Synthesis 2020; 52(17): 2483-2496
DOI: 10.1055/s-0040-1707185
short review
© Georg Thieme Verlag Stuttgart · New York

Catch It If You Can: Copper-Catalyzed (Transfer) Hydrogenation Reactions and Coupling Reactions by Intercepting Reactive Intermediates Thereof

Authors


This work was supported by the Deutsche Forschungsgemeinschaft (DFG) (German Research Council) (Emmy Noether Fellowship for J.F.T., TE1101/2-1) and by the Fonds der Chemischen Industrie (Liebig-Stipendium­ for J.F.T.).
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Publication History

Received: 21 May 2020

Accepted after revision: 18 June 2020

Publication Date:
13 July 2020 (online)


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Abstract

The key reactive intermediate of copper(I)-catalyzed alkyne semihydrogenations is a vinylcopper(I) complex. This intermediate can be exploited as a starting point for a variety of trapping reactions. In this manner, an alkyne semihydrogenation can be turned into a dihydrogen­-mediated coupling reaction. Therefore, the development of copper-catalyzed (transfer) hydrogenation reactions is closely intertwined with the corresponding reductive trapping reactions. This short review highlights and conceptualizes the results in this area so far, with H2-mediated carbon–carbon and carbon–heteroatom bond-forming reactions emerging under both a transfer hydrogenation setting as well as with the direct use of H2. In all cases, highly selective catalysts are required that give rise to atom-economic multicomponent coupling reactions with rapidly rising molecular complexity. The coupling reactions are put into perspective by presenting the corresponding (transfer) hydrogenation processes first.

1 Introduction: H2-Mediated C–C Bond-Forming Reactions

2 Accessing Copper(I) Hydride Complexes as Key Reagents for Coupling Reactions; Requirements for Successful Trapping Reactions

3 Homogeneous Copper-Catalyzed Transfer Hydrogenations

4 Trapping of Reactive Intermediates of Alkyne Transfer Semi­hydrogenation Reactions: First Steps Towards Hydrogenative Alkyne Functionalizations

5 Copper(I)-Catalyzed Alkyne Semihydrogenations

6 Copper(I)-Catalyzed H2-Mediated Alkyne Functionalizations; Trapping of Reactive Intermediates from Catalytic Hydrogenations

6.1 A Detour: Copper(I)-Catalyzed Allylic Reductions, Catalytic Generation of Hydride Nucleophiles from H2

6.2 Trapping with Allylic Electrophiles: A Copper(I)-Catalyzed Hydro­allylation Reaction of Alkynes

6.3 Trapping with Aryl Iodides

7 Conclusion