title: Diastereodivergent Catalysis Using Modularly Designed Organocatalysts: Synthesis of both cis- and trans-Fused Pyrano[2,3-b]pyrans.
abstract: Both enantiomers of cis- and trans-fused 3,4,4a,8a-tetrahydro-2H,5H-pyrano[2,3-b]pyran-7-carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse-electron-demand hetero-Diels-Alder/oxa-Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self-assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249-0698, USA.
authors.forename: Huicai
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249-0698, USA.
authors.forename: Swapna
authors.initials: S
authors.lastname: Konda
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249-0698, USA. cong.zhao@utsa.edu.
authors.forename: John C-G
authors.initials: JC
authors.lastname: Zhao
keywords: asymmetric catalysis; heterocycles; organocatalysis; self-assembly; synthetic methods