Organocatalyzed Birch Reduction Driven by Visible Light

2020 ◽  
Author(s):  
Justin P. Cole ◽  
Dian-Feng Chen ◽  
Max Kudisch ◽  
Ryan M. Pearson ◽  
Chern-Hooi Lim ◽  
...  
Keyword(s):  
Visible Light ◽  
Alkali Metals ◽  
High Energy ◽  
Cryogenic Liquid ◽  
Solvated Electrons ◽  
Mole Percent ◽  
Birch Reduction ◽  
Application Potential ◽  
Molecular Complexity ◽  
High Energy Chemical

<p>The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes—valuable intermediates for building molecular complexity. This reaction historically requires dangerous alkali metals and cryogenic liquid ammonia as the solvent, severely limiting application potential and scalability. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light. Using low catalyst loadings (<1 mole percent), benzene and other functionalized arenes can be selectively transformed to 1,4-cyclohexadienes in good yields. Mechanistic studies support that this unprecedented visible light induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible light photons to affect a single, high energy chemical transformation, likely proceeding through a solvated electron.</p>

Organocatalyzed Birch Reduction Driven by Visible Light

2020 ◽  
Author(s):  
Justin P. Cole ◽  
Dian-Feng Chen ◽  
Max Kudisch ◽  
Ryan M. Pearson ◽  
Chern-Hooi Lim ◽  
...  
Keyword(s):  
Visible Light ◽  
Alkali Metals ◽  
High Energy ◽  
Cryogenic Liquid ◽  
Solvated Electrons ◽  
Mole Percent ◽  
Birch Reduction ◽  
Application Potential ◽  
Molecular Complexity ◽  
High Energy Chemical

<p>The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes—valuable intermediates for building molecular complexity. This reaction historically requires dangerous alkali metals and cryogenic liquid ammonia as the solvent, severely limiting application potential and scalability. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light. Using low catalyst loadings (<1 mole percent), benzene and other functionalized arenes can be selectively transformed to 1,4-cyclohexadienes in good yields. Mechanistic studies support that this unprecedented visible light induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible light photons to affect a single, high energy chemical transformation, likely proceeding through a solvated electron.</p>

Low-Temperature Diffusion of Transition Metals at the Presence of Radiation Defects in Silicon

2011 ◽  
Vol 178-179 ◽  
pp. 421-426
Author(s):  
Jan Vobecký ◽  
Volodymyr Komarnitskyy ◽  
Vít Záhlava ◽  
Pavel Hazdra
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Carrier Lifetime ◽  
High Energy ◽  
Deep Levels ◽  
Radiation Defects ◽  
Metal Atoms ◽  
Temperature Diffusion ◽  
Concentration Enhancement ◽  
Application Potential

Low-temperature diffusion of Cr, Mo, Ni, Pd, Pt, and V in silicon diodes is compared in the range 450 - 800 oC. Before the diffusion, the diodes were implanted with high-energy He2+ to assess, if the radiation defects enhance the concentration of metal atoms at electrically active sites and what is the application potential for carrier lifetime control. The devices were characterized using AES, XPS, DLTS, OCVD carrier lifetime and diode electrical parameters. The metal atoms are divided into two groups. The Pt, Pd and V form deep levels in increased extent at the presence of radiation defects above 600 oC, which reduces the excess carrier lifetime. It is shown as a special case that the co-diffusion of Ni and V from a NiV surface layer results fully in the concentration enhancement of the V atoms. The enhancement of the acceptor level V-/0 (EC 0.203 eV) and donor level V0/+ (EC 0.442 eV) resembles the behavior of substitutional Pts. The second group is represented by the Mo and Cr. They easily form oxides, which can make their diffusion into a bulk more difficult or impossible. Only a slight enhancement of the Cr-related deep levels by the radiation defects has been found above 700 oC.

Preparation of annular TiO2 nanoparticles constructed by high-energy surfaces and enhanced visible-light photocatalytic activity

2017 ◽  
Vol 41 (15) ◽  
pp. 7562-7570 ◽  
Author(s):  
Fanxia Kong ◽  
Yuguo Xia ◽  
Xiuling Jiao ◽  
Dairong Chen
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Tio2 Nanoparticles ◽  
High Energy ◽  
Etching Process ◽  
Visible Light Photocatalytic Activity ◽  
Energy Surfaces ◽  
Visible Light Photocatalytic

Annular TiO2 nanoparticles were synthesized through a combined solvothermal and etching process.

scholarly journals Visible Light-Enabled Paternò-Büchi Reaction via Triplet Energy Transfer for the Synthesis of Oxetanes

2020 ◽  
Author(s):  
Katie Rykaczewski ◽  
Corinna Schindler
Keyword(s):  
Energy Transfer ◽  
Visible Light ◽  
Uv Light ◽  
Cycloaddition Reaction ◽  
High Energy ◽  
Triplet Energy ◽  
Reaction Conditions ◽  
Triplet Energy Transfer

<div> <p>One of the most efficient ways to synthesize oxetanes is the light-enabled [2+2] cycloaddition reaction of carbonyls and alkenes, referred to as the Paternò-Büchi reaction. The reaction conditions for this transformation typically require the use of high energy UV light to excite the carbonyl, limiting the applications, safety, and scalability. We herein report the development of a visible light-mediated Paternò-Büchi reaction protocol that relies on triplet energy transfer from an iridium-based photocatalyst to the carbonyl substrates. This mode of activation is demonstrated for a variety of aryl glyoxylates and negates the need for both, visible light-absorbing carbonyl starting materials or UV light to enable access to a variety of functionalized oxetanes in up to 99% yield.</p> </div> <br>

scholarly journals Visible-Light Photoswitching of G-Quadruplex Ligand Binding Mode Allows Reversible Control of G-Tetrad Structure

2020 ◽  
Author(s):  
Michael O'Hagan ◽  
Javier Ramos Soriano ◽  
Susanta Haldar ◽  
Juan Carlos Morales ◽  
Adrian Mulholland ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Visible Light ◽  
Uv Light ◽  
Binding Mode ◽  
High Energy ◽  
Light Sources ◽  
Biologically Relevant ◽  
G Quadruplex ◽  
Potential Applications ◽  
Robust Regulation

<div><p>Photoresponsive ligands for G-quadruplex oligonucleotides (G4) offer exciting opportunities for the reversible regulation of these assemblies with potential applications in biological chemistry and responsive nanotechnology. However, achieving the robust regulation of G4 ligand activity with low-energy visible light sources that are easily accessible and compatible with biological systems remains a significant challenge to realizing these applications. Herein, we report the G4-binding properties of a photoresponsive dithienylethene (DTE). We demonstrate the first example of G4-specific acceleration of the photoswitching kinetics of a small molecule and the visible-light mediated switching of the G4 ligand binding mode in physiologically-relevant conditions, which in turn allows control over the G4 tetrad structure of telomeric G4 in potassium buffer. The process is fully reversible and avoids the need for high-energy UV light. This affords an efficient, practical and biologically-relevant means of control that may be applied in the generation of new responsive G4/ligand supramolecular systems.</p></div><br>

AB024. Photo-oxidation of N-retinylidene-N-retinylethanolamine in vitro by high-energy visible light

2018 ◽  
Vol 3 ◽  
pp. AB024-AB024
Author(s):  
Marie-Christine Lambert ◽  
Mathieu Ouellette ◽  
Élodie Boisselier ◽  
Patrick J. Rochette
Keyword(s):  
Visible Light ◽  
High Energy ◽  
Photo Oxidation

Visible Light Active Nanocomposites for Photocatalytic Applications

2021 ◽  
pp. 709-729
Author(s):  
Rohini Singh ◽  
Suman Dutta
Keyword(s):  
Visible Light ◽  
Industrial Development ◽  
Hydrogen Generation ◽  
Dye Degradation ◽  
Industrial Effluents ◽  
High Energy ◽  
Effluent Treatment ◽  
Photocatalytic Hydrogen Generation ◽  
Visible Light Active ◽  
Alternative Sources

This chapter explores the concept of visible light active nanocomposites for the enhanced photocatalytic hydrogen generation and dye degradation. Since the late 1960s, A. Fujishima has been involved in unfolding the fascinating characteristics of titanium dioxide (TiO2) as semiconductor oxide. The increased growth in population and industrial development has tremendously increased the generation of waste products and consumption of energy worldwide. This situation creates an immense need of clean and sustainable alternative sources of energy. Hydrogen, having a high energy capacity, is considered as a reliable fuel for the future energy requirements. In addition to that, due to the rapid industrialisation, our water is being contaminated with various harmful industrial effluents. This chapter illustrates the significance of visible light nanocomposites for the photocatalytic application of hydrogen generation for future energy security and dye degradation for the effective effluent treatment of textile industries.

scholarly journals Novel 3DOM BiVO4/TiO2 nanocomposites for highly enhanced photocatalytic activity

2015 ◽  
Vol 3 (42) ◽  
pp. 21244-21256 ◽  
Author(s):  
Meryam Zalfani ◽  
Benoit van der Schueren ◽  
Zhi-Yi Hu ◽  
Joanna C. Rooke ◽  
Ramzi Bourguiga ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Photocatalytic Performance ◽  
High Energy ◽  
Inverse Opal ◽  
High Energy Electrons ◽  
Inverse Opal Structure ◽  
Long Lifetime

BiVO4 nanoparticles in the 3DOM TiO2 inverse opal structure act as a sensitizer to absorb visible light and to transfer efficiently high energy electrons to TiO2 to ensure long lifetime of photogenerated charges and keep them well separated, explaining the extraordinarily high photocatalytic performance of 3DOM BiVO4/TiO2 nanocomposites.

Modulating high-energy visible light absorption to attain neutral-state black electrochromic polymers

2016 ◽  
Vol 4 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Wei Teng Neo ◽  
Ching Mui Cho ◽  
Zugui Shi ◽  
Soo-Jin Chua ◽  
Jianwei Xu
Keyword(s):  
Visible Light ◽  
Light Absorption ◽  
High Energy ◽  
Visible Light Absorption ◽  
Neutral State ◽  
Electrochromic Polymers

Neutral-state black electrochromic polymers were achieved by incorporating an additional donor to enhance the blue-absorption.

scholarly journals On the age vs depth and optical clarity of deep ice at the South Pole

1995 ◽  
Vol 41 (139) ◽  
pp. 445-454
Author(s):  
Keyword(s):  
Visible Light ◽  
High Energy ◽  
Dust Concentration ◽  
Cherenkov Light ◽  
South Pole ◽  
The South ◽  
High Energy Neutrino ◽  
Arrival Times ◽  
Energy Neutrino ◽  
Crystal Boundaries

AbstractThe first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800-1000 m in ice at the South Pole, During the 1995-96 season, as many as six more strings will be deployed at greater depths. Provided absorption, scattering and refraction of visible light are sufficiently small, the trajectory of a muon into which a neutrino converts can be determined by using the array of phototubes to measure the arrival times of Cherenkov light emitted by the muon. To help in deciding on the depth for implantation of the six new strings, we discuss models of age vs depth for South Pole ice, we estimate mean free paths for scattering from bubbles and dust as a function of depth and we assess distortion of light paths due to refraction at crystal boundaries and interfaces between air-hydrate inclusions and normal ice. We conclude that the interval 1600-2100 m will be suitably transparent for a future 1 km3 observatory except possibly in a region a few tens of meters thick at a depth corresponding to a peak in the dust concentration at 60 k year BP.

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