SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) as an efficient heterogeneous and recyclable nanocatalyst for N‐arylation of indoles through Ullmann‐type coupling reactions

SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) was found to serve as a heterogeneous and recyclable nanocatalyst for N‐arylation of indoles with aryl iodides under a low catalyst loading (0.3 mol% of Pd) through Ullmann‐type C? N coupling reactions. A variety of aryl iodides could be aminated to provide the N‐arylated products in good to excellent yields without the need of an inert atmosphere. Also, this catalyst was found to be an efficient system for the N‐arylation of other nitrogen‐containing heterocycles with aryl iodides. The heterogeneous palladium catalyst could be recovered by simple filtration of the reaction solution and reused for six cycles without significant loss in its activity. Copyright © 2015 John Wiley & Sons, Ltd.     

CuI catalyst heterogenized on melamine-pyridines immobilized SBA-15: Heterogeneous and recyclable nanocatalyst for Ullmann-type CN coupling reactions

The present study reports the procedure conducted in SBA-15/CCPy/CuI preparation as a new Mesoporous nanocatalyst, whereas melamine bearing pyridine groups on SBA-15 are used to secure CuI catalyst as capping agent. The resultant catalyst was specified by conducting TEM, FESEM, WDX, ICP, and EDS. The SBA-15/CCPy/CuI catalytic behavior was studied to N-arylation of indole, imidazole, pyrazole, benzyl amine, and aniline by coupling reactions of Ullmann-type CN. Also, the heterogeneous catalyst may simply be recovered via filtration and used again for seven cycles with no considerable loss in activity. The findings revealed the privileges of the present method, including the high product yield, experimental simplicity, low catalyst loading, broad substrate scope, and short reaction times.     

CuI heterogenized on thiosemicarbazide modified‐multi walled carbon nanotubes (thiosemicarbazide‐MWCNTs‐CuI): Novel heterogeneous and reusable nanocatalyst in the C‐N Ullmann coupling reactions

Herein we described the synthesis of novel thiosemicarbazide‐MWCNTs‐CuI nanocatalyst by covalent grafting of thiosemicarbazide on carbon nanotubes surface and subsequent coordination with CuI catalyst. The formation of nanocatalyst was analyzed by Raman spectroscopy, energy dispersive spectroscopy (EDS), wavelength‐dispersive X‐ray spectroscopy (WDX) and ICP analysis. The morphology of the nanocatalyst was characterized using scanning and transmission electron microscopes (SEM and TEM). Additionally, the (thiosemicarbazide‐MWCNTs‐CuI) nanocatalyst was successfully employed in the N ‐arylation of indole, amines and imidazoles through intermolecular C(aryl)‐N bond formation from the corresponding aryl halides (Ar–I, Ar–Br, Ar–Cl) with amines through Ullmann‐type coupling reactions. Interestingly, the novel catalyst could be recovered and recycled five times.     

Copper‐catalyzed C‐N coupling reaction of tosylhydrazones

Tosylhydrazones are a kind of labile and highly reactive compounds, which are apt to be transformed into reactive diazo compounds and then into extremely reactive carbenes under the basic condition. In order to fulfil the valuable C‐N coupling reaction, diaryliodonium salts are evaluated and prove to be a class of efficient electrophiles. The reaction with ligand‐free copper salt as catalyst shows a wide range of substrate scope. A plausible mechanism is proposed.     

Synthesis and characterization of MCM‐41‐Biurea‐Pd as a heterogeneous nanocatalyst and using its catalytic efficacy in C–C,C–N and C–O coupling reactions

MCM‐41‐Biurea‐Pd is introduced as a new, heterogeneous and reusable catalyst for C–C and C–heteroatom bond formation between various aryl halides, phenols and amines, in the presence of Ph₃SnCl (Stille reaction) in PEG‐400 as a green solvent at room temperature. The structure of the functionalized MCM‐41 was analysed using various techniques.     

Suzuki and Heck cross‐coupling reactions using ferromagnetic nanoparticle‐supported palladium complex as an efficient and recyclable heterogeneous nanocatalyst in sodium dodecylsulfate micelles

A novel heterogeneous Pd catalyst was synthesized by anchoring Pd(II) onto 4′‐(4‐hydroxyphenyl)‐2,2′:6′,2″‐terpyridine‐coated Fe₃O₄ (FMNPs@TPy‐Pd). This catalyst has been demonstrated for the first time as a recoverable and reusable heterogeneous nanocatalyst in Suzuki and Heck cross‐coupling reactions. The catalyst is very easy to handle and is environmentally safe and economical. FMNPs@TPy‐Pd was characterized using transmission and scanning electron microscopies, X‐ray diffraction, and Fourier transform infrared and energy‐dispersive X‐ray spectroscopies.     

An efficient,mild and selective Ullmann‐type N‐arylation of indoles catalysed by Pd immobilized on amidoxime‐functionalized mesoporous SBA‐15 as heterogeneous and recyclable nanocatalyst

A wide range of N‐arylated indoles were selectively synthesized through intermolecular C(aryl)? N bond formation from the corresponding aryl iodides and indoles through Ullmann‐type coupling reactions in the presence of a catalytic amount of Pd immobilized on amidoxime‐functionalized mesoporous SBA‐15 (SBA‐15/AO/Pd(0)) under mild reaction conditions. These cross‐coupled products were obtained in excellent yields under mild conditions at extremely low palladium loading (ca 0.3 mol%), and the heterogeneous catalyst can be readily recovered by simple filtration and reused seven times with loss in its activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Polymer supported copper(II) amine‐imine complexes in the C‐N and A3 coupling reactions

New polymer supported Cu(II) complexes based on an epoxy functionalized gel type resin were prepared using the multi‐stage procedures. The reactions of epoxy groups with ethylenediamine or tris(2‐aminoethyl)amine, and then NH₂ groups with salicylaldehydes were used for the preparation of a series of amine‐imine functionalized polymer supports. Copper(II) acetate was used as a source of metal ions. The complexes were characterized using ICP‐OES, FTIR, DR UV–Vis and TGA techniques, and tested as catalysts in two model C‐N and a series of A³ coupling reactions. Their catalytic activity was rather low in the C‐N coupling reactions between imidazole and iodobenzene or phenylboronic acid. However, the second of the reactions could be conducted effectively under milder conditions. The complexes were efficient used as recyclable catalysts in the A³ coupling reactions. A series of aromatic aldehydes and secondary amines and phenylacetylene could be coupled using 1% mol catalyst.     

Biguanidine‐functionalized chitosan to immobilize palladium nanoparticles as a novel,efficient and recyclable heterogeneous nanocatalyst for Suzuki–Miyaura coupling reactions

Biguanidine‐functionalized chitosan was synthesized and combined with palladium nanoparticles to yield a recyclable, environmentally benign, heterogeneous catalytic system for the Suzuki–Miyaura C–C coupling reaction. The catalyst was characterized using various techniques. The catalyst was used in Suzuki cross‐coupling reactions of various aryl halides, including less reactive chlorobenzenes, with phenylboronic acid to give biaryls without any additive or ligand. A reusability test demonstrated that the catalyst was highly efficient even after six runs. Solid‐phase poisoning and leaching tests indicated that the catalyst has a heterogeneous nature. Copyright © 2016 John Wiley & Sons, Ltd.     

Betti base‐modified magnetic nanoparticles as a novel basic nanocatalyst in Knoevenagel condensation and its related palladium nanocatalyst in Suzuki coupling reactions

Betti base‐modified Fe₃O₄ nanoparticles have been successfully designed and synthesized for the first time through the condensation of Fe₃O₄ magnetic nanoparticles coated by (3‐aminopropyl)triethoxysilane with β‐naphthol and benzaldehyde. Their application as a novel magnetic nanocatalyst in the Knoevenagel condensation and also application to immobilization of palladium nanoparticles for Suzuki coupling reactions have been investigated which opens a new field for application of Betti base derivatives in organic transformations. The synthesized inorganic–organic hybrid nanocatalyst has been fully been characterized using Fourier transform infrared, X‐ray diffraction, vibrating sample magnetometry, transmission and scanning electron microscopies, energy‐dispersive X‐ray, wavelength‐dispersive X‐ray and X‐ray photoelectron spectroscopies and inductively coupled plasma techniques. The catalyst was easily separated with the assistance of an external magnet from the reaction mixture and reused for several consecutive runs with no significant loss of its catalytic efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

Schiff base complex of palladium immobilized on magnetic nanoparticles: an efficient and recyclable nanocatalyst for CC coupling reactions

A Schiff base complex of palladium anchored on Fe₃O₄ magnetic nanoparticles as an efficient and magnetically reusable nanocatalyst is reported for C? C bond formation through Heck and Suzuki reactions. The catalyst was easily recovered and reused several times without significant loss of its catalytic efficiency or palladium leaching. The magnetic nanocatalyst was characterized using Fourier transform infrared and inductively coupled plasma atomic emission spectroscopies, thermogravimetric analysis, vibrating sample magnetometry, and transmission and scanning electron microscopies. Copyright © 2016 John Wiley & Sons, Ltd.     

Pd‐ Dithizone grafted onto magnetic nanoparticles and study of its catalyticactivity in C‐C and C‐N coupling reactions

In this paper, we report a simple, facile and efficient method for the synthesis of Fe₃O₄/SiO₂‐DTZ‐Pd. The immobilized palladium was an efficient catalyst without addition of phosphine ligands for Stille, Heck and N‐arylation reactions. This method has some advantages such as high yields and easy work up of products. In addition, the catalyst can be recovered using a magnet and reused several times without significant loss of its catalytic activity. This catalyst was characterized by various physico‐chemical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and inductively coupled plasma (ICP).     

Pd‐SBT@MCM‐41: As an efficient,stable and recyclable organometallic catalyst for C‐C coupling reactions and synthesis of 5‐substituted tetrazoles

A palladium S‐benzylisothiourea complex was anchored on functionalized MCM‐41 (Pd‐SBT@MCM‐41) and applied as efficient and reusable catalyst for the synthesis of 5‐substituted 1H –tetrazoles using [2 + 3] cycloaddition reaction of various organic nitriles with sodium azide (NaN₃) in poly(ethylene glycol) (PEG) as green solvent. Also this catalyst was applied as an versatile organometallic catalyst for Suzuki cross‐coupling reaction of aryl halides and phenylboronic acid (PhB(OH)₂) or sodium tetraphenyl borate (NaB(Ph)₄). This nanocatalyst was characterized by thermal gravimetric analysis (TGA), X‐ray Diffraction (XRD), scanning electron microscopy (SEM), inductively Coupled Plasma (ICP) and N₂ adsorption–desorption isotherms techniques. Recovery of the catalyst is easily achieved by centrifugation for several consecutive runs.     

Pd(0)‐ S‐propyl‐2‐aminobenzothioate immobilized onto functionalized magnetic nanoporous MCM‐41 as efficient and recyclable nanocatalyst for the Suzuki,Stille and Heck cross coupling reactions

The present work describes the use of Pd(0)‐ S‐propyl‐2‐aminobenzothioate Complex immobilized onto functionalized magnetic nanoporous MCM‐41(Fe₃O₄@MCM‐41@Pd‐SPATB) as efficient and recyclable nano‐organometallic catalyst for C–C bond formation between various aryl halides with phenylboronic acid (Suzuki reaction), aryl halides with triphenyltin chloride (Stille reaction), and aryl halides with n‐butyl acrylate (Heck reaction). All the reactions were carried out in PEG‐400 as green solvent with short reaction time and good to excellent yields. This catalyst was characterized by FT‐IR spectroscopy, XRD, TGA, VSM, ICP‐OES, TEM, EDX and SEM techniques. Ease of operation, high efficiency, recovery and reusability for five continuous cycles without significant loss of its catalytic activities or metal leaching are the noteworthy features of the currently employed heterogeneous catalytic system.     

Chemo‐selective copper‐catalyzed C‐O coupling reactions of phenols with aryl/vinyl halides using enaminone as efficient ligand

The copper‐catalyzed Ullmann C‐O coupling reactions between phenols and aryl/vinyl halides have been efficiently performed by employing (E)‐3‐(dimethylamino)‐1‐(2‐hydroxyphenyl)prop‐2‐en‐1‐one, an easily available enaminone, as ligand. This new ligand is advantageous for its easy availability, broad applicability and good efficiency. Copyright © 2012 John Wiley & Sons, Ltd.     

Ligandless heterogeneous palladium: an efficient and recyclable catalyst for Suzuki‐type cross‐coupling reaction

A mild and efficient ligand‐free Suzuki‐type cross‐coupling reaction of benzoyl chlorides and arylboronic acids catalyzed by heterogeneous Pd/C was developed. Benzoyl chlorides undergo cross‐coupling with electronically diverse arylboronic acids to give biaryl ketones in excellent yield, under aqueous media and optimum temperature. The application of 3 mol% of 10 wt% Pd/C to the cross‐coupling delivers utmost efficiency, and could be reused up to many consecutive cycles without any loss in activity. This method proceeds under aqueous media and a recyclable catalytic system, offering an environmentally benign alternative to the existing protocols. Copyright © 2014 John Wiley & Sons, Ltd.     

Copper‐Catalyzed Oxidative C−H Bond Functionalization of N‐Allylbenzamide for Regioselective C−N and C−O Bond Formation

Copper‐catalyzed oxidative couplings of N‐allylbenzamides for C?N and C?O bond formations have been developed through C?H bond functionalization. To demonstrate the utility of this approach, it was applied to the synthesis of β‐aminoimides and imides. To the best of our knowledge, these are the first examples in which different classes of N‐containing compounds have been directly prepared from the readily available N‐allylbenzamides using an inexpensive catalyst/oxidant/base (CuSO₄/TBHP/Cs₂CO₃) system.     

Selected Copper‐Based Reactions for C−N,C−O,C−S,and C−C Bond Formation

Metal‐catalyzed cross‐coupling reactions belong to the most important transformations in organic synthesis. Copper catalysis has received great attention owing to the low toxicity and low cost of copper. However, traditional Ullmann‐type couplings suffer from limited substrate scopes and harsh reaction conditions. The introduction of several bidentate ligands, such as amino acids, diamines, 1,3‐diketones, and oxalic diamides, over the past two decades has totally changed this situation as these ligands enable the copper‐catalyzed coupling of aryl halides and nucleophiles at both low reaction temperatures and catalyst loadings. The reaction scope has also been greatly expanded, rendering this copper‐based cross‐coupling attractive for both academia and industry. In this Review, we have summarized the latest progress in the development of useful reaction conditions for the coupling of (hetero)aryl halides with different nucleophiles. Additionally, recent advances in copper‐catalyzed coupling reactions with aryl boronates and the copper‐based trifluoromethylation of aromatic electrophiles will be discussed.     

Nicotine functionalized‐silica palladium (II) complex: a highly efficient,environmentally benign and recyclable nanocatalyst for C‐C bond forming reactions under mild conditions

An environmentally friendly silica‐grafted nicotine‐based palladium(II) complex was successfully prepared and evaluated for the first time as novel and efficient nanocatalyst in C‐C bond forming reactions. Grafted‐nicotine in this catalytic system plays an important role, and as an effective ligand and a quaternary ammonium salt demonstrates an efficient stabilizing effect on the Pd(II) species by a synergistic effect of coordination and electrostatic interactions. The catalyst was well characterized by FT‐IR, CHN, XRD, TEM, SEM–EDX, ICP and TG analysis, and demonstrated a highly efficient catalytic activity in the reaction system under phosphine‐free and low Pd loading conditions, and the coupled products were produced in good to excellent yields. Furthermore, the catalyst can be easily recovered and reused without a significant loss of activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of Methylene‐Bridged Biscarbazole Alkaloids by using an Ullmann‐type Coupling: First Total Synthesis of Murrastifoline‐C and Murrafoline‐E

We describe the total synthesis of methylene‐bridged biscarbazole alkaloids by using a late‐stage Ullmann‐type coupling of fully functionalised carbazole subunits. The carbazole derivatives were synthesised via a sequence of palladium(0)‐ and palladium(II)‐catalysed coupling reactions. Our approach has provided bismurrayafoline‐A, bismurrayafolinol, chrestifolines B–D, and the first total synthesis of murrastifoline‐C and murrafoline‐E.