title: Reversible Oxidative Addition at Carbon.
abstract: The reactivity of N-heterocyclic carbenes (NHCs) and cyclic alkyl amino carbenes (cAACs) with arylboronate esters is reported. The reaction with NHCs leads to the reversible formation of thermally stable Lewis acid/base adducts Ar-B(OR)2⋅NHC (Add1-Add6). Addition of cAACMeto the catecholboronate esters 4-R-C6H4-Bcat (R=Me, OMe) also afforded the adducts 4-R-C6H4Bcat⋅cAACMe(Add7, R=Me and Add8, R=OMe), which react further at room temperature to give the cAACMering-expanded products RER1 and RER2. The boronate esters Ar-B(OR)2of pinacol, neopentylglycol, and ethyleneglycol react with cAAC at RT via reversible B-C oxidative addition to the carbene carbon atom to afford cAACMe(B{OR}2)(Ar) (BCA1-BCA6). NMR studies of cAACMe(Bneop)(4-Me-C6H4) (BCA4) demonstrate the reversible nature of this oxidative addition process.
authors.affiliation: Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Antonius F
authors.initials: AF
authors.lastname: Eichhorn
authors.affiliation: Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Fuchs
authors.affiliation: Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Flock
authors.affiliation: Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Todd B
authors.identifier: 0000-0002-9990-0169
authors.initials: TB
authors.lastname: Marder
authors.affiliation: Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Udo
authors.identifier: 0000-0002-0759-1806
authors.initials: U
authors.lastname: Radius
keywords: B−C bond activation; N-heterocyclic carbenes; arylboronate esters; cyclic alkyl amino carbenes