Iron‐Catalyzed Direct Arylation of Unactivated Arenes with Aryl Halides

Liu, Wei; Cao, Hao; Lei, Aiwen

doi:10.1002/anie.200906870

Cited by 174 publications

(16 citation statements)

References 85 publications

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“…During the course of our studies on the iron-catalyzed coupling reaction of aryl halides with arenes, 8 we found that iron is not essential for the coupling to take place. After investigation of better conditions for the coupling in the absence of any transition metals, the system shown in Scheme 3 was found to be effective.…”

Section: ç Tert-butoxide-mediated Coupling With Arenesmentioning

confidence: 97%

Transition-metal-free Coupling Reactions of Aryl Halides

2012

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Transition metal catalysis plays a leading role in C(sp 2 )C(sp 2 ) bond formation through substitution reactions. On the other hand, a similar type of substitution reaction has recently been achieved without the aid of transition-metal catalysts. In this review, recent transition-metal-free coupling reactions of aryl halides with arenes, alkenes, or aryl Grignard reagents are summarized in view of S RN 1 reaction. Ç IntroductionAryl halides (ArX), readily available aryl electrophiles, do not undergo S N 2 nor S N 1 reaction. Instead, they are usually activated by reduction to participate in substitution reactions, even though the overall processes are not reduction or oxidation. Transition metal catalysis plays a dominant role to make use of ArX for substitution reactions in such a way.1,2 In particular, palladium is versatile to catalyze the coupling reaction of ArX with nucleophiles such as arenes, alkenes, and aryl Grignard reagents (Scheme 1).3 The generally accepted catalytic cycle consists of oxidative addition of ArX to a Pd(0) complex (i), reaction of the resulting ArPd II X with a nucleophile (ii), and reductive elimination to give the coupling product with regeneration of the Pd(0) complex (iii). ArX is activated by two electron reduction in step i, whereas two electron oxidation takes place in step iii.Single electron reduction also is effective for activation of aryl halides, 4 leading them to the substitution reaction (S RN 1 reaction) with anionic nucleophiles (R ¹ ) (Scheme 2). 5 Radical anion [ArX] •¹ , produced by single electron transfer (SET) from single electron donor Y in the initiation step (a), is converted into an aryl radical (Ar •¹ to ArX gives the coupling product (ArR) and regenerates [ArX] •¹ (e). S RN 1 reaction includes reduction of ArX (steps a and e) and oxidation giving coupling products (step e), as same as the palladium-catalyzed reaction. A major difference between these is the number of electrons involved in the redox processes. S RN 1 reaction features high efficiency that such a small unit as a single electron works as a catalyst, avoiding the use of expensive transition-metal catalysts. Although S RN 1 reaction is expected to have ability to connect the aryl group of aryl halides to sp 2 -carbons as same as transition metal catalysis, 6,7 the scope on anionic nucleophiles has been limited mainly to heteroatom anions and sp 3 -carboanions such as enolates. No reports are available for use of arenes, alkenes, or aryl Grignard reagents as (pro)nucleophiles in S RN 1 reaction.We have recently developed the transition-metal-free coupling reactions of aryl halides with arenes, alkenes, or aryl Grignard reagents (Scheme 1: ac). All the reactions are considered to proceed within the boundary of S RN 1 mechanism. In this Highlight Review, we summarize our work on the transition-metal-free coupling reactions in addition to related reactions reported by others. Ç tert-Butoxide-mediated Coupling with ArenesDuring the course of our studies on the iron-catalyzed coupling r...

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Section: ç Tert-butoxide-mediated Coupling With Arenesmentioning

confidence: 97%

Transition-metal-free Coupling Reactions of Aryl Halides

2012

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“…22 In the past few decades, direct arylation has developed into a promising synthetic method compared to traditional cross-coupling methods because it occurs with less synthetic steps, higher atom economy, and forms only environmentally benign byproducts. While a variety of transition metals have been discovered to promote these transformations (Scheme 1), 21,[24][25][26] including Pd, 22 Cu, [27][28][29][30][31][32][33][34] Ru, [35][36][37][38][39] Rh, [40][41][42][43] Ir, 44,45 Ni, [46][47][48][49] Co, [50][51][52] Fe, [53][54][55] Au, 56,57 literature reports in this field has been dominated by Pd-catalyzed direct arylation due to its high efficiency and broad scope. As a consequence, the recent 10 years have witnessed the intense development of Pd-catalyzed direct arylation as a powerful tool to prepare well-defined π-conjugated polymers.…”

Section: Introductionmentioning

confidence: 99%

Improving the efficiency and sustainability of catalysts for direct arylation polymerization (DArP)

Thompson

2021

Journal of Polymer Science

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In the past decade, direct arylation polymerization (DArP) has rapidly developed as a sustainable synthetic protocol for cost-effective, atom-economical preparation of conjugated polymers. By circumventing monomer functionalization with toxic transmetallating reagents such as organostannane and organoboron required for Stille-Migita and Suzuki-Miyaura polymerization methods, DArP proceeds through a metal-catalyzed C H activation pathway for the preparation of highperformance conjugated polymer materials. This review evaluates the development of several classes of efficient catalysts/catalytic systems from small-molecule studies to polymerizations, including the mechanisms involved in these transformations and how they inspire catalyst and monomer design for defect-free conjugated polymer synthesis. Recent advances in developing more sustainable first-row transition metal catalysts for DArP are also highlighted, and the fundamental understanding of these efficient and sustainable catalysts should motivate the pursuit for the next generation of catalytic design to enable more effective and environmentally friendly conjugated polymer synthesis.

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“…Among them, C-H (bond) activation, cross-dehalogenative coupling, C-H (bond) functionalization, and catalytic direct arylation are generally employed. Although pioneering reports on the use of alternative metals for direct arylation have been published (Cu [25], Fe [26], Ni [27], Ir [28] or Co [29]), second-row transition metals in low oxidation states (Rh [30][31][32][33], Ru [34][35][36][37][38], and especially Pd [39][40][41][42][43]) are preferred as catalysts for these cross-dehalogenative couplings. The ligands required usually depend on the nature of the haloarene coupling partner.…”

Section: Introductionmentioning

confidence: 99%

Direct Arylation in the Presence of Palladium Pincer Complexes

et al. 2021

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Direct arylation is an atom-economical alternative to more established procedures such as Stille, Suzuki or Negishi arylation reactions. In comparison with other palladium sources and ligands, the use of palladium pincer complexes as catalysts or pre-catalysts for direct arylation has resulted in improved efficiency, higher reaction yields, and advantageous reaction conditions. In addition to a revision of the literature concerning intra- and intermolecular direct arylation reactions performed in the presence of palladium pincer complexes, the role of these remarkably active catalysts will also be discussed.

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Iron‐Catalyzed Direct Arylation of Unactivated Arenes with Aryl Halides

Cited by 174 publications

References 85 publications

Transition-metal-free Coupling Reactions of Aryl Halides

Transition-metal-free Coupling Reactions of Aryl Halides

Improving the efficiency and sustainability of catalysts for direct arylation polymerization (DArP)

Direct Arylation in the Presence of Palladium Pincer Complexes

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