title: Enantioselective synthesis of 4H-pyranonaphthoquinones via sequential squaramide and silver catalysis.
abstract: An enantioselective one-pot Michael addition/hydroalkoxylation reaction between 2-hydroxy-1,4-naphthoquinones and alkyne-tethered nitroalkenes catalyzed by a cinchona-derived squaramide and a silver(I) salt has been developed. The sequential protocol provides a direct access to 4H-pyranonaphthoquinones in moderate to very good yields and good to excellent enantioselectivities at a very low catalyst loading (0.5 mol%) of the squaramide.
authors.affiliation: Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany. enders@rwth-aachen.de.
authors.forename: Uğur
authors.initials: U
authors.lastname: Kaya
authors.forename: Pankaj
authors.initials: P
authors.lastname: Chauhan
authors.forename: Daniel
authors.initials: D
authors.lastname: Hack
authors.forename: Kristina
authors.initials: K
authors.lastname: Deckers
authors.forename: Rakesh
authors.initials: R
authors.lastname: Puttreddy
authors.forename: Kari
authors.initials: K
authors.lastname: Rissanen
authors.forename: Dieter
authors.initials: D
authors.lastname: Enders