Iron/Zinc-Co-catalyzed Directed Arylation and Alkenylation of C(sp<sup>3</sup>)–H Bonds with Organoborates

Ilies, Laurean; Itabashi, Yuki; Shang, Rui; Nakamura, Eiichi

doi:10.1021/acscatal.6b02927

Cited by 47 publications

(32 citation statements)

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“…Iron-catalyzed C(sp 2 )-H arylation of ferrocenes aromatic rings with TAM DG.The activation of C(sp 3 )-H is generally more challenging than C(sp 2 )-H due to their lower acidity [43,44]. In analogy with previous reports on iron-catalyzed C(sp 3 )-H arylations enabled by 8-AQ DGs, TAM DG was found operative under similar conditions [40,45]. A broad range of substrates 8 was functionalized in good yields with a complete selectivity of the primary over the secondary C-H bond, rendering an organometallic C-H activation mechanism likely to be operative under present conditions (Scheme 4).…”

supporting

confidence: 61%

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Lanzi

Cera

2020

Molecules

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3d transition metals-catalyzed C-H bond functionalizations represent nowadays an important tool in organic synthesis, appearing as the most promising alternative to cross-coupling reactions. Among 3d transition metals, iron found widespread application due to its availability and benign nature, and it was established as an efficient catalyst in organic synthesis. In this context, the use of ortho-orientating directing groups (DGs) turned out to be necessary for promoting selective iron-catalyzed C-H functionalization reactions. Very recently, triazoles DGs were demonstrated to be more than an excellent alternative to the commonly employed 8-aminoquinoline (AQ) DG, as a result of their modular synthesis as well as the mild reaction conditions applied for their removal. In addition, their tunable geometry and electronics allowed for new unprecedented reactivities in iron-catalyzed C-H activation methodologies that will be summarized within this review. Scheme 2. Triazole-assisted C(sp 2 )-H arylation; (a) Aryl amides functionalizations; (b) Acrylamide functionalization; (c) Removal of TAM DG.The deprotection of TAM DG was carried out under acidic conditions, leading to ortho-arylated benzoic acid 5b in high yields (Scheme 2c). TAM DG was found applicable for C-H arylations of ferrocene derivatives 6 as well [42]. Again, the combination of diphosphine ligand dppe and 2,3dichlorobutane (2,3-DCB) as external oxidant was found essential for the transformation. The use of an in situ-formed Ar2Zn•MgBr2(TMEDA) organometallic base allowed for the conversion of amides 6a-b into racemic products 7a-b in good yields. Noteworthy, the use of a chiral ligand such as R,R-Scheme 2. Triazole-assisted C(sp 2 )-H arylation; (a) Aryl amides functionalizations; (b) Acrylamide functionalization; (c) Removal of TAM DG.The deprotection of TAM DG was carried out under acidic conditions, leading to ortho-arylated benzoic acid 5b in high yields (Scheme 2c). TAM DG was found applicable for C-H arylations of ferrocene derivatives 6 as well [42]. Again, the combination of diphosphine ligand dppe and Molecules 2020, 25, 1806 4 of 26 2,3-dichlorobutane (2,3-DCB) as external oxidant was found essential for the transformation. The use of an in situ-formed Ar 2 Zn•MgBr 2 (TMEDA) organometallic base allowed for the conversion of amides 6a-b into racemic products 7a-b in good yields. Noteworthy, the use of a chiral ligand such as R,R-chiraphos led to the formation of a planar chiral ferrocene derivative 7c with moderate enantiomeric ratio (Scheme 3). Molecules 2020, 25, x FOR PEER REVIEW 4 of 27 chiraphos led to the formation of a planar chiral ferrocene derivative 7c with moderate enantiomeric ratio (Scheme 3). Scheme 3. Iron-catalyzed C(sp 2 )-H arylation of ferrocenes aromatic rings with TAM DG.The activation of C(sp 3 )-H is generally more challenging than C(sp 2 )-H due to their lower acidity [43,44]. In analogy with previous reports on iron-catalyzed C(sp 3 )-H arylations enabled by 8-AQ DGs, TAM DG was found operative under similar conditions [...

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confidence: 61%

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Lanzi

Cera

2020

Molecules

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“…Alternatively, organoborate reagents were employed in an Fe-catalysed transformation, albeit restricted to few examples of alkenylated products (3 cases). 488 …”

Section: Bidentate Dgsmentioning

confidence: 99%

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

et al. 2018

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“…Nakamura later showed that organoboronates could also be used for β-arylations (Scheme 2a) and alkenylations (Scheme 2b) with iron catalysis and Zn co-catalysis. [20] The high reactivity of organozinc reagents used previously (Scheme 1a) was proposed to lead to incorporation of two aryl ligands on iron, which caused the reduction of Fe to an inactive species, along with the formation of a biaryl side-product. [16] The subsequent use of less reactive organoboronates as the coupling partner suppressed this competing mechanism, enabling both arylation and alkenylation in good yields with only trace amounts of homocoupling of the aryl or alkenyl boronates.…”

Section: C-c Bond Forming Reactionsmentioning

confidence: 99%

Base Metal Catalysis in Directed C(sp³)−H Functionalisation

John‐Campbell¹,

Bull²

2019

Adv Synth Catal

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Directed C(sp 3)-H functionalization has made enormous progress in recent years, but has largely been restricted to catalysis using noble metals, particularly palladium. However, since 2013, there have been prominent advances that exploit the reactivity of abundant first row transition metals for a multitude of new bond formations. The use of base metal catalysis for C-H functionalization can provide huge advantages in terms of cost and sustainability compared to methods using noble metals. This review covers all examples, to end 2018, of auxiliary assisted, base metal catalyzed C(sp 3)-H functionalization reactions. Successful examples are reported with Fe, Co, Ni and Cu catalysis with monodentate or bidentate directing groups for C-N, CO , C-S and CC bond forming reactions. This review aims to highlight the current state of this field and potential for expansion and so scope and limitations are highlighted. Notably, examples to date have required sterically activated α-disubstituted substrates, particularly propanamide derivatives with bidentate directing groups, such as 8-aminoquinoline amides. Monodentate quinoline and thioamide directing groups have also been used with Co catalysis for C-N and CC bond formations. Mechanistic details are provided to outline the nature of the proposed organometallic intermediates and potential reaction pathways. We hope this review will stimulate further development in this growing and important field.

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Iron/Zinc-Co-catalyzed Directed Arylation and Alkenylation of C(sp³)–H Bonds with Organoborates

Cited by 47 publications

References 49 publications

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

Base Metal Catalysis in Directed C(sp³)−H Functionalisation

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Iron/Zinc-Co-catalyzed Directed Arylation and Alkenylation of C(sp3)–H Bonds with Organoborates

Cited by 47 publications

References 49 publications

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

Base Metal Catalysis in Directed C(sp3)−H Functionalisation

Contact Info

Product

Resources

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Iron/Zinc-Co-catalyzed Directed Arylation and Alkenylation of C(sp³)–H Bonds with Organoborates

Base Metal Catalysis in Directed C(sp³)−H Functionalisation