Water-Promoted Mild and General Michaelis-Arbuzov Reaction of Triaryl Phosphites and Aryl Iodides by Palladium Catalysis

A Pd-catalyzed relatively general Michaelis-Arbuzov reaction of triaryl phosphites and aryl iodides for preparing useful aryl phosphonates was developed. Interestingly, water can greatly facilitate the reaction through a water-participating phosphonium intermediate rearrangement process, which also makes the reaction conditions rather mild. In comparison with the known methods, this reaction is milder and more general, as it exhibits excellent functional group tolerance, can be applied to various triaryl phosphites and aryl iodides, and can be extended to aryl phosphonites and phosphinites. A gram-scale reaction with a low catalyst loading also revealed its practicality and potential in large-scale preparation.

Tf2O/DMSO-mediated dual activation of aryl phosphinate to access various aryl phosphonates

A metal-free method for the dual activation of aryl phosphinate has been developed; the P-H and P-O bonds are sequentially activated by the Tf2O/DMSO system. Without the requirement of metals and unstable P-reagents, this one-pot procedure provides a convenient and practical access to a variety of aryl phosphonates. A mechanism involving twice generation of electrophilic P-species and two SN-processes is proposed on the basis of the control experiments.

Transition-Metal-Free Photoredox Phosphonation of Aryl C-N and C-X Bonds in Aqueous Solvent Mixtures

Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using 10H-phenothiazine, an inexpensive commodity chemical, as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in the presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods. The transformation also proceeds under atmospheric conditions, which further differentiates it from current methods that require inert atmosphere. Mechanistic work using fluorescence quenching experiments and radical trapping approaches support the proposed mechanism.

New Nanomagnetic Heterogeneous Cobalt Catalyst for the Synthesis of Aryl Nitriles and Biaryls

Cobalt nanoparticles immobilized on magnetic chitosan (Fe3O4@CS-Co) have been prepared. They were identified using various techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, thermogravimetric analysis, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy analysis and applied efficiently as a cobalt catalyst in the cyanation and fluoride-/palladium-free Hiyama reactions of different types of aryl halides employing K4[Fe(CN)6]·3H2O and triethoxyphenylsilane, respectively. After each reaction, the catalyst was isolated and reused for the second run. The catalytic activity of the catalyst was not lost apparently even after five runs. No considerable changes in its chemical structure and morphology were observed. It is worth to note that in this paper, the cobalt catalyst has been used for the first time for the cyanation of aryl halides.

Design of Carbon-carbon and Carbon-heteroatom Bond Formation Reactions under Green Conditions

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The development of C-C and C-heteroatom (C-N, C-O and C-P) bond reactions is a field of significant interest and has received momentous attention in modern organic chemistry. These reactions have been exploited in the synthesis of pharmaceuticals, agrochemicals and molecules of interest in materials science. With the increasing awareness of global warming and the use of renewable energies, it is of paramount importance to reduce the usage of hazardous chemicals in both industrial and academic research and to achieve a healthier environment through green practices. Green chemistry is a rapidly emerging approach that shows us a path for the sustainable growth of future science and technologies. In the recent past, healthy growth has been recorded in a number of organic reactions in aqueous media, which are environment-friendly and energy conserving. This review documents the literature on the development of green methodologies involving the design of C-C, C-O, C-N and C-P bond formations of coupling and condensed reactions. It emphasizes the exceptional practices and important advances achieved using alternative green tools, such as microwave (MW), high-speed ball milling (HSBM) and ultrasound irradiation techniques, and a variety of reusable catalysts and green solvents, with attention to water.

g-C3N4/γ-Fe2O3/TiO2/Pd: a new magnetically separable photocatalyst for visible-light-driven fluoride-free Hiyama and Suzuki–Miyaura cross-coupling reactions at room temperature

g-C₃N₄/γ-Fe₂O₃/TiO₂/Pd is developed as a new magnetically separable photocatalyst for efficient fluoride-free Hiyama and Suzuki–Miyaura cross-coupling reactions at room temperature under visible light irradiation.

C–P bond construction catalyzed by NiII immobilized on aminated Fe3O4@TiO2 yolk–shell NPs functionalized by (3-glycidyloxypropyl)trimethoxysilane (Fe3O4@TiO2 YS-GLYMO-UNNiII) in green media

An efficient, versatile and novel method for the C–P cross-coupling reaction with a high yield of products using Fe₃O₄@TiO₂YS-GLYMO-UNNi^II as a magnetic nanostructured catalyst in the presence of WERSA was reported.

New Developments on the Hirao Reactions, Especially from "Green" Point of View

BACKGROUND

The Hirao reaction discovered ca. 35 years ago is an important P-C coupling protocol between dialkyl phosphites and aryl halides in the presence of Pd(PPh3)4 as the catalyst and a base to provide aryl phosphonates. Then, the reaction was extended to other Preagents, such as secondary phosphine oxides and H-phosphinates and to other aryl and hetaryl derivatives to afford also phosphinic esters and tertiary phosphine oxides. Instead of the Pd(PPh3)4 catalyst, Pd(OAc)2 and Ni-salts were also applied as catalyst precursors together with a number of mono- and bidentate P-ligands.

OBJECTIVE

In our review, we undertook to summarize the target reaction with a special stress on the developments attained in the last 6 years, hence this paper is an update of our earlier reviews in a similar topic.

CONCLUSIONS

"Greener" syntheses aimed at utilizing phase transfer catalytic and microwave-assisted approaches, even under "P-ligand-free. or even solvent-free conditions are the up-to date versions of the classical Hirao reaction. The mechanism of the reaction is also in the focus these days.

P-Arylation of secondary phosphine oxides catalyzed by nickel-supported nanoparticles

Nickel-supported nanoparticles were used as catalysts for ligand-free Hirao coupling between secondary phosphine oxides and aryl halides.

P-arylation of aryl halides by an environmentally compatible method

In this paper, palladium–DABCO complex supported on magnetic nanoparticles was successfully used as a new magnetically recoverable heterogeneous catalyst for the synthesis of arylphosphonates via P-arylation of different types of aryl halides (aryl iodides/bromides/chlorides and benzene boronic acid/sulfonate), with phosphite esters (triethyl/triphenyl/tri-iso-propyl/diethyl/diphenyl/di-iso-propyl phosphite) in neat water without using any additive. The heterogeneous catalyst was easily isolated from the reaction mixture by an external magnet and reused five times without significant degradation in its activity.

Correction: Pd complex of an NNN pincer ligand supported on γ-Fe2O3@SiO2 magnetic nanoparticles: a new catalyst for Heck, Suzuki and Sonogashira coupling reactions

Correction for ‘Pd complex of an NNN pincer ligand supported on γ-Fe₂O₃@SiO₂ magnetic nanoparticles: a new catalyst for Heck, Suzuki and Sonogashira coupling reactions’ by Sara Sobhani et al., New J. Chem., 2015, 39, 7076–7085.

Synthesis of arylphosphonates catalyzed by Pd-imino-Py-γ-Fe2O3 as a new magnetically recyclable heterogeneous catalyst in pure water without requiring any additive

Arylphosphonates were synthesized in the presence of Pd-imino-Py-γ-Fe₂O₃ in pure water without using any additive.

Pd complex of an NNN pincer ligand supported on γ-Fe2O3@SiO2 magnetic nanoparticles: a new catalyst for Heck, Suzuki and Sonogashira coupling reactions

Pd-BIP-γ-Fe₂O₃@SiO₂ was used successfully as an air- and moisture-stable magnetically recyclable catalyst for Heck, Suzuki and Sonogashira coupling reactions.

Pyridine-grafted graphene oxide: a reusable acid–base bifunctional catalyst for the one-pot synthesis of β-phosphonomalonates via a cascade Knoevenagel–phospha Michael addition reaction in water

Py–GO as a new acid–base bifunctional catalyst was synthesized and employed for the one-pot synthesis of β-phosphonomalonates in water.