E–Z isomerization in Suzuki cross-couplings of haloenones: ligand effects and evidence for a separate catalytic cycle

2018 ◽  
Vol 16 (7) ◽  
pp. 1134-1143 ◽  
Author(s):  
Navneet K. Chehal ◽  
Peter H. M. Budzelaar ◽  
Philip G. Hultin
Keyword(s):  
Cross Coupling ◽  
Catalytic Cycle ◽  
Coupling Reactions ◽  
Present Evidence ◽  
Ligand Effects ◽  
Cross Coupling Reactions

We present evidence for a palladocyclic enolate-like pathway for isomerization of enones occurring during Suzuki cross-coupling reactions.

scholarly journals The significance of phosphoniocarbynes in halocarbyne cross-coupling reactions

2020 ◽  
Vol 56 (42) ◽  
pp. 5673-5676 ◽  
Author(s):  
Liam K. Burt ◽  
Richard L. Cordiner ◽  
Anthony F. Hill ◽  
Richard A. Manzano ◽  
Jörg Wagler
Keyword(s):  
Cross Coupling ◽  
Catalytic Cycle ◽  
Coupling Reactions ◽  
Cross Coupling Reactions

Competent intermediates as well as productive and non-productive tangents have been identified in the catalytic cycle for palladium(0)–copper(i) mediated synthesis of propargylidynes via cross coupling reactions of bromocarbyne complexes with alkynes.

Cu(I)/Cu(III) catalytic cycle involved in Ullmann-type cross-coupling reactions

2014 ◽  
Vol 86 (3) ◽  
pp. 345-360 ◽  
Author(s):  
Xavi Ribas ◽  
Imma Güell
Keyword(s):  
Bond Formation ◽  
Cross Coupling ◽  
Catalytic Cycle ◽  
Model Systems ◽  
Coupling Reactions ◽  
Research Groups ◽  
Model Compounds ◽  
General Methodology ◽  
The Past ◽  
Cross Coupling Reactions

Abstract Copper-catalyzed cross-coupling reactions for C–heteroatom bond formation have attracted numerous research groups in the past 15 years aiming at finding more efficient methodologies under milder conditions. The use of auxiliary ligands has tremendously improved Ullmann-type couplings although a general methodology for different heteroatom-nucleophiles is still lacking. Mechanistic insights are seen as a clue for designing new effective, broad-scope and general methodologies. In this review we describe the widely discussed mechanistic options for this reaction and the use of model compounds to unravel key mechanistic aspects for copper-catalyzed C–heteroatom transformations. Stable aryl-Cu(III) species in model systems are shown to be reliable active catalysts in the coupling of a broad nucleophile scope such as phenols, amides, sulfides, selenides, phosphites, halides and also activated methylene susbtrates for carbon–carbon couplings.

Transient and stable interm ediates in cross-coupling reactions

1988 ◽  
Vol 326 (1592) ◽  
pp. 587-594 ◽  
Keyword(s):  
Cross Coupling ◽  
Platinum Complexes ◽  
Palladium Complexes ◽  
Catalytic Cycle ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Label Distribution ◽  
Sequential Formation ◽  
Bromide Complex

The mechanism of catalytic cross coupling mediated by palladium complexes has been examined. This has involved the successful in situ generation of a biphosphine palladium(0) species, and then observation of the sequential formation of an η 2 -olefin complex and an η 1 -alkenyl bromide complex on addition of an alkene. The latter is a stable isolable species, which reacts rapidly with added arylmagnesium halides; only the η2-olefin complex is observed after this step at —80 °C. The contribution of these intermediates to the catalytic cycle of cross coupling was tested, employing a 13C-labelled alkenyl iodide, and determ ining the label distribution in both palladium complex and product. On this basis it was dem onstrated that the η 1 -alkenyl iodide is a true interm ediate in cross coupling, and the reaction cycle occurs w ithout the intervention of a second molecule of substrate. Platinum complexes are more stable than their isostructural palladium analogues. All the interm ediates in a slow but sustainable catalytic cycle have been characterised in solution. Oxidative addition of the alkenyl bromide is profoundly accelerated by one-electron oxidizing agents.

Dual Nickel/Palladium-Catalyzed Reductive Cross-Coupling Reactions Between Two Phenol Derivatives

2020 ◽  
Author(s):  
Baojian Xiong ◽  
Yue Li ◽  
Yin Wei ◽  
Søren Kramer ◽  
Zhong Lian
Keyword(s):  
Functional Group ◽  
Low Cost ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Phenol Derivatives ◽  
Cross Coupling Reactions ◽  
Palladium Catalyzed ◽  
One Step ◽  
Aryl Tosylates ◽  
Low Sensitivity

Cross-coupling between substrates that can be easily derived from phenols is highly attractive due to the abundance and low cost of phenols. Here, we report a dual nickel/palladium-catalyzed reductive cross-coupling between aryl tosylates and aryl triflates; both substrates can be accessed in just one step from readily available phenols. The reaction has a broad functional group tolerance and substrate scope (>60 examples). Furthermore, it displays low sensitivity to steric effects demonstrated by the synthesis of a 2,2’disubstituted biaryl and a fully substituted aryl product. The widespread presence of phenols in natural products and pharmaceuticals allow for straightforward late-stage functionalization, illustrated with examples such as Ezetimibe and tyrosine. NMR spectroscopy and DFT calculations indicate that the nickel catalyst is responsible for activating the aryl triflate, while the palladium catalyst preferentially reacts with the aryl tosylate.

An Iron-Based Catalyst Enables The Enantioconvergent Synthesis of Chiral 1,1-Diarylalkanes Through a Suzuki-Miyaura Cross-Coupling Reaction

2020 ◽  
Author(s):  
Chet Tyrol ◽  
Nang Yone ◽  
Connor Gallin ◽  
Jeffery Byers
Keyword(s):  
Coupling Reaction ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Radical Intermediates ◽  
Cross Coupling Reactions ◽  
Cross Coupling Reaction ◽  
Boronic Esters ◽  
Carbon Centered Radical ◽  
Iron Based ◽  
High Yields

By using an iron-based catalyst, access to enantioenriched 1,1-diarylakanes was enabled through an enantioselective Suzuki-Miyaura crosscoupling reaction. The combination of a chiral cyanobis(oxazoline) ligand framework and 1,3,5-trimethoxybenzene additive were essential to afford high yields and enantioselectivities in cross-coupling reactions between unactivated aryl boronic esters and a variety of benzylic chlorides, including challenging ortho-substituted benzylic chloride substrates. Mechanistic investigations implicate a stereoconvergent pathway involving carbon-centered radical intermediates.

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