In Situ Generation of Radical Initiators: Air Stable Amine-Borane Complexes Promote Atom Transfer Radical Additions of Alkyl Halides to Alkenes

2020 ◽  
Author(s):  
Virginie Liautard ◽  
Marine Delgado ◽  
Boris Colin ◽  
Laurent Chabaud ◽  
Guillaume Michaud ◽  
...  
Keyword(s):  
Molecular Level ◽  
Radical Cyclization ◽  
Alkyl Halides ◽  
Atom Transfer ◽  
Organic Transformations ◽  
Radical Intermediate ◽  
Radical Chain ◽  
Initiation Step ◽  
Radical Initiators

Despite their instability, carbon-centered radicals have been involved as intermediates in many organic transformations that are essential to mankind. Radical polymerization,1-5 for example, provides a large part of polyacrylates and polystyrenes used as commodities in our everyday life. On a molecular level, the outcome of radical-mediated reactions is usually very different from those obtained via classical ionic based organic reactions. This is known since the 1930’s6 and has witnessed extensive developments such as radical cyclization or Atom Transfer Radical Additions (ATRA)7-9 . Radical processes10 typically begin with an initiation step in which the first radical species is created. It is eventually followed by one or several transfer steps which ultimately conduct to the formation of the main radical intermediate responsible for the reaction. The propagation steps of the radical chain are a succession of radical based transformations which, combined, outline the expected transformation.

In Situ Generation of Radical Initiators: Air Stable Amine-Borane Complexes Promote Atom Transfer Radical Additions of Alkyl Halides to Alkenes

2020 ◽  
Author(s):  
Virginie Liautard ◽  
Marine Delgado ◽  
Boris Colin ◽  
Laurent Chabaud ◽  
Guillaume Michaud ◽  
...  
Keyword(s):  
Molecular Level ◽  
Radical Cyclization ◽  
Alkyl Halides ◽  
Atom Transfer ◽  
Organic Transformations ◽  
Radical Intermediate ◽  
Radical Chain ◽  
Initiation Step ◽  
Radical Initiators

Despite their instability, carbon-centered radicals have been involved as intermediates in many organic transformations that are essential to mankind. Radical polymerization,1-5 for example, provides a large part of polyacrylates and polystyrenes used as commodities in our everyday life. On a molecular level, the outcome of radical-mediated reactions is usually very different from those obtained via classical ionic based organic reactions. This is known since the 1930’s6 and has witnessed extensive developments such as radical cyclization or Atom Transfer Radical Additions (ATRA)7-9 . Radical processes10 typically begin with an initiation step in which the first radical species is created. It is eventually followed by one or several transfer steps which ultimately conduct to the formation of the main radical intermediate responsible for the reaction. The propagation steps of the radical chain are a succession of radical based transformations which, combined, outline the expected transformation.

Sulfamides Direct Radical-Mediated Chlorination of Aliphatic C–H Bonds

2019 ◽  
Author(s):  
Melanie Short ◽  
Mina Shehata ◽  
Matthew Sanders ◽  
Jennifer Roizen
Keyword(s):  
Hydrogen Atom ◽  
Transfer Reaction ◽  
Hydrogen Atom Transfer ◽  
Chain Propagation ◽  
Propagation Mechanism ◽  
Atom Transfer ◽  
Radical Chain ◽  
Radical Intermediates ◽  
Transfer Processes ◽  
Unusual Position

Sulfamides guide intermolecular chlorine transfer to gamma-C(sp<sup>3</sup>) centers. This unusual position-selectivity arises because accessed sulfamidyl radical intermediates engage in otherwise rare 1,6-hydrogen-atom transfer processes. The disclosed chlorine-transfer reaction relies on a light-initiated radical chain-propagation mechanism to oxidize C(sp<sup>3</sup>)-H bonds.

Sulfamides Direct Radical-Mediated Chlorination of Aliphatic C–H Bonds

2019 ◽  
Author(s):  
Melanie Short ◽  
Mina Shehata ◽  
Matthew Sanders ◽  
Jennifer Roizen
Keyword(s):  
Hydrogen Atom ◽  
Transfer Reaction ◽  
Hydrogen Atom Transfer ◽  
Chain Propagation ◽  
Propagation Mechanism ◽  
Atom Transfer ◽  
Radical Chain ◽  
Radical Intermediates ◽  
Transfer Processes ◽  
Unusual Position

Sulfamides guide intermolecular chlorine transfer to gamma-C(sp<sup>3</sup>) centers. This unusual position-selectivity arises because accessed sulfamidyl radical intermediates engage in otherwise rare 1,6-hydrogen-atom transfer processes. The disclosed chlorine-transfer reaction relies on a light-initiated radical chain-propagation mechanism to oxidize C(sp<sup>3</sup>)-H bonds.

Catalyst- and Silane- Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Kousuke Ebisawa ◽  
Kana Izumi ◽  
Yuka Ooka ◽  
Hiroaki Kato ◽  
Sayori Kanazawa ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Hydrogen Atom Transfer ◽  
Biologically Active ◽  
Atom Transfer ◽  
High Concentration ◽  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction

Catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal catalyzed-hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of non-conjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, <i>N</i>-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect in the solvent, thermal dependency, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

Synthesis of sandwich type acyclic tetra-nuclear silver(I)-N-heterocyclic carbene complexes for wound healing applications

2020 ◽  
Vol 75 (9-10) ◽  
pp. 369-376
Author(s):  
Ayesha Riaz ◽  
Muhammad Adnan Iqbal ◽  
Haq Nawaz Bhatti ◽  
Muhammad Shahid
Keyword(s):  
Alkyl Halides ◽  
Wound Contraction ◽  
Spectroscopic Techniques ◽  
Open Chain ◽  
Standard Drug ◽  
Sandwich Type ◽  
Benzimidazolium Salts ◽  
Multistep Reaction

AbstractTwo meta-xylyl linked tetrakis-benzimidazolium salts (L1-L2) as multidentate ligands and two respective silver complexes (C1 and C2) were synthesized. A multistep reaction was done at room temperature, starting with simple benzimidazole and alkyl halides, going through precursors and salt formation by reflux and finally in situ deprotonation of tetrabenzimidazolium salts with Ag2O to yield respective tetra-nuclear Ag(I)-N-heterocyclic Carbene (NHC) complexes. Propyl and butyl groups were bonded at the terminal positions of tetra-azolium open chain salts. Characterization of compounds was done by analytical and spectroscopic techniques. On the basis of spectroscopic data, a chemical structure with open chains having four Ag(I) ions sandwiched between NHC layers was established. Potential of synthesized complexes (C1 & C2) for wound contraction was evaluated and compared with standard wound contraction gel. Percentage wound contraction of both complexes was found very close to that of standard drug used in parallel.

Atom-transfer radical cyclization of α-bromocarboxamides under organophotocatalytic conditions

2021 ◽  
Vol 69 ◽  
pp. 152952
Author(s):  
Naoki Tsuchiya ◽  
Yusei Nakashima ◽  
Goki Hirata ◽  
Takashi Nishikata
Keyword(s):  
Radical Cyclization ◽  
Atom Transfer ◽  
Atom Transfer Radical Cyclization

In situ nanoscale visualization of solvent effects on molecular crystal surfaces

CrystEngComm ◽  
2021 ◽  
Author(s):  
Mikkel Herzberg ◽  
Anders Støttrup Larsen ◽  
Tue Hassenkam ◽  
Anders Østergaard Madsen ◽  
Jukka Rantanen
Keyword(s):  
Solid Solution ◽  
Solvent Effects ◽  
Molecular Crystal ◽  
Rational Design ◽  
Molecular Level ◽  
Molecular Crystals ◽  
Crystal Surfaces ◽  
Solution Interface ◽  
Atomic Force

Solvents can dramatically affect molecular crystals. Obtaining favorable properties for these crystals requires rational design based on molecular level understanding of the solid-solution interface. Here we show how atomic force...

scholarly journals An In-Situ Reaction Route to Molecular Level Dispersed Bisimide and ZnO Nanorod Hybrids with Efficient Photo-Induced Charge Transfer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Chunzheng Lv ◽  
Lirong He ◽  
Jiahong Tang ◽  
Feng Yang ◽  
Chuhong Zhang
Keyword(s):  
Charge Transfer ◽  
Electric Field ◽  
Self Assembly ◽  
Molecular Level ◽  
Surface Photovoltage ◽  
Zno Nanorod ◽  
In Situ Reaction ◽  
Perylene Bisimide ◽  
Induced Charge

AbstractAs an important photoconductive hybrid material, perylene/ZnO has attracted tremendous attention for photovoltaic-related applications, but generally faces a great challenge to design molecular level dispersed perylenes/ZnO nanohybrids due to easy phase separation between perylenes and ZnO nanocrystals. In this work, we reported an in-situ reaction method to prepare molecular level dispersed H-aggregates of perylene bisimide/ZnO nanorod hybrids. Surface photovoltage and electric field-induced surface photovoltage spectrum show that the photovoltage intensities of nanorod hybrids increased dramatically for 100 times compared with that of pristine perylene bisimide. The enhancement of photovoltage intensities resulting from two aspects: (1) the photo-generated electrons transfer from perylene bisimide to ZnO nanorod due to the electric field formed on the interface of perylene bisimide/ZnO; (2) the H-aggregates of perylene bisimide in ZnO nanorod composites, which is beneficial for photo-generated charge separation and transportation. The introduction of ordered self-assembly thiol-functionalized perylene-3,4,9,10-tetracarboxylic diimide (T-PTCDI)/ ZnO nanorod composites induces a significant improvement in incident photo-to-electron conversion efficiency. This work provides a novel mentality to boost photo-induced charge transfer efficiency, which brings new inspiration for the preparation of the highly efficient solar cell.

Insertion Reaction of 2-Halo-N-allylanilines with K2S Involving Trisulfur Radical Anion: Synthesis of Benzothiazole Derivatives under Transition-Metal-Free Conditions

Synthesis ◽  
2020 ◽  
Author(s):  
Yan-Wei Zhao ◽  
Shun-Yi Wang ◽  
Xin-Yu Liu ◽  
Tian Jiang ◽  
Weidong Rao
Keyword(s):  
Transition Metal ◽  
Radical Anion ◽  
Radical Cyclization ◽  
Transition Metal Catalysis ◽  
Insertion Reaction ◽  
Metal Catalysis ◽  
Metal Free ◽  
Benzothiazole Derivatives

AbstractA synthesis of benzothiazole derivatives through the reaction of 2-halo-N-allylanilines with K2S in DMF is developed. The trisulfur radical anion S3·–, which is generated in situ from K2S in DMF, initiates the reaction without transition-metal catalysis or other additives. In addition, two C–S bonds are formed and heteroaromatization of benzothiazole is triggered by radical cyclization and H-shift.

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