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1.
J Environ Manage ; 332: 117398, 2023 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-36738721

RESUMO

Capturing CO2 has become increasingly important. However, wide industrial applications of conventional CO2 capture technologies are limited by their slow CO2 sorption and desorption kinetics. Accordingly, this research is designed to overcome the challenge by synthesizing mesoporous MgO nanoparticles (MgO-NPs) with a new method that uses PEG 1500 as a soft template. MgO surface structure is nonstoichiometric due to its distinctive shape; the abundant Lewis base sites provided by oxygen vacancies promote CO2 capture. Adding 2 wt % MgO-NPs to 20 wt % monoethanolamine (MEA) can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by ∼3000% and can increase the CO2 absorption capacity within the breakthrough time by ∼3660%. The data suggest that MgO-NPs can accelerate the rate and increase CO2 desorption capacity by up to ∼8740% and ∼2290% at 90 °C, respectively. Also, the excellent stability of the system within 50 cycles is verified. These findings demonstrate a new strategy to innovate MEA absorbents currently widely used in commercial post-combustion CO2 capture plants.


Assuntos
Dióxido de Carbono , Óxido de Magnésio , Dióxido de Carbono/química , Óxido de Magnésio/química , Bases de Lewis , Etanolamina/química , Cinética
2.
Int J Mol Sci ; 24(3)2023 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-36768447

RESUMO

The cycloaddition of CO2 into epoxides to form cyclic carbonates is a highly sought-after reaction for its potential to both reduce and use CO2, which is a greenhouse gas. In this paper, we present experimental and theoretical studies and a mechanistic approach for three catalytic systems. First, as Lewis base catalysts, imidazole and its derivatives, then as a Lewis acid catalyst, ZnI2 alone, and after that, the combined system of ZnI2 and imidazole. In the former, we aimed to discover the reasons for the varied reactivities of five Lewis base catalysts. Furthermore, we succeeded in reproducing the experimental results and trends using DFT. To add, we emphasized the importance of non-covalent interactions and their role in reactivity. In our case, the presence of a hydrogen bond was a key factor in decreasing the reactivity of some catalysts, thus leading to lower conversion rates. Finally, mechanistically understanding this 100% atom economy reaction can aid experimental chemists in designing better and more efficient catalytic systems.


Assuntos
Dióxido de Carbono , Bases de Lewis , Reação de Cicloadição , Compostos de Epóxi , Imidazóis
3.
Molecules ; 28(2)2023 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-36677814

RESUMO

Polymer electrolytes for lithium metal batteries have aroused widespread interest because of their flexibility and excellent processability. However, the low ambient ionic conductivity and conventional fabrication process hinder their large-scale application. Herein, a novel polyethylene-oxide-based composite polymer electrolyte is designed and fabricated by introducing nano-SiO2 aerogel as an inorganic filler. The Lewis acid-base interaction between SiO2 and anions from Li salts facilitates the dissociation of Li+. Moreover, the SiO2 interacts with ether oxygen (EO) groups, which weakens the interaction between Li+ and EO groups. This synergistic effect produces more free Li+ in the electrolyte. Additionally, the facile rheology-tuning UV polymerization method achieves continuous coating and has potential for scalable fabrication. The composite polymer electrolyte exhibits high ambient ionic conductivity (0.68 mS cm-1) and mechanical properties (e.g., the elastic modulus of 150 MPa). Stable lithium plating/stripping for 1400 h in Li//Li symmetrical cells at 0.1 mA cm-2 is achieved. Furthermore, LiFePO4//Li full cells deliver superior discharge capacity (153 mAh g-1 at 0.5 C) and cycling stability (with a retention rate of 92.3% at 0.5 C after 250 cycles) at ambient temperature. This work provides a promising strategy for polymer-based lithium metal batteries.


Assuntos
Eletrólitos , Lítio , Polimerização , Íons , Éteres , Etil-Éteres , Bases de Lewis , Oxigênio , Dióxido de Silício
4.
Environ Sci Pollut Res Int ; 30(13): 37946-37960, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36576627

RESUMO

In this study, the production of activated carbon based on almond shells by microwave heating with KOH activation and then the modification of activated carbon with phosphorus and oxygen as a result of hydrothermal heating with phosphoric acid were carried out to increase the Cd(II) and Pb(II) adsorption efficiency. The resulting materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal analyzer (TG-DTA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nitrogen adsorption. Adsorption performance, kinetics and thermodynamics of phosphorus, and oxygen-doped activated carbons were evaluated. The results showed that the adsorption of both Cd(II) and Pb(II) on phosphorus and oxygen-doped activated carbons obeyed the Langmuir isotherm and pseudo-second-order kinetics. The adsorption capacity values (Qm) obtained from the Langmuir isotherm for Cd(II) and Pb(II) adsorption were 185.18 mg/g and 54.64 mg/g, respectively. At the same time, the adsorption mechanism of Pb(II) and Cd(II) on the respective adsorbents was evaluated. As a result of phosphorus and oxygen atoms, Lewis base sites on carbon atoms and Lewis acid sites on phosphorus atoms are likely to form on the surface. These Lewis base sites can act as important active sites in adsorption reactions, especially of positively charged Pb(II) and Cd(II) ions.


Assuntos
Prunus dulcis , Poluentes Químicos da Água , Cádmio/análise , Chumbo , Fósforo , Adsorção , Micro-Ondas , Oxigênio , Carvão Vegetal/química , Bases de Lewis , Poluentes Químicos da Água/análise , Cinética , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier
5.
Org Lett ; 24(47): 8603-8608, 2022 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-36403156

RESUMO

A chiral Lewis base catalyzed enantioselective N-allylic alkylation of 2-hydroxypyridines and MBH carbonates is documented, affording a convenient access to N-alkylated 2-pyridones with up to 99% ee and 99% yield. Experimental and computational studies have revealed that the strong hydrogen bond interaction between the chiral Lewis base catalyst and 2-hydroxypyridines plays a crucial role in this reaction for the reactivity, chemoselectivity, and enantioselectivity.


Assuntos
Bases de Lewis , Piridonas , Alquilação , Ligação de Hidrogênio
6.
Int J Mol Sci ; 23(21)2022 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-36361812

RESUMO

The effects of Lewis basicity and acidity on σ-hole interactions were investigated using two sets of carbon-containing complexes. In Set I, the effect of Lewis basicity was studied by substituting the X3/X atom(s) of the NC-C6H2-X3 and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F3 and F-C-X3 (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centers. Concerning the Lewis basicity effect, higher negative interaction energies (Eint) were observed for the F-C-F3∙∙∙NC-C6H2-X3 complexes compared with the F-C-F3∙∙∙NCX analogs. Moreover, significant Eint was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X3/X atom(s). Among Set I complexes, the highest negative Eint was ascribed to the F-C-F3∙∙∙NC-C6H2-I3 complex with a value of -1.23 kcal/mol. For Set II complexes, Eint values of F-C-X3 bearing complexes were noted within the -1.05 to -2.08 kcal/mol scope, while they ranged from -0.82 to -1.20 kcal/mol for the W-C-F3 analogs. However, Vs,max quantities exhibited higher values in the case of W-C-F3 molecules compared with F-C-X3; preferable negative Eint were ascribed to the F-C-X3 bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X3 substituents. Dispersion forces (Edisp) were identified as the dominant forces for these interactions. The obtained results provide a foundation for fields such as crystal engineering and supramolecular chemistry studies that focus on understanding the characteristics of carbon-bearing complexes.


Assuntos
Carbono , Bases de Lewis , Bases de Lewis/química , Ácidos de Lewis/química , Elétrons
7.
J Org Chem ; 87(22): 15224-15249, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36318089

RESUMO

The amino group in aminocarboxylic acids is sufficiently basic to be protonated in strong acids, and consequently, ionization of the carboxylic acid to an acylium ion is blocked due to charge-charge repulsion. Thus, acylation of aromatic compounds is significantly retarded in Friedel-Craft type reactions. We found that Friedel-Crafts acylation with aminocarboxylic acids can proceed smoothly even in a strong Brønsted acid (triflic acid, TfOH) if the Lewis base P4O10 is added. Here we describe the Friedel-Crafts acylation reactions of anthranilic acid and α- to δ-aminocarboxylic acids with benzene derivatives in the presence of P4O10. Non-amino-containing carboxylic acids as well as N-containing heteroaromatic carboxylic acids are available, and α-amino acids can be directly utilized without any protective group. Most substrates afford acylation products in high yields, although some epimerization/racemization may occur. Density functional theory (DFT) calculations suggested that P4O10 neutralizes the protonated amine, converting the N-H covalent bond to a N-hydrogen bond and allowing the carboxylic acid OH functionality to serve as a good leaving group.


Assuntos
Ácidos , Bases de Lewis , Acilação , Ácidos Carboxílicos , Ligação de Hidrogênio
8.
Dalton Trans ; 51(43): 16668-16680, 2022 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-36278834

RESUMO

trans-Anethole (trans-AN) is widely applied in food, daily necessities, and pharmaceuticals and is typically available from inefficient natural oil extraction or complex organic transformations over mineral acid or noble metals. Here, a green and sustainable route was developed to stereoselectively produce trans-AN (ca. 90% selectivity) over an organic polymeric phosphonate-hafnium catalyst (PAS-Hf) through the cascade transfer hydrogenation and dehydration of biomass-based 4'-methoxypropiophenone (4-MOPP), with an environmental impact factor (E-factor) of 47.73. The porous structure and the enhanced hydrophobicity of the spherical catalyst PAS-Hf ensured the formation of more accessible and stable Lewis (Hf4+) and Brønsted (SO3H) acid active sites, which could be used for rapid conversion of biomass-based 4-MOPP to AN (100% conversion, 97.2% yield) in 0.5-2 h (TOF: 9.3 h-1). Density functional theory (DFT) calculations elucidated that the addition of PAS-Hf could remarkably facilitate the overall conversion process by decreasing the reaction energy barrier (151.33 to 48.27 kJ mol-1) of the rate-determining step. The good thermal stability and heterogeneity of the bifunctional catalyst were responsible for its constant activity during at least five consecutive cycles. The synergistic/relay catalysis of Lewis acid-base and Brønsted acid species could be extended to more than ten kinds of aldehydes and ketones. This acid-base multi-catalytic protocol has considerable potential in cascade biomass conversion via heterogeneous catalysis without any base additive.


Assuntos
Derivados de Alilbenzenos , Catálise , Anisóis , Bases de Lewis , Interações Hidrofóbicas e Hidrofílicas
9.
Molecules ; 27(18)2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36144714

RESUMO

In this review, we discuss Friedel-Crafts-type aromatic amidation and acylation reactions, not exhaustively, but mainly based on our research results. The electrophilic species involved are isocyanate cation and acylium cation, respectively, and both have a common +C=O structure, which can be generated from carboxylic acid functionalities in a strong Brønsted acid. Carbamates substituted with methyl salicylate can be easily ionized to the isocyanate cation upon (di)protonation of the salicylate. Carboxylic acids can be used directly as a source of acylium cations. However, aminocarboxylic acids are inert in acidic media because two positively charged sites, ammonium and acylium cation, will be generated, resulting in energetically unfavorable charge-charge repulsion. Nevertheless, the aromatic acylation of aminocarboxylic acids can be achieved by using tailored phosphoric acid esters as Lewis bases to abrogate the charge-charge repulsion. Both examples tame the superelectrophilic character.


Assuntos
Compostos de Amônio , Bases de Lewis , Ácidos , Acilação , Carbamatos , Ácidos Carboxílicos , Cátions/química , Isocianatos/química , Estrutura Molecular , Organofosfatos , Salicilatos
10.
Nat Chem ; 14(10): 1118-1125, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36050380

RESUMO

Amines are prominent in natural products, pharmaceutical agents and agrochemicals. Moreover, they are synthetically valuable building blocks for the construction of complex organic molecules and functional materials. However, amines, especially aliphatic and aromatic amines with free N-H bonds, tend to coordinate with transition metals and deactivate the catalyst, posing a tremendous challenge to applying Lewis basic amines in the amination of olefins. Here we present an example of oxidative amination of simple olefins with various Lewis basic amines. The combination of a palladium catalyst, 2,6-dimethyl-1,4-benzoquinone and a phosphorous ligand leads to the efficient synthesis of alkyl and aryl allylamines. A series of allylamines were obtained with good yields and excellent regio- and stereoselectivities. Intramolecular amination to synthesize tetrahydropyrrole and piperidine derivatives was also realized. Mechanistic investigations reveal that the reaction undergoes allylic C(sp3)-H activation and subsequent functionalization.


Assuntos
Alcenos , Paládio , Agroquímicos , Alcenos/química , Aminação , Aminas/química , Catálise , Bases de Lewis , Ligantes , Estresse Oxidativo , Paládio/química , Preparações Farmacêuticas , Piperidinas
11.
J Am Chem Soc ; 144(35): 16206-16216, 2022 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-36001853

RESUMO

Functionalized alicyclic amines are important building blocks for the synthesis of bioactive natural compounds and drugs. Existing methods of functionalization are typically limited to the synthesis of protected amines or the use of highly basic organometallic reagents that can compromise functional group tolerance. Here, we report a novel approach that enables the transformation of O-benzoyl hydroxylamines into α-functionalized cyclic secondary amines by means of a copper-catalyzed regio-, stereo-, and chemoselective coupling with allenes and bis(pinacolato)diboron. A key feature of the present transformation is the use of a catalytic Lewis base additive which inhibits the competing C-N bond forming reaction between the catalytically generated boron-substituted allylcopper intermediate with the O-benzoyl hydroxylamine, thus enabling in situ transformation of the latter into an alicyclic imine which undergoes selective C-C bond formation with the allylcopper species.


Assuntos
Aminas , Cobre , Aminas/química , Catálise , Cobre/química , Iminas , Bases de Lewis
12.
Acc Chem Res ; 55(18): 2708-2727, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36043467

RESUMO

ConspectusAsymmetric organocatalysis has been considered to be an efficient and reliable strategy for the stereoselective preparation of optically active chemicals. In particular, chiral tertiary amines as Lewis base organocatalysts bearing core structures including quinuclidine, dimethylaminopyridine (DMAP), N-methylimidazole (NMI), amidine, etc. have provided new and powerful tools for various chemical transformations. However, due to the limitations in structural complexity, synthetic difficulty, low catalytic efficiency, and high cost, the industrial application of such catalysts is still far from being widely adopted. Therefore, the development of new chiral tertiary amine catalysts with higher activity and selectivity is greatly desired.In order to address the contradiction between activity and selectivity caused by the ortho group, a bicyclic imidazole structure bearing a relatively large bond angle ∠θ was designed as the skeleton of our new catalysts. 6,7-Dihydro-5H-pyrrolo[1,2-a]imidazole (abbreviated as DPI) and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine (abbreviated as TIP) are two of the utilized skeletons. In addition to obtaining satisfactory catalytic activity, excellent enantioselectivity would also be expected because the stereocontrol R group is neither far nor close to the catalytic active site (sp2-N atom) and is adjustable. Based on this skeleton, a family of chiral bicyclic imidazole catalysts were easily prepared and successfully applied in several enantioselective reactions for the synthesis of a variety of valuable chiral compounds.6,7-Dihydro-5H-pyrrolo[1,2-a]imidazole (abbreviated as DPI) is the predominantly utilized skeleton. First, HO-DPI, the key intermediate of the designed chiral bicyclic imidazole catalysts, could be efficiently synthesized from imidazole and acrolein, then separated by kinetic resolution or optical resolution. Second, Alkoxy-DPI, the alkyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized by a one-step alkylation from HO-DPI. This type of catalyst has been successfully applied in asymmetric Steglich rearrangement (C-acylation rearrangement of O-acylated azlactones), asymmetric phosphorylation of lactams, and a sequential four-step acylation reaction. Third, Acyloxy-DPI, the acyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized with a one-step acetylative kinetic resolution from racemic HO-DPI or acylation from enantiopure HO-DPI. The catalyst AcO-DPI has been successfully applied in enantioselective Black rearrangement and in direct enantioselective C-acylation of 3-substituted benzofuran-2(3H)-ones and 2-oxindoles. Fourth, Alkyl-DPI was synthesized via a two-step reaction from racemic HO-DPI and separated easily by resolution. The catalyst Cy-DPI has been successfully applied in dynamic kinetic resolution of 3-hydroxyphthalides through enantioselective O-acylation. Cy-PDPI was synthesized through a Cu-catalyzed amidation from Cy-DPI and successfully applied in the kinetic resolution of secondary alcohols with good to excellent enantioselectivities. Finally, the carbamate type chiral bicyclic imidazole catalysts, Carbamate-DPI, were readily synthesized from HO-DPI, and the catalyst Ad-DPI bearing a bulky adamantyl group was successfully applied in the synthesis of the anti-COVID-19 drug remdesivir via asymmetric phosphorylation. Alongside our initial work, this Account also introduces four elegant studies by other groups concerning asymmetric phosphorylation utilizing chiral bicyclic imidazole catalysts.In summary, this Account focuses on the chiral bicyclic imidazole catalysts developed in our group and provides an overview on their design, synthesis, and application that will serve as inspiration for the exploration of new organocatalysts and related reactions.


Assuntos
Benzofuranos , Bases de Lewis , Acroleína , Amidinas , Aminas , Carbamatos , Catálise , Imidazóis/química , Lactamas/química , Oxindóis , Piridinas , Quinuclidinas , Estereoisomerismo
13.
J Colloid Interface Sci ; 628(Pt A): 758-768, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-35961244

RESUMO

Graphene is of great interest for many far-reaching applications that involve interparticle interactions in adsorbents, coatings, and composites. A deep understanding of the surface components has been crucial but achieving the most accurate and reliable values of these, unaffected by experimental conditions or the analytical techniques used, remains a major challenge. To this end, we have proposed in this paper a novel approach for the first time, to the best of our knowledge, to determine London dispersive and specific (polar) components including the Lewis acid-base character of the surface free energy of graphene materials (graphene oxide (GO), reduced graphene oxide (rGO), and graphite) using inverse gas chromatography (IGC) technique at an infinite dilution. We have estimated the London dispersive surface energy values of graphite, GO, and rGO as van der Waals interaction to be 156-179, 89-106, and 110-119 mJ m-2, respectively, in the temperature range of 320-360 K. These are attributable to the surface properties impacted by the oxygen moieties, defects, and micropores on the carbon frameworks. Further, the acceptor (KA) and donor (KD) parameters of GO were found to be 0.71 and 0.96, respectively, while those of rGO were 0.54 and 1.05. Notably, the GO is more of the Lewis acid character that could be amphoteric, while the Lewis base characteristics of both GO and rGO are not significantly changed. These results provide foundational knowledge to understand the physicochemical properties of graphene surfaces, which should be helpful to designing interface engineering in various applications.


Assuntos
Grafite , Carbono , Cromatografia Gasosa/métodos , Grafite/química , Ácidos de Lewis , Bases de Lewis , Oxigênio , Temperatura
14.
Chem Asian J ; 17(21): e202200746, 2022 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-36031710

RESUMO

Although GPE still has the risk of shuttling due to the incomplete removal of liquid electrolytes compared to SPE, which has the most promise of eliminating polysulfide shuttling, researchers have made abundant efforts to eliminate as much of the polysulfide shuttling effect as possible while retaining the unique advantages of GPE. For example, physical barrier to polysulfides by improving the pore size of GPE or fabricating multidimensional structures by different preparation methods. Further chemical adsorption of polysulfides by adding nanofillers to increase polar sites to create polar-polar interactions with polysulfides or to create Lewis acid-base interactions. However, although chemical adsorption can indeed highly immobilize polysulfides, it still brings disadvantages such as loss of active material. Therefore, other researchers have employed GPE with ion-selective permeability that has electrostatic repulsive force or steric hindrance to polysulfides to better inhibit polysulfide shuttling. However, modifying only the cathode side is not enough to enhance this overall properties of Li-S cells. These problems of poor Li+ transport, lithium dendrite growth, and poor SEI due to uneven lithium ion deposit on Li anode side still affect the overall performance of Li-S cells. Therefore, a GPE to improve these problems on the Li anode side is summarized below. Compared with an all-solid electrolyte, GPE, which has a partially liquid electrolyte, clearly has advantages such as strong interfacial contact, good anode interface compatibility, and high flexibility. However, it is still not comparable to the ionic conductivity, etc. of pure liquid electrolyte only. Therefore, the problems on the lithium metal anode side are mainly focused on the lithium ion transport problems and the problems of lithium dendrite growth and inhomogeneous SEI at the lithium anode interface. Facing the problems in these two aspects, researchers have given many improvement solutions respectively. For the lithium ion transport problem, researchers have instead provided pathways for lithium ion transport by adding amorphous nanofibers or nanofillers to reduce the crystallinity of the polymer and improve the ionic conductivity. Alternatively, the migration number of lithium ions can be increased by limiting the anions in the electrolyte. As for the interfacial problems of lithium anodes, researchers have effectively suppressed the growth of lithium dendrites or inhomogeneous lithium plating/stripping phenomena mainly by adding nanofillers to increase the mechanical strength of GPE or by participating in the generation of SEI.


Assuntos
Lítio , Polímeros , Lítio/química , Polímeros/química , Eletrólitos/química , Eletrodos , Íons/química , Enxofre , Bases de Lewis
15.
Angew Chem Int Ed Engl ; 61(40): e202207475, 2022 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-35881564

RESUMO

Herein we report a method for the synthesis of α-aryl acrylamides leveraging polar S-to-C aryl migrations induced by a Lewis basic organocatalyst. In contrast to previously reported radical aryl migrations of sulfonyl acrylimides, this polar process enables subsequent elimination, ultimately leading to a formal aryl/hydrogen exchange including SO2 extrusion. This reaction is selective for electron-deficient aromatic groups, while tolerating a variety of substituents on nitrogen and in the ß-position, and it delivers useful building blocks for further transformations, including cycloaddition and cyclisation reactions. The mechanism was investigated in detail using quantum chemical calculations, which unexpectedly revealed the Lewis base to be involved in several decisive steps.


Assuntos
Hidrogênio , Bases de Lewis , Acrilamidas , Reação de Cicloadição , Nitrogênio
16.
Chem Asian J ; 17(18): e202200611, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-35883252

RESUMO

Heavier analogues of carbonyls, in the form of "R2 E=O" (E=Si, Ge, Sn, Pb), feature a high polar E=O double bond. In contrast to carbonyl compounds, heavier analogues are extremely unstable and prone to proceed head-to-tail oligomerization. Thus, the isolation of such species under ambient conditions is a challenging synthetic target in main group chemistry. In recent years, much progress has been achieved in the synthesis and isolation of a variety of Lewis base/acid, Lewis base-stabilized and even Lewis acid/base free heavier analogues. These compounds exhibit interesting reactivities, such as small molecule activation and metathesis reactions, indicating the potential of heavier analogues in synthetic chemistry. This review summarizes the recent achievements in the chemistry of Lewis base and/or acid stabilized heavier analogues of carbonyls, including synthetic approaches, structural parameters and reactivity of these isolable compounds.


Assuntos
Bases de Lewis , Estrutura Molecular
17.
J Am Chem Soc ; 144(29): 13294-13301, 2022 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-35820071

RESUMO

A new strategy is described for the Lewis base-catalyzed bromochlorination of unsaturated systems that is mechanistically distinct from prior methodologies. The novelty of this method hinges on the utilization of thionyl chloride as a latent chloride source in combination with as little as 1 mol % of triphenylphosphine or triphenylphosphine oxide as Lewis basic activators. This metal-free, catalytic chemo-, regio-, and diastereoselective bromochlorination of alkenes and alkynes exhibits excellent site selectivity in polyunsaturated systems and provides access to a wide variety of vicinal bromochlorides with up to >20:1 regio- and diastereoselectivity. The precision installation of Br, Cl, and I in various combinations is also demonstrated by simply varying the commercial halogenating reagents employed. Notably, when a chiral Lewis base promoter is employed, an enantioselective bromochlorination of chalcones is possible with up to a 92:8 enantiomeric ratio when utilizing only 1-3 mol % of (DHQD)2PHAL.


Assuntos
Cloretos , Bases de Lewis , Alcenos , Catálise , Halogênios , Estereoisomerismo
18.
Chemphyschem ; 23(20): e202200273, 2022 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-35738996

RESUMO

MP2/aug-cc-pVTZ calculations were performed on systems containing a proton or a lithium cation located between two π-electron systems or between π-electron and σ-electron units. The proton or the lithium cation attached to the acetylene or its derivative may be treated as the Lewis acid unit while the remaining part of the complex, the π-electron species or the dihydrogen, act as the Lewis base through their π-electrons or σ-electrons, respectively. The complexes analysed here are linked by the π⋅⋅⋅H+ /Li+ ⋅⋅⋅π and π⋅⋅⋅H+ /Li+ ⋅⋅⋅σ interactions. It is discussed whether these interactions are classified as hydrogen and lithium bonds. Therefore, different definitions of the latter interactions are presented. The Electron Localization Function (ELF) and the Natural Bond Orbital (NBO) approaches were applied to analyse the above-mentioned complexes. The unique properties of interactions with the proton and with the lithium cation that occur in complexes analysed here are described.


Assuntos
Elétrons , Lítio , Lítio/química , Prótons , Bases de Lewis/química , Ácidos de Lewis/química , Modelos Moleculares , Ligação de Hidrogênio , Íons , Hidrogênio/química , Acetileno/química
19.
J Chromatogr A ; 1675: 463131, 2022 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-35617805

RESUMO

Since Saint-Flour and Papirer first introduced Gutmann's acceptor number and donor number parameters into the inverse gas chromatography (IGC) field in 1982, IGC has become an important technology for the measurement of surface Lewis acid-base properties of solid materials. However, introducing new roles of Lewis acid-base parameters, especially using them to predict material properties rather than just explain material properties, is an important aspect in developing IGC technology. In this paper, we first introduce the Schultz and Abraham methods for measurement of acid-base properties and discuss the traditional role of acid-base parameters. Then, we present a relation between the ratio of acid-base constants, Ka/Kb, and triboelectric charge density of some polymers to prove the possible new application field of IGC.


Assuntos
Ácidos de Lewis , Polímeros , Cromatografia Gasosa/métodos , Ácidos de Lewis/química , Bases de Lewis/química , Polímeros/química , Propriedades de Superfície , Termodinâmica
20.
Inorg Chem ; 61(16): 6101-6109, 2022 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-35420789

RESUMO

Several new isostructural lanthanide metal-organic frameworks (Ln-MOFs), {[Ln2(L)3DMA4]·2DMA}n (1-Ln, where Ln = Eu, Tb, or EuxTb1-x), were first constructed via the solvothermal reactions of 4,6-di(4-carboxyphenyl)pyrimidine and Ln3+ ions. 1-Ln exhibits a 4-connected two-dimensional framework endowed with uncoordinated Lewis base sites. An exploration of luminescence sensing demonstrated 1-Eu can be used for the selectivity detection of dimetridazole and metronidazole antibiotics in other antibiotics, blood plasma, and urine, acting as an exceptional recyclable luminescent probe. More importantly, the luminescent inks of 1-Ln are invisible, color adjustable, and stabilized, which may greatly improve their anticounterfeiting applications.


Assuntos
Elementos da Série dos Lantanídeos , Estruturas Metalorgânicas , Antibacterianos/farmacologia , Elementos da Série dos Lantanídeos/química , Bases de Lewis , Luminescência
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