Polyaniline nanofiber supported FeCl3: An efficient and reusable heterogeneous catalyst for the acylation of alcohols and amines with acetic acid

Ordered mesoporous carbon assisted Fe-N-C for efficient oxygen reduction catalysis in both acidic and alkaline media

Fe-N-C catalyst obtained by high temperature pyrolysis is one of the most promising electrocatalysts for non-precious metal oxygen reduction reaction (ORR). However, up to now, the lesser density of active sites results in a substantial performance gap between the Fe-N-C materials and the conventional Pt/C ORR catalysts. Herein, an N-doped mesoporous carbon is employed as the support for the dispersion of poly-m-phenylenediamine. With high specific surface areas of 1526 m² g^-1, the as-prepared Fe-N-C materials show the half-wave potential of 0.89 V and 0.79 V in 0.1 M KOH and 0.5 M H₂SO₄, respectively. Notably, the superior methanol tolerance, as well as excellent stability, makes our Fe-N-C materials as competitive candidates for oxygen electrochemical catalysis.

Benzochalcogendiazole-based conjugated molecules: investigating the effects of substituents and heteroatom juggling

A convenient and effective synthetic approach for benzochalcogendiazole-based small molecules has been achieved using polyaniline (PANI)-anchored palladium as a heterogeneous catalyst. The photophysical properties of the synthesized benzochalcogendiazole-based small molecules, having different terminal substituents, have been compared. Moreover, the structural aspects, including the packing patterns and non-bonding interactions of the conjugated molecules, have been investigated using the single crystal X-ray diffraction (SCXRD) technique.

Comparison on surface properties and desulfurization of MnO2 and pyrolusite blended activated carbon by steam activation

In this study, MnO₂ and pyrolusite were used as the catalysts to prepare modified activated carbon, that is, AC-Mn and AC-P, respectively, from coals by blending method and steam activation. The Brunauer-Emmett-Teller (BET) results indicated that the AC-P had higher surface areas and micropore volumes than the AC-Mn with the same blending ratio. The relative contents of basic functional groups (i.e., C = O, π-π*) on AC-P were slightly lower than those on AC-Mn, while both contained the same main metal species, namely, MnO. The desulfurization results showed that with 3 wt% of blending ratio, AC-Mn3 and AC-P3 had higher sulfur capacities at 220 and 205 mg/g, respectively, which were much higher than for the blank one (149.6 mg/g). Moreover, the AC-P had relatively higher sulfur capacity than the AC-Mn with the same contents of Mn, which might be attributed to the existence of other metals in pyrolusite. After the desulfurization process, MnO were gradually transferred into MnSO₄, and the relative contents of basic functional groups decreased evidently for both AC-Mn3 and AC-P3. The results demonstrated that pyrolusite could be one good alternative to MnO₂ to prepare modified activated carbon for desulfurization.

IMPLICATIONS

MnO₂ and pyrolusite were used as the additives to prepare modified activated carbon from coals by a blending method and by steam activation, that is, AC-Mn and AC-P, respectively. The AC-P had higher surface areas and micropore volumes than the AC-Mn with the same blending ratio. The AC-Mn and AC-P had higher sulfur capacities than a blank one. Moreover, the AC-P had relatively higher sulfur capacity than the AC-Mn with the same contents of Mn. The results demonstrated that pyrolusite could be one good alternative to MnO₂ to prepare modified activated carbon for desulfurizatio.

A computational study on the mechanism of ynamide-mediated amide bond formation from carboxylic acids and amines

This paper reports a computational study elucidating the reaction mechanism for ynamide-mediated amide bond formation from carboxylic acids and amines. The mechanisms have been studied in detail for ynamide hydrocarboxylation and the subsequent aminolysis of the resulting adduct by an amine. Ynamide hydrocarboxylation is kinetically favorable and thermodynamically irreversible, resulting in the formation of a key low-lying intermediate CP1 featuring geminal vinylic acyloxy and sulfonamide groups. The aminolysis of CP1 by the amine is proposed to be catalyzed by the carboxylic acid itself that imparts favourable bifunctional effects. In the proposed key transition state TSaminolysis-acid-iso2, the amine undergoes direct nucleophilic substitution at the acyl of CP1 to replace the enolate group in a concerted way, which is promoted by secondary hydrogen bonding of carboxylic acid with both the amine and CP1. These secondary interactions are suggested to increase the nucleophilicity of the amine and to activate the C_acyl-O bond to be cleaved, thereby stabilizing the aminolysis transition state. The concerted aminolysis mechanism is competitive with the classic stepwise nucleophilic acyl substitution mechanism that features sequential amine addition to acyl/intramolecular proton transfer/C-O bond cleavage and a key tetrahedral intermediate. Based on the mechanistic model, the carboxylic acid substrate effect and studies of more acidic CF₃SO₃H as the catalyst are in good agreement with the experimental observations, lending further support for the mechanistic model. The bifunctional catalytic effect of the carboxylic acid substrate may widely play a role in related amide bond-forming reactions and peptide formation chemistry.

Synthesis of a Fe3O4@P4VP@metal–organic framework core–shell structure and studies of its aerobic oxidation reactivity

A novel core–shell magnetic Fe₃O₄@P4VP@MIL-100(Fe) composite material has been synthesized and its aerobic oxidation activity has been extensively studied.

An Fe3O4@P4VP@FeCl3 core–shell heterogeneous catalyst for aerobic oxidation of alcohols and benzylic oxidation reaction

A novel Fe₃O₄@P4VP@FeCl₃ core–shell catalyst has been developed through coordination interaction between P4VP and FeCl₃, which was utilized in selective oxidation of alcohols using molecular oxygen as the oxidant.

Polyaniline coated on celite, a heterogeneous support for palladium: applications in catalytic Suzuki and one-pot Suzuki–aldol reactions

Polyaniline was heterogenized on celite particles and used as a support for palladium metal ions. The catalyst was found to be effective in Suzuki–Miyaura and its one-pot aldol reactions.

Catalytic amide formation from non-activated carboxylic acids and amines

The amide functionality is found in a wide variety of biological and synthetic structures such as proteins, polymers, pesticides and pharmaceuticals. Due to the fact that synthetic amides are still mainly produced by the aid of coupling reagents with poor atom-economy, the direct catalytic formation of amides from carboxylic acids and amines has become a field of emerging importance. A general, efficient and selective catalytic method for this transformation would meet well with the increasing demands for green chemistry procedures. This review covers catalytic and synthetically relevant methods for direct condensation of carboxylic acids and amines. A comprehensive overview of homogeneous and heterogeneous catalytic methods is presented, covering biocatalysts, Lewis acid catalysts based on boron and metals as well an assortment of other types of catalysts.

ZSM-5-SO3H: An Efficient Catalyst for Acylation of Sulfonamides Amines, Alcohols, and Phenols under Solvent-Free Conditions

Sulfonamides amines, alcohols, and phenols were efficiently acylated with carboxylic acid anhydrides and chlorides using ZSM-5-SO₃H as catalyst under mild and solvent-free conditions. Also, direct esterification of alcohols with carboxylic acids occurred readily in the presence of this catalyst. Different types of amides and esters were obtained in moderate to high yields and purity after a simple workup. No chromatographic separation is needed for isolation of the acylated product. The catalyst was recovered and reused for up to four times without a noticeable decrease in catalytic activity.