Phosphinoquinoline supported CoII, NiII, and FeII complexes: divergent behaviour upon reduction.

The reduction of [CoLBr2], a CoII complex supported by a diisopropylphosphinoquinoline (L) ligand, induced a ligand coupling giving access to a (PNNP) supported CoII complex which was isolated in 70% yield. This complex was formed using a minimum of 2 equivalents of a reductant (either Mn or KC8). The fate of [CoLBr2] in the presence of 1 equivalent of a reductant was more difficult to study; nevertheless, a CoI complex was characterised in the solid state. In order to determine whether this ligand coupling could occur with other 3d metals, L supported FeII and NiII complexes were synthesised. While no compound could be identified upon reduction of [FeLBr2], both [NiLBr2] and [NiL2Br](Br) led to the reduction at the metal center allowing the isolation of an original Ni0 trimer in a satisfactory yield. This study shows the different behaviours of these 3d metal complexes in the presence of a reductant.

Cobalt-Catalyzed Reductive Cross-Coupling To Construct Csp3-Csp3 Bonds via Csp3-S and Csp3-X Bonds Activation.

A cross-electrophilic coupling of benzyl sulfonium salts with alkyl halides forming Csp3-Csp3 bonds is described by using a Co-based catalytic system. The activation of the stable Csp3-S bond of benzyl sulfonium salts under mild reaction conditions leads to various functionalized alkyl derivatives. Preliminary mechanistic studies suggest the involvement of alkyl radicals formed from both alkyl halides and benzyl sulfoniums through a single electron transfer.

Cobalt Complexes Supported by Phosphinoquinoline Ligands for the Catalyzed Hydrosilylation of Carbonyl Compounds.

P,N phosphinoquinoline based ligands differing by the nature of the phosphorus substituent (i Pr, Ph) were employed to synthesize a series of cobalt(II) complexes ([LCoBr2 ], [L2 CoBr](PF6 ) and [L'2 CoBr](PF6 )). The latter were obtained in high yield and characterized among others by X-ray analysis and elemental analysis. Complex [L2 CoBr](PF6 ) showed a very good catalytic activity for the hydrosilylation of various ketones. The catalysis proceeds at a low catalytic loading (1 mol %) with only 1 equivalent of Ph2 SiH2 in mild conditions and was efficient with aliphatic or aromatic ketones giving moderate to excellent yields of the corresponding silylated ether.

Cobalt Bromide-Catalyzed Negishi-Type Cross-Coupling of Amides.

Herein, we describe a novel Negishi-type cross-coupling of amides employing only cobalt bromide salt as the catalyst. This original reaction is highly tolerant to various glutarimide amides as well as organozinc coupling partners. These conditions also allow the performance of the cross-coupling reaction in an eco-compatible solvent such as ethyl acetate on a large scale.

CO2 activation by electrogenerated divalent samarium for aryl halide carboxylation.

The reductive carboxylation of aryl halides has been investigated using a samarium electrode as a sacrificial anode to yield the corresponding benzoic acids, providing a smooth strategy for CO2 activation. Carboxylation occurred after an efficient reduction of carbon dioxide mediated by an electrogenerated Sm(ii)-complex acting as a strong monoelectronic reductive reagent.

CoI -Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines.

The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr2 /1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.

Control of the dual emission from a thermally activated delayed fluorescence emitter containing phenothiazine units in organic light-emitting diodes.

The development of single-component organic dual light-emitting molecules is of interest for a range of applications including white organic light-emitting diodes. Herein, a new thermally-activated delayed fluorescent molecule containing 4,6-bis-phenyl phenothiazine as donor units and 2-thiophene-1,3,5-triazine as acceptor unit was synthesized using a simple cost-effective method. This compound shows two stable molecular conformations due to the presence of the phenothiazine units in its molecular structure. These conformers exhibit different photophysical properties in both solution and thin films. The electroluminescence properties of this novel emitter were then examined in organic light-emitting diodes and the results provide useful insights into the influence of the device architecture on the dual emission characteristics. The experimental results were consistent with the optical simulations and the optimized architecture led to the fabrication of electroluminescent devices with an external quantum efficiency of 11.5% and a maximum luminance value of 10 370 cd m-2.

N-Boc-Amides in Cross-Coupling Reactions.

Since 2015, the use of amides as electrophilic partners in cross-coupling reactions has experienced exponential growth. Diverse amide derivatives have been studied and among them N-Boc-amides have shown good activities towards various cross-coupling reactions and presents, in our view, an important synthetic usefulness. This review describes the recent developments of these chemical transformations involving N-Boc-amides.

Synthesis by a Cost-Effective Method and Electroluminescence of a Novel Efficient Yellowish-Green Thermally Activated Delayed Fluorescent Molecule.

A new thermally activated delayed fluorescent molecule, TRZ 3(Ph-PTZ), containing three phenothiazines as donor units and a 2,4,6-triphenyl-1,3,5-triazine as the acceptor unit was synthesized using a simple cost-effective method based on a cobalt catalyzed cross-coupling. This compound was tested in organic light-emitting diodes and was found to show superior yellowish-green electroluminescence performance with a maximum external quantum efficiency of 17.4% and a maximum luminance value of 7430 cd/m2.

Cobalt-Catalyzed Esterification of Amides.

The first cobalt-catalyzed amide activation of N-Boc-amides, and their conversion into esters, is reported here. This new methodology presents a very practical process that does not require an inert atmosphere, uses an inexpensive cobalt catalyst, and proceeds under mild reaction conditions. This catalytic system has a broad substrate scope and has been shown to be highly efficient, with catalyst loadings as low as 1 mol %.

Cobalt-Catalyzed Enantio- and Diastereoselective Intramolecular Hydroacylation of Trisubstituted Alkenes.

Enantio- and diastereoselective synthesis of trans-2,3-disubstituted indanones is achieved by intramolecular hydroacylation of 2-alkenylbenzaldehydes bearing trisubstituted alkenyl groups under cobalt-chiral diphosphine catalysis. Notably, a high level of enantioselectivity is induced regardless of the stereochemistry (E/Z ratio) of the alkenyl group of the starting material. Deuterium-labeling experiments shed light on the productive reaction pathways of the E- and Z-isomers.

Cobalt-Catalyzed Carbozincation of Ynamides.

An original cobalt-catalyzed ynamide carbozincation leading mainly to diverse 3-aryl enamides with mild reaction conditions and good functional-group tolerance has been developed. This reaction displays an excellent regio- and total stereoselectivity and opens the way to appealing synthetic applications. Moreover, this approach allows the selective synthesis of biologically relevant 3,5-disubstituted oxazolone frameworks.

Cobalt-Catalyzed Reductive Cross-Coupling Between Styryl and Benzyl Halides.

A simple and efficient protocol for the direct reductive cross-coupling between alkenyl and benzyl halides using a Co/Mn system has been developed. This reaction proceeds smoothly in the presence of [CoBr2 (PPh3 )2 ] as the catalyst, with NaI as an additive in acetonitrile with a broad scope of functionalized alkenyl and benzyl halides. Different functional groups are tolerated on both coupling partners, thus, significantly extending the general scope of transition-metal-catalyzed benzylation of alkenyl halides. Moderate to excellent yields were also obtained. From a mechanistic point of view, a radical chain mechanism was proposed. This reaction is stereospecific and some studies suggest the retention of the double-bond configuration.

Characterization of the ultraviolet-visible photoproducts of thiophanate-methyl using high performance liquid chromatography coupled with high resolution tandem mass spectrometry-Detection in grapes and tomatoes.

UV-visible irradiation of thiophanate-methyl (TM) led to the formation of nine photoproducts that were characterized by high performance liquid chromatography coupled with high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Although carbendazime has been reported in the literature to be the major metabolite and photoproduct of thiophanate-methyl, it was not detected in this study. However, an isomer of carbendazime referred as PP2, which was unambiguously characterized owing to CID experiments, was found in great abundance. Grape berries and cherry tomatoes treated with aqueous solutions of thiophanate-methyl were submitted to irradiation under laboratory conditions. TM and PP2 were detected in both peel and flesh of berries. The ability of TM and PP2 to pass through the fruit skin has been shown to be highly compound and matrix dependent. In vitro bioassays on Vibrio fischeri bacteria showed that the global ecotoxicity of the TM solution increases significantly with the irradiation time. PP2 should likely contribute to this ecotoxicity enhancement since in silico estimations for Daphnia magna provide a LC50 value seven times lower for PP2 than for the parent molecule.

A practical cobalt-catalyzed cross-coupling of benzylic zinc reagents with aryl and heteroaryl bromides or chlorides.

A catalytic system consisting of 5 mol% CoCl2 and 10 mol% isoquinoline allows a convenient cross-coupling of benzylic zinc reagents with various aryl and heteroaryl bromides or chlorides leading to polyfunctionalized diaryl- and aryl-heteroaryl-methane derivatives.

"(Diphosphine)Nickel"-catalyzed negishi cross-coupling: an experimental and theoretical study.

The use of a strongly donating "(bis-dialkylphosphine)Ni" fragment promotes the catalytic coupling of a large range of ArCl and ArZnCl derivatives under mild conditions. Stoichiometric mechanistic investigations and DFT calculations prove that a Ni(0) /Ni(II) cycle is operative in this system.

Reductive cross-coupling reactions between two electrophiles.

Reductive cross-electrophile coupling reactions have recently been developed to a versatile and sustainable synthetic tool for selective C-C bond formation. The employment of cheap and abundant electrophiles avoids the pre-formation and handling of organometallic reagents. In situ reductive coupling is effected in the presence of a transition-metal catalyst (Ni, Co, Pd, Fe) and a suitable metallic reductant (Mn, Zn, Mg). This Concept article assesses the current state of the art and summarizes recent protocols with various combinations of alkyl, alkenyl, allyl, and aryl reagents and highlights key mechanistic studies.

Cobalt-catalyzed electrophilic amination of arylzincs with N-chloroamines.

Roles reversed: An efficient cobalt-catalyzed electrophilic amination of arylzinc reagents has been achieved. A variety of functionalized arylzincs and N-chloroamines were coupled under mild conditions (see scheme). Both secondary and tertiary arylamines were obtained in moderate to excellent yields.

Cobalt-catalysed synthesis of highly substituted styrene derivatives via arylzincation of alkynes.

A new two-step procedure was developed by carbozincation of internal and terminal alkynes to synthesise highly functionalised vinylzinc bromides. Various tri and tetrasubstituted alkenes were prepared in moderate to good yields under mild reaction conditions in a stereo-selective manner. This methodology represents an interesting alternative to previously known methods.

Cobalt-catalyzed vinylation of aromatic halides using ß-halostyrene: experimental and DFT studies.

A new protocol for the direct cobalt-catalyzed vinylation of aryl halides using ß-halostyrene has been developed in order to form functionalized stilbenes. A variety of aromatic halides featuring different reactive group were employed. This method proceeded smoothly with a total retention of the double bond configuration in the presence of triphenylphosphine as ligand. Preliminary DFT calculations rationalize these results and proposed a reaction pathway in agreement with the experimental conditions. This procedure offers a new route to the stereoselective synthesis of stilbenes.