloaddition of benzyne to 3-bromo-5-carboxymethylpyran-2-one) can be transformed into 3,3'-dicarboxymethyl-1,1'-binaphthyl by Ni-mediated dimerization.