On the comparable activity in plasmonic photocatalytic and thermocatalytic oxidative homocoupling of alkynes over prereduced copper ferrite

Despite of extensive attention on the copper-based heterogeneous oxidative homocoupling of alkynes(OHA)to 1,3-diynes,the photocatalytic OHA is scarcely investigated.By screening copper-containing spinel catalysts,we discovered that a prereduced copper ferrite(CuFe2O4)not only can catalyze the thermocatalytic OHA but also is efficient for the photocatalytic OHA under visible light irradiation.It is found that the sol-gel combustion(SG)method and the partial reduction at 250 ℃ can result in the optimal CuFe2O4-SG-250 catalyst showing high activity and stability.Surface oxidized Cu2O is evidenced to be the active species for the thermocatalytic OHA,whereas metallic copper nanopaticles(CuNPs)are identified as the active sites for the photocatalytic OHA.The efficiency of photocatalytic OHA at ambient temperature is comparable to that of thermocatalytic OHA at 120 ℃,and the CuFe2O4-SG-250 catalyst can be magnetically separated and reused at least five times.The localized surface plasmon resonance effect of CuNPs contributes to visible light-induced photocatalytic OHA.

Cerium Salt Promoted Homocoupling Reaction of Dialkylanilines in Water

Highly regioselective homocoupling of N,N-dialkylanilines can be achieved in water with cerium reagents, in which various N,N,N′,N′-tetraalkylbenzidines are obtained from N,N-dialkylanilines either by direct oxidation by cerium（Ⅳ）reagents or by cerium（Ⅲ） reagents in the presence of hydroperoxide.

An Efficient and Practical Process for Pd/Cu Cocatalyzed Homocoupling Reaction of Terminal Alkynes Using Sodium Percarbonate as a Dual Reagent in Aqueous Media

A new process for the Pd/Cu co-catalyzed homocoupling reaction of terminal alkynes was developed. The reaction was carried out in aqueous media with sodium percarbonate as both a clean oxidant and a base. Meanwhile, a palladium complex immobilized on a synthetic PS-PEG400-PPh2 resin was used as the catalyst, which may be recovered by simple filtration and reused for several times with high activity.

Homocoupling of Aryl Iodides Catalyzed by Cyclopalladated Complexes of Tertiary Arylamines

Homocoupling of aryl iodides catalyzed by cyclopalladated complexes of tertiary arylamines gives symmetric biaryls with good yields in DMA or ionic liquid [Bmim]BF4. This catalytic alternative of the Ullmann reaction has proved to be sensitive to both electronic and steric factors of substrates.

Homocoupling of Polyfluorovinylstannanes Mediated by a Novel Combination of CuCl/2,2'-Dipyridyl. Stereospecific Syn-thesis of Polyfluorinated Alka-2,4-dienes

A new homocoupling methodology mediated by a novel combination of CuCl-2,2'-dipyridyl and its application to the synthesis of substituted polyfluorinated alka-2,4-dienes are described.

Homocoupling of Aryl Bromides Catalyzed by Nickel Chloride in Pyridine

Pyridine was used as a solvent for homocoupling of aryl bromides catalyzed by nickel chloride/triarylphosphine in the presence of zinc and recycled easily. Triphenylphosphine was the best ligand for nickel in this coupling reaction.

Synthesis of [2,2’]Bifuranyl-5,5’-dicarboxylic Acid Esters Wd Reductive Homocoupling of 5-Bromofuran-2-carboxylates Using Alcohols as Reductants

Herein,we describe an environmentally benign and cost.efective protocol for the synthesis of valuable bifuranyl dicarboylates,starting with a-bromination of readily accessible furan-2-carboylates by LiBr and K_(2)S_(2)O_(8).Furthermore,the bromination intermediate product 5-bromofuran-2-carboxylates were then conducted in a palladium-catalyzed reductive homocoupling reactions in the pres-ence of alcohols to afford bifuranyl dicarboxylates.One of the final products in this protocol,[2,2']bifuran-5,5'-dicarboxylic acid es-ters,are essential monomers of poly(ethylene bifuranoate),which can be served as an green and versatile alternative polymer for traditional poly(ethylene terephthalate)that is currently common in technical plastics.

Palladium-catalyzed oxidative homocoupling of 2-arylquinazolinones

Pd-catalyzed oxidative homocoupling of 2-arylquinazolinones was successfully developed for the direct construction of biaryls via C—H bond activation.New well-defined structure that possessed two quinazolinone units was obtained with high efficiency and atomic economy.The protocols offer an efficient approach to the synthetically useful and functionalized biaryls in good yields using quinazolinone as a directing group.

Phenazine-based supramolecular photosensitizing assemblies:A“smart”selectivity control on catalytic activity of Pd(Ⅱ)nanoparticles

Photosensitizing supramolecular assemblies based on a phenazine derivative(PPA)have been developed,which show a strong affinity toward Pd2+ions to generate supramolecular ensemble PPA@Pd nanoparticles(NPs).The PPA@Pd NPs catalyse the Suzuki cross-coupled reaction under mild conditions(aerial conditions,mixed aqueous media,and visible light radiations).Although PPA@Pd NPs exhibit a strong affinity for arylboronic acid and could catalyse homocoupling of arylboronic acid,the preference of PPA assemblies for aryl halide directed the course of reactions toward the formation of cross-coupled products.The electron-rich PPA assemblies not only facilitate the oxidative addition step through photoinduced electron transfer to Pd^(2+)ions but also bring the reactants closer to the catalytic sites by selective interactions with aryl halides in the presence of arylboronic acid under visible light irradiation.The efficiency of PPA@Pd NPs to catalyse the Suzuki crosscoupled reaction has been demonstrated for the synthesis of unsymmetrically substituted terphenyl derivatives.

Ligand-free Copper-catalyzed Synthesis of Symmetrical Diynes from 1,1-Dibromo-1 -alkenes

Symmetrical diynes were synthesized by ligand-free copper-catalyzed homocoupling reaction of 1,1-dibromo-1- alkenes using a DBU/DMSO system at room temperature in good to excellent yields.

Efficient Construction of Highly-fused Diperylene Bismides by Cu/Oxalic Diamide-promoted Zipper-mode Double C—H Activation

Copper/oxalic diamide-promoted dimerization of tetrachlorinated perylene bisimide to construct highly-fused diperylene bisimides through Ullmann coupling and zipper-mode double C—H activation has been developed in this study.This one-step reaction combining homocoupling with C—H activation proceeded smoothly under the action of inexpensive metal-ligand system.This protocol is expected to expand the available synthetic tools for condensed ring systems of perylene bisimide(PBIs).

Mechanistic elucidation of the role of metal oxidation states in nickel mediated electrocatalytic coupling of benzyl halides

We present the mechanistic understanding of an electrochemically-driven nickel-catalyzed coupling reaction.Computational analysis reveals that the spin density is mostly residing on the nickel(Ni)center when Ni^(II) is reduced to NiI.Ni-mediated halogen atom abstraction through outer-sphere electron-transfer pathway to yield coupling products under mild conditions is demonstrated.Importantly,we have elucidated the role of Ni^(I) and Ni^(0) for successive coupling of benzyl bromide and benzyl chloride derivatives,respectively,to corresponding bibenzyl products.The Ni-catalyst bearing a PN^(3) P-ligand is an effective catalyst,producing a strong ligand effect on the reactivity and selectivity for the homocoupling reactions.