scholarly journals A Bond-Weakening Borinate Catalyst that Improves the Scope of the Photoredox α-C–H Alkylation of Alcohols

Synthesis ◽  
2020 ◽  
Vol 52 (15) ◽  
pp. 2171-2189
Author(s):  
Kounosuke Oisaki ◽  
Motomu Kanai ◽  
Kentaro Sakai
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Organic Synthesis ◽  
Hydroxy Group ◽  
Functional Group ◽  
Chemical Yield ◽  
Catalyst System ◽  
Hydrogen Atom Transfer ◽  
Hybrid Catalyst ◽  
Site Selective

The development of catalyst-controlled, site-selective C(sp3)–H functionalization reactions is currently a major challenge in organic synthesis. In this paper, a novel bond-weakening catalyst that recognizes the hydroxy group of alcohols through formation of a borate is described. An electron-deficient borinic acid–ethanolamine complex enhances the chemical yield of the α-C–H alkylation of alcohols when used in conjunction with a photoredox catalyst and a hydrogen atom transfer catalyst under irradiation with visible light. This ternary hybrid catalyst system can, for example, be applied to functional-group-enriched­ peptides.

scholarly journals Site-selective redox isomerizations of furanosides using a combined arylboronic acid/photoredox catalyst system

2020 ◽  
Vol 11 (6) ◽  
pp. 1531-1537 ◽  
Author(s):  
Victoria Dimakos ◽  
Daniel Gorelik ◽  
Hsin Y. Su ◽  
Graham E. Garrett ◽  
Gregory Hughes ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Ribonucleotide Reductase ◽  
Boronic Acid ◽  
Catalyst System ◽  
Hydrogen Atom Transfer ◽  
Synthetic Analog ◽  
Arylboronic Acid ◽  
System P ◽  
Combined Action ◽  
Site Selective

The combined action of boronic acid, photoredox catalyst and hydrogen atom transfer mediator enables the transformation of furanosides to 2-keto-3-deoxyfuranosides, a synthetic analog of the process catalyzed by the ribonucleotide reductase enzymes.

1.9 Oxygen-Centered Radicals

2021 ◽  
Author(s):  
J. Zhang ◽  
D. Liu ◽  
Y. Chen
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Organic Synthesis ◽  
Reactive Intermediates ◽  
Radical Addition ◽  
Hydrogen Atom Transfer ◽  
Reaction Conditions ◽  
Recent Advances ◽  
Carbon Carbon Bonds ◽  
Induced Reaction

AbstractOxygen-centered radicals (R1O•) are reactive intermediates in organic synthesis, with versatile synthetic utilities in processes such as hydrogen-atom transfer (HAT), β-fragmentation, radical addition to unsaturated carbon–carbon bonds, and rearrangement reactions. In this review, we focus on recent advances in the generation and transformation of oxygen-centered radicals, including (alkyl-, α-oxo-, aryl-) carboxyl, alkoxyl, aminoxyl, phenoxyl, and vinyloxyl radicals, and compare the reactivity of oxygen-centered radicals under traditional reaction conditions with their reactivity under visible-light-induced reaction conditions.

Arylation of Amide and Urea C(sp3)–H Bonds with Aryl Tosylates Generated In Situ from Phenols

Synlett ◽  
2017 ◽  
Vol 28 (19) ◽  
pp. 2581-2586 ◽  
Author(s):  
Wen-Jun Zhou ◽  
Da-Gang Yu ◽  
Yong-Yuan Gui ◽  
Xiao-Wang Chen
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Room Temperature ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Nickel Catalysis ◽  
Direct Transformation ◽  
Aryl Tosylates ◽  
High Yields

The arylation of amide and urea C(sp3)–H bonds with aryl tosylates generated in situ from phenols has been realized at room temperature by combining visible-light-photoredox catalysis, hydrogen-atom-transfer catalysis, and nickel catalysis. This streamlined protocol permits rapid functionalization of phenols and direct transformation of α-amino C(sp3)–H bonds. The C(sp3)–H arylation products are obtained in high yields with good functional-group tolerance at low catalyst loadings.

scholarly journals Investigations on the 1,2-Hydrogen Atom Transfer Reactivity of Alkoxyl Radicals under Visible-Light-Induced Reaction Conditions

Synlett ◽  
2020 ◽  
Author(s):  
Yiyun Chen ◽  
Dan Liu ◽  
Jing Zhang
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Visible Light ◽  
Organic Synthesis ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Alkoxyl Radical ◽  
Induced Reaction ◽  
Key Questions

AbstractThe alkoxyl radicals have demonstrated superior hydrogen atom transfer reactivity in organic synthesis due to the strong oxygen–hydrogen bond dissociation energy. However, only the intermolecular hydrogen atom transfer (HAT) and intramolecular 1,5-HAT have been widely studied and synthetically utilized for C(sp3)–H functionalization. This Account summarizes our investigations on the unusual 1,2-HAT reactivity of alkoxyl radicals under visible-light-induced reaction conditions for the α-C–H functionalization. Various mechanistic investigations were discussed in this Account to address three key questions to validate the 1,2-HAT reactivity of alkoxyl radicals.1 Introduction2 Could Aldehydes/Ketones Be the Sole Reaction Intermediate for the α-C–H Allylation? NO3 Is the Alkoxyl Radical Absolutely Involved in the Reaction? YES4 Does the 1,2-HAT of Alkoxyl Radicals Irrefutably Exist? YES5 Conclusion

Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups ◽  
The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

Visible light photoredox-catalysed remote C–H functionalisation enabled by 1,5-hydrogen atom transfer (1,5-HAT)

2021 ◽  
Author(s):  
Weisi Guo ◽  
Qian Wang ◽  
Jieping Zhu
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer

The generation of heteroatom-centred radicals followed by intramolecular 1,5-HAT and functionalisation of the translocated carbon-centred radical is an efficient way to functionalize chemo- and regio-selectively the remote unactivated C(sp3)–H bond.

Carbonylative Coupling of Simple Alkanes and Alkenes Enabled by Organic Photoredox Catalysis

2021 ◽  
Author(s):  
Ling Chen ◽  
Jing Hou ◽  
Ming Zheng ◽  
Le-Wu Zhan ◽  
Wan-Ying Tang ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Transfer Process ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Photoredox Catalysis ◽  
Visible Light Driven

A visible-light-driven direct carbonylative coupling of simple alkanes and alkenes via the combination of the hydrogen atom transfer process and photoredox catalysis has been demonstrated. Employing the N-alkoxyazinium salt as...

Bromotrifluoromethane: A Useful Reagent for Hydrotrifluoromethylation of Alkenes and Alkynes

Synlett ◽  
2018 ◽  
Vol 29 (08) ◽  
pp. 1028-1032 ◽  
Author(s):  
Xing Zheng ◽  
Xingang Zhang ◽  
Yu-Yan Ren
Keyword(s):  
Visible Light ◽  
Organic Synthesis ◽  
Functional Group ◽  
Mild Conditions ◽  
Industrial Material ◽  
Reaction Proceeds

Bromotrifluoromethane (CF3Br) is a simple, inexpensive and abundant industrial material employed as a trifluoromethylating reagent. However, only limited strategies using CF3Br as a fluorine source are reported. Herein, we describe a visible-light-induced hydrotrifluoromethylation of alkenes and alkynes with CF3Br. The reaction proceeds under mild conditions with good functional group tolerance, providing a new route for the application of BrCF3 in organic synthesis.

scholarly journals Dual Cobalt and Photoredox Catalysis Enabled Intermolecular Oxidative Hydrofunctionalization

2020 ◽  
Author(s):  
Han-Li Sun ◽  
Fan Yang ◽  
Wei-Ting Ye ◽  
Jun-Jie Wang ◽  
Rong Zhu
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Electrochemical Analysis ◽  
Hydrogen Atom Transfer ◽  
Redox Process ◽  
Photochemical Oxidation ◽  
Atom Transfer ◽  
Photoredox Catalysis ◽  
Wide Range ◽  
Selective Alkylation

A general protocol has been developed for the Markovnikov-selective intermolecular hydrofunctionalization based on visible-light-mediated Co/Ru dual catalysis. The key feature involves the photochemical oxidation of an organocobalt(III) intermediate derived from hydrogen atom transfer, which is supported by electrochemical analysis, quenching studies and stoichiometric experiments. This unique redox process enables the efficient branch-selective alkylation of pharmaceutically important nucleophiles (phenols, sulfonamides and various N-heterocycles) using a wide range of alkenes including moderately electron-deficient ones. Moreover, light-gated polar functionalization via organocobalt species was demonstrated.

Iminyl Radical-Triggered 1,5-Hydrogen-Atom Transfer/Heck-Type Coupling by Visible-Light Photoredox Catalysis

2019 ◽  
Vol 84 (10) ◽  
pp. 6475-6482 ◽  
Author(s):  
Li Chen ◽  
Li-Na Guo ◽  
Zhi-Yong Ma ◽  
Yu-Rui Gu ◽  
Junjie Zhang ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Photoredox Catalysis ◽  
Type Coupling
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