scholarly journals NHCs and Visible Light-mediated Photoredox Co-catalyzed Radical 1,2-Dicarbonylation of Alkenes for 1,4-Diketones

2021 ◽  
Author(s):  
Lihong Wang ◽  
Jiaqiong Sun ◽  
Jiuli Xia ◽  
Mingrui Li ◽  
Lianjin Zhang ◽  
...  
Keyword(s):  
Value Added ◽  
Direct Access ◽  
Acyl Radical ◽  
Reaction Conditions ◽  
Ketyl Radical ◽  
Alkyl Radicals ◽  
Keto Acids ◽  
Acyl Radicals ◽  
Quenching Process ◽  
Selectivity Control

Alkenes are ubiquitous, and radical difunctionalization of alkenes represents one of the most practical approaches to constructing value-added compounds. Dicarbonylation of alkenes provides direct access to value-added 1,4-dicarbonyl compounds. However, selectivity control for unsymmetric 1,2-dicarbonylation is an unclosed challenge. We herein describe NHCs and photocatalysis co-catalyzed three competent radical 1,2-dicarbonylation of alkenes by distinguishing two carbonyl groups, providing structurally diversified 1,4-diketones. Mechanistic studies indicated that NHCs-stabilized ketyl-type radicals originate from aroyl fluorides via oxidative quenching process of excited photocatalysis, and acyl radicals are generated from single-electron-oxidation of α-keto acids. Distinct properties of acyl radical and NHCs-stabilized ketyl radical contributed to selectivity control. Transient acyl radicals are rapidly added to alkenes delivering alkyl radicals, which undergo subsequent radical-radical cross-coupling with ketyl-type radicals, affording 1,2-dicarbonylation products. This transformation features mild reaction conditions, broad substruct scope, and excellent selectivity, providing a general and practical approach for the dicarbonylation of olefins.

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 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.

scholarly journals Switchable radical carbonylation by polarity-regulation

2021 ◽  
Author(s):  
Bin Lu ◽  
Xiaotian Qi ◽  
Wen-Jing Xiao ◽  
Jia-Rong Chen
Keyword(s):  
Value Added ◽  
Radical Cations ◽  
Acyl Radical ◽  
Alkyl Radicals ◽  
Radical Intermediates ◽  
New Strategy ◽  
Visible Light Driven ◽  
Polarity Regulation ◽  
Nitrogen Radical ◽  
Value Added Products

Carbonylation reactions involving CO as readily available C1 synthons have become one of the most important tools for construction of carbonyl compounds from feedstock chemicals in modern chemical synthesis. Whereas numerous catalytic methods for carbonylation reactions proceeding via ionic or radical pathways have been reported, an inherent limitation to these methods is the need to control switchable single and double carbonylative formation of value-added products from the same and simple starting materials. Here we describe a new strategy that exploits simple visible-light-driven photoredox catalysis to regulate the polarity of coupling partners to drive switchable radical carbonylation reactions. Controlled trap of various alkyl radicals by single or double CO thereby proceed smoothly with excellent selectivity in the presence of various amine nucleophiles at room temperature, generating valuable amides and α-ketoamides in a versatile and controlled fashion. Combined experimental and DFT computational studies suggest that trap of the initially formed acyl radical by the second molecule of CO to form α-ketoacyl radical is a facile but reversible process; and photoredox-catalyzed SET oxidation of natural nucleophilic amines into relatively electrophilic nitrogen radical cations is responsible for switchable coupling with such two radical intermediates.

scholarly journals Acyl Radical Chemistry via Visible-Light Photoredox Catalysis

Synthesis ◽  
2018 ◽  
Vol 51 (02) ◽  
pp. 303-333 ◽  
Author(s):  
Ming-Yu Ngai ◽  
Arghya Banerjee ◽  
Zhen Lei
Keyword(s):  
Visible Light ◽  
Carboxylic Acids ◽  
Easy Access ◽  
Hypervalent Iodine ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Diverse Range ◽  
Acyl Chlorides ◽  
Keto Acids ◽  
Acyl Radicals

Visible-light photoredox catalysis enables easy access to acyl radicals under mild reaction conditions. Reactive acyl radicals, generated from various acyl precursors such as aldehydes, α-keto acids, carboxylic acids, anhydrides, acyl thioesters, acyl chlorides, or acyl silanes, can undergo a diverse range of synthetically useful transformations, which were previously difficult or inaccessible. This review summarizes the recent progress on visible-light-driven acyl radical generation using transition-metal photoredox catalysts, metallaphotocatalysts, hypervalent iodine catalysts or organic photocatalysts.1 Introduction2 The Scope of This Review3 Aldehydes as a Source of Acyl Radicals4 α-Keto Acids as a Source of Acyl Radicals5 Carboxylic Acids as a Source of Acyl Radicals6 Anhydrides as a Source of Acyl Radicals7 Acyl Thioesters as a Source of Acyl Radicals8 Acyl Chlorides as a Source of Acyl Radicals9 Acyl Silanes as a Source of Acyl Radicals10 Conclusions and Future Outlook

scholarly journals Recent Advances in Photocatalytic Transformation of Carbohydrates Into Valuable Platform Chemicals

2021 ◽  
Vol 3 ◽  
Author(s):  
Huan Chen ◽  
Kun Wan ◽  
Fangjuan Zheng ◽  
Zhuo Zhang ◽  
Hongyu Zhang ◽  
...  
Keyword(s):  
Solar Energy ◽  
Scientific Community ◽  
Value Added ◽  
Reaction Pathways ◽  
Future Perspective ◽  
Reaction Conditions ◽  
Catalytic Systems ◽  
Selective Transformation ◽  
Platform Chemicals ◽  
Broad Interest

In response to the less accessible fossil resources and deteriorating environmental problems, catalytic conversion of the abundant and renewable lignocellulosic biomass to replace fossil resources for the production of value-added chemicals and fuels is of great importance. Depolymerization of carbohydrate and its derivatives can obtain a series of C5-C6 monosaccharides (e.g., glucose and xylose) and their derived platform compounds (e.g., HMF and furfural). Selective transformation of lignocellulose using sustainable solar energy via photocatalysis has attract broad interest from a growing scientific community. The unique photogenerated reactive species (e.g., h+, e−, •OH, •O2−, and 1O2), novel reaction pathways as well as the mild reaction conditions make photocatalysis a “dream reaction.” This review is aimed to provide an overview of the up-to-date contributions achieved in the selective photocatalytic transformation of carbohydrate and its derivatives. Photocatalytic methods, properties and merits of different catalytic systems are well summarized. We then put forward future perspective and challenges in this field.

Direct Acyl Radical Addition to 2H-Indazoles Using Ag-Catalyzed Decarboxylative Cross-Coupling of α-Keto Acids

2018 ◽  
Vol 20 (9) ◽  
pp. 2711-2715 ◽  
Author(s):  
Ganganna Bogonda ◽  
Hun Young Kim ◽  
Kyungsoo Oh
Keyword(s):  
Cross Coupling ◽  
Radical Addition ◽  
Acyl Radical ◽  
Keto Acids

scholarly journals P142: Perspectives of medical students and undergraduate students on their experience as medical scribes in the Saint John Regional Hospital Emergency Department

CJEM ◽  
2020 ◽  
Vol 22 (S1) ◽  
pp. S115-S116
Author(s):  
I. Abelev ◽  
D. Lewis ◽  
J. Fraser ◽  
P. Atkinson
Keyword(s):  
Medical Students ◽  
Undergraduate Students ◽  
Medical Profession ◽  
Value Added ◽  
School Curriculum ◽  
Health Care Team ◽  
Direct Access ◽  
Theory Approach ◽  
Medical Terminology ◽  
Structured Interviews

Introduction: Electronic medical records (EMR) have placed increasing demand on emergency physicians and may contribute to physician burnout and stress. The use of scribes to reduce workload and increase productivity in emergency departments (ED) has been reported. This objective of this study was to evaluate the educational and experiential value of scribing among medical and undergraduate students. We asked: “Will undergraduates be willing to scribe in exchange for clinical exposure and experience?”; and, “Should scribing be integrated into the medical school curriculum?” Methods: A mixed-methods model was employed. The study population included 5 undergraduate, and 5 medical students. Scribes received technical training on how to take physician notes. Undergraduate students were provided with optional resources to familiarize themselves with common medical terminology. Scribes were assigned to physicians based on availability. An exit interview and semi-structured interviews were conducted at the conclusion of the study. Interviews were transcribed and coded into thematic coding trees. A constructivist grounded theory approach was used to analyze the results. Themes were reviewed and verified by two members of the research team. Results: Undergraduate students preferred volunteering in the ED over other volunteer experiences (5/5); citing direct access to the medical field (5/5), demystification of the medical profession (4/5), resume building (5/5), and perceived value added to the health care team (5/5) as main motivators to continue scribing. Medical students felt scribing should be integrated into their curriculum (4/5) because it complemented their shadowing experience by providing unique value that shadowing did not. Based on survey results, five undergraduate students would be required to cover 40 volunteer hours per week. Conclusion: A student volunteer model of scribing is worthwhile to students and may be feasible; however, scribe availability, potentially high scribe turnover, and limited time to develop a rapport with their physician may impact any efficiency benefit scribes might provide. Importantly, scribing may be an invaluable experience for directing career goals and ensuring that students intrinsically interested in medicine pursue the profession. Medical students suggested that scribing could be added to the year one curriculum to help them develop a framework for how to take histories and manage patients.

scholarly journals Novel Effect of Zinc Nitrate/Vanadyl Oxalate for Selective Catalytic Oxidation of α-Hydroxy Esters to α-Keto Esters with Molecular Oxygen: An In Situ ATR-IR Study

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1281 ◽  
Author(s):  
Yongwei Ju ◽  
Zhongtian Du ◽  
Chuhong Xiao ◽  
Xingfei Li ◽  
Shuang Li
Keyword(s):  
Catalytic Activity ◽  
Catalytic Oxidation ◽  
Molecular Oxygen ◽  
Aerobic Oxidation ◽  
Value Added ◽  
Attenuated Total Reflection ◽  
Reaction Conditions ◽  
Keto Esters ◽  
Selective Catalytic Oxidation ◽  
Hydroxy Esters

Selective oxidation of α-hydroxy esters is one of the most important methods to prepare high value-added α-keto esters. An efficient catalytic system consisting of Zn(NO3)2/VOC2O4 is reported for catalytic oxidation of α-hydroxy esters with molecular oxygen. Up to 99% conversion of methyl DL-mandelate or methyl lactate could be facilely obtained with high selectivity for its corresponding α-keto ester under mild reaction conditions. Zn(NO3)2 exhibited higher catalytic activity in combination with VOC2O4 compared with Fe(NO3)3 and different nitric oxidative gases were detected by situ attenuated total reflection infrared (ATR-IR) spectroscopy. UV-vis and ATR-IR results indicated that coordination complex formed in Zn(NO3)2 in CH3CN solution was quite different from Fe(NO3)3; it is proposed that the charge-transfer from Zn2+ to coordinated nitrate groups might account for the generation of different nitric oxidative gases. The XPS result indicate that nitric oxidative gas derived from the interaction of Zn(NO3)2 with VOC2O4 could be in favor of oxidizing VOC2O4 to generate active vanadium (V) species. It might account for different catalytic activity of Zn(NO3)2 or Fe(NO3)3 combined with VOC2O4. This work contributes to further development of efficient aerobic oxidation under mild reaction conditions.

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