title: Decarboxylative [4+2] Cycloaddition by Synergistic Palladium and Organocatalysis.
abstract: A novel reaction based on synergistic catalysis, combining palladium- and organocatalysis has been developed. The palladium catalyst activates vinyl benzoxazinanones via a decarboxylation to undergo a [4+2] cycloaddition with iminium-ion activated α,β-unsaturated aldehydes. The reaction is demonstrated to proceed for a number of combinations of vinyl benzoxazinanones reacting with α,β-unsaturated aldehydes, providing highly substituted vinyl tetrahydroquinolines in good to high yields, and excellent enantio- and diastereoselectivities (>98 % ee and >20:1 d.r.). The palladium catalyst used in the synergistic catalysis can be re-used in a one-pot sequential coupling reaction with an aromatic boronic acid forming the coupling product in 95 % yield, >20:1 d.r. and 99 % ee.
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Lars A
authors.initials: LA
authors.lastname: Leth
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Florian
authors.initials: F
authors.lastname: Glaus
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Marta
authors.initials: M
authors.lastname: Meazza
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Liang
authors.initials: L
authors.lastname: Fu
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Mathias K
authors.initials: MK
authors.lastname: Thøgersen
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Emma A
authors.initials: EA
authors.lastname: Bitsch
authors.affiliation: Department of Chemistry, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Karl Anker
authors.initials: KA
authors.lastname: Jørgensen
keywords: asymmetric catalysis; cycloaddition; decarboxylation; heterocycles; synergistic catalysis