Several new mono- and difluoromethylation reactions of cinnamic acids using an Eosin Y catalytic system are reported. An efficient alkene fluoromethylation of α,β-unsaturated carboxylic acids was accomplished under ambient temperature and metal-free conditions, with a wide range of functional group tolerance. A mechanism that involves a radical process is proposed for this reaction.

The use of a dual palladium/organic photoredox catalytic system enables the directed arylation of arenes with aryldiazonium salts with a broad substrate scope at room temperature under mild reaction conditions. This study thus serves as not only an alternative route for the biaryl motifs but also a new example for the application of an organic photoredox catalyst.

•Mild and operationally simple reaction condition was used.•An organo-photoredox catalyst was used in this developed protocol.•A radical reaction mechanism is proposed.9,10-Dihydro-10-methylacridine (AcrH2), a NADH coenzyme model compound, as an organo-photoredox catalyst is demonstrated for the cross-coupling of aryl diazonium salts with (hetero)arenes. Under mild and operationally simple conditions, this new photocatalytic protocol has been applied to arylation of a wide variety of (hetero)arenes and tolerates various functional groups.A NADH coenzyme model compound (AcrH2), as an organo-photoredox catalyst is demonstrated for the cross-coupling of aryl diazonium salts with (hetero)arenes under mild and operationally simple conditions.Download high-res image (108KB)Download full-size image

An efficient method for Cu-catalyzed decarboxylative trifluoromethylation of β-ketoacids to achieve α-trifluoromethyl ketones was developed. A wide variety of synthetically useful α-trifluoromethyl ketones were obtained in modest to good yields under mild reaction conditions. The present method also exhibits good functional-group compatibility.

A photoredox catalytic method has been developed for the direct C2 alkylation of pyridine N-oxides. This reaction is compatible with a range of synthetically relevant functional groups for providing efficient synthesis of a variety of C2-alkylated pyridine N-oxides under mild conditions. Mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.

A copper(I)-catalyzed ring-opening cyanation of cyclopropanols was developed. The reaction provides an alternative method to achieve β-cyano ketones efficiently. This reaction exhibits good functional group compatibility under mild conditions and can be scaled up to the gram scale. Preliminary mechanistic studies suggest that the reaction might go through a free radical process.

A general and efficient method for the direct alkynylation of unactivated C(sp3)–H bonds under metal-free conditions is described. The reaction performs smoothly under mild conditions and shows excellent functional-group tolerance. Initial mechanistic investigation indicates that the reaction may involve a radical pathway.

A photoredox catalytic method was developed for the direct cyanation of alkyltrifluoroborates. This reaction provides a new and useful transformation of the easily available alkyltrifluoroborates. The photocatalytic reaction can tolerate a variety of functional groups with mild reaction conditions. Mechanistic investigations are consistent with the present reaction following a radical pathway.

A novel catalyst-free decarboxylative amidation of α-keto acids with amines under mild conditions has been developed. Advantages of the new protocol include avoidance of metal catalysts and high levels of functional group tolerance. In addition, the reaction can be scaled up and shows high chemoselectivity. Preliminary mechanistic studies suggest that singlet oxygen, generated from oxygen under irradiation, is the key promoter for this catalyst-free transformation.

The KI-catalyzed reaction of acetone with aromatic carboxylic acids is achieved, leading to α-acyloxycarbonyl compounds in good to excellent yields under mild reaction conditions. The present method exhibits good functional-group compatibility. Notably, this reaction system is even suitable for cinnamic acid, 3-phenylpropiolic acid and 4-phenylbutanoic acid. A kinetic isotope effect (KIE) study indicates that C–H cleavage of the acetone is the rate-limiting step in the catalytic cycle.

In this work, Pd–Cu/γ-Al2O3 is prepared by the impregnation method and investigated for selective oxygenization of cyclopentene to cyclopentanone. A series of bimetallic Pd–Cu/γ-Al2O3 nanocatalysts were prepared and the structures characterized by XRD, XPS and TEM. We determined that the obtained Pd–Cu/γ-Al2O3 (molar ratio Pd:Cu = 5:1) was an efficient catalyst for the oxygenization of cyclopentene to cyclopentanone with >95% selectivity and >85% conversion (100 °C, 1 MPa initial O2 pressure, 7 h).A series of γ-Al2O3 supported Pd–Cu bimetallic nanocatalysts are investigated for the selective oxygenization of cyclopentene to cyclopentanone.

An effective strategy for synthesis of Cu nanoparticles is designed, these nanoparticles have high catalytic activity in conjugate addition of B2(pin)2 and α,β-unsaturated ketones. The reaction of protodeboration can proceed with adding NaOtBu. In this way, a new method to reduce the conjugated alkenes of α,β-unsaturated ketones is developed with organoboranes as intermediates. Cu nanocrystals also have excellent performance in gram-scale reaction and recycling experiment. A possible mechanism is proposed.

The cross-coupling reaction of allyl boron ester with 1°/2°/3°-halogenated alkanes in the presence of copper has been developed for the first time, which provides a mild and efficient method for the construction of saturated C(sp3)–C(sp3) bonds. This protocol shows excellent compatibility with the nonactivated primary, secondary, and even tertiary halogenated alkanes under mild conditions.

A copper-catalysed ring-opening trifluoromethylation reaction of cyclopropanols has been developed. Various β-trifluoromethyl ketones are obtained in good to excellent yields under mild reaction conditions. The present method also exhibits good functional-group compatibility. The mechanism of this new ring-opening trifluoromethylation reaction was investigated by radical trapping reactions.

Furfural is a biomass-based bulk chemical and its derivatives have potential applications as renewable fuels and chemicals. A water-tolerant and stable solid acid catalyst modified hydrated tantalum oxide (TA-p) was developed for catalytic conversion of D-xylose to furfural in water–organic solvent biphasic system. This process was performed both in a batch reactor and a continuous fixed-bed reactor. In the batch process, D-xylose conversion and furfural yield were significantly affected by the organic solvent, reaction temperature and reaction time. 1-Butanol, which could be obtained through the fermentation of biomass-based carbohydrates, was selected as organic phase and the highest furfural yield of 59% was achieved with D-xylose conversion of 96% at 180 °C in the continuous process. Moreover, the long-time stability test for 80 h under the optimal conditions showed the excellent stability of TA-p catalyst.

Several γ-Al2O3 supported Pd–Ni bimetallic nanocatalysts (Pd–Ni (x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd–Ni/Al2O3 samples were confirmed to generate Pd–Ni bimetallic nanoparticles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd–Ni (1:1)/Al2O3 (PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.γ-Al2O3 supported Pd–Ni bimetallic nanocatalysts were used for selective hydrogenation of cyclopentadiene to cyclopentene.

An iron(III)-catalyzed selective oxidation of 5-HMF to 2,5-DFF in air at room temperature was developed. This approach gives 2,5-DFF with good selectivity and yields. Additionally, a two-step process was developed for the oxidation of 2,5-DFF to 2,5-FDCA at remarkably high substrate concentrations. This work demonstrates unequivocally the great potential of iron as a cheap and earth-abundant catalyst for the development of new protocols for the conversion of biomass to value-added chemicals.An iron(III)-catalyzed selective oxidation of 5-HMF to 2,5-DFF in air at room temperature was developed. This work demonstrates unequivocally the great potential of iron as a cheap and earth-abundant catalyst for the development of new protocols for the conversion of biomass to value-added chemicals.

Taking advantage of Pd(OAc)2-catalyzed dinitration reactions with Bi(NO3)3·5H2O in trifluoroethanol (TFE) and trifluoroacetic acid (TFA), we have developed an efficient and practical method for the synthesis of secondary dinitro-aromatic amines. The products could be applied to the preparation of 5-amine-N-methyl-benzimidazolone, the azo-dyes, economic advantages. The method has also been expanded to the dinitration reaction of some tertiary aromatic amines.

Silver-catalyzed C(sp2)–H functionalization/C–O cyclization has been developed. The scalable reaction proceeds at room temperature in an open flask. The present method exhibits good functional-group compatibility because of the mild reaction conditions. Using a AgNO3 catalyst and a (NH4)2S2O8 oxidant in CH2Cl2/H2O solvent, various lactones are obtained in good to excellent yields. A kinetic isotope effect (KIE) study indicates that the reaction may occur via a radical process.

A transition-metal-free synthetic method of various ynones via decarboxylative alkynylation of α-keto acids is described. The reaction is carried out under mild conditions and exhibits remarkable tolerance of functional groups. The mechanism of a radical process is proposed in the reaction.

An efficient Cu-promoted reductive coupling of aryl iodides with 1,1,1-trifluoro-2-iodoethane has been developed. This reaction could occur in good yields under milder conditions as compared with previous studies. The reaction tolerated nitro, formyl, ester, ether, carbonyl, sulfonyl, and even azo groups.

A silver-mediated decarboxylative C–S cross-coupling reaction of aliphatic carboxylic acid is described. This reaction occurs smoothly under mild conditions and shows good tolerance of functional groups. It provides an alternative approach for the synthesis of alkyl aryl sulfides.

The protocol of the reductive amination of aromatic aldehydes using ammonium formate and Hantzsch ester is described. It is a mild, convenient, acid- and catalyst-free system applied for the synthesis of both symmetric and asymmetric aromatic secondary amines.

This work reports a hard self-template method to synthesize core/shell like Fe3O4@C microparticles, in which the Pd nanocrystals can be alternatively incorporated into the carbon shells. The Fe3O4@polyaniline core/shell microspheres were first synthesized as the precursor by in situ polymerization of aniline onto the surface of the Fe3O4 microspheres. In a subsequent carbonization of the precursor under a vacuum oven, the Fe3O4 core was preserved and the polyaniline shell transferred into carbon shells enveloping the magnetic sphere, forming magnetic Fe3O4@C microspheres. The Pd ions could be impregnated into the polyaniline shell, and thus the obtained composites were transformed into Fe3O4@C/Pd microspheres under the same vacuum heating progress. The as-obtained system demonstrates superparamagnetic characteristics, which would benefit its potential application in nanocatalysts. This strategy provides an efficient approach for tailoring core/shell materials with desired functionalities and structures by adjusting the precursors and structure-directing agents.

An efficient Cu-catalyzed intramolecular hydroarylation reaction of alkynes has been developed. The reaction is accomplished under mild conditions and shows good tolerance to both electron-rich and electron-deficient aryl nucleophiles. A series of aryl, heteroaryl, alkyl, and even N-group attached alkynes are all suitable substrates for the intramolecular hydroarylation.

A 2,2-azobis(isobutyronitrile) (AIBN) catalyzed oxidative cleavage of gem-disubstituted alkenes with molecular oxygen as the oxidant has been described. Carbonyl compounds were obtained as the desired products in high yield under mild conditions. Based on previous documents and current experimental results, a relatively reasonable mechanism is proposed.

Cu-catalyzed decarboxylative alkynylation of quaternary α-cyano acetate salts with alkynyl bromides and alkynyl chlorides is described. This new reaction can be used for preparing functionalized butynenitrile derivatives.

LiOtBu was found to efficiently promote the α-alkylation reaction of ketones with primary alcohols, without the addition of any transition metal catalyst.

A biomimetic method has been developed to transform α,β-epoxy ketones or 1,2-diketones into corresponding β-hydroxy ketones or α-hydroxy ketones using a catalytic amount of BNAH or BNA+Br−. The regeneration of BNAH or BNA+Br− is achieved by a mixture of HCOOH/Et3N. A radical mechanism is proposed to explain these observations.Figure optionsDownload full-size imageDownload as PowerPoint slide

A new type of water-soluble polymer-supported NADH co-enzyme model-PAA (polyacrylic acid)-supported Hantzsch 1,4-dihydropyridine ester (PAA–HEH) was designed and synthesized. Catalytic amount of the supported reagent was used in the hydrogenation of α,β-epoxy ketones to the corresponding β-hydroxy ketones and showed great catalytic efficiency in the reduction reaction. This PAA–HEH was an optimal potential for recycling use.

A novel magnetically recoverable organic hydride compound was successfully constructed by using silica-coated magnetic nanoparticles as a support. An as-prepared magnetic organic hydride compound, BNAH (1-benzyl-1,4-dihydronicotinamide), showed efficient activity in the catalytic reduction of α,β-epoxy ketones. After reaction, the magnetic nanoparticle-supported BNAH can be separated by simple magnetic separation which made the separation of the product easier.

CuI nanoparticles efficiently catalyzed the C–S cross coupling of aryl and alkyl thiols with aryl halides in the absence of ligands on water under mild conditions. A wide range of diaryl sulfides and aryl alkyl sulfides are synthesized in good to excellent yields utilizing this protocol. This procedure is particularly noteworthy given its mild conditions, avoiding the undesired formation of disulfides through oxidation of thiols. The recovery and successful reutilization of the catalyst is described. Furthermore, the directed synthesis of bisarylated product is presented.

A novel synthetic protocol for 2-aminophenyl sulfide derivatives via the reactions of benzothiazole with aryl iodides was reported for the first time. The reactions were catalyzed by CuCl with tetrabutylammonium hydroxide as the base and water as the solvent without ligand at 50 °C or room temperature. A variety of aryl iodides underwent the C–S cross-coupling reaction with benzothiazole to afford smoothly the corresponding products in excellent yield.

Graphene/acridine (G-Acr) hybrid structures were synthesized through covalent functionalization of graphene oxide with 9-(4-aminophenyl)acridine (APA) and its derivatives. The G-Acr hybrids were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometry, thermal gravimetric analysis and Raman spectroscopy. X-ray photoelectron spectroscopy confirms that the binding energies of APA and its derivatives shifted to higher values, revealing pronounced charge transfer at the interface of graphene and organic molecules.

In this work, an efficient CuSO4-catalyzed S-arylation of thiols with aryl and heteroaryl boronic acids at room temperature is established. This catalytic system can tolerate a wide variety of thiols and arylboronic acids in the presence of only 5 mol % of CuSO4 as the catalyst and inexpensive 1,10-phen·H2O as the ligand. Moreover, this catalytic system used environment-friendly solvent (EtOH) and oxidant (oxygen).

An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins under mild conditions is described. High yields of products were achieved with n-Bu4N+OAc– as base. Significantly, the temperature of the Heck reaction of diverse nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.

CuI-nanoparticles-catalyzed selective synthesis of phenols, anilines, and thiophenols from aryl halides was developed in the absence of both ligands and organic solvents. Anilines were formed selectively with ammonia competing with hydroxylation and thiophenols were generated selectively with sulfur powder after subsequent reduction competing with hydroxylation and amination.

An efficient Csp–CH2CF3 bond-forming reaction via Pd-catalyzed 2,2,2-trifluoroethylation of aryl and alkyl terminal alkynes has been developed. This protocol proceeds under mild conditions using the readily available and cheap reagent CF3CH2I as the source of the CH2CF3 group. Various terminal aryl alkynes as well as alkylacetylenes can be transformed into the corresponding trifluoroethylated products in good-to-excellent yields. The method is tolerant of carbonyl, nitro, ester, cyano, and even formyl groups.

CuI nanoparticles efficiently catalyzed the C–S cross coupling of aryl and alkyl thiols with aryl halides in the absence of ligands on water under mild conditions. A wide range of diaryl sulfides and aryl alkyl sulfides are synthesized in good to excellent yields utilizing this protocol. This procedure is particularly noteworthy given its mild conditions, avoiding the undesired formation of disulfides through oxidation of thiols. The recovery and successful reutilization of the catalyst is described. Furthermore, the directed synthesis of bisarylated product is presented.

A photoredox catalytic method was developed for the direct cyanation of alkyltrifluoroborates. This reaction provides a new and useful transformation of the easily available alkyltrifluoroborates. The photocatalytic reaction can tolerate a variety of functional groups with mild reaction conditions. Mechanistic investigations are consistent with the present reaction following a radical pathway.

The protocol of the reductive amination of aromatic aldehydes using ammonium formate and Hantzsch ester is described. It is a mild, convenient, acid- and catalyst-free system applied for the synthesis of both symmetric and asymmetric aromatic secondary amines.

A copper-catalysed ring-opening trifluoromethylation reaction of cyclopropanols has been developed. Various β-trifluoromethyl ketones are obtained in good to excellent yields under mild reaction conditions. The present method also exhibits good functional-group compatibility. The mechanism of this new ring-opening trifluoromethylation reaction was investigated by radical trapping reactions.

The KI-catalyzed reaction of acetone with aromatic carboxylic acids is achieved, leading to α-acyloxycarbonyl compounds in good to excellent yields under mild reaction conditions. The present method exhibits good functional-group compatibility. Notably, this reaction system is even suitable for cinnamic acid, 3-phenylpropiolic acid and 4-phenylbutanoic acid. A kinetic isotope effect (KIE) study indicates that C–H cleavage of the acetone is the rate-limiting step in the catalytic cycle.

This work reports a hard self-template method to synthesize core/shell like Fe3O4@C microparticles, in which the Pd nanocrystals can be alternatively incorporated into the carbon shells. The Fe3O4@polyaniline core/shell microspheres were first synthesized as the precursor by in situ polymerization of aniline onto the surface of the Fe3O4 microspheres. In a subsequent carbonization of the precursor under a vacuum oven, the Fe3O4 core was preserved and the polyaniline shell transferred into carbon shells enveloping the magnetic sphere, forming magnetic Fe3O4@C microspheres. The Pd ions could be impregnated into the polyaniline shell, and thus the obtained composites were transformed into Fe3O4@C/Pd microspheres under the same vacuum heating progress. The as-obtained system demonstrates superparamagnetic characteristics, which would benefit its potential application in nanocatalysts. This strategy provides an efficient approach for tailoring core/shell materials with desired functionalities and structures by adjusting the precursors and structure-directing agents.

A general and effective method for the synthesis of amides through decarboxylative amidation of α-keto acids with amines has been developed. The reaction proceeded smoothly to afford the corresponding amide products in good yield under air and shows excellent functional group tolerance. In addition, the protocol can be further applied in the synthesis of heterocyclic compounds like benzimidazoles.

A copper(I)-catalyzed ring-opening cyanation of cyclopropanols was developed. The reaction provides an alternative method to achieve β-cyano ketones efficiently. This reaction exhibits good functional group compatibility under mild conditions and can be scaled up to the gram scale. Preliminary mechanistic studies suggest that the reaction might go through a free radical process.