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10 pages, 1643 KiB

Open AccessArticle

Evaluation of 3,3′-Triazolyl Biisoquinoline N,N′-Dioxide Catalysts for Asymmetric Hydrosilylation of Hydrazones with Trichlorosilane

by Shiyu Sun, Changgong Xu, Jamielyn Jarvis, Phillip Nader, Brandon Naumann, Abigail Soliven, Roberto Peverati and Norito Takenaka

Catalysts 2021, 11(9), 1103; https://doi.org/10.3390/catal11091103 - 14 Sep 2021

Cited by 3 | Viewed by 1919

Abstract

A new class of axial-chiral biisoquinoline N,N′-dioxides was evaluated as catalysts for the enantioselective hydrosilylation of acyl hydrazones with trichlorosilane. While these catalysts provided poor to moderate reactivity and enantioselectivity, this study represents the first example of the organocatalytic asymmetric [...] Read more.

A new class of axial-chiral biisoquinoline N,N′-dioxides was evaluated as catalysts for the enantioselective hydrosilylation of acyl hydrazones with trichlorosilane. While these catalysts provided poor to moderate reactivity and enantioselectivity, this study represents the first example of the organocatalytic asymmetric reduction of acyl hydrazones. In addition, the structures and energies of two possible diastereomeric catalyst–trichlorosilane complexes (2a–HSiCl₃) were analyzed using density functional theory calculations. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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11 pages, 1334 KiB

Open AccessArticle

Immobilization of an Iridium(I)-NHC-Phosphine Catalyst for Hydrogenation Reactions under Batch and Flow Conditions

by Henrietta Kovács, Krisztina Orosz, Gábor Papp, Ferenc Joó and Henrietta Horváth

Catalysts 2021, 11(6), 656; https://doi.org/10.3390/catal11060656 - 22 May 2021

Cited by 2 | Viewed by 2492

Abstract

Na₂[Ir(cod)(emim)(mtppts)] (1) with high catalytic activity in various organic- and aqueous-phase hydrogenation reactions was immobilized on several types of commercially available ion-exchange supports. The resulting heterogeneous catalyst was investigated in batch reactions and in an H-Cube flow [...] Read more.

Na₂[Ir(cod)(emim)(mtppts)] (1) with high catalytic activity in various organic- and aqueous-phase hydrogenation reactions was immobilized on several types of commercially available ion-exchange supports. The resulting heterogeneous catalyst was investigated in batch reactions and in an H-Cube flow reactor in the hydrogenation of phenylacetylene, diphenylacetylene, 1-hexyne, and benzylideneacetone. Under proper conditions, the catalyst was highly selective in the hydrogenation of alkynes to alkenes, and demonstrated excellent selectivity in C=C over C=O hydrogenation; furthermore, it displayed remarkable stability. Activity of 1 in hydrogenation of levulinic acid to γ-valerolactone was also assessed. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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12 pages, 2647 KiB

Open AccessArticle

N-Heterocyclic Carbene Functionalized Covalent Organic Framework for Transesterification of Glycerol with Dialkyl Carbonates

by Yuying Chai, Yaling Li, Hui Hu, Chaoyuan Zeng, Shenglin Wang, Huanjun Xu and Yanan Gao

Catalysts 2021, 11(4), 423; https://doi.org/10.3390/catal11040423 - 26 Mar 2021

Cited by 8 | Viewed by 3817

Abstract

The development of a heterogeneous catalyst through the combination of novel carrier and powerful catalytic active sites is of particular interest. Herein, the successful integration of an N-Heterocyclic carbene (NHC) moiety into a covalent organic framework (COF) was achieved by coupling 4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayl) [...] Read more.

The development of a heterogeneous catalyst through the combination of novel carrier and powerful catalytic active sites is of particular interest. Herein, the successful integration of an N-Heterocyclic carbene (NHC) moiety into a covalent organic framework (COF) was achieved by coupling 4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayl) tetraaniline (PyTTA) and equimolar 4,7-bis(4-formylphenyl)-1-methyl-1H-benzimidazole (IM) and 2′3′5′6′-tetrafluoro-[1,1′:4′,1′′-terphenyl]-4,4′-dicarbaldehyde (4F) followed by ionization with 1-bromobutane (C₄H₉Br) and then deprotonation upon addition of a base. The resulting material exhibited promising heterogeneous catalytic activity towards transesterification reaction of glycerol with dialkyl carbonate. Moreover, good recyclability granted no substantial loss of activity upon five cycles. Combination of COFs and NHCs might synergize their characteristics, thus providing more possibilities for creating new patterns of catalytic reactivity. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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16 pages, 7982 KiB

Open AccessArticle

Rapid Sequentially Palladium Catalyzed Four-Component Synthesis of Novel Fluorescent Biaryl-Substituted Isoxazoles

by Tobias Deden, Lars May, Guido J. Reiss and Thomas J. J. Müller

Catalysts 2020, 10(12), 1412; https://doi.org/10.3390/catal10121412 - 03 Dec 2020

Cited by 5 | Viewed by 1929

Abstract

A series of novel 3- and 5-biaryl-substituted isoxazoles was prepared by a rapid microwave-assisted four-component three-step synthesis: concatenating Sonogashira coupling, cyclocondensation, and Suzuki coupling in a one-pot fashion. The Pd-catalyst was successfully employed in the sense of a sequentially catalyzed process, i.e., without [...] Read more.

A series of novel 3- and 5-biaryl-substituted isoxazoles was prepared by a rapid microwave-assisted four-component three-step synthesis: concatenating Sonogashira coupling, cyclocondensation, and Suzuki coupling in a one-pot fashion. The Pd-catalyst was successfully employed in the sense of a sequentially catalyzed process, i.e., without the addition of further catalyst loading. Biaryl-substituted isoxazoles with donor–acceptor decoration possess remarkable photophysical properties, such as high fluorescence quantum yields in solution up to Φ_F = 0.86 and large Stokes shifts up to 10,000 cm⁻¹. The experimental absorption and emission characteristics can be reproduced and rationalized by computations on the DFT (density functional theory) and TDDFT (time-dependent density functional theory) level of theory. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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18 pages, 2447 KiB

Open AccessArticle

Redox Isomerization of Allylic Alcohols Catalyzed by New Water-Soluble Rh(I)-N-Heterocyclic Carbene Complexes

by Csilla Enikő Czégéni, Marianna Fekete, Eszter Tóbiás, Antal Udvardy, Henrietta Horváth, Gábor Papp and Ferenc Joó

Catalysts 2020, 10(11), 1361; https://doi.org/10.3390/catal10111361 - 23 Nov 2020

Cited by 6 | Viewed by 2554

Abstract

New water-soluble, N-heterocyclic carbene (NHC) or mixed NHC/tertiary phosphine complexes [RhCl(cod)(sSIMes)], Na₂[Rh(bmim)(cod)(mtppts)], and [Rh(bmim)(cod)(pta)]BF₄ were synthetized and applied for the first time as catalysts in redox isomerization of allylic alcohols in aqueous media. [RhCl(cod)(sSIMes)] (with added sulfonated [...] Read more.

New water-soluble, N-heterocyclic carbene (NHC) or mixed NHC/tertiary phosphine complexes [RhCl(cod)(sSIMes)], Na₂[Rh(bmim)(cod)(mtppts)], and [Rh(bmim)(cod)(pta)]BF₄ were synthetized and applied for the first time as catalysts in redox isomerization of allylic alcohols in aqueous media. [RhCl(cod)(sSIMes)] (with added sulfonated triphenylphosphine) and [Rh(bmim)(cod)(pta)]BF₄ catalyzed selectively the transformation of allylic alcohols to the corresponding ketones. The highest catalytic activity, TOF = 152 h⁻¹ (TOF = (mol reacted substrate) × (mol catalyst × time)⁻¹) was observed in redox isomerization of hept-1-en-3-ol ([S]/[cat] = 100). The catalysts were reused in the aqueous phase at least three times, with only modest loss of the catalytic activity and selectivity. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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17 pages, 4386 KiB

Open AccessArticle

Synthesis and Investigation of Pinane-Based Chiral Tridentate Ligands in the Asymmetric Addition of Diethylzinc to Aldehydes

by Mounir Raji, Tam Minh Le, Ferenc Fülöp and Zsolt Szakonyi

Catalysts 2020, 10(5), 474; https://doi.org/10.3390/catal10050474 - 26 Apr 2020

Cited by 6 | Viewed by 2477

Abstract

A library of pinane-based chiral aminodiols, derived from natural (−)-β-pinene, were prepared and applied as chiral catalysts in the addition of diethylzinc to aldehydes. (−)-β-Pinene was reacted to provide 3-methylenenopinone, followed by a reduction of the carbonyl function to [...] Read more.

A library of pinane-based chiral aminodiols, derived from natural (−)-β-pinene, were prepared and applied as chiral catalysts in the addition of diethylzinc to aldehydes. (−)-β-Pinene was reacted to provide 3-methylenenopinone, followed by a reduction of the carbonyl function to give a key allylic alcohol intermediate. Stereoselective epoxidation of the latter and subsequent ring opening of the resulting oxirane with primary and secondary amines afforded aminodiols. The regioselectivity of the ring closure of the N-substituted secondary aminodiols with formaldehyde was examined and exclusive formation of oxazolidines was observed. Treatment of the allylic alcohol with benzyl bromide provided the corresponding O-benzyl derivative, which was transformed into O-benzyl aminodiols by aminolysis. Ring closure of the N-isopropyl aminodiol derivative with formaldehyde resulted in spirooxazolidine. The obtained potential catalysts were applied in the reaction of both aromatic and aliphatic aldehydes to diethylzinc providing moderate to good enantioselectivities (up to 87% ee). Through the use of molecular modeling at an ab initio level, this phenomenon was interpreted in terms of competing reaction pathways. Molecular modeling at the RHF/LANL2DZ level of theory was successfully applied for interpretation of the stereochemical outcome of the reactions leading to display excellent (R) enantioselectivity in the examined transformation. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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16 pages, 1889 KiB

Open AccessArticle

Selective Hydration of Nitriles to Corresponding Amides in Air with Rh(I)-N-Heterocyclic Complex Catalysts

by Csilla Enikő Czégéni, Sourav De, Antal Udvardy, Nóra Judit Derzsi, Gergely Papp, Gábor Papp and Ferenc Joó

Catalysts 2020, 10(1), 125; https://doi.org/10.3390/catal10010125 - 16 Jan 2020

Cited by 14 | Viewed by 4409

Abstract

A new synthetic method for obtaining [RhCl(cod)(NHC)] complexes (1–4) (cod = η⁴-1,5-cyclooctadiene, NHC = N-heterocyclic carbene: IMes, SIMes, IPr, and SIPr, respectively) is reported together with the catalytic properties of 1–4 in nitrile hydration. [...] Read more.

A new synthetic method for obtaining [RhCl(cod)(NHC)] complexes (1–4) (cod = η⁴-1,5-cyclooctadiene, NHC = N-heterocyclic carbene: IMes, SIMes, IPr, and SIPr, respectively) is reported together with the catalytic properties of 1–4 in nitrile hydration. In addition to the characterization of 1–4 in solution by ¹³C NMR spectroscopy, the structures of complexes 3, and 4 have been established also in the solid state with single-crystal X-ray diffraction analysis. The Rh(I)-NHC complexes displayed excellent catalytic activity in hydration of aromatic nitriles (up to TOF = 276 h⁻¹) in water/2-propanol (1/1 v/v) mixtures in air. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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9 pages, 3181 KiB

Open AccessArticle

Structural Properties and Catalytic Activity of Binary Poly (vinyl alcohol)/Al₂O₃ Nanocomposite Film for Synthesis of Thiazoles

by Sayed M. Riyadh, Khaled D. Khalil and Ali H. Bashal

Catalysts 2020, 10(1), 100; https://doi.org/10.3390/catal10010100 - 10 Jan 2020

Cited by 21 | Viewed by 3522

Abstract

A solution casting technique was applied to prepare a binary poly (vinyl alcohol)/Al₂O₃ nanocomposite. The structural properties of nanocomposite were investigated using Fourier-transform infrared spectra, field emission scanning electron microscope, energy dispersive X-ray analyses, and X-ray diffraction. The hybrid PVA/Al [...] Read more.

A solution casting technique was applied to prepare a binary poly (vinyl alcohol)/Al₂O₃ nanocomposite. The structural properties of nanocomposite were investigated using Fourier-transform infrared spectra, field emission scanning electron microscope, energy dispersive X-ray analyses, and X-ray diffraction. The hybrid PVA/Al₂O₃ film exhibited a conspicuous catalytic performance for synthesis of thiazole derivatives under mild reaction conditions. Moreover, the optimization of catalytic efficiency and reusability of this nanocomposite have been investigated. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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Review

Jump to: Research

21 pages, 3991 KiB

Open AccessReview

Recent Approaches to Chiral 1,4-Dihydropyridines and their Fused Analogues

by Martins Rucins, Aiva Plotniece, Eiva Bernotiene, Wei-Bor Tsai and Arkadij Sobolev

Catalysts 2020, 10(9), 1019; https://doi.org/10.3390/catal10091019 - 04 Sep 2020

Cited by 26 | Viewed by 4623

Abstract

The purpose of this review is to highlight recent developments in the synthesis of chiral 1,4-dihydropyridines and their fused analogues. 1,4-Dihydropyridines are among the most active calcium antagonists that are used for the treatment of hypertension. Enantiomers of unsymmetrical 1,4-dihydropyridines often show different [...] Read more.

The purpose of this review is to highlight recent developments in the synthesis of chiral 1,4-dihydropyridines and their fused analogues. 1,4-Dihydropyridines are among the most active calcium antagonists that are used for the treatment of hypertension. Enantiomers of unsymmetrical 1,4-dihydropyridines often show different biological activities and may have even an opposite action profile. Hantzsch synthesis usually produces racemic mixtures of unsymmetrical 1,4-dihydropyridines. Therefore, the development of stereoselective synthesis of 1,4-dihydropyridines is one of the priorities of medicinal chemistry. Over the years, numerous methodologies have been developed for the production of enantiopure 1,4-dihydropyridines, such as stereoselective synthesis using chiral auxiliaries and chiral cyclocondensation partners, chromatographical methods, resolution of diastereomeric 1,4-dihydropyridine salts, enzyme catalysed kinetic resolution, or asymmetrisation of ester groups of 1,4-dihydropyridines. These approaches have been studied in detail and are relatively well established. The catalytic asymmetric approach holds the greatest promise in delivering the most practical and widely applicable methods. Substantial progress has been made toward the development of enantioselective organocatalytic methods for the construction of the chiral dihydropyridines. However, most of them do not provide a convenient way to pharmacologically important 1,4-dihydropyridine-3,5-dicarboxylates. Organocatalytic enantioselective desymmetrisation of prochiral 1,4-dihydropyridine-3,5-dicarbaldehydes also has great promise in the synthesis of pharmacologically important 1,4-dihydropyridine-3,5-dicarboxylates. Full article

(This article belongs to the Special Issue Catalysis in Heterocyclic and Organometallic Synthesis)

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