Highly Efficient Base Catalyzed N‐alkylation of Amines with Alcohols and β‐Alkylation of Secondary Alcohols with Primary Alcohols

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Highly Efficient Base Catalyzed N-alkylation of Amines with Alcohols and β-Alkylation of Secondary Alcohols with Primary Alcohols

The Cover Feature represents two different roads available to carry out the N-alkylation of amines with alcohols. The first road is wide and taken by many people; it consists of transition metal catalysis operating via the well-known “borrowing-hydrogen” pathway. In contrast, the findings reported by M. T. Johnson, O. F. Wendt and co-workers in their Research Article lays out a road less travelled, using the presence of air along with catalytic amount of base to reach the final goal. As indicated by the magnification, the methodology has a broader scope than shown and can be applied to similar reactions, one example in the report being the β-alkylation of secondary alcohols with primary alcohols. More information can be found in the Research Article by M. T. Johnson, O. F. Wendt and co-workers.


Catalytic Conversion of Levulinic Acid to Pyrrolidone under Mild Conditions with Disordered Mesoporous Silica‐Supported Pt Catalyst

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Catalytic Conversion of Levulinic Acid to Pyrrolidone under Mild Conditions with Disordered Mesoporous Silica-Supported Pt Catalyst

Biomass-derived! A non-acidic mesoporous silica-supported Pt catalyst was developed to produce biomass-derived 5-methylpyrrolidone under room temperature and atmospheric hydrogen. The suitable mesoporous structure created high dispersion of Pt species and accelerated the reaction processes. The isomerization of imine to enamine on the catalyst made this conversion easy under mild conditions.


Abstract

Catalytic conversion of biomass-derived levulinic acid (LA) into high-valued 5-methylpyrrolidones has become an attractive case in studies of biomass utilization. Herein, we developed a disordered mesoporous Pt/MNS catalyst for this reductive amination process under room temperature and atmospheric pressure of hydrogen. The disordered mesoporous structures in support of Pt/MNS catalyst led the formation of highly dispersed Pt species via confinement effect, providing high specific area for enhancing the catalytic sites. With the synergistic effect between highly dispersed Pt species and mesoporous structures, 5-methylpyrrolidones were successfully synthesized from biomass-derived LA and primary amines with high selectivity. Mechanism studies indicated that introducing protonic acid would promote the reductive-amination process, and enamine intermediates could be detected during the in-situ DRIFT tests. Density functional theory (DFT) calculation confirmed that the hydrogenation of enamine intermediate was more accessible than that of imide intermediates, leading the excellent performance of the Pt/MNS catalyst. This work provided a green method to produce 5-methylpyrrolidone and revealed the impact of catalyst structural characteristics on the reaction process.

Construction of [NbO]6−x‐xS Structure to Change Charge Density and Regulate Spontaneous Polarization to Achieve Efficient Pyro‐Photo‐Electric Water Splitting System of NaNbO3

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Construction of [NbO]6−x-xS Structure to Change Charge Density and Regulate Spontaneous Polarization to Achieve Efficient Pyro-Photo-Electric Water Splitting System of NaNbO3

The changed interaction between S−Nb−S in [NbO]6−x-xS structure, and the constructed [NbO]6−x-xS structure realized the regulation of charge density change and spontaneous polarization. S-doping weakens the S−Nb−S interaction in the [NbO]6−x-xS structure, which effectively improves the performance of the pyro-photo-electric synergistic water splitting system.


Abstract

Pyroelectric materials in the field of photoelectrochemical (PEC) water splitting still face the problems of difficult low spontaneous polarization intensity and excessive carrier recombination. Based on the above problems, we altered the interaction between S−Nb−S in the [NbO]6−x-xS structure, and the constructed [NbO]6−x-xS structure achieved the regulation of charge density change and spontaneous polarization. The results show that under the stimulation of light and temperature fluctuations, the current density of the NS-4 photoanode is as high as 0.574 mA/cm2 at 1.23 VRHE, which is about 1.59 times higher than the pure NaNbO3 current density value, and the NS −4 photoanode achieves IPCE value of 16.08 %. The first-principles density-functional theory calculations (DFT) reveal the principle of the [NbO]6−x-xS structure for the suppression function of the carrier recombination and the improvement function of the pyroelectric effect. The analysis shows that the S-doping leads to the weakening of S−Nb−S interactions in the [NbO]6−x-xS structure, which improves the pyroelectric effect and suppresses the photo/pyro-generated carrier recombination, and effectively enhances the performance of the pyro-photo-electric synergistic water splitting system. This work promotes the development of pyroelectric materials in the field of photoelectrochemical water splitting.

Acyclic Cucurbit[n]urils: Effective Taste Masking Nanocontainers for Cationic Bitter Compounds

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Acyclic Cucurbit[n]urils: Effective Taste Masking Nanocontainers for Cationic Bitter Compounds

Highly water-soluble acyclic cucurbiturils (ACBs) can include cationic drugs to lead to efficient masking of their bitter taste. Two-bottle preference (TBP) tests on mice show that all ACBs are tasteless to mammals. ACBs are discovered to mask the bitterness of berberine and denatonium benzoate, but not quinine hydrochloride, due to different binding modes.


Abstract

New acyclic cucurbit[n]urils (ACBs) with eight carboxylate groups were synthesized. These hosts are highly soluble in water, and can form stable inclusion complexes with cationic bitter compounds. ACBs are confirmed to be non-toxic and biocompatible. Two-bottle preference (TBP) tests on mice show that all ACBs are tasteless to mammals. ACBs are discovered to mask the bitterness of berberine and denatonium benzoate, but not quinine hydrochloride, due to different binding modes.

A Case of Convergent Evolution: The Bacterial Sesquiterpene Synthase for 1‐epi‐Cubenol from Nonomuraea coxensis

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A Case of Convergent Evolution: The Bacterial Sesquiterpene Synthase for 1-epi-Cubenol from Nonomuraea coxensis

A high yielding sesquiterpene synthase for (+)-1-epi-cubenol from the actinomycete Nonomuraea coxensis was investigated for its cyclisation mechanism by isotopic labelling experiments. Several derivatives of (+)-1-epi-cubenol and of the plant derived compounds (−)-cubenol and (−)-1-epi-cubenol have been prepared, including an epoxide that is known as a natural product from brown algae.


Abstract

A terpene synthase from Nonomuraea coxensis was identified as (+)-1-epi-cubenol synthase. The enzyme is phylogenetically unrelated to the known enzyme of the same function that is widespread in streptomycetes. Isotopic labelling experiments were performed to unambiguously assign the NMR data and to investigate hydrogen migrations during terpene cyclisations. Epoxidations of (+)-1-epi-cubenol and of the plant derived compounds (−)-cubenol and (−)-1-epi-cubenol confirmed the structure of a natural product isolated from the brown alga Dictyopteris divaricata and allowed to conclude on its absolute configuration. The crystal structures of the epoxides from (+)- and (−)-1-epi-cubenol and the acid catalysed conversion into an isomeric ketone are reported.

Expanding the Genetic Code: Incorporation of Functional Secondary Amines via Stop Codon Suppression

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Expanding the Genetic Code: Incorporation of Functional Secondary Amines via Stop Codon Suppression

Herein we synthesized a panel of non-canonical amino acids (ncAAs) harboring functional secondary amines inspired by organocatalysts. After their synthesis and characterization, D/L-pyrrolidine- and D/L-piperidine-based ncAAs were successfully site-specifically incorporated into proteins via stop codon suppression methodology. To demonstrate the utility of these ncAAs, the catalytic performance of the obtained artificial enzymes was investigated in a model Michael addition reaction.


Abstract

Enzymes are attractive catalysts for chemical industries, and their use has become a mature alternative to conventional chemical methods. However, biocatalytic approaches are often restricted to metabolic and less complex reactivities, given the limited amount of functional groups present. This drawback can be addressed by incorporating non-canonical amino acids (ncAAs) harboring new-to-nature chemical groups. Inspired by organocatalysis, we report the design, synthesis and characterization of a panel of ncAAs harboring functional secondary amines and their cellular incorporation into different protein scaffolds. D/L-pyrrolidine- and D/L-piperidine-based ncAAs were successfully site-specifically incorporated into proteins via stop codon suppression methodology. To demonstrate the utility of these ncAAs, the catalytic performance of the obtained artificial enzymes was investigated in a model Michael addition reaction. The incorporation of pyrrolidine- and piperidine- based ncAAs significantly expands the available toolbox for protein engineering and chemical biology applications.

Theoretical Prediction of Electrocatalytic Reduction of CO2 Using a 2D Catalyst Composed of 3 d Transition Metal and Hexaamine Dipyrazino Quinoxaline

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Theoretical Prediction of Electrocatalytic Reduction of CO2 Using a 2D Catalyst Composed of 3 d Transition Metal and Hexaamine Dipyrazino Quinoxaline

Computational screening of 2D materials composed of 3d transition metal and hexaamine dipyrazino quinoxalineas efficient catalysts for carbon dioxide reduction reactions.


Abstract

Transition metals and organic ligands combine to form metal-organic frameworks (MOFs), which possess distinct active sites, large specific surface areas and stable porous structures, giving them considerable promise for CO2 reduction electrocatalysis. In the present study, using spin polarisation density-functional theory, a series of 2D MOFs constructed from 3d transition metal and hexamethylene dipyrazoline quinoxaline(HADQ) were investigated. The calculated binding energies between HADQ and metal atoms for the ten TM-HADQ monolayers were strong sufficient to stably disperse the metal atoms in the HADQ monolayers. Of the ten catalysts tested, seven (Sc, Ni, Cu, Zn, Ti, V and Cr) exhibited high CO2 reduction selectivity, while Mn, Fe and Co required pH values above 2.350, 6.461 and 6.363, respectively, to exhibit CO2 reduction selectivity. HCOOH was the most important producer for Sc, Zn, Ni and Mn, while CH4 was the main producer for Ti, Cr, Fe and V. Cu and Co were less selective, producing HCHO, CH3OH, and CH4 simultaneously at the same rate-determining step and limiting potential. The Cu-HADQ catalyst had a high overpotential for the HCHO product (1.022 V), while the other catalysts had lower overpotentials between 0.016 V and 0.792 V. Thus, these results predict TM-HADQ to show excellent activity in CO2 electrocatalytic reduction and to become a promising electrocatalyst for CO2 reduction.

In Situ DRIFTS Analysis during Hydrogenation of 1‐Pentyne and Olefin Purification with Ag Nanoparticles

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In Situ DRIFTS Analysis during Hydrogenation of 1-Pentyne and Olefin Purification with Ag Nanoparticles

Different −C≡C− and −C=C− adsorbed species were observed on the supports and catalysts surface using in situ DRIFT analysis: The species are responsible for the activity and high selectivity during the hydrogenation reaction. The role of the supports and electronic properties of Ag nanoparticles improve the H2 dissociative chemisorption; promoting the high selectivity and the catalytic performance.


Abstract

The catalytic performance of nanoparticles (NPs) of Ag anchored on different supports was evaluated during the selective hydrogenation of 1-pentyne and the purification of a mixture of 1-pentene/1-pentyne (70/30 vol %). The catalysts were identified: Ag/Al (Ag supported on ɣ-Al2O3), Ag/Al−Mg (Ag supported on ɣ-Al2O3 modified with Mg), Ag/Ca (Ag supported on CaCO3) and Ag/RX3 (Ag supported on activated carbon-type: RX3). In addition, in situ DRIFTS analysis of 1-pentyne adsorption on each support, catalyst, and 1-pentyne hydrogenation were investigated. The results showed that the synthesized catalysts were active and very selective (≥85 %) for obtaining the desired product (1-pentene). Different adsorbed species (−C≡C− and −C=C−) were observed on the supports and catalysts surface using in situ DRIFT analysis, which can be correlated to the activity and high selectivity reached. The role of the supports and electronic properties over Ag improve the H2 dissociative chemisorption during the hydrogenation reactions; promoting the selectivity and the high catalytic performance. Ag/Al and Ag/Al−Mg were the most active catalysts. This was due to the synergism between the active Ag/Ag+ species and the supports (electronic effects). The results show that Ag/Al and Ag/Al−Mg catalysts have favorable properties and are promising for the alkyne hydrogenation and olefin purification reactions.

Binary Metallic CuCo5S8 Anode for High Volumetric Sodium‐Ion Storage

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Binary Metallic CuCo5S8 Anode for High Volumetric Sodium-Ion Storage

Binary metallic CuCo5S8 is successfully synthesized and evaluated as a CA-free anode in sodium-ion batteries. Because of the metallic properties of the material, the CA-free anode exhibits superior rate and cyclic performances. The high electrode density and multi-electron transfer during the charge-discharge process enable CuCo5S8 anode to display an outstanding volumetric capacity.


Abstract

With the rapid improvement of compact smart devices, fabricating anode materials with high volumetric capacity has gained substantial interest for future sodium-ion batteries (SIBs) applications. Herein, a novel bimetal sulfide CuCo5S8 material is proposed with enhanced volumetric capacity due to the intrinsic metallic electronic conductivity of the material and multi-electron transfer during electrochemical procedures. Due to the intrinsic metallic behavior, the conducting additive (CA) could be removed from the electrode fabrication without scarifying the high rate capability. The CA-free CuCo5S8 electrode can achieve a high volumetric capacity of 1436.4 mA h cm−3 at a current density of 0.2 A g−1 and 100 % capacity retention over 2000 cycles in SIBs, outperforming most metal chalcogenides, owing to the enhanced electrode density. Reversible conversion reactions are revealed by combined measurements for sodium systems. The proposed new strategy offers a viable approach for developing innovative anode materials with high-volumetric capacity.

Surface Passivation of LiCoO2 by Solid Electrolyte Nanoshell for High Interfacial Stability and Conductivity

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Surface Passivation of LiCoO2 by Solid Electrolyte Nanoshell for High Interfacial Stability and Conductivity

A multifunctional hierarchical core@double-shell structured LiCoO2 (MS-LCO) cathode material using a scalable sol–gel method. The MS-LCO cathode material comprised an outer shell with fast lithium-ion conductivity, a La/Zr co-doped inner shell, and a bulk LiCoO2 core.


Abstract

The practical application of lithium cobalt oxide (LiCoO2) cathodes at high voltages is hindered by the instability of the surface structure and side reactions with the electrolyte. Herein, we prepared a multifunctional hierarchical core@double-shell structured LiCoO2 (MS-LCO) cathode material using a scalable sol–gel method. The MS-LCO cathode material comprised an outer shell with fast lithium-ion conductivity, a La/Zr co-doped inner shell, and a bulk LiCoO2 core. The outermost shell prevented direct contact between the electrolyte and LiCoO2 core, which alleviated the electrolyte decomposition and loss of active cobalt, while the La/Zr co-doped shell improved the structural stability at higher voltages in a half-cell with a liquid electrolyte. The MS-LCO cathode exhibited a stable capacity of 163.1 mAh g−1 after 500 cycles at 0.5 C, and a high specific capacity of 166.8 mAh g−1 at 2 C. In addition, a solid lithium battery with the surface-passivated MS-LCO cathode and a polyethylene oxide (PEO)-based inorganic/organic composite electrolyte retained 85.8 % of its initial discharge capacity after 150 cycles at a charging cutoff voltage of 4.3 V. Thus, the introduction of a surface-passivating shell can effectively suppress the decomposition of PEO caused by highly reactive oxygen species in LiCoO2 at high voltages.