Subtle effects of ligand backbone on the efficiency of iron-diphos catalysed Negishi cross-coupling reactions

Clifton, Jamie; Habraken, Evi R. M.; Pringle, Paul G.; Manners, Ian

doi:10.1039/c5cy00851d

Cited by 9 publications

(10 citation statements)

References 44 publications

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“…While organomanganese compounds recently have received only limited attention in this context, 30 the use of organozinc reagents in so-called Negishi cross-coupling reactions has been pursued more actively. Most protocols employed diarylzinc compounds, [31][32][33] which are prepared from a zinc ha-lide and two equivalents of a preformed Grignard reagent. Thus, the latter are not completely avoided.…”

Section: Substrate Scope: Nucleophilesmentioning

confidence: 99%

Iron-Catalyzed Cross-Coupling: Mechanistic Insight for Rational Applications in Synthesis

Parchomyk

Koszinowski

2017

Synthesis

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Iron-catalyzed cross-coupling reactions provide a promising way to form new carbon–carbon bonds and build up molecular complexity. This short review presents recent advances in the synthetic application of these reactions as well as in the elucidation of their mechanism. It also highlights remaining problems and aims at pointing out ways toward possible remedies.1 Introduction2 Synthesis: Recent Accomplishments and Unsolved Problems2.1 Substrate Scope: Electrophiles2.2 Substrate Scope: Nucleophiles2.3 Catalyst Activity and Chemoselectivity2.4 Stereoselectivity2.5 Practical Aspects3 Mechanism: Recent Insights and Open Questions3.1 Transmetallation and Activation of the Iron Precatalyst3.2 Coupling via Oxidative Addition and Reductive Elimination3.3 Coupling via C–X Bond Homolysis and Radical Rebound3.4 Coupling via Bimolecular C–X Bond Homolysis3.5 Other Reactions of Organoiron Species with Electrophiles4 Toward Rational Reaction Improvement5 Conclusion

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Section: Substrate Scope: Nucleophilesmentioning

confidence: 99%

Iron-Catalyzed Cross-Coupling: Mechanistic Insight for Rational Applications in Synthesis

Parchomyk

Koszinowski

2017

Synthesis

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“…Iron complexes of chelating diphosphines are active pre-catalysts in a range of carbon-carbon bond forming processes, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and as such have formed the basis of a number of mechanistic studies with magnesium-, 22,24,29,30 boron-, 27,30 and zinc-based 22 coupling partners. We now report on our detailed investigations on the use of iron diphosphine complexes as precatalysts in a representative Negishi cross-coupling reaction with benzyl halide substrates.…”

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confidence: 99%

The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling

et al. 2018

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Iron-catalysed cross-coupling is undergoing explosive development, however, mechanistic understanding lags far behind synthetic methodology. Herein we find the activity of irondiphosphine complexes in the Negishi coupling of benzyl halides is strongly dependent on the diphosphine but the ligand does not appear to be coordinated to the iron during turn-over.This was determined using time-resolved in operando X-ray absorption fine structure spectroscopy, employing a custom-made flow-cell and confirmed by 31 P NMR spectroscopy.While the diphosphine ligands tested are all able to coordinate to iron(II), in the presence of excess zinc(II), as in the catalytic reaction, they coordinate predominantly to the zinc. Furthermore, combined synthetic and kinetic investigations implicate the formation of a putative mixed Fe-Zn(dpbz) species prior to the rate-limiting step of catalysis. These unexpected findings may not only impact upon the field of iron-catalysed Negishi cross-

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“…Benzyl chloride is chosen for ligand screening in the Negishi coupling, since it is the more challenging benchmark substrate than benzyl bromide. The reaction was carried out under the reaction condition previously reported by Bedford [10] and Pringle: [11] diaryl zinc was formed in situ by addition of aryl magnesium bromide to ZnCl 2 in THF, and iron catalyst were prepared in situ by mixing FeCl 2 with diphos ligand. A trend in selectivity for the desired cross coupling product 3 a was observed: the mixed PPh 2 /PCy 2 diphos ligands L1 , L2 , L4 , L6 , L8 outperformed their PPh 2 congeners, i. e. dppbz, dpth, L3 , L5 , L7 , respectively (Entries 1, 2, 4, 7, 9, 10, 12–15).…”

Section: Resultsmentioning

confidence: 99%

“…Consequently, they found that, when using softer aryl zinc nucleophiles instead of aryl Grignard reagents, FeCl 2 ligated by 1,2‐bis(diphenylphosphino)benzene (dppbz) exhibited significant activity and higher selectivity (Scheme 1a) [10] . Later, bis(diarylphosphino)thiophene (dpth) [11] was also successfully applied in iron‐catalyzed Negishi cross‐couplings (Scheme 1a). Considering that diaryl zinc reagents are generally prepared by the reactions of ZnCl 2 with the corresponding Grignard reagents or other nucleophiles, directly using aryl Grignard reagents as nucleophiles is an atom‐economic route to synthesize diarylmethanes.…”

Section: Introductionmentioning

confidence: 99%

Mixed Alkyl/Aryl Diphos Ligands for Iron‐Catalyzed Negishi and Kumada Cross Coupling Towards the Synthesis of Diarylmethane

Wang

Liu

et al. 2021

ChemCatChem

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Mixed alkyl/aryl diphos ligands have been prepared and their application in iron‐catalyzed cross coupling of benzylic chlorides with diaryl zinc (Negishi) or aryl Grignard reagents (Kumada) towards the synthesis of diarylmethane has been evaluated. The iron−diphos catalytic system exhibited the enhanced activity and selectivity in the two coupling reactions. The electron‐rich mixed PPh2/PCy2 ligands outperformed their symmetrical PPh2 congeners, and led to decreased homocoupling byproduct formation. It indicates that the electronic effect of the ligands plays an important role in the catalytic performance. The Fe catalyst supported by L8 bearing an electron‐rich PCy2 substituent and a sterically demanding tert‐butyl on ethene backbone exhibited the best catalytic performance and good functional group tolerance in the two cross coupling reactions.

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Subtle effects of ligand backbone on the efficiency of iron-diphos catalysed Negishi cross-coupling reactions

Abstract: † Electronic supplementary information (ESI) available: synthesis and characterisation of the ligands and the method used for the catalytic runs. See

Cited by 9 publications

References 44 publications

Iron-Catalyzed Cross-Coupling: Mechanistic Insight for Rational Applications in Synthesis

Iron-Catalyzed Cross-Coupling: Mechanistic Insight for Rational Applications in Synthesis

The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling

Mixed Alkyl/Aryl Diphos Ligands for Iron‐Catalyzed Negishi and Kumada Cross Coupling Towards the Synthesis of Diarylmethane

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