Review
Biochemistry & Molecular Biology
Young-Ho Oh, Dong Wook Kim, Sungyul Lee
Summary: Ionic liquids (ILs) have great potential as organocatalysts/promoters in chemical reactions, using their ionic nature and interactions with functional groups in substrates to enhance reaction rates. However, the full application of ILs as organocatalysts/promoters has not been achieved yet.
Article
Chemistry, Multidisciplinary
Keqiang Xu, Jinhan Li, Fangming Liu, Xijie Chen, Tete Zhao, Fangyi Cheng
Summary: This study presents a new strategy to enhance carbon utilization and selectivity of CO2 methanation under acidic conditions by using crown ether decoration on Cu catalysts. Experimental results demonstrate that crown ether modification enhances the interfacial electric field, stabilizes reaction intermediates, and accelerates water dissociation, resulting in high methane production efficiency.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Xiao-Feng Xia, Quan Huang, Tian-Yu Sun, Yuqin Jiang, Guoxia Ran
Summary: This study describes the development of a desaturation and beta-fluorination reaction of cyclic amides, which is achieved through an oxidative-promoted selective hydrogen atom-transfer/isomerization/electrophilic fluorination process. Furthermore, the discovery also allows for alpha, beta-dehydrogenation and gamma-di-fluorination of N-aryl lactams.
Article
Biochemistry & Molecular Biology
Young-Ho Oh, Wonhyuck Yun, Chul-Hee Kim, Sung-Woo Jang, Sung-Sik Lee, Sungyul Lee, Dong-Wook Kim
Summary: The study reveals the crucial role of crown ether promoters in the intra- and inter-molecular organocatalysis of S(N)2 fluorination, with calculated and experimentally observed results supporting the mechanism and efficacy. The participation of metal salt CsF in the reaction is briefly discussed in terms of its role as a contact ion pair or a free nucleophile F-.
Article
Environmental Sciences
Jian Pan, Mengqian Qian, Yu Li, Haiqiang Wang, Baohong Guan
Summary: Metal-free catalysts play a crucial role in water treatment by effectively removing harmful quinoline derivatives and reducing chemical oxygen demand. This study demonstrates the use of fluorinated ceramic honeycomb as a catalyst for stable catalytic ozonation, generating free reactive oxygen species and efficiently degrading the target compound.
Article
Environmental Sciences
Jian Pan, Mengqian Qian, Yu Li, Haiqiang Wang, Baohong Guan
Summary: A metal-free catalyst, fluorinated ceramic honeycomb, was prepared to catalyze the ozonation of 4-methylquinoline with high efficiency in degrading and removing COD. The catalyst surface contains abundant active acid sites, enhancing the ozone decomposition to generate reactive oxygen species, with free hydroxyl radicals playing a major role in the degradation and COD removal of 4-Meq.
Article
Chemistry, Physical
Shuhao An, Chenbao Lu, Qing Xu, Cheng Lian, Changjun Peng, Jun Hu, Xiaodong Zhuang, Honglai Liu
Summary: A crown ether and cobalt-porphyrin-based COF was developed for catalytic reduction of carbon dioxide, showing remarkable performance with high Faradaic efficiencies and maximum turnover frequency. The crown ether units enhanced the hydrophilicity, electron transfer ability, and binding capacity of the COF, leading to its excellent catalytic performance.
ACS ENERGY LETTERS
(2021)
Article
Chemistry, Organic
Apoorva Malik, Pragati R. Sharma, Rakesh K. Sharma
Summary: We report a class of quaternary ammonium Cinchona-functionalized crown ether-strapped calix[4]-arene phase-transfer catalysts for the efficient enantioselective alpha-alkylation of glycine imines. The catalyst exhibits excellent catalytic performance at 0.1 mol % catalytic loading, affording the desired alpha-alkylated glycinates with 98% yield and 99.9% ee. The catalyst could be recovered and recycled up to 30 test cycles without a significant drop in activity.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Review
Chemistry, Physical
Young-Ho Oh, Ju Gyeong Jeong, Dong Wook Kim, Sungyul Lee
Summary: In this article, we review the studies on crown ether-facilitated nucleophilic reactions using metal salts, with a focus on the mechanistic features and experimental verification of the contact ion-pair (CIP) mechanism of metal salts. Kinetic measurements and quantum chemical methods are employed for the analysis. The use of chiral crown ethers and derivatives for enantioselective nucleophilic processes is also discussed.
Review
Chemistry, Physical
Noelia Mota, Elena Millan Ordonez, Barbara Pawelec, Jose Luis G. Fierro, Rufino M. Navarro
Summary: This review presents the latest progress in the synthesis of bifunctional/hybrid catalytic systems for the CO2-to-DME process, discussing the challenges of combining metal and acid functionalities in the catalyst, and the different strategies employed to improve DME formation efficiency.
Article
Chemistry, Physical
Gabryelle C. Marcal, Josefredo R. Pliego
Summary: The trifluoromethyl anion is a reactive species that is useful for organic synthesis, but its potential is limited due to its instability and susceptibility to elimination reactions. Complexation of the KCF3 salt with crown ethers can increase its stability. Theoretical investigations have been conducted on the generation, stability, and reactivity of the CF3- anion in the K+(18-crown-6)(CF3-) complex towards different substrates. The results indicate that TESCF3 is a good source of the CF3- anion, while HCF3 is less effective. The elimination of CF2 takes place via the dimeric species [K+(18-crown-6)(CF3-)](2) with a barrier energy of 18.7 kcal mol(-1), and the transient carbene interacts with another CF3- to form CF2CF3-. Six substrates were investigated for the SNAr reaction with the K+(18-crown-6)(CF3-) complex, and two activating groups are needed for a favorable reaction.
COMPUTATIONAL AND THEORETICAL CHEMISTRY
(2023)
Article
Chemistry, Physical
Josefredo R. Pliego Jr
Summary: This study provides relevant data on the structure of CuF species in solution and the corresponding solvation thermodynamics, as well as the coordination states and solvation free energy of Cu+ and Ag+ ions in acetonitrile. The results reveal the tricoordinate structure of Cu+ and Ag+ ions, the dissociative mechanism for ligand exchange, and the predominant tricoordinate complex of CuF. The results suggest that CuF may play an important role in copper catalyzed fluorination in acetonitrile solution.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Medicinal
Sandip S. Shinde, Kim-Viktoria Bolik, Simone Maschauer, Olaf Prante
Summary: This study developed TBMA-I as a PTC for F-18-fluorination reactions, demonstrating its favorable elution efficiency and potential application in labeling reactions.
Article
Chemistry, Physical
Vishal Kumar Rawat, Kosuke Higashida, Masaya Sawamura
Summary: In this study, a gold(I) complex with an imidazo[1,5-a]pyridin-3-ylidene ligand bearing a 2,2'-bipyridine moiety at the C5 position was used as a template for constructing heterobimetallic cooperative catalysts. The in situ generated gold-zinc bimetallic systems facilitated intermolecular nucleophilic anti-addition reactions between nonactivated internal alkynes and O-nucleophiles such as carboxylic acids and phenols. DFT calculations supported the proposed cooperative action of the cationic gold atom and the zinc salt site for activating the alkyne and the carboxylic acid, respectively.
Review
Chemistry, Multidisciplinary
Debabrata Bagchi, Soumyabrata Roy, Saurav Ch Sarma, Sebastian C. Peter
Summary: Electrocatalytic CO2 reduction is a promising avenue for achieving sustainable energy economy and global climate change targets. However, the lack of suitable cathode materials hinders its commercialization. Current catalysts suffer from low reaction rates, insufficient product selectivity, and stability issues. Overcoming these challenges requires an integrated approach involving catalytic design, mechanistic understanding, and efficient process engineering.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Physical
Isac C. Nogueira, Josefredo R. Pliego Jr
Summary: The study investigated the mechanism and active species of phase transfer catalyzed alkylation of phenol through calculations and modeling, revealing that the tetrabutylammonium ion complex is the active species in the catalysis. However, for the tetraethylammonium and tetrapropylammonium cations, another more complex aggregate may be involved in the process.
MOLECULAR CATALYSIS
(2021)
Article
Chemistry, Physical
Josefredo R. Pliego Jr
Summary: The successful palladium catalysis using biaryl monophosphine ligand for fluorination of aryl halides with inorganic fluoride salts has been a challenge transformation for several decades. However, the catalytic process suffers from the issue of off-cycle transformation due to ligand modification and formation of regioisomers, highlighting the importance of further ligand design. The theoretical calculations have provided insights into the mechanism of the catalysis and regioisomers formation, indicating the potential for more effective catalysis through rational ligand design.
MOLECULAR CATALYSIS
(2021)
Article
Chemistry, Physical
Josefredo R. Pliego Jr
Summary: The coordination structure and stability of CuF species in acetonitrile solution were investigated using various computational methods, revealing that CuF ion is stable in the CuF(CH3CN)(4) species but prone to dissociation in solution.
CHEMICAL PHYSICS LETTERS
(2022)
Article
Biochemistry & Molecular Biology
Fernando M. Lisboa, Josefredo R. Pliego
Summary: The reactivity of fluoride ion towards alkyl halides is influenced by the solvent environment. In polar aprotic solvents, it produces substantial E2 product, whereas in polar protic solvents it shows high selectivity for S(N)2 reactions. Addition of tert-butanol to acetonitrile solvent can modulate the reactivity and selectivity of TBAF. The TBAF(tert-butanol) complex plays a key role in increasing the S(N)2 selectivity.
JOURNAL OF MOLECULAR MODELING
(2022)
Article
Chemistry, Inorganic & Nuclear
Josefredo R. Pliego Jr
Summary: The addition of fluorine to organic molecules in the late stage of synthesis has become a hot topic in the past decade. Catalytic methods using fluoride salts as reagents, especially in combination with copper organometallic catalysis, have shown great potential. Recent experimental advances have been made in copper-mediated fluorination, and a deep understanding of the reaction mechanism and free energy profile is essential for developing an efficient catalytic process.
JOURNAL OF ORGANOMETALLIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Josefredo R. Pliego Jr
Summary: This study provides a detailed analysis of the nucleophilic fluorination reaction catalyzed by copper. The reaction proceeds via a cationic mechanism and the calculated free energy profiles provide insights into the reaction kinetics. The experimental results are in good agreement with the theoretical values, demonstrating the importance of this study.
MOLECULAR CATALYSIS
(2022)
Article
Chemistry, Physical
Josefredo R. Pliego Jr
Summary: This study provides relevant data on the structure of CuF species in solution and the corresponding solvation thermodynamics, as well as the coordination states and solvation free energy of Cu+ and Ag+ ions in acetonitrile. The results reveal the tricoordinate structure of Cu+ and Ag+ ions, the dissociative mechanism for ligand exchange, and the predominant tricoordinate complex of CuF. The results suggest that CuF may play an important role in copper catalyzed fluorination in acetonitrile solution.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Organic
Virginia C. Rufino, Josefredo R. Pliego
Summary: The addition reactions between primary amines and alpha,beta-unsaturated aldehydes and ketones have been studied theoretically. The results show that the formation of aza-Michael products is favored by the nucleophilic attack of the primary amine. Acetic acid, which can be present as a stabilizer, acts as a catalyst for proton transfer and imine formation. The study also emphasizes the importance of catalysts for reactions in aprotic solvents.
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Inorganic & Nuclear
Annelise S. Melo, Marcelo S. Valle, Josefredo R. Pliego Jr
Summary: A new phase transfer system combining 18-crown-6 and the bulky fluorinated alcohol was effective for the nucleophilic fluorination of alkyl halides. Under mild conditions with acetonitrile solvent, a primary alkyl bromide was fluorinated in 24 hours, yielding 80% and minimal elimination product. The choice of the fluorinated alcohol was based on thermodynamic analysis and theoretical calculations regarding complex stability and solubilization of the KF salt.
JOURNAL OF FLUORINE CHEMISTRY
(2023)
Article
Chemistry, Physical
Josefredo. R. Pliego Jr, Karla. L. Lopes
Summary: This study reports the important functionalization process of halogenation of organic compounds, where the reactive benzylic hydrogen can react with photochemically generated Br atom. The free energy profile of the reaction steps and the microkinetic analysis of reaction rate and product distribution were carried out using the B2GP-PLYP method. The results indicate that polar solvent accelerates the reaction rate compared to apolar solvent, and the reactivity of different benzylic substrates is influenced by different functional groups.
COMPUTATIONAL AND THEORETICAL CHEMISTRY
(2023)
Article
Chemistry, Physical
Gabryelle C. Marcal, Josefredo R. Pliego
Summary: The trifluoromethyl anion is a reactive species that is useful for organic synthesis, but its potential is limited due to its instability and susceptibility to elimination reactions. Complexation of the KCF3 salt with crown ethers can increase its stability. Theoretical investigations have been conducted on the generation, stability, and reactivity of the CF3- anion in the K+(18-crown-6)(CF3-) complex towards different substrates. The results indicate that TESCF3 is a good source of the CF3- anion, while HCF3 is less effective. The elimination of CF2 takes place via the dimeric species [K+(18-crown-6)(CF3-)](2) with a barrier energy of 18.7 kcal mol(-1), and the transient carbene interacts with another CF3- to form CF2CF3-. Six substrates were investigated for the SNAr reaction with the K+(18-crown-6)(CF3-) complex, and two activating groups are needed for a favorable reaction.
COMPUTATIONAL AND THEORETICAL CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Josefredo R. Pliego Jr
Summary: This study analyzes the use of metrics in the field of chemistry in Brazil and evaluates its effectiveness. The main findings suggest that the use of impact factor should be supplemented with the cited half-life of journals, and a composite metric called influence factor is proposed. The study also indicates that the h-index is no longer a reliable metric, while the individual h-index is more accurate. Analysis of a subset of the top 500 most productive Brazilian chemists shows that the hi-index significantly affects the ranking order.
Article
Chemistry, Multidisciplinary
Isac C. Nogueira, Josefredo R. Pliego
Summary: The classical alkylation reaction of benzene with isopropyl chloride catalyzed by AlCl3 and Al2Cl6 was studied using reliable calculations. The formation of Al2Cl6 dimers was found to be more dominant, with the mechanism involving the formation of CH3CHCH3+center dot center dot center dot Al2Cl7- ion pair being the rate-determining step. The study also considered the solubility of Al2Cl6 in the reaction.
JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Josefredo R. Pliego Jr
Summary: This study used a regular solution model to explain the formation conditions of azeotropes by deriving a mathematical expression.
Article
Chemistry, Physical
Virginia C. Rufino, Josefredo R. Pliego Jr
Summary: The study tested a cluster-continuum approach based on the cluster expansion method for solvation of 16 cations and 32 anions in aqueous solution, achieving a significant improvement of the SMD model with mean absolute deviations of 2.3 kcal mol(-1) for cations and 2.9 kcal mol(-1) for anions. The introduction of empirical γ(N) parameters produced linear regression lines, indicating good performance of this approximated cluster expansion method.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)