Gram-Scale Preparation of Pd@PANI: A Practical Catalyst Reagent for Copper-Free and Ligand-Free Sonogashira Couplings

Palladium nanoparticles on the polyaniline (Pd@PANI) catalyst are now easily prepared on a gram scale through the oxidative polymerization of aniline in the presence of PdCl₂ by using air as a clean oxidant. The material is found to be very stable and can be stored for more than one year without deactivation. Thus, it may become a commercial reagent in organic synthesis, depending on its application scopes. This article reported the first example of Pd@PANI-catalyzed Sonogashira couplings free of copper and ligands

Dehydration of Aldoximes Using PhSe(O)OH as the <i>Pre</i>-Catalyst in Air

PhSe­(O)­OH was found to be a good <i>pre</i>-catalyst for aldoxime dehydrations in open air. Compared with the previously reported (PhSe)₂-H₂O₂ system, it is more stable and milder, affording broader application scopes due to a higher functional group tolerance. The control experiments for mechanism study disclosed that air was the key factor for the reaction to maintain enough concentration of PhSeOH, which should be the real catalytic species

Heck Reactions Catalyzed by Ultrasmall and Uniform Pd Nanoparticles Supported on Polyaniline

Using air as the oxidant instead of the traditionally employed persulfates, the smaller and more uniform Pd nanoparticles (around 2 nm) supported on polyaniline (Pd@PANI) can be easily fabricated by the oxidation–polymerization of aniline with PdCl₂. This material is an efficient and environmentally friendly catalyst for Heck reactions due to its recyclability, low loading, and ligand-free and mild reaction conditions. It was even tolerant to sulfur-containing substrates. This work reports the Pd@PANI-catalyzed Heck reactions with very wide substrate scopes, and discloses the catalytic mechanisms based on experimental findings and results of catalyst analysis and characterization

Advanced MnO_<i>x</i>/TiO₂ Catalyst with Preferentially Exposed Anatase {001} Facet for Low-Temperature SCR of NO

MnO_<i>x</i>/TiO₂ (anatase) nanosheets (NS) with a preferentially exposed {001} facet was found to be a better catalyst for selective catalytic reduction (SCR) of NO than conventionally employed MnO_<i>x</i>/TiO₂ nanoparticles (NP) with the {101} facet preferentially exposed, affording both high NO conversion and high N₂ selectivity at 80–280 °C. Further investigations indicated that Mn³⁺ as the major species on TiO₂ (NS) was incorporated into octahedral vacancies with a lower polymerization degree, resulting in high catalytic activity for SCR and low activity for NH₃ oxidation, thus restraining the undesirable N₂O generation. In comparison, on the surface of TiO₂ (NP), Mn⁴⁺ as the major species was incorporated into tetrahedral vacancies in a highly polymerized state, leading to lower NO conversion and lower N₂ selectivity. The results indicate that it is possible to enhance the low-temperature SCR activity of the catalysts by tailoring the preferentially exposed facet of TiO₂