Masazumi Tamura

Transamidation of amides with amines under solvent-free conditions using a CeO2 catalyst

Among various metal oxides, cerium oxide (CeO2) shows the highest catalytic activity for transamidation of picolinamide with n-octylamine. CeO2 acts as a reusable and effective heterogeneous catalyst for transamidation under solvent-free conditions. Transamidation of a variety of amides and amines produced the corresponding N-alkyl amides in high yields. This method provides the first example of a heterogeneous catalyst for transamidation using aliphatic amines as substrates. Characterization of acid–base properties and kinetic studies suggest that the cooperation of the weak Lewis acid sites and adjacent strong base sites play important roles in the transamidation reaction.

CeO2-catalysed one-pot selective synthesis of esters from nitriles and alcohols

Thirteen kinds of metal oxides were tested for one-pot selective synthesis of esters from nitriles and alcohols. Ceria (CeO2) showed more than two orders of magnitude higher activity than the other oxides. CeO2 acted as a reusable and effective catalyst for the ester synthesis from various nitriles and alcohols under neutral and solvent-free conditions at 160 °C. This method provides a rare example for the synthesis of heteroaromatic esters, which have been difficult to synthesize by conventional catalytic esterification methods. Valuable esters such as picolinic acid alkyl esters and niacin benzyl esters were synthesized, demonstrating a practical aspect of the present method. Kinetic studies suggested the following reaction mechanism: (1) H2O and ROH dissociate on CeO2, (2) nucleophilic attack of hydroxyl species (OHδ−) to the adsorbed nitrile on CeO2, leading to the formation of the primary amide, (3) nucleophilic attack of alkoxide species (ORδ−) to the amide as the rate-limiting step.

Size- and support-dependent selective amine cross-coupling with platinum nanocluster catalysts

γ-Alumina-supported Pt nanoclusters with an average particle size of 0.8 nm, Pt/Al2O3-0.8, act as an effective heterogeneous catalyst for mono-N-alkylation of amines with different amines. To establish a catalyst design concept, systematic studies on the structure–activity relationship are carried out, combined with characterization by Pt L3-edge XAFS (X-ray absorption fine structure), X-ray photoelectron spectroscopy (XPS), and infrared (IR) study of CO adsorption. By changing the particle size of Pt over the size range of 0.8–24 nm, it is demonstrated that the present reaction is a structure-sensitive reaction, demanding coordinatively unsaturated Pt atoms on metallic nanoclusters. The support also affects the activity and electronic state of Pt. The electron density of Pt increases with basicity of the support oxide, and the support with moderate basicity (Al2O3) gives the highest activity probably due to a moderate electron density of Pt. Kinetic studies suggest that the present reaction proceeds through a “hydrogen-borrowing” mechanism.