Chiral dienes from enantiomerically pure enones. Highly stereoselective intramolecular Diels–Alder reaction involving ethenesulfonates

Abstract

Chiral dienes 2, easily prepared from α,β-unsaturated γ-alkoxy ketones, are subjected to inter- and intramolecular Diels–Alder reactions. Intermolecular cycloadditions of dienes 2 with 4-phenyl-1,2,4-triazole-3,5(2H)-dione 3 are found to be diastereoselective. Thermal or high pressure-induced intramolecular cycloadditions of trienes 8, featuring a sulfonate moiety connecting a diene and a dienophile, are found to proceed with high diastereoselectivity to give sultones 11 and 12. An interesting domino process is observed when enone 5 is reacted with sodium hydride. In this reaction sequence, the decahydropyrano[2,3,4-de]chromene derivative 15 was formed. NMR spectroscopic studies allowed the assignments of the configurations of the bi- and tri-cyclic products.