Shannon S. Stahl

article

Sustainable Pd(OAc)₂/Hydroquinone Cocatalyst System for Cis‐Selective Dibenzoyloxylation of 1,3‐Cyclohexadiene

Alexios G. Stamoulis, Peng Geng, Michael A. Schmidt, Martin D. Eastgate, more

Angewandte Chemie International Edition > 60 > 43 > 23182 - 23186

The 1,4‐diacyloxylation of 1,3‐cyclohexadiene (CHD) affords valuable stereochemically defined scaffolds for natural product and pharmaceutical synthesis. Existing cis‐selective diacyloxylation protocols require superstoichiometric quantities of benzoquinone (BQ) or MnO₂, which limit process sustainability and large‐scale application. In this report, reaction development and mechanistic studies are...

article

Sustainable Pd(OAc)₂/Hydroquinone Cocatalyst System for Cis‐Selective Dibenzoyloxylation of 1,3‐Cyclohexadiene

Alexios G. Stamoulis, Peng Geng, Michael A. Schmidt, Martin D. Eastgate, more

Angewandte Chemie > 133 > 43 > 23366 - 23370

The 1,4‐diacyloxylation of 1,3‐cyclohexadiene (CHD) affords valuable stereochemically defined scaffolds for natural product and pharmaceutical synthesis. Existing cis‐selective diacyloxylation protocols require superstoichiometric quantities of benzoquinone (BQ) or MnO₂, which limit process sustainability and large‐scale application. In this report, reaction development and mechanistic studies are...

article

Catalytic Behavior of Mono‐N‐Protected Amino‐Acid Ligands in Ligand‐Accelerated C−H Activation by Palladium(II)

Chase A. Salazar, Joseph J. Gair, Kaylin N. Flesch, Ilia A. Guzei, more

Angewandte Chemie International Edition > 59 > 27 > 10873 - 10877

Mono‐N‐protected amino acids (MPAAs) are increasingly common ligands in Pd‐catalyzed C−H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C−H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand‐accelerated catalysis: the ability to support catalytic turnover at substoichiometric...

article

Catalytic Behavior of Mono‐N‐Protected Amino‐Acid Ligands in Ligand‐Accelerated C−H Activation by Palladium(II)

Chase A. Salazar, Joseph J. Gair, Kaylin N. Flesch, Ilia A. Guzei, more

Angewandte Chemie > 132 > 27 > 10965 - 10969

Mono‐N‐protected amino acids (MPAAs) are increasingly common ligands in Pd‐catalyzed C−H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C−H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand‐accelerated catalysis: the ability to support catalytic turnover at substoichiometric...

article

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

Paige E. Piszel, Aristidis Vasilopoulos, Shannon S. Stahl

Angewandte Chemie > 131 > 35 > 12339 - 12343

The aerobic Cu/ABNO catalyzed oxidative coupling of alcohols and amines is highlighted in the synthesis of amide bonds in diverse drug‐like molecules (ABNO=9‐azabicyclo[3.3.1]nonane N‐oxyl). The robust method leverages the privileged reactivity of alcohols bearing electronegative hetero‐ atoms (O, F, N, Cl) in the β‐position. The reaction tolerates over 20 unique functional groups and is demonstrated...

article

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

Paige E. Piszel, Aristidis Vasilopoulos, Shannon S. Stahl

Angewandte Chemie International Edition > 58 > 35 > 12211 - 12215

The aerobic Cu/ABNO catalyzed oxidative coupling of alcohols and amines is highlighted in the synthesis of amide bonds in diverse drug‐like molecules (ABNO=9‐azabicyclo[3.3.1]nonane N‐oxyl). The robust method leverages the privileged reactivity of alcohols bearing electronegative hetero‐ atoms (O, F, N, Cl) in the β‐position. The reaction tolerates over 20 unique functional groups and is demonstrated...

article

Merging Photochemistry with Electrochemistry: Functional‐Group Tolerant Electrochemical Amination of C(sp³)−H Bonds

Fei Wang, Shannon S. Stahl

Angewandte Chemie > 131 > 19 > 6451 - 6456

Direct amination of C(sp³)−H bonds is of broad interest in the realm of C−H functionalization because of the prevalence of nitrogen heterocycles and amines in pharmaceuticals and natural products. Reported here is a combined electrochemical/photochemical method for dehydrogenative C(sp³)−H/N−H coupling that exhibits good reactivity with both sp² and sp³ N−H bonds. The results show how use of iodide...

article

Merging Photochemistry with Electrochemistry: Functional‐Group Tolerant Electrochemical Amination of C(sp³)−H Bonds

Fei Wang, Shannon S. Stahl

Angewandte Chemie International Edition > 58 > 19 > 6385 - 6390

Direct amination of C(sp³)−H bonds is of broad interest in the realm of C−H functionalization because of the prevalence of nitrogen heterocycles and amines in pharmaceuticals and natural products. Reported here is a combined electrochemical/photochemical method for dehydrogenative C(sp³)−H/N−H coupling that exhibits good reactivity with both sp² and sp³ N−H bonds. The results show how use of iodide...

article

Electrochemical Functional‐Group‐Tolerant Shono‐type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators

Fei Wang, Mohammad Rafiee, Shannon S. Stahl

Angewandte Chemie > 130 > 22 > 6796 - 6800

An electrochemical method has been developed for α‐oxygenations of cyclic carbamates by using a bicyclic aminoxyl as a mediator and water as the nucleophile. The mediated electrochemical process enables substrate oxygenation to proceed at a potential that is approximately 1 V lower than the redox potential of the carbamate substrate. This feature allows for functional‐group compatibility that is inaccessible...

article

Electrochemical Functional‐Group‐Tolerant Shono‐type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators

Fei Wang, Mohammad Rafiee, Shannon S. Stahl

Angewandte Chemie International Edition > 57 > 22 > 6686 - 6690

An electrochemical method has been developed for α‐oxygenations of cyclic carbamates by using a bicyclic aminoxyl as a mediator and water as the nucleophile. The mediated electrochemical process enables substrate oxygenation to proceed at a potential that is approximately 1 V lower than the redox potential of the carbamate substrate. This feature allows for functional‐group compatibility that is inaccessible...

article

Noncovalent Immobilization of Molecular Electrocatalysts for Chemical Synthesis: Efficient Electrochemical Alcohol Oxidation with a Pyrene–TEMPO Conjugate

Amit Das, Shannon S. Stahl

Angewandte Chemie International Edition > 56 > 30 > 8892 - 8897

Electrocatalytic methods for organic synthesis could offer sustainable alternatives to traditional redox reactions, but strategies are needed to enhance the performance of molecular catalysts designed for this purpose. The synthesis of a pyrene‐tethered TEMPO derivative (TEMPO=2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl) is described, which undergoes facile in situ noncovalent immobilization onto a carbon...

article

Noncovalent Immobilization of Molecular Electrocatalysts for Chemical Synthesis: Efficient Electrochemical Alcohol Oxidation with a Pyrene–TEMPO Conjugate

Amit Das, Shannon S. Stahl

Angewandte Chemie > 129 > 30 > 9018 - 9023

Electrocatalytic methods for organic synthesis could offer sustainable alternatives to traditional redox reactions, but strategies are needed to enhance the performance of molecular catalysts designed for this purpose. The synthesis of a pyrene‐tethered TEMPO derivative (TEMPO=2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl) is described, which undergoes facile in situ noncovalent immobilization onto a carbon...

article

Detection of Palladium(I) in Aerobic Oxidation Catalysis

Jonathan N. Jaworski, Scott D. McCann, Ilia A. Guzei, Shannon S. Stahl

Angewandte Chemie International Edition > 56 > 13 > 3605 - 3610

Palladium(II)‐catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non‐oxidative cross‐coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Herein, we report the identification and characterization of a dimeric Pd^I species in two...

article

Detection of Palladium(I) in Aerobic Oxidation Catalysis

Jonathan N. Jaworski, Scott D. McCann, Ilia A. Guzei, Shannon S. Stahl

Angewandte Chemie > 129 > 13 > 3659 - 3664

Palladium(II)‐catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non‐oxidative cross‐coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Herein, we report the identification and characterization of a dimeric Pd^I species in two...

chapter

N-Heterocyclic Carbenes as Ligands for High-Oxidation-State Metal Complexes and Oxidation Catalysis

Michelle M. Rogers, Shannon S. Stahl

Topics in Organometallic Chemistry > N-Heterocyclic Carbenes in Transition Metal Catalysis > 21-46

N-Heterocyclic carbenes (NHCs) possess properties that are ideally suited for their use as ligands in transition-metal oxidation chemistry and catalysis. Their strong sigma-donating ability stabilizes metals in high oxidation states, and their high M—L bond dissociation energies reduce their tendency to dissociate and undergo oxidative decomposition of the free carbene. In this chapter, we summarize...

chapter

Palladium-Catalyzed Oxidation Reactions: Comparison of Benzoquinone and Molecular Oxygen as Stoichiometric Oxidants

Brian V. Popp, Shannon S. Stahl

Topics in Organometallic Chemistry > Organometallic Oxidation Catalysis > 149-189

Palladium-catalyzed oxidation reactions are among the most diverse methods available for the selective oxidation of organic molecules, and benzoquinone is one of the most widely used terminal oxidants for these reactions. Over the past decade, however, numerous reactions have been reported that utilize molecular oxygen as the sole oxidant. This chapter outlines the fundamental reactivity of benzoquinone...

article

Chinon‐katalysierte, selektive Oxidation organischer Moleküle

Alison E. Wendlandt, Shannon S. Stahl

Angewandte Chemie > 127 > 49 > 14848 - 14868

Chinone sind gebräuchliche, stöchiometrisch eingesetzte Reagentien in der organischen Chemie. para‐Chinone mit hohem Reduktionspotential wie DDQ und Chloranil werden verbreitet angewendet und fördern normalerweise die Hydridabstraktion. In den letzten Jahren wurden viele katalytische Anwendungen dieser Methoden entwickelt, wobei das oxidierte Chinon in situ mithilfe von Übergangsmetallen, O₂ oder...

article

Quinone‐Catalyzed Selective Oxidation of Organic Molecules

Alison E. Wendlandt, Shannon S. Stahl

Angewandte Chemie International Edition > 54 > 49 > 14638 - 14658

Quinones are common stoichiometric reagents in organic chemistry. Para‐quinones with high reduction potentials, such as DDQ and chloranil, are widely used and typically promote hydride abstraction. In recent years, many catalytic applications of these methods have been achieved by using transition metals, electrochemistry, or O₂ to regenerate the oxidized quinone in situ. Complementary studies have...

article

Palladium-catalyzed aerobic acetoxylation of benzene using NOx-based redox mediators

Susan L. Zultanski, Shannon S. Stahl

Journal of Organometallic Chemistry > 2015 > 793 > C > 263-268

Palladium-catalyzed methods for C–H oxygenation with O₂ as the stoichiometric oxidant are limited. Here, we describe the use of nitrite and nitrate sources as NO_x-based redox mediators in the acetoxylation of benzene. The conditions completely avoid formation of biphenyl as a side product, and strongly favor formation of phenyl acetate over nitrobenzene (PhOAc:PhNO₂ ratios up to 40:1). Under the optimized...

article

Integration of Anodic and Cathodic Catalysts of Earth-Abundant Materials for Efficient, Scalable CO₂ Reduction

Rishi Parajuli, James B. Gerken, Kunttal Keyshar, Ian Sullivan, more

Topics in Catalysis > 2015 > 58 > 1 > 57-66

A fully integrated electrochemical cell for co-production of formate (HCOO⁻) and oxygen (O₂) from carbon dioxide (CO₂) and water using only earth-abundant elements has been developed. The process converts CO₂ to formate using electrons derived from anodic water oxidation. A novel cathodic catalyst system, consisting of a tin (Sn) cathode in combination with the soluble heterocycle 2-picoline, was...

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Search results for: Shannon S. Stahl

Sustainable Pd(OAc)₂/Hydroquinone Cocatalyst System for Cis‐Selective Dibenzoyloxylation of 1,3‐Cyclohexadiene

Sustainable Pd(OAc)₂/Hydroquinone Cocatalyst System for Cis‐Selective Dibenzoyloxylation of 1,3‐Cyclohexadiene

Catalytic Behavior of Mono‐N‐Protected Amino‐Acid Ligands in Ligand‐Accelerated C−H Activation by Palladium(II)

Catalytic Behavior of Mono‐N‐Protected Amino‐Acid Ligands in Ligand‐Accelerated C−H Activation by Palladium(II)

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

Merging Photochemistry with Electrochemistry: Functional‐Group Tolerant Electrochemical Amination of C(sp³)−H Bonds

Merging Photochemistry with Electrochemistry: Functional‐Group Tolerant Electrochemical Amination of C(sp³)−H Bonds

Electrochemical Functional‐Group‐Tolerant Shono‐type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators

Electrochemical Functional‐Group‐Tolerant Shono‐type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators

Noncovalent Immobilization of Molecular Electrocatalysts for Chemical Synthesis: Efficient Electrochemical Alcohol Oxidation with a Pyrene–TEMPO Conjugate

Noncovalent Immobilization of Molecular Electrocatalysts for Chemical Synthesis: Efficient Electrochemical Alcohol Oxidation with a Pyrene–TEMPO Conjugate

Detection of Palladium(I) in Aerobic Oxidation Catalysis

Detection of Palladium(I) in Aerobic Oxidation Catalysis

N-Heterocyclic Carbenes as Ligands for High-Oxidation-State Metal Complexes and Oxidation Catalysis

Palladium-Catalyzed Oxidation Reactions: Comparison of Benzoquinone and Molecular Oxygen as Stoichiometric Oxidants

Chinon‐katalysierte, selektive Oxidation organischer Moleküle

Quinone‐Catalyzed Selective Oxidation of Organic Molecules

Palladium-catalyzed aerobic acetoxylation of benzene using NOx-based redox mediators

Integration of Anodic and Cathodic Catalysts of Earth-Abundant Materials for Efficient, Scalable CO₂ Reduction

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