On the Radical Nature of Iron‐Catalyzed Cross‐Coupling Reactions

Hedström, Anna; Izakian, Zakieh; Vreto, Irma; Wallentin, Carl‐Johan; Norrby, Per‐Ola

doi:10.1002/chem.201406096

Cited by 74 publications

(65 citation statements)

References 121 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[19] Thef ormation of iron(I) catalysts under similar reaction conditions was recently shown by various studies. [20] Thec oordination of pentadienoates to iron catalysts under similar reaction conditions was proposed, by Sun and Fürstner, to operate in the ring-opening methylation of 2-pyrones to (2Z)-hexadienoates. [6] Accordingly,weperformed sequential cross-couplings with 4-acetoxy-6-methyl-2-pyrone.…”

Section: Methodsmentioning

confidence: 94%

Iron‐Catalyzed Cross‐Coupling of Alkenyl Acetates

et al. 2015

View full text Add to dashboard Cite

Dedicated to Professor Manfred Scheer on the occasion of his 60th birthday.Abstract: Stable CÀOl inkages are generally unreactive in cross-coupling reactions which mostly employm ore electrophilic halides or activated esters (triflates,t osylates). Acetates are cheapand easily accessible electrophiles but have not been used in cross-couplings because the strong C À Obond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is as elective iron-catalyzed crosscoupling of diverse alkenyl acetates,a nd it operates under mild reaction conditions (0 8 8C, 2h)w ith al igand-free catalyst (1-2 mol %).The recent developments of selective iron-catalyzed crosscoupling reactions rival their conventional palladium-and nickel-catalyzed counterparts in terms of reactivity and scope while displaying higher sustainability and operational simplicity.[1] However,t he use of non-activated halide-free electrophiles remains at rue challenge for all cross-coupling methods (Scheme 1).[2] Oxygen-based electrophiles are especially attractive starting materials because of their ubiquitous occurrence in biomass-derived chemicals and facile preparation from alcohols or carbonyl compounds.H owever,t he general stability of CÀObonds has limited the scope of most cross-coupling methods to activated esters (triflate,t osylate or in benzyl/allyl position). There are very few nickel-or rhodium-catalyzed protocols which employ non-activated ester derivatives at elevated temperatures.[3]Iron-catalyzed cross-coupling was reported with alkenyl pivalates and aryl carbamates/sulfamates (Scheme 2) where the undesired carbonyl/sulfonyl attack is suppressed by steric shielding (tert-butyl) or electronic deactivation (OR, NR 2 ). [4] To the best of our knowledge,t here are no reports of ironcatalyzed cross-coupling reactions of simple unbiased esters. Among them, organic acetates are an especially attractive class of cheap,halide-free CÀOelectrophiles bearing asmall, nonhazardous leaving group,a nd is easily accessible by various acetylation protocols.[5] However,t he considerable electrophilicity and acidity (pK a 24), and low bond dissociation energy of the acetyl À Ob ond appear to prohibit, on thermodynamic grounds,t he use of acetates in coupling reactions with highly basic/nucleophilic organometallic reagents.C onsistently,a ll known cross-coupling protocols involve mild organoboron/zinc species.[3] Thus,iron-catalyzed cross-couplings between organic acetates and Grignard reagents requires an especially active catalyst which operates under kinetic control where the competing deprotonation and acetylation pathways are suppressed. We envisioned capitalizing on the combination of a) al igand-free,l ow-valent iron catalyst which favors rapid oxidative addition of the nonactivated electrophile,b )Grignard reagents as good nucleophiles which exhibit rapid transmetalation, and c) low temperatures/short reaction times to achieve selective crosscoupling of alkenyl acetates.Similar reaction conditions have been reported for t...

show abstract

Section: Methodsmentioning

confidence: 94%

Iron‐Catalyzed Cross‐Coupling of Alkenyl Acetates

et al. 2015

View full text Add to dashboard Cite

show abstract

“…[6a] In this work, they found that 20 mol% Fe(acac) 3 -CuI (1 : 1), partnered with 2 equivalents of K 3 PO 4 as a base in DMSO, displayed the highest catalytic activity. It was noticed that in the control experiments, the use of either copper or iron catalyst alone gave much poorer results or even no reaction, strongly indicating a synergistic effect between two metals.…”

Section: Introductionmentioning

confidence: 97%

“…Fortunately, the past decade has witnessed great progress in the utilization of such transition-metal catalysts, such as those involving iron or copper metals. [3] Iron and copper are both highly abundant in the Earth's crust, and they are generally considered to be environmentally friendly. In addition, in contrast to precious metals, iron and copper are inexpensive and readily available, which will greatly favor their large-scale application in the chemical industry.…”

Section: Introductionmentioning

confidence: 99%

“…His research interests include earth-abundant metal catalysis and metallosupramolecular chemistry. 3 /CuI cocatalyst, they successfully applied the same catalyst system to the preparation of indoles and diphenyl ethers, as well as sulfides. Interestingly, Vogel's group reported a similar Fe(acac) 3 /CuI cocatalyst system for Sonogashira couplings in the same year.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, Vogel's group reported a similar Fe(acac) 3 /CuI cocatalyst system for Sonogashira couplings in the same year. [10] They used 10 mol% Fe(acac) 3 /CuI (1 : 1) in combination with 2 equivalents of Cs 2 CO 3 and NMP as the solvent for the catalytic reactions. Although Vogel's method also showed good to excellent catalytic activity towards the reactions of both aryl iodides and alkyl alkynes, aryl bromides were not suited in this case.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Application of Copper/Iron Cocatalysis in Cross-Coupling Reactions

Mao

Yan

Rong

et al. 2016

The Chemical Record

View full text Add to dashboard Cite

For conventional cross-couplings in organic chemistry, precious metal (such as Pd or Rh) complexes have been the preferable choices as catalysts. However, their high cost, toxicity, and potential contamination of products limit their massive applications on some occasions, particularly in the pharmaceutical industry, where close monitoring of the metal contamination of products is required. Therefore, the use of metals that are less expensive and less toxic than Pd or Rh can be greatly advantageous and earth abundant metal (such Fe or Cu) catalysts have shown promise for replacing the precious metals. Interestingly, a certain copper catalyst combined with an iron catalyst displays higher catalytic efficiency than itself in various coupling reactions. Notably, ligand-free conditions make such protocols more useful and practical in many cases. In this account, we summarize the recent progress made in this increasingly attractive topic by describing successful examples, including our own work in the literature, regarding effective copper/iron cocatalysis. In addition, a few examples involving a magnetic and readily recyclable CuFe2 O4 nanoparticle cocatalyst are also included.

show abstract

A Radical Pathway for Direct Substitution of Benzyl Alcohols with Water‐Soluble Copper Catalyst in Water

et al. 2016

View full text Add to dashboard Cite

We have developed a novel strategy for the direct substitution of benzyl alcohols with anthranilic acids using water‐soluble copper catalysts through a radical pathway in water, which offers efficient and environmentally friendly N‐, S‐, and C‐benzylations under neutral conditions. Radical scavengers strongly inhibited the benzylation. Radical clock experiments using α‐cyclopropylbenzyl alcohol were conducted to observe the rapid isomerization of the cyclopropylmethyl radical to the allylmethyl radical. Hammett plots could be fitted to a two‐parameter Hammett relationship containing both radical and polar contributions [log (kX/kH)=−1.24 σ.–0.38 σ, R2=0.99]. The relative parameter ρ./ρ of 3.3 suggested that these reactions involved a strong radical character with minor polar influence at the transition state.magnified image

show abstract

On the Radical Nature of Iron‐Catalyzed Cross‐Coupling Reactions

Cited by 74 publications

References 121 publications

Iron‐Catalyzed Cross‐Coupling of Alkenyl Acetates

Iron‐Catalyzed Cross‐Coupling of Alkenyl Acetates

The Application of Copper/Iron Cocatalysis in Cross-Coupling Reactions

A Radical Pathway for Direct Substitution of Benzyl Alcohols with Water‐Soluble Copper Catalyst in Water

Contact Info

Product

Resources

About