Search

This Account presents palladium-complex-catalyzed oxidative couplings mainly developed by the author's group, including oxidative amination and silylation of terminal alkenes, direct oxidative arylation of aromatic compounds, and oxidative difunctionalization of 1,3-dienes. The catalytic cycles in these representative reactions feature re-oxidation of the palladium species with molecular oxygen as the terminal oxidant. Varying the combination of palladium catalyst and re-oxidant enables the formation of a variety of bonds through dehydrogenative cross-coupling reactions. 1 Introduction 2 Oxidative Amination of Terminal Alkenes 3 Direct Oxidative Arylation of Aromatic Compounds 4 Oxidative Silylation of Terminal Alkenes 5 Oxidative Difunctionalization of 1,3-Dienes 6 Conclusions and Perspectives [ABSTRACT FROM AUTHOR]

This article discusses the use of boronic acids in the synthesis of phenols, which are important compounds found in natural products and pharmaceuticals. The researchers focus on developing environmentally friendly and sustainable methods for preparing phenols from boronic acids. They explore different photocatalysts and solvents to optimize the oxidation reaction. The study finds that anthraquinone is an effective photocatalyst and 2-Me-THF is the best solvent for the reaction. The researchers aim to provide a more sustainable protocol for the oxidation of boronic acids. Another study described in the document investigates the photochemical aerobic oxidation of boronic acids to phenols. The researchers tested different additives and found that N,N'-diisopropylethylamine (DIPEA) was the most suitable base, resulting in the complete formation of phenol. They also explored the range of substrates and found that various aryl-substituted boronic acids could be converted into the corresponding phenols with moderate to excellent yields. Mechanistic studies suggested a mixed pathway involving the generation of a superoxide anion and the formation of hydrogen peroxide. Overall, this study presents an environmentally friendly and efficient method for the oxidation of boronic acids. [Extracted from the article]

This article discusses a study on the synthesis of furo- and thienoquinoline compounds using a biomimetic catalyst inspired by quino enzymes. The researchers found that a wide range of 2-hetarylanilines participated well in the reaction, yielding the desired products in moderate to high yields. They also demonstrated the versatility of the reaction by performing various coupling reactions and functionalizing the synthesized compounds. Mechanistic studies suggested that the reaction involves a sequence of dehydrogenation, transamination, cyclization, and secondary-amine dehydrogenation. The presence of an iron ion was found to improve the catalysis. [Extracted from the article]

[9] However, most of these processes require a high reaction temperature and a long reaction time because the high oxidation potentials of alkylboronic acids ( I E i SB red sb 2.0 V vs SCE for secondary boronic acids) are usually kinetically unfavorable to direct oxidation by molecular oxygen. To test the reactivity of tertiary-alkylboronic acids, we selected the cheaper pinacol ester of I tert i -butylboronic acid as the alkyl precursor, and the reaction proceeded smoothly to produce the expected product B 4d b in 88% yield. By using an electrochemical strategy, [8] Lei and co-workers developed a Mn(III)-catalyzed alkyl radical cascade cyclization reaction through electrolysis of alkylboronic acids, providing a new strategy for generating alkyl radicals. Keywords: manganese catalysis; denitroalkylation; alkylboronic acids; nitrostyrenes; radical reaction; aerobic oxidation EN manganese catalysis denitroalkylation alkylboronic acids nitrostyrenes radical reaction aerobic oxidation 1597 1602 6 07/31/23 20230815 NES 230815 Graph Their unique stability, low toxicity, and easy preparation make alkylboronic acids good versatile building blocks in organic synthesis, and the construction of carbon-carbon bonds by using commercially available alkylboronic acids instead of preformed organic halides or aliphatic acids has received increasing attention in recent decades. [Extracted from the article]

Tetraethylthiuram disulfide (TETD) is one of the most important thiuram-class rubber vulcanization accelerators and a 'star molecule' in other areas. The development of a mild, efficient, low-cost, safe, and sustainable approach to produce TETD is extremely desirable. Here, we developed a much-improved route to synthesize TETD using MoS2 as the catalyst and ethanol as the solvent. A packed-bed microflow strategy was implemented to accelerate the catalytic process. TETD was obtained with an excellent yield and purity within a short residence time. Besides, this continuous process did not generate any waste salts, rendering it a sustainable method for producing thiuram-type compounds. [ABSTRACT FROM AUTHOR]

The photoirradiation of toluene derivatives with two equivalents of bromine in benzotrifluoride–water provided a satisfactory yield of the corresponding benzoic acid derivatives. Either a fluorescent lamp, blue LED (454 nm), or UV LED (385 nm) was used for the photoreaction. The reaction pathway might proceed through the dibromination of benzylic carbon, generation of the benzylic radical via oxidative C–H abstraction, formation of benzoyl bromide, and hydrolysis of carboxylic acid. [ABSTRACT FROM AUTHOR]

Ferrocenium-doped manganese(IV) oxide (Fc+ /MnO2) was synthesized through accelerated decomposition of KMnO4 in the presence of ferrocenium ion (Fc+) generated by concentrated sulfuric acid. The corresponding catalysts enabled highly efficient oxidation of alcohols with aldehyde or ketone. [ABSTRACT FROM AUTHOR]

A ligand-free palladium-catalyzed aerobic oxidative carbonylation of amines for the synthesis of ureas, particular unsymmetrically N,N′-disubstituted ureas, which cannot be accessed by any other palladium-catalyzed oxidative carbonylation of amines to date, is presented. An array of symmetrical and unsymmetrical ureas were straightforwardly synthesized by using inexpensive, readily available, stable, and safe amines with good to excellent yields under a pressure of 1 atm. This novel method employs oxygen as the sole oxidant and offers an attractive alternative to transition-metal-based oxidant systems [ABSTRACT FROM AUTHOR]

A new aerobic oxidation system consisting of Cu(I)I, 2,2'-bipyridine, N-methyl imidazole, and a mesoionic hydroxyamide was developed, with which selective oxidation of a broad range of benzylic alcohols was achieved. [ABSTRACT FROM AUTHOR]

Here, we highlight the recent development of aerobic oxidation catalysis via hypervalent I(III) and I(V) intermediates. The described chemistry intercepts reactive intermediates generated during aldehyde autoxidation to accomplish the oxidation of aryl iodides. The aerobically generated hypervalent iodine intermediates are utilized to couple an array of substrate functionalization chemistry to the reduction of O2. 1 Introduction 2 Chemistry of Aerobically Generated I(III) Intermediates 3 Chemistry of Aerobically Generated I(V) Intermediates 4 Conclusions. [ABSTRACT FROM AUTHOR]

A controlled aerobic oxidation of primary benzylic alcohols to the corresponding benzaldehydes by using polystyrene-poly(ethylene glycol) (PS-PEG) resin-supported triazine-based polyethyleneamine dendrimer-copper complexes [PS-PEG-TD2-Cu(II)] was developed. In particular, PS-PEG-TD2-Cu(OAc)2 efficiently catalyzed the aerobic oxidation of benzylic alcohols in the presence of a catalytic amount of TEMPO under atmospheric conditions to give the corresponding aldehydes in up to quantitative yield. The catalyst was readily recovered by simple filtration and reused four times without significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

We develop 3,5-di-tertbutylphenol as a strategic substrate for the evaluation of biomimetic Cu2 -O2 complexes intended to mimic the activity of tyrosinase. We describe a practical and scalable synthesis and validate its use in an aerobic ortho-oxygenation catalyzed by N,N'- di-tert-butylethylenediamine and [Cu(CH3 CN)4 ]PF6. [ABSTRACT FROM AUTHOR]

An iron-catalyzed aerobic oxidation of (alkyl)(aryl)azinylmethanes has been developed leading to tertiary alcohols in moderate to good yields. Hock rearrangement was identified as a major side reaction leading to a complex mixture of undesired products. Addition of thiourea sometimes allows inhibiting this side reaction and steers the reaction towards the desired products. [ABSTRACT FROM AUTHOR]

An efficient palladium-catalyzed aerobic oxidative cyclization has been developed to synthesize a variety of pyrrolizidine and indolizidine derivatives from simple aliphatic alkenyl amides in moderate to good yields. The reaction features the capability of accessing various Nheterocycles and the use of molecular oxygen (1 atm) as the green oxidant. [ABSTRACT FROM AUTHOR]

A concise and efficient aerobic oxidation and oxygenation approach for the construction of 2-aroylquinolines has been developed through copper-catalyzed annulation of anilines, acetaldehydes, and dioxygen. 2,2,6,6-Tetramethylpiperidine-1-oxyl was employed to direct the selectivity toward the desired 2-aroyl products. Molecular oxygen was used in this transformation as an environmentally benign source of oxygen. [ABSTRACT FROM AUTHOR]

Oxidative carbene catalysis is a quickly growing field in organic synthesis. However, these catalytic protocols traditionally rely on the stoichiometric addition of a high-molecular-weight oxidant, providing these reactions with a high E-factor. Here, we review efforts to replace high-molecular-weight oxidants with oxygen using a biomimetic system of coupled electron-transfer mediators. Two reactions are discussed: the aerobic oxidative esterification of aldehydes and the aerobic oxidative NHC-catalyzed enantioselective formation of dihydropyranones. 1 Introduction 2 Biomimetic Oxidations 3 Oxidative NHC Catalysis 4 NHC-Catalyzed Aerobic Oxidative Esterification of a,β-Unsaturated Aldehydes 5 Aerobic Enantioselective Synthesis of Dihydropyranones 6 Conclusion. [ABSTRACT FROM AUTHOR]

The importance of aromatic carbon-heteroatom bonds to the function of natural products, electronic materials, and pharmaceutically active compounds motivates considerable effort to improve the efficiency of constructing these bonds. Melanogenesis, which is a ubiquitous process by which organisms produce pigments, generates functional materials with high heteroatom content from simple phenolic precursors at the sole expense of reducing molecular oxygen to water. This article outlines our efforts towards the development of a tyrosinase mimic for the aerobic oxygenation of phenols that were inspired by melanogenesis, and highlights its potential to functionalize multiple aromatic C-H bonds in a single operation. [ABSTRACT FROM AUTHOR]

The copper-catalyzed asymmetric a-hydroxylation of β-ketophosphonates, using in situ generated nitrosocarbonyl compounds as electrophilic source of oxygen, is reported. The reaction merges aerobic oxidation and Lewis acid catalysis. α-Aminoxy-β-ketophosphonates were synthesized in high yields (up to 97% yield) and high enantioselectivities (up to >99% ee). [ABSTRACT FROM AUTHOR]

5-Ethyl-3-methyl-2',4':3',5'-di-O-methylenedioxy-riboflavinium perchlorate (DMRFlEt+ClO4 -) is readily derived from commercially available vitamin B2 (riboflavin) and exhibits high catalytic activity for the oxidation of organic sulfides under an oxygen atmosphere (1 atm) with the assistance of hydrazine hydrate as a reductant. This is an inexpensive, convenient, and environmentally benign method for the selective oxidative transformation of sulfides into sulfoxides. [ABSTRACT FROM AUTHOR]

A novel transition-metal-free aerobic oxidative C-C bond-cleavage method has been developed. Oxygen, the ideal oxidant, was used as the oxidizing reagent. The dimeric intermediate and 18O-isotopic-labeling control experiments partially disclosed the reaction mechanism. [ABSTRACT FROM AUTHOR]

A copper-catalyzed aerobic oxidative method for the synthesis of primary aryl amides has been developed, and the direct oxygenation of (aryl)methanamines to primary aryl amides by molecular oxygen showed convenient, practical, and environment-friendly advantages. This method will find wide application in chemistry and biology. [ABSTRACT FROM AUTHOR]

An efficient oxidation of sulfides with air catalyzed by the combination of potassium nitrate with pyridinium tribromide under transition-metal-free conditions was reported. By replacing pyridinium tribromide with bromine, the reaction system was also useful in the oxidation of alcohols. All reactions afforded the corresponding products in good to excellent yields with high chemoselectivities. [ABSTRACT FROM AUTHOR]

A novel method for conversion of N'-arylhydrazides to N',N'- diarylhydrazides via aerobic oxidation has been achieved. The aerobic reaction was performed using CuCl2 as a catalyst in NH3-H2O-MeOH to give good yields under mild conditions. The mechanism of the reaction is also discussed. [ABSTRACT FROM AUTHOR]