Studies on chemo- and diastereo-selectivity of the Diels-Alder reactions of sulfinyltoluquinones with cyclopentadiene

Sulfinyltoluquinones (2a-2c) were submitted to thermal or catalyzed [4+2] cycloaddition reactions with cyclopentadiene. For p-tolylsulfmyltoluquinones (2b) and (2c), almost complete C2-C3-chemo- and unlike-diastereoselectivity was achieved by catalysis with ZnBr2, yielding adducts 6. Under thermal conditions, Diels-Alder reaction took place at the C5-C6 double bonds of quinones 2a-2c, generating mixtures of diastereoisomeric like- and unlike-adducts 4. Key words: Diels-Alder reaction, sulfinyltoluquinones, sulfinyl group, stereochemical control, Ti-facial selectivity. On a soumis les sulfinyltoluquinones (2a-2c) a des reactions de cycloaddition thermiques ou catalysees avec le cyclopentadiene. Avec le ZnBr2 comme catalyseur, les p-tolylsulfmyltoluquinones (2b) et (2c) conduisent a 1a formation des adduits 6 et al diastereoselectivite chimique et dissemblable au niveau de 1a liaison C2-C3 est pratiquement complete. Dans des conditions thermiques, 1a reaction de Diels-Alder se produit au niveau des doubles liaisons C5-C6 des quinones 2a-2c qui conduit a 1a formation d'adduits 4 sous 1a forme de melanges diastereomeres semblables et dissemblables. Mots-cles : reaction de Diels-Alder, sulfinyltoluquinones, groupe sulfinyle, controle stereochimique, selectivite de 1a face n. [Traduit par 1a Redaction]
Introduction The Diels-Alder (DA) reaction remains as one of the most powerful methods for the construction of cyclic systems with potential for stereochemical control of up to four stereogenic centers [...]