Control of the ring selectivity in Diels-Alder reactions of naphthazarins mediated by sulfur functions

Article abstract of DOI:10.1016/S0040-4039(00)73100-5

Ring selectivity of Diels-Alder reactions of naphthazarin thioderivatives with cyclopentadiene is controlled by choosing the adequate sulfur substituent: p-tolylsulfonyl and p-tolylsulfinyl (under BF₃·OEt₂ catalysis) derivatives give cycloaddition only on the C-6 substituted tautomer. The opposite ring selectivity (exclusive reaction on the C-2 substituted tautomer) is achieved in the reaction of the p-tolylsulfonyl derivative at -78°C.