title: Expanding the Scope of Primary Amine Catalysis: Stereoselective Synthesis of Indanedione-Fused 2,6-Disubstituted trans-Spirocyclohexanones.
abstract: A cinchona-alkaloid-derived chiral primary-amine-catalyzed enantioselective method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spirocyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes bearing an additional α-substitution on the cyclohexanone ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels-Alder reaction and a stepwise Michael addition, for the formation of corresponding products.
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: G
authors.initials: G
authors.lastname: Madhusudhan Reddy
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: Chi-Ting
authors.initials: CT
authors.lastname: Ko
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: Kai-Hong
authors.initials: KH
authors.lastname: Hsieh
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: Chia-Jui
authors.initials: CJ
authors.lastname: Lee
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: Utpal
authors.initials: U
authors.lastname: Das
authors.affiliation: Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan, ROC.
authors.forename: Wenwei
authors.initials: W
authors.lastname: Lin