The First Organocatalytic Hetero-Domino Knoevenagel-Diels-Alder-Epimerization Reactions: Diastereoselective Synthesis of Highly Substituted Spiro[cyclohexane-1,2′-indan]-1′,3′,4-triones

Abstract

L-Proline and pyrrolidine catalyzed the three component hetero-domino Knoevenagel-Diels-Alder-Epimerization reactions of readily available precursors enones 1a-i, arylaldehydes 2a-i and 1,3-indandione 3 to furnish highly substituted prochiral spiro[cyclohexane-1,2′-indan]-1′,3′,4-triones 5a-i in a highly diastereo­selective fashion with excellent yields. We demonstrate the first L-proline and pyrrolidine catalyzed epimerization reactions of trans-spiranes 6a-i to cis-spiranes 5a-i. Prochiral spiranes 5a-i are excellent­ starting materials for the synthesis of benzoannelated centro­polyquinanes.