title: Mechanistic Studies on a Cooperative NHC Organocatalysis/Palladium Catalysis System: Uncovering Significant Lessons for Mixed Chiral Pd(NHC)(PR3) Catalyst Design.
abstract: A comprehensive investigation of the mechanism of the highly enantioselective Pd(PPh3)4/NHC-catalyzed annulation of vinyl benzoxazinanones and enals has been conducted. A study of reaction orders supports the postulated cooperative catalysis. Interestingly, a detailed investigation of the catalytically active palladium species pointed toward a dual role of the NHC acting as an organocatalyst and forming a novel mixed ligand Pd/NHC/phosphine complex. The catalytically active Pd/NHC/phosphine complex represents a new class of chiral palladium catalyst. Remarkably, phosphine plays a crucial role in this transformation. These complexes could be characterized by X-ray crystallographic analysis and employed as catalysts for the enantioselective [4 + 1] annulation reaction of vinyl benzoxazinones and sulfur ylides in good yields and good enantioselectivities.
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Chang
authors.identifier: 0000-0003-4022-9582
authors.initials: C
authors.lastname: Guo
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Janssen-Müller
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Mirco
authors.initials: M
authors.lastname: Fleige
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lerchen
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
authors.forename: Frank
authors.identifier: 0000-0002-0648-956X
authors.initials: F
authors.lastname: Glorius