Difluoromethylene insertion into fluoroalkyl copper complexes.

Herein, we report the insertion of a difluoromethylene into 1,1,2,2-tetrafluoro-2-arylethyl copper complexes to synthesize extended perfluoroalkyl-bridged compounds that have various functional groups on each edge (ArCFCF(CF)R, R = arenes, halogens, alkyl, alkenyl, and benzyloxycarbonyl). Further, the one-pot syntheses of perfluoroalkyl-bridged compounds from aryl boronic acid esters were carried out.

Regioselective C-F Bond Transformations of Silyl Difluoroenolates.

Herein, we report the development of a nickel-catalyzed cross-coupling reaction of silyl difluoroenolates with aryl zinc reagents via C-F bond cleavage. Treatment of a stoichiometric amount of Ni(0)/-heterocyclic carbene (NHC) with silyl difluoroenolates in the presence of a lithium salt resulted in C-F bond cleavage to selectively afford the corresponding ()-alkenyl Ni complexes. On the basis of the observations, we developed a catalytic cross-coupling reaction that selectively delivers a single geometric isomer of a fluoroenolate.

Nickel-Catalyzed Exhaustive Hydrodefluorination of Perfluoroalkyl Arenes.

Perfluoroalkyl compounds are persistent environmental pollutants due to their strong C(sp)-F bonds. Hydrodefluorination has emerged as a potential alternative disposal method for perfluoroalkyl compounds. Although the transformation of trifluoromethyl arenes into the corresponding methyl arenes has been studied by several research groups, hydrodefluorination reactions of longer perfluoroalkyl chains remain rare.

Helix-forming aliphatic homo-δ-peptide foldamers based on the conformational restriction effects of cyclopropane.

Considerable effort has been directed toward developing artificial peptide-based foldamers. However, detailed structural analysis of δ-peptide foldamers consisting of only aliphatic δ-amino acids has not been reported. Herein, we rationally designed and stereoselectively synthesized aliphatic homo-δ-peptides forming a stable helical structure by using a chiral cyclopropane δ-amino acid as a monomer unit.

Transition and regulation mechanism of bacterial biota in Kishu saba-narezushi (mackerel narezushi) during its fermentation step.

The transition of the bacterial biota of Kishu saba-narezushi (mackerel-narezushi) in the Hidaka region of Wakayama prefecture, Japan, was analyzed using amplicon sequencing based on the V3-V4 variable region of the 16S rRNA gene. In the non-fermented sample (0 day), the major genus with the highest abundance ratio was Staphylococcus. In the early stage (fermentation for 2 days), however, the genus Lactococcus became a dominant species, and in the later stage (fermentation for 5 days), the abundance ratio of the genus Lactobacillus increased significantly.

Metabolic regulation adapting to high methanol environment in the methylotrophic yeast Ogataea methanolica.

Since methylotrophic yeasts such as Ogataea methanolica can use methanol as a sole carbon feedstock, they could be applied to produce valuable products from methanol, a next-generation energy source synthesized from natural gases, using genetic engineering tools. In this study, metabolite profiling of O. methanolica was conducted under glucose (Glc) and low and high methanol (L- and H-MeOH) conditions to show the adaptation mechanism to a H-MeOH environment.

Palladium-Catalyzed Decarboxylative Alkynylation of α-Acyloxyketones by C(sp )-O Bond Cleavage.

Palladium-catalyzed decarboxylative alkynylation of α-acyloxyketones triggered by C(sp )-O bond cleavage is disclosed. The decarboxylation strategy featuring a neutral reaction condition enabled an unprecedent catalytic alkynylation of a ketone enolate. The reaction was applied to a variety of substrates, giving desired products in good yields.

Nickel-catalyzed hydrocarboxylation of ynamides with CO and HO: observation of unexpected regioselectivity.

We describe the nickel-catalyzed hydrocarboxylation of ynamides with CO and HO to afford a variety of α-amino-α,β-unsaturated esters with high regioselectivities. The selective α-carboxylation of ynamides with this catalytic protocol is unexpected in view of the electronic bias of ynamides and is in sharp contrast to our previous study in which a stoichiometric amount of Ni(0) was used to form a β-carboxylated product exclusively. We revealed that this unexpected C-C bond formation was induced by the combination of Zn and MgBr.

Nickel-Catalyzed Intramolecular C-O Bond Formation: Synthesis of Cyclic Enol Ethers.

An efficient and exceptionally mild intramolecular nickel-catalyzed carbon-oxygen bond-forming reaction between vinyl halides and primary, secondary, and tertiary alcohols has been achieved. Zinc powder was found to be an essential additive for obtaining high catalyst turnover and yields. This operationally simple method allows direct access to cyclic vinyl ethers in high yields in a single step.

Copper-Catalyzed Reaction of Trifluoromethylketones with Aldehydes via a Copper Difluoroenolate.

A copper-catalyzed reaction of easily accessible α,α,α-trifluoromethylketones with various aldehydes affords difluoro-methylene compounds in the presence of diboron and NaOtBu. The key process of the reaction is the formation of a copper difluoroenolate by 1,2-addition of a borylcopper intermediate to α,α,α-trifluoromethylketones and subsequent β-fluoride elimination. Mechanistic studies including the isolation and characterization of a possible anionic copper alkoxide intermediate are also described.

Synthesis, characterization, and unique catalytic activities of a fluorinated nickel enolate.

We have synthesized a new nickel enolate [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] featuring fluorine atoms on the enolate moiety via B(C6F5)3-promoted C-F bond activation of α,α,α-trifluoroacetophenone. X-ray diffraction study of [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] revealed that the complex had adopted an η(3)-oxallyl coordination mode in the crystal lattice. The reaction of (t)BuNC with [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] resulted in the coordination of isocyanide to the nickel center to form a C-bound enolate complex.

Palladium-catalyzed coupling reaction of perfluoroarenes with diarylzinc compounds.

This report describes the first Pd(0)-catalyzed cross-coupling of hexafluorobenzene (C6F6) with diarylzinc compounds to give a variety of pentafluorophenyl arenes. This reaction could be applied to other perfluoroarenes, such as octafluorotoluene, pentafluoropyridine, and perfluoronaphthalene, to give the corresponding polyfluorinated coupling products. The optimal ligand in this catalytic reaction was PCy3 , and lithium iodide was indispensable as an additive for the coupling reaction.

Palladium-catalyzed coupling reactions of tetrafluoroethylene with arylzinc compounds.

Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date.