Celite-Polyaniline supported palladium catalyst for chemoselective hydrogenation reactions

A Review on Polyaniline-Supported Catalyst for Organic Transformations

Organic transformations are very important in synthetic organic chemistry and are used immensely in pharmaceuticals. Polyaniline is a marvelous and exceptional conducting polymer because of its extensive and valuable applications. Various modified polyaniline derivatives were developed by researchers and explored as solid heterogeneous catalysts for synthesizing important organic compounds through different organic transformations. Polyaniline-supported catalysts have many advantages: easy synthesis, environmental stability, environmental friendliness, high yield, short reaction times, the requirement for green solvent or solventless medium, and excellent reusability. In past years, polyaniline-supported catalysts have been widely used in various important organic syntheses under solvent-free or green reaction conditions. Hence, here is a comprehensive, detailed review of the application of polyaniline catalysts in organic transformations with all of their advantages and future scope.

Transition Metal-Catalyzed Transformations of Chalcones

Chalcones are a class of naturally occurring flavonoid compounds associated to a variety of biological and pharmacological properties. Several reviews have been published describing the synthesis and biological properties of a vast array of analogues. However, overviews on the reactivity of chalcones has only been explored in a few accounts. To fill this gap, a systematic survey on the most recent developments in the transition metal-catalyzed transformation of chalcones was performed. The chemistry of copper, palladium, zinc, iron, manganese, nickel, ruthenium, cobalt, rhodium, iridium, silver, indium, gold, titanium, platinum, among others, as versatile catalysts will be highlighted, covering the literature from year 2000 to 2023, in more than 380 publications.

Ruthenium-Catalyzed Reductive Coupling of Epoxides with Primary Alcohols via Hydrogen Transfer Catalysis

Herein, we report the ruthenium-catalyzed synthesis of β-alkylated secondary alcohols via the regioselective ring-opening of epoxides with feedstock primary alcohols. The reaction utilized alcohol as the carbon source and the terminal reductant. Kinetic and labeling experiments elucidate the hydrogen transfer catalysis that operates via tandem Markovnikov selective transfer hydrogenation of terminal epoxides and hydrogen transfer-mediated cross-coupling of the resulting alcohol with primary alcohol substrates. A broad scope (40 examples including drugs/natural product derivatives) and excellent regioselectivity for a variety of substrates were shown.

A palladium polyaniline complex: a simple and efficient catalyst for batch and flow Suzuki-Miyaura cross-couplings

A novel palladium polyaniline complex (Pd@PANI) was synthesized via a one-pot method using a low concentration of hydrogen peroxide (3 wt%) as a mild oxidant. Pd@PANI was employed to catalyze Suzuki-Miyaura cross-couplings with 0.11 ppm levels of palladium and high turnover numbers (up to 6.1 × 10⁴). Various aromatic halides and aromatic boric acids were used as reaction partners to prepare the biaryl compounds in high yields. Application of the method in the synthesis of D-fructose derivatives was also performed. Furthermore, the catalyst was evaluated under a flow process to provide the corresponding products in good yields with shorter residence times and lower temperatures in more convenient operations compared with the batch conditions.

Methanol as a hydrogen source: room-temperature highly-selective transfer hydrogenation of α,β-unsaturated ketones

The described system offers an ideal, user-friendly protocol for the chemoselective homogeneous hydrogenation of α,β-unsaturated ketones at room temperature using methanol as a liquid organic hydrogen carrier. Excellent yields were achieved with an in situ-prepared phosphine-free Cp*Ir(III)/bipyridonate complex. Chemoselective reduction with other reducible functionalities and late-stage functionalization were also explored.

Reduction of imines with a reusable bimetallic PdCo-Fe3O4 catalyst at room temperature under atmospheric pressure of H2

Bimetallic nanocatalysts have been used for the development of organic reactions, owing to the synergistic effect between the transition metals. A new procedure for synthesizing amines by the reduction of imines with H₂ at atmospheric pressure and room temperature in the presence of PdCo–Fe₃O₄ nanoparticles is reported. The straightforward procedure, mild reaction conditions, high turnover number, and recyclability extend the scope of this reaction to practical applications.

A catalytic procedure that has mild reaction conditions, high turnover number, and the recyclability of the catalyst is presented, whereby the synthesis of amines through the reduction of imines employing PdCo–Fe₃O₄ under atmospheric pressure of H₂ is achieved.

One-Pot Synthesis of 3-Substituted 4H-Quinolizin-4-ones via Alkyne Substrate Control Strategy

Three-substituted 4H-quinolizin-4-ones were obtained via a facile method with good selectivity and high efficiency. On the basis of alkyne substrate control, the mild and cost-efficient reaction has a broad substrate scope (20 examples, up to 93% yield) and is also easy to scale up. Active sites on the products allow for further modifications. The alkyne substrate control strategy could be further extended to achieve more complex three-substituted 4H-quinolizin-4-one skeletons.

Monodisperse NiPd alloy nanoparticles decorated on mesoporous graphitic carbon nitride as a catalyst for the highly efficient chemoselective reduction of α,β-unsaturated ketone compounds

The study reported chemoselective reduction with selectivity (>99%) by the catalytic transfer hydrogenation of α,β-unsaturated ketones with a catalyst of NiPd alloy nanoparticles decorated on mesoporous graphitic carbon nitride (NiPd/mpg-C₃N₄).

Benzochalcogendiazole-based conjugated molecules: investigating the effects of substituents and heteroatom juggling

A convenient and effective synthetic approach for benzochalcogendiazole-based small molecules has been achieved using polyaniline (PANI)-anchored palladium as a heterogeneous catalyst. The photophysical properties of the synthesized benzochalcogendiazole-based small molecules, having different terminal substituents, have been compared. Moreover, the structural aspects, including the packing patterns and non-bonding interactions of the conjugated molecules, have been investigated using the single crystal X-ray diffraction (SCXRD) technique.