Iron-catalyzed C–H/N–H activation by triazole guidance: versatile alkyne annulation

Cera, Gianpiero; Haven, Tobias; Ackermann, Lutz

doi:10.1039/c7cc03376a

Cited by 59 publications

(29 citation statements)

References 55 publications

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“…Alkyne insertion reactions have emerged as a powerful tool for the formation of cyclic compounds. Thus, several protocols through transition metal-catalyzed C-H activation have been established with alkynes to form isoquinolones [24][25][26][27][28] or indoles. [29][30][31][32] The use of alkyne as a coupling partner can also lead to the direct formation of polysubstituted arenes.…”

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confidence: 99%

Chemodivergent Nickel(0)-Catalyzed Arene C–F Activation with Alkynes: Unprecedented C–F/C–H Double Insertion

et al. 2019

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Nickel-catalyzed C-F activations enabled chemo-divergent CC formation with alkynes by chelation assistance. The judicious choice of the alkynes electronic properties allowed the selective synthesis of double-insertion aromatic homologation or alkyne mono-annulation products by C-F/C-H activation. Based on the unambiguous crystallographic characterization of an unprecedented 9-membered nickelocyclic intermediate and extensive DFT studies, a plausible mechanistic rationale was established for the selective C-F activation and the chemodivergent catalysis.

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confidence: 99%

Chemodivergent Nickel(0)-Catalyzed Arene C–F Activation with Alkynes: Unprecedented C–F/C–H Double Insertion

et al. 2019

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“…Interestingly, they always observed a lack of reactivity, leading to hypothesize an important contribution of the Thorpe-Ingold effect on the catalytic manifold [70]. Hence, the introduction of a new triazole TAH (triazolyldihydrogenmethyl) DG, being devoid of the gem-disubstitution, was demonstrated to be necessary for the synthesis of decorated isoquinolones 39 [71]. The use of an in situ-formed iPr 2 Zn•MgBr 2 (TMEDA) organometallic base was mandatory to promote the catalytic annulation with alkynes, along with the use of 1,2-DCIB as the oxidant.…”

Section: Iron-catalyzed C-h Functionalizations With Alkynes and Allenesmentioning

confidence: 99%

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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“…In a follow-up study, Ackermann and co-workers developed a triazole-directed Fe-catalyzed C-H functionalization/annulation process involving the use of disubstituted alkynes for the preparation of isoquinolone derivatives. [36] Whereas the success of the previously used TAM group was partially due to the gemdisubstitution on the methylene backbone, the absence of this feature was strictly required for this tandem process. A number of symmetrical and unsymmetrical alkynes regioselectively furnished the corresponding 3,4-substituted isoquinolone derivatives (Scheme 17).…”

Section: C-h Alkynylationsmentioning

confidence: 99%

Metal‐Catalyzed C–H Functionalization Processes with “Click”‐Triazole Assistance

Guerrero

Correa

2018

Eur J Org Chem

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The functionalization of otherwise unreactive C–H bonds holds great promise for reducing reliance on existing functional groups while improving energy efficiency and atom economy. One of the most powerful strategies exploits chelation assistance through reversible coordination with metal catalysts. This microreview summarizes the most recent advances in the use of 1,2,3‐triazoles as versatile directing groups in the field of C–H functionalization. The main feature is the modular and straightforward assembly of the required triazoles through “click” chemistry, and such procedures therefore constitute practical synthetic tools of utmost importance for the late‐stage diversification of “click compounds”, which are ubiquitous moieties in drug discovery and material science.

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Iron-catalyzed C–H/N–H activation by triazole guidance: versatile alkyne annulation

Abstract: Iron-catalyzed C-H/N-H functionalizations were achieved by the aid of modular triazole amides. The alkyne annulation allowed for the expedient synthesis of valuable isoquinolone scaffolds with high levels of chemo-, site- and regio-selectivities.

Cited by 59 publications

References 55 publications

Chemodivergent Nickel(0)-Catalyzed Arene C–F Activation with Alkynes: Unprecedented C–F/C–H Double Insertion

Chemodivergent Nickel(0)-Catalyzed Arene C–F Activation with Alkynes: Unprecedented C–F/C–H Double Insertion

Iron-Catalyzed C–H Functionalizations under Triazole-Assistance

Metal‐Catalyzed C–H Functionalization Processes with “Click”‐Triazole Assistance

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