45 research outputs found
Ti–Pd Alloys as Heterogeneous Catalysts for Hydrogen Autotransfer Reaction and Catalytic Improvement by Hydrogenation Effects
Ti−Pd alloys were investigated as heterogeneous catalysts for hydrogen autotransfer reactions. This is the first reported study of alloys as catalysts for hydrogen‐borrowing reactions using alcohols. We improved the catalytic activities of alloys by increasing their specific surface areas via a hydrogenation−powdering process. The reactivities and selectivities of hydrogenated Ti−Pd alloys [Ti−Pd (Hy) ] were higher than those of non‐hydrogenated alloy catalysts in N‐alkylation by hydrogen autotransfer using alcohols. A plausible catalytic cycle is proposed based on control studies and deuterium labelling experiments
Transition-Metal Complexes with Nano-Sized Phosphine and Pyridine Ligands-Catalysis, Fluxional Behavior and Molecular Recognition
Nano-sized phosphine and pyridine ligands having tetraphenylphenyl-, m-terphenyl-, poly(benzylether) moieties were synthesized. These ligands showed a remarkable effect on homogeneous transition metal catalyzed reactions. Pd(II) complexes with tetraphenylphenyl substituted pyridine ligands show high catalytic activities for oxidation of ketones suppressing Pd black formation and maintains the catalytic activity for a long time. Rh(I) complex catalysts with m-terphenyl substituted phosphine ligands showed remarkable rate acceleration in the hydrosilylation of ketones. In addition, several phosphinocalixarene ligands were synthesized and their coordination studies with Pd(II), Pt(II), Ru(II), Ir(I), and Rh(I) metals were documented. Ir(I) and Rh(I) cationic complexes with a 1,3,5-triphosphinocalix[6]arene ligand showed dynamic behavior with size-selective molecular recognition
Palladium-Catalyzed Intermolecular Oxidative Amination of Alkenes with Amines, Using Molecular Oxygen as Terminal Oxidant
In this review, we summarize recent progress from our group with regard to Pd-catalyzed oxidative amination of alkenes with amines. Intermolecular oxidative amination of alkenes with secondary anilines was induced using a palladium-complex catalyst combined with molybdovanadophosphate as a co-catalyst under dioxygen, leading to allylic amines and enamines in good yields with high selectivities. The reaction proceeded efficiently, using molecular oxygen as the terminal oxidant. In addition, palladium-catalyzed oxidative amination of alkenes with anilines as primary amines was achieved using molecular oxygen as the sole oxidant, producing (Z)-N-alkenyl-substituted anilines in high yields
Low-Valent Niobium-Catalyzed Intermolecular [2 + 2 + 2] Cycloaddition of <i>tert</i>-Butylacetylene and Arylnitriles to Form 2,3,6-Trisubstituted Pyridine Derivatives
A catalytic
system based on low-valent niobium has been developed,
consisting of NbCl<sub>5</sub>, Zn, and an alkoxysilane. This combination
has been shown to be an efficient catalyst for the synthesis of pyridine
derivatives from the intermolecular cycloaddition of alkynes and nitriles
via a niobacyclopentadiene intermediate
FeCl<sub>3</sub>‑Assisted Niobium-Catalyzed Cycloaddition of Nitriles and Alkynes: Synthesis of Alkyl- and Arylpyrimidines Based on Independent Functions of NbCl<sub>5</sub> and FeCl<sub>3</sub> Lewis Acids
NbCl<sub>5</sub>-catalyzed
[2 + 2 + 2] cycloaddition of nitriles
with alkynes was used to synthesize pyrimidine derivatives. In this
reaction, the use of individual Lewis acids, namely NbCl<sub>5</sub> and FeCl<sub>3</sub>, is a key strategy for achieving the reaction
using a catalytic amount of NbCl<sub>5</sub>. The roles of the two
Lewis acids were investigated using FT-IR spectroscopy. The results
showed that NbCl<sub>5</sub> served as an efficient Lewis acid catalyst
for nitrile activation, whereas FeCl<sub>3</sub> showed stronger Lewis
acidity toward pyrimidines, releasing NbCl<sub>5</sub> into the catalytic
cycle
Strategy for the Synthesis of Pyrimidine Derivatives: NbCl<sub>5</sub>‑Mediated Cycloaddition of Alkynes and Nitriles
Intermolecular cycloadditions of alkynes (terminal alkynes
and internal alkynes) with aryl nitriles were successfully achieved,
using an NbCl<sub>5</sub> complex, to give substituted pyrimidine
derivatives in high yields with excellent chemo- and regioselectivity