title: Mechanistic investigation of the Ru-catalyzed hydroamidation of terminal alkynes.
abstract: The ruthenium-catalyzed hydroamidation of terminal alkynes has evolved to become a broadly applicable tool for the synthesis of enamides and enimides. Depending on the catalyst system employed, the reaction leads chemo-, regio-, and stereoselectively to a single diastereoisomer. Herein, we present a comprehensive mechanistic study of the ruthenium-catalyzed hydroamidation of terminal alkynes, which includes deuterium-labeling, in situ IR, in situ NMR, and in situ ESI-MS experiments complemented by computational studies. The results support the involvement of ruthenium-hydride and ruthenium-vinylidene species as the key intermediates. They are best explained by a reaction pathway that consists of an oxidative addition of the amide, followed by insertion of a π-coordinated alkyne into a ruthenium-hydride bond, rearrangement to a vinylidene species, nucleophilic attack of the amide, and finally reductive elimination of the product.
authors.affiliation: Fachbereich Chemie and State Reaserch Center OPTIMAS, TU Kaiserslautern, Erwin-Schrödinger-Strasse 52-54, 67663 Kaiserslautern, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Arndt
authors.forename: Kifah S M
authors.initials: KS
authors.lastname: Salih
authors.forename: Andreas
authors.initials: A
authors.lastname: Fromm
authors.forename: Lukas J
authors.initials: LJ
authors.lastname: Goossen
authors.forename: Fabian
authors.initials: F
authors.lastname: Menges
authors.forename: Gereon
authors.initials: G
authors.lastname: Niedner-Schatteburg
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000480:Alkynes; D000577:Amides; D012428:Ruthenium