Practical copper-catalyzed N-arylation of amines with 20% aqueous solution of n-Bu4NOH

Molaei, Hamidreza; Ghanbari, Mohammad

doi:10.1016/j.cclet.2011.12.015

Cited by 10 publications

(5 citation statements)

References 37 publications

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“…Similarly, a lack of generalization also exists for solvent selection and anions coordinated to the Cu sources. 41,73,74 Herein, we restrict our studies to the reaction conditions used in Watson's protocol for CL amination (Scheme 3), that is, Cu(OAc) 2 as the Cu source (1 equiv), NEt 3 (2 equiv), acetonitrile solvent, aerial O 2 , and room temperature.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…There is no general set of reaction conditions which differ largely for closely related N-nucleophilic substrates. ,− In many cases, the addition of water and bases is either beneficial , or detrimental , to the overall reaction outcome. Similarly, a lack of generalization also exists for solvent selection and anions coordinated to the Cu sources. ,, Herein, we restrict our studies to the reaction conditions used in Watson’s protocol for CL amination (Scheme ), that is, Cu(OAc) 2 as the Cu source (1 equiv), NEt 3 (2 equiv), acetonitrile solvent, aerial O 2 , and room temperature.…”

Section: Resultsmentioning

confidence: 99%

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Entering Chemical Space with Theoretical Underpinning of the Mechanistic Pathways in the Chan–Lam Amination

2022

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Recent years have witnessed a growing interest in the development of efficient copper-based catalytic systems following the Chan−Lam (CL) reaction protocol for the C−N bond formation. Though CL amination has been widely explored experimentally, it is quite underdeveloped from a mechanistic standpoint. Extensive theoretical investigations are carried out to unravel the mechanistic pathways of the CL reaction. We report in detail the fundamental reaction steps involved in Cu-catalyzed carbon−heteroatom bond formation reactions, particularly the CLbased amination. An in-depth examination of this study provides some interesting insights into little known pathways such as the denucleation of dimeric copper acetate, the disproportionation of the Cu(II) complex, and the regeneration of Cu(II) from Cu(I) intermediates. The rate-determining step of 26.0 kcal mol −1 involves the disproportionation and reductive elimination of the Cu(II) intermediate. The mechanism for the inhibitory effect of pinacol (BPin) esters, off-cycle reaction routes, and influence of amine substrates are elaborated in this context. For a series of heteroarene substrates, it was observed that the catalyst generation energy span correlates with the experimentally observed reaction outcome. The calculated results are in agreement with the experimental observations based on spectroscopic and kinetic studies.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Entering Chemical Space with Theoretical Underpinning of the Mechanistic Pathways in the Chan–Lam Amination

2022

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“…The most commonly employed catalyst in CEL couplings is Cu(OAc) 2 , or more precisely Cu 2 (OAc) 4 . Cu(OTf) 2 typically shows similar activities. , CuCl 2 , Cu(NO 3 ) 2 , Cu(ClO 4 ) 2 , and CuSO 4 are less active, ,,,− although Stahl showed that Cu(ClO 4 ) 2 can be activated by addition of 1 equiv of acetate . The anion dependence has be rationalized by formation of an acetate-bridged dinuclear copper–boron complex as an intermediate prior to transmetalation ( A , Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…Earlyand even currentwork on CEL couplings thus report optimized reaction conditions which differ strongly even for closely related substrates such as amines, anilines, tetrazoles, , aminopyridines, and aminophenols . In these optimized reaction protocols, water typically needs to be removed , (when it is not beneficial − ) the addition of base is essential (or unnecessary ,− ), solvent dependence is strong, but completely empirical, and copper sources with acetate or triflate anions work best, , with the exception of those cases where they do not. ,, Only lately have more general protocols for CEL couplings of N-nucleophiles emerged. Watson et al reported a modified protocol with stoichiometric amounts of copper and addition of B(OH) 3 and excess amine, which is generally applicable to a larger variety of amines and anilines .…”

Section: Introductionmentioning

confidence: 99%

Chan–Evans–Lam Couplings with Copper Iminoarylsulfonate Complexes: Scope and Mechanism

2018

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Copper(II) pyridyliminoarylsulfonate complexes with chloride or triflate counteranions were employed in Chan–Evans–Lam (CEL) couplings of N-nucleophiles and arylboronic acids. The complexes avoided typical side reactions in CEL couplings, and an excess of boronic acid was not required. Water was tolerated, and addition of neither base nor other additives was necessary. Primary amines, acyclic and cyclic secondary amines, anilines, aminophenol, imidazole, pyrazole, and phenyltetrazole can be quantitatively arylated at either 25 or 50 °C with 2.5 mol % of the catalyst. Reaction kinetics were investigated in detail. Kinetic and spectroscopic studies provide evidence for the formation of unproductive copper–substrate complexes. Formation of an aniline–phenylboronic acid adduct was responsible for the zero-order dependence of reaction rates on phenylboronic acid concentration. Kinetic evidence indicates that the order of reaction steps is transmetalation, nucleophile coordination, and oxidation. Couplings performed poorly with electron-deficient arylboronic acids, due to a slower Cu(II)/Cu(III) oxidation in the catalytic cycle. Photoredox catalysis partially resolved this problem, but addition of copper acetate as an external oxidant proved to be more efficient.

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“…Similar to the Ullmann coupling, it was thought that the stability of the copper(I) species in solution is the main contributor to reactivity, but this is made difficult in part by the instability of copper(I) under typical atmospheric conditions [30] . Copper(II)‐catalyzed or copper(II)/cobalt(II) co‐catalyzed C−N cross‐coupling of 1 H ‐pyrrole and phenylboronic acid have been reported by Batey, [31] Ghanbari, [32] Aberi, [33] and Allahresani [34] as shown in Scheme 1 a .…”

Section: Introductionmentioning

confidence: 99%

Cu‐Catalyzed Chan–Evans–Lam Coupling Reactions of 2‐Nitroimidazole with Aryl Boronic Acids: An Effort toward New Bioactive Agents against S. pneumoniae

Raju

Sheridan

Hauer

et al. 2022

Chemistry & Biodiversity

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The coupling of phenylboronic acids with poorly-activated imidazoles is studied as a model system to explore the use of copper-catalyzed Chan -Evans-Lam (CEL) coupling for targeted CÀ N bond forming reactions. Optimized CEL reaction conditions are reported for four phenanthroline-based ligand systems, where the ligand 4,5-diazafluoren-9-one (dafo, L2) with 1 molar equivalent of potassium carbonate yielded the highest reactivity. The substrate 2-nitroimidazole (also known as azomycin) has documented antimicrobial activity against a range of microbes. Here N-arylation of 2-nitroimidazole with a range of aryl boronic acids has been successfully developed by copper(II)-catalyzed CEL reactions. Azomycin and a range of newly arylated azomycin derivatives were screened against S. pneumoniae, where 1-(4-(benzyloxy)phenyl)-2-nitro-1H-imidazole (3d) was demonstrated to have a minimal inhibition concentration value of 3.3 μg/mL.

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Practical copper-catalyzed N-arylation of amines with 20% aqueous solution of n-Bu4NOH

Cited by 10 publications

References 37 publications

Entering Chemical Space with Theoretical Underpinning of the Mechanistic Pathways in the Chan–Lam Amination

Entering Chemical Space with Theoretical Underpinning of the Mechanistic Pathways in the Chan–Lam Amination

Chan–Evans–Lam Couplings with Copper Iminoarylsulfonate Complexes: Scope and Mechanism

Cu‐Catalyzed Chan–Evans–Lam Coupling Reactions of 2‐Nitroimidazole with Aryl Boronic Acids: An Effort toward New Bioactive Agents against S. pneumoniae

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