Titanium Dioxide\nSupported Ru Nanoparticles as Efficient\nCatalysts for Microwave-Assisted Sustainable Organic Transformations

Microwave-assisted\norganic transformation is currently\ngaining\nprominence in the field of benign organic synthesis. In this work,\nwe reported Ru nanoparticles (NPs) (<5 nm) supported on titanium\ndioxide (TiO<sub>2</sub>) using the facile and fast molten-salt method\nand employed for reductive <i>N</i>-alkylation reactions,\nnitroarenes to amines and levulinic acid (LA) to levulinate ester\nunder microwave irradiation (MWI). Reductive <i>N</i>-alkylation\nof nitrobenzene and furfural to the respective secondary amines via\ncatalytic transfer hydrogenation with conventional heating (CH) involves\nlonger reaction times, lower selectivity, and low yields. Moreover,\nthe catalytic applications of Ru/TiO<sub>2</sub> were explored for\nthe reductive amination of nitrobenzene and furfural with excellent\nconversion (>99%) and selectivity (85%) toward <i>N</i>-(furan-2-ylmethyl)\naniline. The Ru/TiO<sub>2</sub> is used as a model to catalyze the\nconversion (>99%) of nitrobenzene in both the reaction, i.e., nitrobenzene\nreduction and one-pot reductive amination, along with LA esterification\nreaction via MWI. To study the efficacy of MWI for nitrobenzene conversion,\nMWI and CH were compared. MWI is proven to accelerate reaction times\nand improve nitrobenzene conversion efficiencies when compared to\nCH by examining the effects of conversion and reaction duration. A\nremarkable synergistic effect has been revealed between small Ru NPs\nand TiO<sub>2</sub> NPs that leads to selective catalytic transformation\nof organic compounds to value-added products. As per the study’s\nfindings, MW is a potentially effective method for improving the conversion\nof nitrobenzene, with Ru/TiO<sub>2</sub> emerging as the most active\ncatalyst compared to as-synthesized Cu/TiO<sub>2</sub>, and Ni/TiO<sub>2</sub>.