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.