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13 pages, 1009 KiB

Open AccessArticle

Efficient Suzuki–Miyaura C-C Cross-Couplings Induced by Novel Heterodinuclear Pd-bpydc-Ln Scaffolds

by Fu Ding, Yanli Li, Pingxuan Yan, Yan Deng, Dongping Wang, Yajing Zhang, Ileana Dragutan, Valerian Dragutan and Kangjun Wang

Molecules 2018, 23(10), 2435; https://doi.org/10.3390/molecules23102435 - 23 Sep 2018

Cited by 14 | Viewed by 4664

Abstract

An easy access to a series of previously unreported heterodinuclear Pd-Ln compounds, Pd-bpydc-La, Pd-bpydc-Ce and Pd-bpydc-Nd (bpydc = 2,2′-bipyridine-5,5′-dicarboxylate) has been developed. The Pd-Ln hybrid networks were effectively applied as catalysts in Suzuki–Miyaura C-C cross-coupling reactions of 4-bromoanisole and 4-bromobenzonitrile with phenylboronic acid, [...] Read more.

An easy access to a series of previously unreported heterodinuclear Pd-Ln compounds, Pd-bpydc-La, Pd-bpydc-Ce and Pd-bpydc-Nd (bpydc = 2,2′-bipyridine-5,5′-dicarboxylate) has been developed. The Pd-Ln hybrid networks were effectively applied as catalysts in Suzuki–Miyaura C-C cross-coupling reactions of 4-bromoanisole and 4-bromobenzonitrile with phenylboronic acid, under mild conditions. A systematic investigation revealed Pd-bpydc-Nd as the most active catalyst. In all cases, reaction yields varied with the base, catalyst loading and substantially augmented with temperature (from 30 to 60 °C). Substituent effects were operative when changing from 4-bromoanisole to 4-bromobenzonitrile. The key role played by the lanthanides, aromatic substrate and base, in modulating the Pd-catalytic cycle has been highlighted. Importantly, the new catalysts proved to be stable in air and vs. functionalities and are quite efficient in Suzuki–Miyaura carbon-carbon bond formation conducted in protic solvents. Full article

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

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14 pages, 2768 KiB

Open AccessArticle

Development of Conjugate Addition of Lithium Dialkylcuprates to Thiochromones: Synthesis of 2-Alkylthiochroman-4-ones and Additional Synthetic Applications

by Shekinah A. Bass, Dynasty M. Parker, Tania J. Bellinger, Aireal S. Eaton, Angelica S. Dibble, Kaata L. Koroma, Sylvia A. Sekyi, David A. Pollard and Fenghai Guo

Molecules 2018, 23(7), 1728; https://doi.org/10.3390/molecules23071728 - 15 Jul 2018

Cited by 7 | Viewed by 5165

Abstract

Lithium dialkylcuprates undergo conjugate addition to thiochromones to afford 2-alkylthiochroman-4-ones in good yields. This approach provide an efficient and general synthetic approach to privileged sulfur-containing structural motifs and valuable precursors for many pharmaceuticals, starting from common substrates-thiochromones. Good yields of 2-alkyl-substituted thiochroman-4-ones are [...] Read more.

Lithium dialkylcuprates undergo conjugate addition to thiochromones to afford 2-alkylthiochroman-4-ones in good yields. This approach provide an efficient and general synthetic approach to privileged sulfur-containing structural motifs and valuable precursors for many pharmaceuticals, starting from common substrates-thiochromones. Good yields of 2-alkyl-substituted thiochroman-4-ones are attained with lithium dialkylcuprates, lithium alkylcyanocuprates or substoichiometric amount of copper salts. The use of commercially available inexpensive alkyllithium reagents will expedite the synthesis of a large library of 2-alkyl substituted thiochroman-4-ones for additional synthetic applications. Full article

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

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7 pages, 2040 KiB

Open AccessArticle

High Conversion of Styrene, Ethylene, and Hydrogen to Linear Monoalkylbenzenes

by David Hermann Lamparelli, Antonio Ricca, Vincenzo Palma and Leone Oliva

Molecules 2018, 23(6), 1260; https://doi.org/10.3390/molecules23061260 - 25 May 2018

Viewed by 2836

Abstract

1-Alkylbenzenes as a precursor of surfactants, can be produced from ethylene, styrene, and hydrogen. These intermediates, lacking tertiary carbons, are environmentally more benign than commercial ones that bear the aromatic ring linked to an internal carbon of the aliphatic chain. The one-pot synthesis [...] Read more.

1-Alkylbenzenes as a precursor of surfactants, can be produced from ethylene, styrene, and hydrogen. These intermediates, lacking tertiary carbons, are environmentally more benign than commercial ones that bear the aromatic ring linked to an internal carbon of the aliphatic chain. The one-pot synthesis of highly linear 1-alkylbenzenes (LABs) through the homogeneous catalysis of olefin poly-insertion from cheap and largely available reagents can be carried out with a high turnover and selectivity. A purposely designed reactor that allows for the fine control of the three components feed, along with temperature, plays a key role in this achievement. A turnover of 194 g of LABs per mmol of catalyst per hour can be obtained with the simultaneous removal of polyethylene as a by-product. Full article

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

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18 pages, 5878 KiB

Open AccessArticle

Poly(urethane-norbornene) Aerogels via Ring Opening Metathesis Polymerization of Dendritic Urethane-Norbornene Monomers: Structure-Property Relationships as a Function of an Aliphatic Versus an Aromatic Core and the Number of Peripheral Norbornene Moieties

by Aspasia Kanellou, George C. Anyfantis, Despoina Chriti, Grigorios Raptopoulos, Marinos Pitsikalis and Patrina Paraskevopoulou

Molecules 2018, 23(5), 1007; https://doi.org/10.3390/molecules23051007 - 25 Apr 2018

Cited by 22 | Viewed by 5264

Abstract

We report the synthesis and characterization of synthetic polymer aerogels based on dendritic-type urethane-norbornene monomers. The core of those monomers is based either on an aromatic/rigid (TIPM/Desmodur RE), or an aliphatic/flexible (Desmodur N3300) triisocyanate. The terminal norbornene groups (three at the tip of [...] Read more.

We report the synthesis and characterization of synthetic polymer aerogels based on dendritic-type urethane-norbornene monomers. The core of those monomers is based either on an aromatic/rigid (TIPM/Desmodur RE), or an aliphatic/flexible (Desmodur N3300) triisocyanate. The terminal norbornene groups (three at the tip of each of the three branches) were polymerized via ROMP using the inexpensive 1st generation Grubbs catalyst. The polymerization/gelation conditions were optimized by varying the amount of the catalyst. The resulting wet-gels were dried either from pentane under ambient pressure at 50 °C, or from t-butanol via freeze-drying, or by using supercritical fluid (SCF) CO₂. Monomers were characterized with high resolution mass spectrometry (HRMS), ¹H- and solid-state ¹³C-NMR. Aerogels were characterized with ATR-FTIR and solid-state ¹³C-NMR. The porous network was probed with N₂-sorption and SEM. The thermal stability of monomers and aerogels was studied with TGA, which also provides evidence for the number of norbornene groups that reacted via ROMP. At low densities (<0.1 g cm⁻³) all aerogels were highly porous (porosity > 90%), mostly macroporous materials; aerogels based on the aliphatic/flexible core were fragile, whereas aerogels containing the aromatic/rigid core were plastic, and at even lower densities (0.03 g cm⁻³) foamy. At higher densities (0.2–0.7 g cm⁻³) all materials were stiff, strong, and hard. At low monomer concentrations all aerogels consisted of discrete primary particles that formed spherical secondary aggregates. At higher monomer concentrations the structure consisted of fused particles with the size of the previous secondary aggregates, due to the low solubility of the developing polymer, which phase-separated and formed a primary particle network. Same-size fused aggregates were observed for both aliphatic and aromatic triisocyanate-derived aerogels, leading to the conclusion that it is not the aliphatic or aromatic core that determines phase separation, but rather the solubility of the polymeric backbone (polynorbornene) that is in both cases the same. The material properties were compared to those of analogous aerogels bearing only one norbornene moiety at the tip of each branch deriving from the same cores. Full article

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

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14 pages, 2591 KiB

Open AccessArticle

Ruthenium(η⁶,η¹-arene-CH₂-NHC) Catalysts for Direct Arylation of 2-Phenylpyridine with (Hetero)Aryl Chlorides in Water

by Nazan Kaloğlu, İsmail Özdemir, Nevin Gürbüz, Hakan Arslan and Pierre H. Dixneuf

Molecules 2018, 23(3), 647; https://doi.org/10.3390/molecules23030647 - 13 Mar 2018

Cited by 22 | Viewed by 4222

Abstract

A series of new benzimidazolium halides were synthesized in good yields as unsymmetrical N-heterocyclic carbene (NHC) precursors containing the N–CH₂–arene group. The benzimidazolium halides were readily converted into ruthenium(II)–NHC complexes with the general formula [RuCl₂(η⁶,η¹ [...] Read more.

A series of new benzimidazolium halides were synthesized in good yields as unsymmetrical N-heterocyclic carbene (NHC) precursors containing the N–CH₂–arene group. The benzimidazolium halides were readily converted into ruthenium(II)–NHC complexes with the general formula [RuCl₂(η⁶,η¹–arene–CH₂–NHC)]. The structures of all new compounds were characterized by ¹H NMR (Nuclear Magnetic Resonance), ¹³C NMR, FT-IR (Fourier Transform Infrared) spectroscopy and elemental analysis techniques. The single crystal structure of one benzimidazole ruthenium complex, 2b, was determined. The complex is best thought of as containing an octahedrally coordinated Ru center with the arene residue occupying three sites, the remaining sites being occupied by a (carbene)C–Ru bond and two Ru–Cl bonds. The catalytic activity of [RuCl₂(η⁶,η¹–arene–CH₂–NHC)] complexes was evaluated in the direct (hetero)arylation of 2-phenylpyridine with (hetero)aryl chlorides in water as the nontoxic reaction medium. These results show that catalysts 2a and 2b were the best for monoarylation with simple phenyl and tolyl chlorides. For functional aryl chlorides, 2d, 2e, and 2c appeared to be the most efficient. Full article

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

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11 pages, 1534 KiB

Open AccessArticle

Gold-Catalyzed Addition of β-Ketoesters to Alkenes: Influence of Electronic and Steric Effects in the Reaction Outcome

by Agustina La-Venia, Mirta P. Mischne and Ernesto G. Mata

Molecules 2018, 23(3), 629; https://doi.org/10.3390/molecules23030629 - 10 Mar 2018

Viewed by 3081

Abstract

The gold-catalyzed intermolecular hydroalkylation of olefins with β-ketoesters represents a conceptually attractive and useful synthetic tool; however, it has been scarcely applied, remaining a challenge for chemists. The aim of the current study was to investigate the addition of these 1,3-diketo-compounds to alkenes [...] Read more.

The gold-catalyzed intermolecular hydroalkylation of olefins with β-ketoesters represents a conceptually attractive and useful synthetic tool; however, it has been scarcely applied, remaining a challenge for chemists. The aim of the current study was to investigate the addition of these 1,3-diketo-compounds to alkenes under gold catalysis conditions, in order to establish the electronic and steric effects of the alkenyl substrates in the reaction outcome. The screening of different catalyst systems and diverse olefins enabled defining the alkenyl requirements and the best reaction conditions to efficiently achieve the coupled products. Full article

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

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449 KiB

Open AccessArticle

Platinum-Catalyzed Allylation of 2,3-Disubstituted Indoles with Allylic Acetates

by Bai-Jing Peng, Wen-Ting Wu and Shyh-Chyun Yang

Molecules 2017, 22(12), 2097; https://doi.org/10.3390/molecules22122097 - 29 Nov 2017

Cited by 5 | Viewed by 3763

Abstract

Given the importance of heterocycle indole derivatives, much effort has been directed toward the development of methods for functionalization of the indole nucleus at N1 and C3 sites. Moreover, the platinum-catalyzed allyation of nucleophiles was an established and efficient way, which has been [...] Read more.

Given the importance of heterocycle indole derivatives, much effort has been directed toward the development of methods for functionalization of the indole nucleus at N1 and C3 sites. Moreover, the platinum-catalyzed allyation of nucleophiles was an established and efficient way, which has been applied to medicinal and organic chemistry. In our research, the platinum-catalyzed 2,3-disubstitued indoles with allylic acetates was investigated under different conditions. Herein, we established a simple, convenient, and efficient method, which afforded high yield of allylated indoles. Full article

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

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Review

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60 pages, 84905 KiB

Open AccessFeature PaperReview

Advances in Magnetic Nanoparticles-Supported Palladium Complexes for Coupling Reactions

by Mahmoud Nasrollahzadeh

Molecules 2018, 23(10), 2532; https://doi.org/10.3390/molecules23102532 - 04 Oct 2018

Cited by 29 | Viewed by 4516

Abstract

Carbon‒carbon (C‒C) and carbon‒heteroatom (C‒X) bonds that form via transition-metal-catalyzed processes have been extensively used in the organic synthesis and preparation of natural products and important compounds such as heterocycles, biologically active molecules, and dendrimers. Among the most significant catalysts, magnetic nanoparticles-supported palladium [...] Read more.

Carbon‒carbon (C‒C) and carbon‒heteroatom (C‒X) bonds that form via transition-metal-catalyzed processes have been extensively used in the organic synthesis and preparation of natural products and important compounds such as heterocycles, biologically active molecules, and dendrimers. Among the most significant catalysts, magnetic nanoparticles-supported palladium complexes are very effective, versatile, and heterogeneous catalysts for a wide range of C‒C and C‒X coupling reactions due to their reusability, thermal stability, and excellent catalytic performance. In this review, recent advances to develop magnetic nanoparticles supported palladium complexes, including their preparation, characterization, catalytic application, and reusability in the formation of both C‒C and C‒X bonds, by authors such as Sonogashira, Heck, Suzuki‒Miyaura, and Stille, and a few examples concerning N-arylation, S-arylation, and C_sp2-P coupling reactions are discussed. Full article

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

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60 pages, 41705 KiB

Open AccessFeature PaperReview

Synthesis and Application of the Transition Metal Complexes of α-Pyridinyl Alcohols, α-Bipyridinyl Alcohols, α,α’-Pyridinyl Diols and α,α’-Bipyridinyl Diols in Homogeneous Catalysis

by Tegene Tole, Johannes Jordaan and Hermanus Vosloo

Molecules 2018, 23(4), 896; https://doi.org/10.3390/molecules23040896 - 12 Apr 2018

Cited by 5 | Viewed by 6675

Abstract

The paper presents a comprehensive survey on the synthetic procedures of transition metal complexes of α-pyridinyl alcoholato, α-bipyridinyl alcoholato, α,α’-pyridinyl dialcoholato and α,α’-bipyridinyl dialcoholato ligands and their coordination chemistry. Greater emphasis is, however, given to the catalytic activity of the complexes [...] Read more.

The paper presents a comprehensive survey on the synthetic procedures of transition metal complexes of α-pyridinyl alcoholato, α-bipyridinyl alcoholato, α,α’-pyridinyl dialcoholato and α,α’-bipyridinyl dialcoholato ligands and their coordination chemistry. Greater emphasis is, however, given to the catalytic activity of the complexes in homogeneous and asymmetric chemical reactions. The multidentate character of the pyridinyl alcohols and/or bipyridinyl diols is of great importance in the complexation with a large number and type of transition metals. The transition metal complexes of pyridinyl alcoholato or bipyridinyl dialcoholato ligands in most cases, and a few pyridinyl alcohols alone, were used as catalysts in homogeneous and chemical asymmetric reactions. In most of the homogeneously catalysed enantioselective chemical reactions, limited numbers and types of pyridinyl alcohols and or bipyridinyl diols were used in the preparation of chiral catalysts that led to a few investigations on the catalytic importance of the pyridinyl alcohols. Full article

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

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