scholarly journals Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

2020 ◽  
Author(s):  
minsoo ju ◽  
Emily Zerull ◽  
Jessica Roberts ◽  
Minxue Huang ◽  
Jennifer Schomaker
Keyword(s):  
Density Functional ◽  
Ligand Design ◽  
Building Blocks ◽  
Hydrogen Atom Transfer ◽  
Enantioselective Synthesis ◽  
Functional Theory ◽  
Nitrene Transfer ◽  
Structure Activity ◽  
Rational Ligand Design ◽  
Sar Analysis

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

scholarly journals Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

2020 ◽  
Author(s):  
minsoo ju ◽  
Emily Zerull ◽  
Jessica Roberts ◽  
Minxue Huang ◽  
Jennifer Schomaker
Keyword(s):  
Density Functional ◽  
Ligand Design ◽  
Building Blocks ◽  
Hydrogen Atom Transfer ◽  
Enantioselective Synthesis ◽  
Functional Theory ◽  
Nitrene Transfer ◽  
Structure Activity ◽  
Rational Ligand Design ◽  
Sar Analysis

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

scholarly journals Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

2020 ◽  
Author(s):  
minsoo ju ◽  
Emily Zerull ◽  
Jessica Roberts ◽  
Minxue Huang ◽  
Jennifer Schomaker
Keyword(s):  
Density Functional ◽  
Ligand Design ◽  
Building Blocks ◽  
Hydrogen Atom Transfer ◽  
Enantioselective Synthesis ◽  
Functional Theory ◽  
Nitrene Transfer ◽  
Structure Activity ◽  
Rational Ligand Design ◽  
Sar Analysis

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

2020 ◽  
Author(s):  
minsoo ju ◽  
Emily Zerull ◽  
Jessica Roberts ◽  
Minxue Huang ◽  
Jennifer Schomaker
Keyword(s):  
Density Functional ◽  
Ligand Design ◽  
Building Blocks ◽  
Hydrogen Atom Transfer ◽  
Enantioselective Synthesis ◽  
Functional Theory ◽  
Nitrene Transfer ◽  
Structure Activity ◽  
Rational Ligand Design ◽  
Sar Analysis

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

scholarly journals Radical-Scavenging and UV-Radiation Absorption Activities of Aaptamine Derivatives: DFT and TD-DFT Studies

2021 ◽  
Author(s):  
Thi Hoai Nam Doan ◽  
Thi Le Anh Nguyen ◽  
Nguyen Thi Ai Nhung ◽  
Duong Tuan Quang ◽  
Duy Quang Dao
Keyword(s):  
Density Functional ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Radiation Absorption ◽  
Functional Theory ◽  
Radical Adduct ◽  
Td Dft ◽  
Potential Applications

Antioxidant and UV absorption activities of three aaptamine derivatives including piperidine[3,2-b]demethyl(oxy)aaptamine (C1), 9-amino-2-ethoxy-8-methoxy-3H-benzo[de][1,6]naphthyridine-3-one (C2), and 2-(sec-butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1-ij][1,6]-naphthyridin-10(9H)-one (C3) were theoretically studied by density functional theory (DFT). Optimized geometries of C1C3 and theirs intrinsic thermochemical properties such as bond dissociation energy, proton affinity, and ionization potential were calculated at DFT/M05-2X/6-311++G(d,p) level of theory in vacuo and in water. The results show that C1C3 exhibited similar potent antioxidant activities, which are comparable to well-known antioxidants such as Trolox or cembrene. The radical scavenging activity of the antioxidants were then investigated by evaluation the Gibbs free energy (ΔrG0) of the reaction between C1C3 and the HOO●/HO● radicals via four mechanisms, including: hydrogen atom transfer (HAT), single electron transfer (SET), proton loss (PL) and radical adduct formation (RAF). Kinetic calculation reveals that HOO● scavenging in water is occurred via HAT mechanism with C1@C19 while RAF is more dominant with C2 and C3. Antioxidant activity of aaptamine derivatives can be classified as C1 > C3 > C2. In addition, all compounds are active in UV-Vis absorption; the excitations of which are determined as π-π* transition. Overall, the results suggest the potential applications of the aaptamines in pharmaceutics and cosmetics, i.e. as sunscreen and antioxidant ingredient<br>

scholarly journals Mechanism and Chemoselectivity of Mn-Catalyzed Intramolecular Nitrene Transfer Reaction: C–H Amination vs. C=C Aziridination

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 292
Author(s):  
Juping Wang ◽  
Kangcheng Zheng ◽  
Ting Li ◽  
Xiaojing Zhan
Keyword(s):  
Density Functional ◽  
Structural Features ◽  
High Reactivity ◽  
Strong Electron ◽  
Functional Theory ◽  
Design Elements ◽  
Nitrene Transfer ◽  
Electrophilic Reactivity ◽  
High Valent ◽  
Orbital Character

The reactivity, mechanism and chemoselectivity of the Mn-catalyzed intramolecular C–H amination versus C=C aziridination of allylic substrate cis-4-hexenylsulfamate are investigated by BP86 density functional theory computations. Emphasis is placed on the origins of high reactivity and high chemoselectivity of Mn catalysis. The N p orbital character of frontier orbitals, a strong electron-withdrawing porphyrazine ligand and a poor π backbonding of high-valent MnIII metal to N atom lead to high electrophilic reactivity of Mn-nitrene. The calculated energy barrier of C–H amination is 9.9 kcal/mol lower than that of C=C aziridination, which indicates that Mn-based catalysis has an excellent level of chemoselectivity towards C–H amination, well consistent with the experimental the product ratio of amintion-to-aziridination I:A (i.e., (Insertion):(Aziridination)) >20:1. This extraordinary chemoselectivity towards C–H amination originates from the structural features of porphyrazine: a rigid ligand with the big π-conjugated bond. Electron-donating substituents can further increase Mn-catalyzed C–H amination reactivity. The controlling factors found in this work may be considered as design elements for an economical and environmentally friendly C–H amination system with high reactivity and high chemoselectivity.

scholarly journals Spectroscopic identification of fragment ions of DNA/RNA building blocks: the case of pyrimidine

2020 ◽  
Vol 22 (30) ◽  
pp. 17275-17290
Author(s):  
Kuntal Chatterjee ◽  
Otto Dopfer
Keyword(s):  
Density Functional Theory ◽  
Infrared Spectroscopy ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Building Blocks ◽  
Functional Theory ◽  
Fragment Ions ◽  
Sequential Loss ◽  
Spectroscopic Identification

The structure of the predominant fragments of the fundamental pyrimidine cation arising from sequential loss of HCN are identified by infrared spectroscopy of tagged ions and dispersion-corrected density functional theory calculations.

scholarly journals Microhydration of protonated biomolecular building blocks: protonated pyrimidine

2020 ◽  
Vol 22 (23) ◽  
pp. 13092-13107
Author(s):  
Kuntal Chatterjee ◽  
Otto Dopfer
Keyword(s):  
Density Functional Theory ◽  
Infrared Spectroscopy ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Building Blocks ◽  
Protonation Site ◽  
Functional Theory

The protonation site and evolution of the hydration network in microsolvated protonated pyrimidine clusters, H+Pym–(H2O)n with n = 1–4, has been explored by infrared spectroscopy and density functional theory calculations.

Sign in / Sign up

Export Citation Format

Share Document