TiO2 nanoparticles decorated with Co-Schiff base-g-C3N4 as an efficient photocatalyst for one-pot visible light-assisted synthesis of benzimidazoles

In this study, a novel heterogeneous visible light-driven nanocatalyst was produced via the complexation of Co(ii) with g-C₃N₄-imine-functionalized TiO₂ nanoparticles. It was characterized using different techniques such as Fourier-transform infrared (FT-IR), energy-dispersive X-ray spectrum (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The catalyst promoted several different transformations in a one-pot reaction sequence: aerobic photooxidation of benzylic alcohols to aldehydes and then the tandem synthesis of benzimidazoles through the dehydrogenative coupling of primary benzylic alcohols and aromatic diamines. The photocatalyst proved to be highly active, robust, selective, and recyclable under organic reaction conditions and provided affordable products with good to high yields. The results proposed that the improved photoactivity predominantly benefits from the synergistic effects of the heterojunction of Co-carbon nitride on TiO₂ nanoparticles. Moreover, this protocol provides standard conditions avoiding undesirable additives and limitations of oxidation methods, and may help to develop a new strategy for the development of photocatalysis based organic transformations.

The Co-g-C₃N₄-imine/TiO₂ nanohybrid promotes different transformations in a one-pot reaction sequence: aerobic photooxidation of benzylic alcohols to aldehydes, and then the tandem synthesis of benzimidazoles.

Catalytic activity of Mg–Al hydrotalcites and derived mixed oxides for imination reactions via an oxidative-dehydrogenation mechanism

A Mg–Al hydrotalcite derived mixed oxide (Mg/Al ratio = 3.0) showed excellent catalytic activity in imination and tandem reactions via an oxidative-dehydrogenation mechanism.

The synthesis of benzimidazoles via a recycled palladium catalysed hydrogen transfer under mild conditions

An efficient synthesis of benzimidazoles was developed by virtue of a recycled palladium catalyzed hydrogen transfer.

Dehydrogenative synthesis of benzimidazoles under mild conditions with supported iridium catalysts

Recyclable Ir/TiO₂ catalysts enable the synthesis of benzimidazoles from primary alcohols and phenylenediamines under mild conditions, i.e. at 120 °C.

A bioinspired catalytic aerobic oxidative C-H functionalization of primary aliphatic amines: synthesis of 1,2-disubstituted benzimidazoles

Aerobic oxidative CH functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems.

Visible light induced green transformation of primary amines to imines using a silicate supported anatase photocatalyst

Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase)-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds.

Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals

Silver nanoparticles catalysis has been of great interest in organic synthesis and has expanded rapidly in the past ten years because of nanosilver catalysts' unique reactivity and selectivity, stability, as well as recyclability in catalytic reactions.

Synthesis of indoles via dehydrogenative N-heterocyclization by supported platinum catalysts

Heterogeneous Pt catalysts (Pt/Nb₂O₅ and Pt/HBEA) show higher turnover number (TON) than previously reported catalysts for the synthesis of indole via acceptorless dehydrogenative cyclization of 2-(2-aminophenyl)ethanol.