scholarly journals Lewis acid–catalyzed domino generation/[2,3]-sigmatropic rearrangement of ammonium ylides to access chiral azabicycles

2021 ◽  
Vol 7 (5) ◽  
pp. eabd5290
Author(s):  
Song Xi ◽  
Jiawei Dong ◽  
Haohua Chen ◽  
Qiuyan Dong ◽  
Jiao Yang ◽  
...  
Keyword(s):  
Density Functional ◽  
Stereoselective Synthesis ◽  
Experimental Studies ◽  
Reaction System ◽  
Density Functional Theory Calculations ◽  
Sigmatropic Rearrangement ◽  
Residual Water ◽  
Nitrogenous Compounds ◽  
Stereogenic Centers ◽  
Quaternary Stereogenic Centers

[2,3]-Sigmatropic rearrangement of ammonium ylides represents a fundamental reaction for stereoselective synthesis of nitrogenous compounds. However, its applicability is limited by the scarcity of efficient, catalytic, and mild methods for generating ammonium ylides. Here, we report silver-catalyzed domino generation/[2,3]-sigmatropic rearrangement of ammonium ylides, furnishing chiral azabicycles with bridgehead quaternary stereogenic centers in high enantiomeric purity (up to 99% ee). A combination of density functional theory calculations and experimental studies revealed that residual water in the reaction system is crucial for the mild reaction conditions by functioning as a proton shuttle to assist carbon-silver bond protonation and C2─H deprotonation to generate the ammonium ylide. This reaction has a broad application scope. Besides the diverse substituents, N-fused azabicycles of various ring sizes are also easily accessed. In addition to silver salts, this strategy has also been successfully implemented by using a stoichiometric amount of nonmetallic I2.

scholarly journals Influence of Varying Functionalization on the Peroxidase Activity of Nickel(II)–Pyridine Macrocycle Catalysts: Mechanistic Insights from Density Functional Theory

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 52
Author(s):  
Jerwin Jay E. Taping ◽  
Junie B. Billones ◽  
Voltaire G. Organo
Keyword(s):  
Density Functional Theory ◽  
Proton Transfer ◽  
Density Functional ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Catalytic Performance ◽  
Stoichiometric Ratio ◽  
Functional Theory ◽  
Pendant Arm ◽  
Spin Singlet

Nickel(II) complexes of mono-functionalized pyridine-tetraazamacrocycles (PyMACs) are a new class of catalysts that possess promising activity similar to biological peroxidases. Experimental studies with ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), substrate) and H2O2 (oxidant) proposed that hydrogen-bonding and proton-transfer reactions facilitated by their pendant arm were responsible for their catalytic activity. In this work, density functional theory calculations were performed to unravel the influence of pendant arm functionalization on the catalytic performance of Ni(II)–PyMACs. Generated frontier orbitals suggested that Ni(II)–PyMACs activate H2O2 by satisfying two requirements: (1) the deprotonation of H2O2 to form the highly nucleophilic HOO−, and (2) the generation of low-spin, singlet state Ni(II)–PyMACs to allow the binding of HOO−. COSMO solvation-based energies revealed that the O–O Ni(II)–hydroperoxo bond, regardless of pendant arm type, ruptures favorably via heterolysis to produce high-spin (S = 1) [(L)Ni3+–O·]2+ and HO−. Aqueous solvation was found crucial in the stabilization of charged species, thereby favoring the heterolytic process over homolytic. The redox reaction of [(L)Ni3+–O·]2+ with ABTS obeyed a 1:2 stoichiometric ratio, followed by proton transfer to produce the final intermediate. The regeneration of Ni(II)–PyMACs at the final step involved the liberation of HO−, which was highly favorable when protons were readily available or when the pKa of the pendant arm was low.

scholarly journals Theoretical and Experimental Studies of the Structural, Phase Stability and Elastic Properties of AlCrTiFeNi Multi-Principle Element Alloy

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4353
Author(s):  
Li Liu ◽  
Ramesh Paudel ◽  
Yong Liu ◽  
Xiao-Liang Zhao ◽  
Jing-Chuan Zhu
Keyword(s):  
Structural Stability ◽  
Deformation Behavior ◽  
Density Functional ◽  
Low Cost ◽  
Structural Phase ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Mixing Enthalpy ◽  
Size Difference ◽  
Valence Electron Concentration

The fundamental challenge for creating the crystal structure model used in a multi-principle element design is the ideal combination of atom components, structural stability, and deformation behavior. However, most of the multi-principle element alloys contain expensive metallic and rare earth elements, which could limit their applicability. Here, a novel design of low-cost AlCrTiFeNi multi-principle element alloy is presented to study the relationship of structure, deformation behavior, and micro-mechanism. This structured prediction of single-phase AlCrTiFeNi by the atomic-size difference, mixing enthalpy ΔHmix and valence electron concentration (VEC), indicate that we can choose the bcc-structured solid solution to design the AlCrTiFeNi multi-principle element alloy. Structural stability prediction by density functional theory calculations (DFT) of single phases has verified that the most advantageous atom occupancy position is (FeCrNi)(AlFeTi). The experimental results showed that the structure of AlCrTiFeNi multi-principle element alloy is bcc1 + bcc2 + L12 phases, which we propose as the fundamental reason for the high strength. Our findings provide a new route by which to design and obtain multi-principle element alloys with targeted properties based on the theoretical predictions, first-principles calculations, and experimental verification.

scholarly journals Computational study of the mechanism and selectivity of ruthenium-catalyzed hydroamidations of terminal alkynes

2015 ◽  
Vol 6 (4) ◽  
pp. 2532-2552 ◽  
Author(s):  
Bholanath Maity ◽  
Lukas J. Gooßen ◽  
Debasis Koley
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Stereoselective Synthesis ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Terminal Alkynes ◽  
Functional Theory

Density functional theory calculations were performed to elucidate the mechanism of the ruthenium-catalyzed hydroamidation of terminal alkynes, a powerful and sustainable method for the stereoselective synthesis of enamides.

Rational design of a molecularly imprinted polymer for dinotefuran: theoretical and experimental studies aimed at the development of an efficient adsorbent for microextraction by packed sorbent

The Analyst ◽  
2018 ◽  
Vol 143 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Camilla Fonseca Silva ◽  
Keyller Bastos Borges ◽  
Clebio Soares do Nascimento
Keyword(s):  
Molecularly Imprinted Polymer ◽  
Density Functional ◽  
Rational Design ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Imprinted Polymer ◽  
Functional Theory ◽  
Molecularly Imprinted ◽  
Functional Monomers ◽  
Packed Sorbent

In this work, we studied theoretically the formation process of a molecularly imprinted polymer (MIP) for dinotefuran (DNF), by testing distinct functional monomers (FM) in various solvents through density functional theory calculations.

(Cu, Ag)-DOPED ZnS WITH WIDE VISIBLE LIGHT RANGE ABSORPTION FOR WATER SPLITTING: A THEORETICAL AND EXPERIMENTAL STUDY

2019 ◽  
Vol 27 (04) ◽  
pp. 1950139
Author(s):  
XIAOBO CHEN ◽  
WEIWEI LIU ◽  
ZHIHAI ZHANG ◽  
WEN YANG ◽  
PEIZHI YANG
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Density Functional ◽  
Energy Levels ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Functional Theory ◽  
Light Region

Photocatalytic water splitting using a semiconductor photocatalyst is a promising process for direct solar energy conversion. In this study, the feasibility of the photocatalytic H2 evolution on (Cu, Ag)- doped ZnS catalysts under visible light irradiation has been investigated by using first-principles density functional theory calculations and experimental studies. The present results reveal that (Cu, Ag)-doped ZnS structures have relatively small formation energy, implying that they are more easily obtained in experiment. Moreover, the absorption is enhanced obviously in the visible-light region for (Cu, Ag)-doped ZnS, but their energy levels are still suitable for water splitting to generate H2, which means that (Cu, Ag)-doped ZnS structures are promising candidate photocatalyst materials for H2 production driven by visible light. ZnS and (Cu, Ag)-doped ZnS were prepared using chemical precipitation method. (Cu, Ag)-doped ZnS samples showed an improved photocatalytic activity compared with undoped ZnS. Ag-doped ZnS (0.15 g L[Formula: see text] has the highest hydrogen evolution rate of 794.6 [Formula: see text]mol[Formula: see text] h[Formula: see text] [Formula: see text] g[Formula: see text] at pH 3 (0.1 M Na2S solution as a sacrificing agent).

scholarly journals Expedient synthesis of E-hydrazone esters and 1H-indazole scaffolds through heterogeneous single-atom platinum catalysis

2019 ◽  
Vol 5 (12) ◽  
pp. eaay1537 ◽  
Author(s):  
Cuibo Liu ◽  
Zhongxin Chen ◽  
Huan Yan ◽  
Shibo Xi ◽  
Kah Meng Yam ◽  
...  
Keyword(s):  
Density Functional ◽  
Stereoselective Synthesis ◽  
Density Functional Theory Calculations ◽  
Building Blocks ◽  
Hydrogenation Reaction ◽  
Biologically Active ◽  
Single Atom ◽  
One Pot ◽  
Platinum Catalysis ◽  
Scalable Synthesis

Unprotected E-hydrazone esters are prized building blocks for the preparation of 1H-indazoles and countless other N-containing biologically active molecules. Despite previous advances, efficient and stereoselective synthesis of these compounds remains nontrivial. Here, we show that Pt single atoms anchored on defect-rich CeO2 nanorods (Pt1/CeO2), in conjunction with the alcoholysis of ammonia borane, promotes exceptionally E-selective hydrogenation of α-diazoesters to afford a wide assortment of N-H hydrazone esters with an overall turnover frequency of up to 566 hours−1 upon reaction completion. The α-diazoester substrates could be generated in situ from readily available carboxylic esters in one-pot hydrogenation reaction. Utility is demonstrated through concise, scalable synthesis of 1H-indazole–derived pharmaceuticals and their 15N-labeled analogs. The present protocol highlights a key mechanistic nuance wherein simultaneous coordination of a Pt site with the diazo N═N and ester carbonyl motifs plays a central role in controlling stereoselectivity, which is supported by density functional theory calculations.

Combined Computational and Experimental Study of the Pressure Dependence of the Structural and Vibrational Properties on Solid Naphthalene C10H8

2018 ◽  
Vol 914 ◽  
pp. 175-181
Author(s):  
Ling Ping Xiao ◽  
Li Zeng ◽  
Xue Yang
Keyword(s):  
Density Functional ◽  
Intramolecular Interaction ◽  
Applied Pressure ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Optical Data ◽  
Vibrational Properties ◽  
Intermolecular Distances ◽  
Almost All

We present high-quality optical data and density functional theory calculations for the structural and vibrational properties of solid naphthalene (C10H8) under pressure up to 21.5 GPa. Our results demonstrate that almost all the modes shift toward higher frequencies and some peaks are broadened with increasing pressure. Comparing the pressure effect on the shortest intermolecular distances and on the bond lengths we confirm the expected result that the intramolecular interaction are less sensitive to pressure than the intermolecular interactions. These findings are shown to be in agreement with experimental results and hint towards the evolution of intermolecular interaction with pressure. Moreover, within our data the lattice modes exhibit more drastic changes than intramolecular modes, which are due to there being greater intermolecular distortions than intramolecular under applied pressure. In combination with theoretical and experimental studies, these results permit detailed characterization of the structural and vibrational changes of naphthalene as a function of pressure.

scholarly journals Theoretical Study of the Effect of Water Clusters on the Enol Content of Acetone as a Model for Understanding the Effect of Water on Enolization Reaction

2021 ◽  
Author(s):  
Zahra Tohidi Nafe ◽  
Nematollah Arshadi
Keyword(s):  
Carbonyl Compounds ◽  
Density Functional ◽  
Water Clusters ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Biochemical Processes ◽  
Small Water ◽  
Effect Of Water ◽  
Practical Conclusion

Abstract The enolization of simple carbonyl compounds is a key reaction for many chemical and biochemical processes. Numerous theoretical and experimental studies have been done to probe aspects of the mechanism of this reaction. In this work, the effect of small water clusters, (H2O)n: n=1-9, on the enol content of acetone is investigated by using density functional theory calculations at the M06 level of theory in the gas and solution phases. The calculations indicated that the formation of hydrogen-bonded assemblies between water clusters and both tautomers of acetone affect the enolization reaction. Among them, the trimeric water cluster has the highest binding energy difference (DEb) in the solution phase and greatly shift the equilibrium in the favor of the enol form. The results also shown that under this condition, the enol content of acetone increased by decreasing the polarity of the solvent. The practical conclusion of this study is that the enol content of carbonyl compounds can be maximized only by addition a defined amount of water.

Di-Palladium Complexes are Active Catalysts for Mono-N-Protected Amino Acid Accelerated Enantioselective C-H Functionalization

2019 ◽  
Author(s):  
Joseph Gair ◽  
Brandon E. Haines ◽  
Alexander S. Filatov ◽  
Djamaladdin G. Musaev ◽  
Jared C. Lewis
Keyword(s):  
Amino Acid ◽  
Density Functional ◽  
Kinetic Method ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Palladium Complexes ◽  
X Ray Diffraction ◽  
Protected Amino Acid ◽  
Palladium Catalyzed ◽  
Method Of Continuous Variation

The role of mono-protected amino acid (MPAA) ligands in accelerating enantioselective cyclopalladation and palladium catalyzed C-H func-tionalization was investigated using kinetic, spectroscopic, and computational methods. Single crystal X-ray diffraction and NMR spectroscopy demonstrate that MPAA ligands bind catalytically competent di-palladium complexes as bridging carboxylates. The catalytic relevance of the observed di-palladium species was evaluated by kinetic analysis. The kinetic method of continuous variation demonstrated that a complex contain-ing a single MPAA-bridged di-palladium core (Pd2(MPAA)1) is an active catalyst for the reactions studied. The experimental studies are con-sistent with density functional theory calculations that indicate enantioinduction can be achieved by a single MPAA ligand bridging a di-palladium catalyst through secondary sphere hydrogen-bonding interactions that lower the barrier to C-H activation of the major enantiomer.<br>

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