title: Enantioselective Organocatalytic Diels-Alder Trapping of Photochemically Generated Hydroxy-o-Quinodimethanes.
abstract: The photoenolization/Diels-Alder strategy offers straightforward access to synthetically valuable benzannulated carbocyclic products. This historical light-triggered process has never before succumbed to efforts to develop an enantioselective catalytic approach. Herein, we demonstrate how asymmetric organocatalysis provides simple yet effective catalytic tools to intercept photochemically generated hydroxy-o-quinodimethanes with high stereoselectivity. We used a chiral organic catalyst, derived from natural cinchona alkaloids, to activate maleimides toward highly stereoselective Diels-Alder reactions. An unconventional mechanism of stereocontrol is operative, wherein the organocatalyst is actively involved in both the photochemical pathway, by leveraging the formation of the reactive photoenol, and the stereoselectivity-defining event.
authors.affiliation: ICIQ-Institute of Chemical Research of Catalonia, Barcelona Institute of Science and Technology, Avenida Països Catalans 16, 43007, Tarragona, Spain.
authors.forename: Luca
authors.initials: L
authors.lastname: Dell'Amico
authors.affiliation: ICIQ-Institute of Chemical Research of Catalonia, Barcelona Institute of Science and Technology, Avenida Països Catalans 16, 43007, Tarragona, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Vega-Peñaloza
authors.affiliation: ICIQ-Institute of Chemical Research of Catalonia, Barcelona Institute of Science and Technology, Avenida Països Catalans 16, 43007, Tarragona, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Cuadros
authors.affiliation: ICREA-Catalan Institution for Research and Advanced Studies, Passeig Lluís Companys 23, 08010, Barcelona, Spain. pmelchiorre@iciq.es.|ICIQ-Institute of Chemical Research of Catalonia, Barcelona Institute of Science and Technology, Avenida Països Catalans 16, 43007, Tarragona, Spain. pmelchiorre@iciq.es.
authors.forename: Paolo
authors.identifier: http://orcid.org/0000-0001-8722-4602
authors.initials: P
authors.lastname: Melchiorre
keywords: Diels-Alder reactions; asymmetric catalysis; organocatalysis; photochemistry; synthetic methods