Synthesis of 3-substituted 2-oxindoles from secondary α-bromo-propionanilides palladium-catalyzed intramolecular cyclization.

In contrast to aromatic halides, coupling reactions involving oxidative addition of alkyl halides, especially secondary or tertiary halides, to transition metals tend to be more challenging. Herein a palladium-catalyzed intramolecular cyclization of α-bromo-propionanilides has been developed, delivering a series of 3-substituted 2-oxindoles in high yields. The method features easy to prepare starting materials, broad substrate scope and excellent functional group tolerance.

Umpolung carbonyls enable direct allylation and olefination of carbohydrates.

Mother Nature has its own arts to build a vast number of carbohydrates; however, there is still a lack of tools for selective functionalization of native carbohydrates through C─C bond formation. Such a long-standing challenge for the synthetic community lies into the intrinsic problems related to the innate properties of carbohydrates, e.g.

Synergistic Relay Reactions To Achieve Redox-Neutral α-Alkylations of Olefinic Alcohols with Ruthenium(II) Catalysis.

Herein, we report a ruthenium-catalyzed redox-neutral α-alkylation of unsaturated alcohols based on a synergistic relay process involving olefin isomerization (chain walking) and umpolung hydrazone addition, which takes advantage of the interaction between the two rather inefficient individual reaction steps to enable an efficient overall process. This transformation shows the compatibility of hydrazone-type "carbanions" and active protons in a one-pot reaction, and at the same time achieves the first Grignard-type nucleophilic addition using olefinic alcohols as latent carbonyl groups, providing a higher yield of the corresponding secondary alcohol than the classical hydrazone addition to aldehydes does. A broad scope of unsaturated alcohols and hydrazones, including some complex structures, can be successfully employed in this reaction, which shows the versatility of this approach and its suitability as an alternative, efficient means for the generation of secondary and tertiary alcohols.

Oxidation of Enones for Regioselective [3+2] Cycloaddition through γ-Enone Radical Intermediates.

Invited for the cover of this issue is the group of Min Zhang and Weiping Su at the Fujian Institute of Research on the Structure of Matter. Read the full text of the article at 10.1002/chem.

Oxidation of Enones for Regioselective [3+2] Cycloaddition through γ-Enone Radical Intermediates.

Herein, an oxidization reaction of enones with a Cu complex that leads to a new type of regioselective [3+2] cycloaddition is reported. Highly functionalized cyclopentenes and spirocyclic compounds are obtained in moderate-to-good yields. This cycloaddition reaction occurred through the formation of γ-enone radicals, providing a rarely explored reactivity pattern for enones.

On the blistering of thermo-sensitive hydrogel: the volume phase transition and mechanical instability.

This paper explores the physical mechanisms responsible for the appearance of small blisters on the surface of temperature sensitive hydrogels as they deswell rapidly during their volume phase transition. For this, we develop a numerical model that couples the processes of hydrogel deswelling and blister growth due to the existence of a thin quasi-impermeable layer on its surface. The model points out that blister inflation originates at defects point under the gel's surface, under the effect of the increasing osmotic pressure in the gel as it undergoes its phase transition.

Photo-driven redox-neutral decarboxylative carbon-hydrogen trifluoromethylation of (hetero)arenes with trifluoroacetic acid.

Catalytic oxidative C-H bond functionalization reactions that proceed without requiring stoichiometric amounts of external oxidants or pre-functionalized oxidizing reagents could maximize the atom- and step-economy in chemical syntheses. However, such a transformation remains elusive. Here, we report that a photo-driven catalytic process enables decarboxylative C-H trifluoromethylation of (hetero)arenes with trifluoroacetic acid as a trifluoromethyl source in good yields in the presence of an external oxidant in far lower than stoichiometric amounts (for example, 0.

Ambient-Temperature Ortho C-H Arylation of Benzoic Acids with Aryl Iodides with Ligand-Supported Palladium Catalyst.

The ambient-temperature ortho C-H arylation of electron-deficient benzoic acids with aryl iodides has been achieved by using an Ac-Ile-OH-supported Pd catalyst. A wide range of unactivated benzoic acids could cross-couple an array of aryl iodides in moderate to excellent yields. The choice of HFIP as a solvent is crucial to realizing the mild C-H arylation, and the beneficial effect of the ligand on the reaction likely stems from the accelerated C-H activation process and the improved catalyst lifetime.

Silver-catalyzed arylation of (hetero)arenes by oxidative decarboxylation of aromatic carboxylic acids.

A long-standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver-catalyzed intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron-deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho-substituted aromatic carboxylic acids, which were a limitation of previously reported methods.

Pd/PR3-catalyzed cross-coupling of aromatic carboxylic acids with electron-deficient polyfluoroarenes via combination of decarboxylation with sp2 C-H cleavage.

By using Pd(TFA)(2)/PCy(3) as a catalyst, a broad range of aromatic carboxylic acids, including heteroaromatic carboxylic acids, efficiently underwent decarboxylative coupling with an array of polyfluoroarenes in the presence of stoichiometric amount of silver salts to generate biaryls. Silver salts were adjusted to the reactivity of aromatic carboxylic acids to efficiently suppress the protodecarboxylation and therefore improve decarboxylative cross-couplings. It was established that the palladium complex containing the PCy(3) ligand was capable of catalyzing the decarboxylation of electron-rich aromatic carboxylic acids, and silver salts promoted the decarboxylation of both electron-rich and -deficient ones.

Pd-catalyzed decarboxylative arylation of silyl enol ester sp3 β-C-H bond under aerobic conditions.

Pd-catalyzed aerobic oxidative coupling of various benzoic acids with silyl enol esters proceeds via a combination of decarboxylation with sp(3) β-C-H bond activation to give Heck-type products. Mechanistic studies reveal this coupling involves in situ generation of olefin from aerobic oxidation of silyl enolate, followed by decarboxylative Heck coupling.

Pd-catalyzed cross-coupling of carboxylic acids with nitroethane via combination of decarboxylation and dehydrogenation.

An unexpected coupling reaction of arene carboxylic acid with nitroethane via a combination of decarboxylation and dehydrogenation is described. The method provides exclusively (E)-beta-nitrostyrenes.

Copper-catalyzed direct alkynylation of electron-deficient polyfluoroarenes with terminal alkynes using O2 as an oxidant.

A copper-catalyzed direct alkynylation of electron-deficient polyfluoroarenes with a wide range of terminal alkynes is realized for the first time. The reaction proceeds under mild conditions with O(2) as an oxidant.

Palladium-catalyzed direct arylation of electron-deficient polyfluoroarenes with arylboronic acids.

The palladium-catalyzed direct arylation of electron-deficient arenes that contain two or more fluorine groups with arylboronic acids was realized. The key to achieving a broad substrate scope with respect to both polyfluorobenzenes and arylboronic acids is the choice of bases depending on acidities of polyfluorobenzenes.

Pd(O2CCF3)2/benzoquinone: a versatile catalyst system for the decarboxylative olefination of arene carboxylic acids.

A versatile palladium catalyst system was developed to effect the decarboxylative Heck coupling of a variety of arenecarboxylic acids with a wide range of olefins. The key to obtaining the efficient catalyst system is the use of 1-adamatanecarboxylic acid as additive. Alkyl-substituted olefins with coordinating groups were observed to provide significantly improved regioselectivity compared with other alkyl-substituted olefins lacking coordinating groups, and the acetate group of allylic ester was also tolerated in this reaction.

Wirelike dinuclear ruthenium complexes connected by bis(ethynyl)oligothiophene.

Preparation and characterization of a series of rodlike binuclear ruthenium polyynediyl complexes capped with redox-active organometallic fragments [(bph)(PPh3)2Ru]+ (bph=N-(benzoyl)-N'-(picolinylidene)-hydrazine) or [(Phtpy)(PPh3)2Ru]2+ (Phtpy=4'-phenyl-2,2':6',2' '-terpyridine) have been carried out. The length of the molecular rods is extended by successive insertion of 2,5-thiophene or 1,4-phenylene spacers in the bridging ligands. Oxidation of thiophene-containing Ru2II,II complexes induces isolation of stable Ru2II,III or Ru2III,III species.

Sensitive determination of nucleic acids using organic nanoparticle fluorescence probes.

This paper describes the preparation of organic nanoparticles by reprecipitation method under sonication and vigorous stirring. Transmission electron microscopy (TEM) was used to characterize the size and size distribution of the luminescent nanoparticles. Their average diameter was about 25 nm with a size variation of +/-18%.