title: Cooperative Reductive Elimination: The Missing Piece in the Oxidative-Coupling Mechanistic Puzzle.
abstract: The reaction between benzoic acid and methylphenylacetylene to form an isocoumarin is catalyzed by Cp*Rh(OAc)2 in the presence of Cu(OAc)2 (H2 O) as an oxidant and a leading example of oxidative-coupling reactions. Its mechanism was elucidated by DFT calculations with the B97D functional. The conventional mechanism, with separate reductive-elimination and reoxidation steps, was found to yield a naphthalene derivative as the major product by CO2 extrusion, contradicting experimental observations. The experimental result was reproduced by an alternative mechanism with a lower barrier: In this case, the copper acetate oxidant plays a key role in the reductive-elimination step, which takes place through a transition state containing both rhodium and copper centers. This cooperative reductive-elimination step would not be accessible with a generic oxidant, which, again, is in agreement with available experimental data.
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avgda. Països Catalans, 16, Tarragona, 43007), Catalonia, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Funes-Ardoiz
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avgda. Països Catalans, 16, Tarragona, 43007), Catalonia, Spain. fmaseras@iciq.es.|Department de Química, Universitat Autònoma de Barcelona, Bellaterra, 08193), Catalonia, Spain. fmaseras@iciq.es.
authors.forename: Feliu
authors.identifier: http://orcid.org/0000-0001-8806-2019
authors.initials: F
authors.lastname: Maseras
keywords: C−C coupling; density functional calculations; oxidative coupling; reaction mechanisms; reductive elimination