Recent Advances on Acyl Radical Enabled Reactions between Aldehydes and Alkenes

2021 ◽  
Author(s):  
Yilin Liu ◽  
Yuejun Ouyang ◽  
Hongxing Zheng ◽  
Hongxin Liu ◽  
Wenting Wei
Keyword(s):  
Hydrogen Atom ◽  
Acyl Radical ◽  
Recent Advances ◽  
Acyl Radicals

Radical-mediated functionalization of alkenes has been emerging as an elegant and straightforward protocol to increase molecule complexity. Moreover, the abstraction of a hydrogen atom from aldehydes to afford acyl radicals...

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

scholarly journals DABCO-promoted photocatalytic C–H functionalization of aldehydes

2021 ◽  
Vol 17 ◽  
pp. 2959-2967
Author(s):  
Bruno Maia da Silva Santos ◽  
Mariana dos Santos Dupim ◽  
Cauê Paula de Souza ◽  
Thiago Messias Cardozo ◽  
Fernanda Gadini Finelli
Keyword(s):  
Hydrogen Atom ◽  
Cross Coupling ◽  
Hydrogen Atom Transfer ◽  
Direct Application ◽  
Atom Transfer ◽  
Organic Base ◽  
Aryl Bromides ◽  
Computational Calculations ◽  
Acyl Radicals ◽  
Aryl Ketones

Herein we present a direct application of DABCO, an inexpensive and broadly accessible organic base, as a hydrogen atom transfer (HAT) abstractor in a photocatalytic strategy for aldehyde C–H activation. The acyl radicals generated in this step were arylated with aryl bromides through a well stablished nickel cross-coupling methodology, leading to a variety of interesting aryl ketones in good yields. We also performed computational calculations to shine light in the HAT step energetics and determined an optimized geometry for the transition state, showing that the hydrogen atom transfer between aldehydes and DABCO is a mildly endergonic, yet sufficiently fast step. The same calculations were performed with quinuclidine, for comparison of both catalysts and the differences are discussed.

scholarly journals Radical Carbonylative Synthesis of Heterocycles by Visible Light Photoredox Catalysis

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1054
Author(s):  
Xiao-Qiang Hu ◽  
Zi-Kui Liu ◽  
Wen-Jing Xiao
Keyword(s):  
Visible Light ◽  
Efficient Synthesis ◽  
Acyl Radical ◽  
Acyl Chlorides ◽  
Aryl Radicals ◽  
Keto Acids ◽  
Acyl Radicals ◽  
Different Types ◽  
The Impact ◽  
Visible Light Photocatalytic

Visible light photocatalytic radical carbonylation has been established as a robust tool for the efficient synthesis of carbonyl-containing compounds. Acyl radicals serve as the key intermediates in these useful transformations and can be generated from the addition of alkyl or aryl radicals to carbon monoxide (CO) or various acyl radical precursors such as aldehydes, carboxylic acids, anhydrides, acyl chlorides or α-keto acids. In this review, we aim to summarize the impact of visible light-induced acyl radical carbonylation reactions on the synthesis of oxygen and nitrogen heterocycles. The discussion is mainly categorized based on different types of acyl radical precursors.

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

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.

1.13 Intramolecular Hydrogen-Atom Transfer

2021 ◽  
Author(s):  
S. Treacy ◽  
X. Zhang ◽  
T. Rovis
Keyword(s):  
Hydrogen Atom ◽  
Functional Groups ◽  
Open Shell ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Stable Carbon ◽  
Radical Reactivity ◽  
Recent Advances ◽  
Synthetic Chemist ◽  
Intramolecular Hydrogen

AbstractRecent advances in intramolecular hydrogen-atom transfer (HAT) have demonstrated significant utility in C—H functionalization through highly reactive open-shell intermediates. The intramolecular transposition of radical reactivity from select functional groups to generate more stable carbon-centered radicals often proceeds with high regioselectivity, providing novel bond disconnections at otherwise inert and largely indistinguishable positions. This chapter explores the functional groups capable of intramolecular HAT to generate remote radicals and the transformations currently available to the synthetic chemist.

Recent Advances on the Photo-Induced Reactions of Acyl Radical

2018 ◽  
Vol 38 (12) ◽  
pp. 3155 ◽  
Author(s):  
Liheng Ruan ◽  
Chunxin Chen ◽  
Xiaoxin Zhang ◽  
Jing Sun
Keyword(s):  
Acyl Radical ◽  
Recent Advances

Synthetic and Computational Studies of Acyl Radical Cyclizations with β-Alkoxyacrylates: Formal Synthesis of (±)-Longianone

2011 ◽  
Vol 64 (4) ◽  
pp. 409 ◽  
Author(s):  
Heather M. Aitken ◽  
Carl H. Schiesser ◽  
Christopher D. Donner
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Radical Cyclizations ◽  
Computational Studies ◽  
Fungal Metabolite ◽  
Acyl Radical ◽  
Functional Theory ◽  
Formal Synthesis ◽  
Acyl Radicals ◽  
Insight Into

An investigation into the cyclization of acyl radicals with mono- and disubstituted β-alkoxyacrylates is described. Ether-tethered acyl radicals, generated directly from the corresponding aldehyde, undergo cyclization to form dioxaspiro heterocyclic systems including 1,7-dioxaspiro[4,4]nonane-4,8-dione and 1,8-dioxaspiro[5,4]decane-5,9-dione. This strategy is applied to a concise formal synthesis of the fungal metabolite longianone. Density functional theory calculations provide insight into the chemistry of the acyl radicals in this study.

scholarly journals Hydrogen Atom Transfer Reactions in Photocatalysis: Recent Advances in C-H Activation

2021 ◽  
Author(s):  
Bruno M. da S. Santos ◽  
Mariana dos S. Dupim ◽  
Pedro H. R Oliveira ◽  
Fernanda G. Finelli
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Transfer Reactions ◽  
Atom Transfer ◽  
Recent Advances ◽  
Atom Transfer Reactions

scholarly journals Divergent functionalization of aldehydes photocatalyzed by neutral eosin Y with sulfone reagents

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jianming Yan ◽  
Haidi Tang ◽  
Eugene Jun Rong Kuek ◽  
Xiangcheng Shi ◽  
Chenguang Liu ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Noble Metal ◽  
Continuous Flow ◽  
Scale Up ◽  
Value Added ◽  
Hydrogen Atom Transfer ◽  
Eosin Y ◽  
Noble Metal Catalysts ◽  
Green Approach ◽  
Acyl Radicals

AbstractWhile aldehydes represent a classic class of electrophilic synthons, the corresponding acyl radicals are inherently nucleophilic, which exhibits umpolung reactivity. Generation of acyl radicals typically requires noble metal catalysts or excess oxidants to be added. Herein, we report a convenient and green approach to access acyl radicals, capitalizing on neutral eosin Y-enabled hydrogen atom transfer (HAT) photocatalysis with aldehydes. The generated acyl radicals underwent SOMOphilic substitutions with various functionalized sulfones (X–SO2R’) to deliver value-added acyl products. The merger of eosin Y photocatalysis and sulfone-based SOMOphiles provides a versatile platform for a wide array of aldehydic C–H functionalizations, including fluoromethylthiolation, arylthiolation, alkynylation, alkenylation and azidation. The present protocol features green characteristics, such as being free of metals, harmful oxidants and additives; step-economic; redox-neutral; and amenable to scale-up assisted by continuous-flow technology.

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