The Way Forward with N‐Heterocyclic Carbenes

Vashi, Preeti R.

doi:10.1002/ejic.200990031

Cited by 6 publications

(2 citation statements)

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“…Vashi and co-workers 34 have explored a green method for the synthesis of chloroquine and its salts (Scheme 10). The method avoids the conventional processes that involve toxic chemicals such as phenol.…”

Section: Short Review Synthesismentioning

confidence: 99%

Methods of Synthesis of Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine: Four Small Molecules Repurposed for Clinical Trials during the Covid-19 Pandemic

Bujuq

2020

Synthesis

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The novel coronavirus (COVID-19) disease has rapidly evolved into a sweeping pandemic despite public health measures. Screening and development of new vaccines and antivirals are expensive and time consuming. However, the repositioning of available drugs is an essential and universal strategy in the development of new drugs and therefore should receive priority attention as well as international government and agency support. Significant drugs such as chloroquine, hydroxychloroquine, favipiravir and remdesivir, are currently undergoing clinical studies to test their efficacy and safety. Some promising results have been achieved thus far in the treatment of COVID-19. In this article we summarize and discuss the most common synthetic strategies to apply in the preparation of these drug molecules. It is hoped that this compendium will provide an accessible useful guide and reference source for scientists, researchers and academia in their battle against COVD-19.1 Introduction2 Synthesis of Chloroquine (CQ) and Hydroxychloroquine (HCQ)2.1 Synthesis of 4,7-Dichloroquinoline 1 2.2 Synthesis of 2-Amino-5-(diethylamino)pentane (Novoldiamine) 2 2.3 Synthesis of 5-(N-Ethyl-N-2-hydroxyethylamino)-2-pentylamine 4 2.4 Developed Methods for Synthesis of Chloroquine and Hydroxychloroquine2.5 Synthesis of (R)-Chloroquine, (S)-Chloroquine, (R)-Hydroxychloroquine and (S)-Hydroxychloroquine3 Synthesis of Favipiravir (Avigan)4 Synthesis of Remdesivir5 Conclusion

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Section: Short Review Synthesismentioning

confidence: 99%

Methods of Synthesis of Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine: Four Small Molecules Repurposed for Clinical Trials during the Covid-19 Pandemic

Bujuq

2020

Synthesis

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“…Thanks to Arduengo, Harlow, and Kline, the above traditional view has been dramatically altered with the availability of heteroatom-stabilized singlet nucleophilic N -heterocyclic carbenes (NHCs), which can be isolated at an ambient air temperature and used as general reagents. Thus, not surprisingly, carbene chemistry has undergone a renaissance during the last 3 decades. − To date, many room-temperature-stable NHCs have been experimentally synthesized and structurally characterized to allow their properties to be scrutinized in all respects. − …”

Section: Introductionmentioning

confidence: 99%

Insights into the Factors Controlling the Origin of Activation Barriers in Group 13 Analogues of the Four-Membered N-Heterocyclic Carbenes

2021

ACS Omega

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The mechanisms of C–H bond insertion and alkene cycloaddition were investigated theoretically using five model systems: group 13 analogues of the four-membered nucleophilic N -heterocyclic carbenes (NHCs) ( 1E ; E = group 13 element). The theoretical findings indicate that, except for 1B with H 2 C=CH 2 , these four-membered NHCs undergo insertion and [1 + 2] cycloaddition reactions with difficulty because their activation barriers are quite high (31 kcal/mol). The theoretically confirmed chemical inertness of the four-membered NHCs 1Ga and 1In might explain why they have been experimentally detected at room temperature. Additionally, our theoretical observations indicate that the reactivity of these four-membered NHCs featuring a central group 13 element follows the order 1B ≫ 1Al > 1Ga > 1In > 1Tl . The theoretical examination suggests that the smaller the atomic radius of the central group 13 element in the four-membered NHC analogue is, the larger the aromaticity of this carbenic molecule is, the higher the basicity of this carbenic molecule in nature is, the larger its nucleophilic attack on other oncoming molecules is, the smaller the barrier heights of its C–H bond insertion and [1 + 2] cycloaddition reactions will be, the higher its exothermicities for these products will be, and thus, the greater its reactivity will be. Moreover, the present theoretical findings reveal that the reactivity of 1B is governed by its highest occupied molecular orbital, a nonbonding sp 2 lone pair orbital. In contrast, the reactivity of the four heavier 1E′ (E′ = Al, Ga, In, and Tl) molecules is mainly determined by their lowest unoccupied molecular orbital, a vacant p−π orbital. The conclusions gained from this study allow many predictions to be made.

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Structural Characterization, Solution Dynamics, and Reactivity of Palladium Complexes with Benzimidazolin‐ 2‐ylidene N‐Heterocyclic Carbene Ligands

et al. 2014

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Mononuclear and halide-bridged dinuclear palladium(II) complexes with symmetrically (1 and 3) and nonsymmetrically (2, 4-6) substituted benzimidazolin-2-ylidene N-heterocyclic carbene ligands were synthesized and characterized by 1 H and 13 C NMR spectroscopy, elemental analysis, and X-ray crystallography. The mononuclear complexes exist as a mixture of cis and trans isomers, and the identity of these was ascertained by NMR spectroscopy and structural characterization. The dinuclear complexes 4-6 with nonsymmetrically substituted benzimidazolin-2-ylidene ligands form rotamers (cis/anti, cis/syn, trans/anti, and trans/syn) at room temperature, which can be transformed to a single rotamer at higher temperatures as evidenced by 1 H NMR spectroscopy.[a] 2131Crystal structure analyses of representative examples show that the Pd II centers are bound in a distorted square-planar environment by halides and carbene C ligands, and the carbene ligands are perpendicular to the Pd-halide plane. All of the complexes were tested for their efficiency as (pre)catalysts in the Suzuki-Miyaura cross-coupling reaction, as well as in hydrodehalogenation reactions, and they show good activity. The Suzuki-Miyaura coupling reactions can be performed under air and in water as an environmentally benign solvent. The most active catalyst for the Suzuki-Miyaura coupling was also used in a sequence together with a "click reaction" to synthesize valuable sterically demanding tripodal triazole ligands.

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The Way Forward with N‐Heterocyclic Carbenes

Cited by 6 publications

References 0 publications

Methods of Synthesis of Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine: Four Small Molecules Repurposed for Clinical Trials during the Covid-19 Pandemic

Methods of Synthesis of Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine: Four Small Molecules Repurposed for Clinical Trials during the Covid-19 Pandemic

Insights into the Factors Controlling the Origin of Activation Barriers in Group 13 Analogues of the Four-Membered N-Heterocyclic Carbenes

Structural Characterization, Solution Dynamics, and Reactivity of Palladium Complexes with Benzimidazolin‐ 2‐ylidene N‐Heterocyclic Carbene Ligands

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