Ionic liquid assisted synthesis of S-heterocycles

Enhanced selectivity of the CO2 reverse water-gas reaction over a Ni2P/CeO2 catalyst

Ni catalysts tend to easily undergo methanation and metal sintering at high temperatures during the CO₂ hydrogenation reaction. Herein, Ni₂P, a typical kind of transition metal phosphide, had been demonstrated to be efficient for use in the reverse water gas (RWGS) reaction. Under weight hourly space velocity (WHSV) values of 150 000 and 300 000 mL g^-1 h^-1, the Ni₂P/CeO₂ catalyst presented a high CO selectivity, better than that of the conventional Ni/CeO₂ catalyst. The activity was also well maintained in a 20 h stability test. Detailed physicochemical characterization proved that the moderate adsorption strength of CO₂, as well as more strong adsorption active sites for H₂ on the Ni₂P/CeO₂ surface, prevented the CO₂ from further hydrogenating to CH₄, which accounted for the remarkable CO selectivity and stability of the CO₂ RWGS reaction.

1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides under "Non-Conventional" Conditions: Green Solvents, Irradiation, and Continuous Flow

The 1,3-dipolar cycloaddition reactions (DCs) of nitrile oxides (NOs) to alkenes and alkynes are useful methods for the synthesis of 2-isoxazolines and isoxazoles respectively, which are important classes of heterocyclic compounds in organic and medicinal chemistry. Most of these reactions are carried out in organic solvents and under thermal activation. Nevertheless the use of supercritical carbon dioxide (scCO₂ ) and ionic liquids (Ils) as alternative solvents and the application of microwave (MW) and ultrasound (US) as alternative activation procedures have evident advantages from the "Green Chemistry" point of view. The critical discussion on the applications of these "unconventional" activation methods and reaction conditions in the 1,3-DCs of NOs is the objective of the present Review.