Polyaniline‐anchored palladium catalyst‐mediated Mizoroki–Heck and Suzuki–Miyaura reactions and one‐pot Wittig–Heck and Wittig–Suzuki reactions

A polyaniline‐anchored palladium catalyst was prepared and screened for coupling reactions of aryl halides. The robust and recyclable catalyst was effective in Mizoroki–Heck and Suzuki–Miyaura reactions of aryl bromides and aryl iodides. The catalyst system was further employed for one‐pot Wittig–Heck and Wittig–Suzuki combinations to build conjugated compounds in good conversions. Copyright © 2014 John Wiley & Sons, Ltd.     

Dinuclear Pd(II)–NHC complex derived from proline and its application toward Mizoroki–Heck reaction performed in water

A novel dinuclear Pd(II)–N‐heterocyclic carbene complex derived from proline was successfully synthesized and its structure was confirmed unambiguously by X‐ray single‐crystal diffraction. Furthermore, the complex was found to be a good catalyst in the Mizoroki–Heck reaction of aryl iodides and bromides with acrylic acid performed in pure water. Copyright © 2012 John Wiley & Sons, Ltd.     

Chugaev‐type bis(acyclic diaminocarbenes) as a new ligand class for the palladium‐catalyzed Mizoroki–Heck reaction

A series of differently substituted Chugaev‐type palladium bis(acyclic diaminocarbene) complexes was screened to identify the most active catalyst for Mizoroki–Heck coupling reactions of aryl bromides with styrene. The best catalyst, which contains three methyl groups on the bis(carbene) ligand, gives excellent coupling yields at 120 °C for both activated and deactivated aryl bromides. However, activity with aryl chlorides is limited to electron‐deficient examples. The optimized catalyst demonstrates limited air and moisture stability, giving reduced yields in couplings of activated aryl bromides in open‐flask conditions. The modular synthesis of this class of catalysts should allow further fine‐tuning of activity in Mizoroki–Heck and related coupling reactions. Copyright © 2012 John Wiley & Sons, Ltd.     

Pd(II) salen complex covalently anchored to multi‐walled carbon nanotubes as a heterogeneous and reusable precatalyst for Mizoroki–Heck and Hiyama cross‐coupling reactions

A Pd(II) salen complex anchored to multi‐walled carbon nanotubes showed excellent catalytic activity and stability for the Mizoroki–Heck and Hiyama cross‐couplings of aryl halides with olefins and phenylsiloxanes. Furthermore, the heterogeneous catalyst could be reused up to four times with the catalytic activity being recovered easily after simple manipulations. Copyright © 2014 John Wiley & Sons, Ltd.     

A PdCl2–ionic liquid brush assembly: an efficient and reusable catalyst for Mizoroki–Heck reaction in neat water

An efficient and reusable heterogeneous catalytic assembly of PdCl₂ held in ionic liquid brushes has been synthesized and an environmentally‐friendly procedure was developed for coupling aryl iodides with acrylic acid. These reactions were conducted in water under aerobic conditions with water‐insoluble or even solid aryl iodides and they proceeded smoothly and cleanly without any organic co‐solvent or other additives. A 0.5 mol% (based on Pd atom) dose of the catalyst was found to be sufficient for Mizoroki–Heck reaction. The catalyst is easily recovered post reaction, via simple filtration, and reused at least eight times without a noticeable loss of activity. The protocol has the advantages of excellent yield, environmental friendliness, and catalyst recyclability. Copyright © 2011 John Wiley & Sons, Ltd.     

Accelerated Heck reaction using ortho‐palladated complex with controlled microwave heating

Palladium‐catalyzed Heck couplings utilizing [Pd{C₆H₂(CH₂CH₂NH₂)‐(OMe)₂,3,4} (µ‐Br)]₂ palladacycle catalyst and microwave irradiation lead to formation of different coupling products. This complex is an active and efficient catalyst for the Heck reaction of aryl iodides, bromides and even less reactive chlorides. The cross‐coupled products were produced in excellent yields. The reaction time was reduced from hours to minutes and full conversion was achieved under microwave irradiation. Copyright © 2009 John Wiley & Sons, Ltd.     

Accelerated Heck reaction using ortho‐palladated complex in a nonaqueous ionic liquid with controlled microwave heating

The activity of {Pd[C₆H₂(CH₂CH₂NH₂)‐(OMe)₂,3,4] (µ‐Br)}₂ complex was investigated in the Heck–Mizoroki C C cross‐coupling reaction under conventional heating and microwave irradiation conditions in molten salt tetrabutylammonium bromide as the solvent and promoter at 130 °C. This complex in these conditions is an active and efficient catalyst for the Heck reaction of aryl iodides, bromides and even chlorides, and also arenesulfonyl chlorides. Copyright © 2011 John Wiley & Sons, Ltd.     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

Magnetically‐recoverable Schiff Base Complex of Pd (II) Immobilized on Fe3O4@SiO2 Nanoparticles: An Efficient Catalyst for Mizoroki‐Heck and Suzuki‐Miyaura Coupling Reactions

The activity of Pd(II)‐Schiff base complex molecules grafted on the surface of Fe₃O₄@SiO₂ particles were investigated in the palladium‐catalyzed coupling reactions of aryl halides with alkenes (Mizoroki‐Heck reaction) and phenylboronic acids (Suzuki‐Miyaura reaction) in the absence of phosphorous ligands. This method shows notable advantages such as heterogeneous nature of the catalyst, excellent yields, short reaction times, easy preparation, simplicity of operation, and cleaner reaction profiles. The catalyst can be separated from the reaction mixture by applying a permanent magnet externally and can be reused for several times without significant loss of activity. Also, the amount of palladium leaching has been determined by ICP analysis.     

Simple kinetic method for distinguishing between homogeneous and heterogeneous mechanisms of catalysis,illustrated by the example of “ligand-free” Suzuki and Heck reactions of aryl iodides and aryl bromides

Using a simple method based on an analysis of the phase trajectories of competing reactions of several substrates, it has been established that the selectivity of catalytically active species in the Suzuki reaction of aryl bromides depends on the nature of the catalyst precursor. This indicates that there is a considerable contribution from heterogeneous catalysis. At the same time, in the reaction involving aryl iodides, when the catalyst concentration in the solution is much higher, the selectivity of the catalyst is precursor-independent, suggesting that homogeneous catalysis is dominant. In the Heck reaction of both aryl bromides and aryl iodides, pure homogeneous catalysis takes place.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Silver sequestration of halides for the activation of Pd(OAc)2 catalyzed Mizoroki‐Heck reaction of 1,1 and 1,2 ‐ Disubstituted alkenes

A ligand free catalytic system consisting of Pd(OAc)₂ (cat) and stoichiometric quantities of silver salts, AgOAc or AgBF₄, exhibit high efficiency in the Mizoroki‐Heck arylation, transforming aryl iodides and 1,1 as well as 1,2 disubstituted alkenes into 1,1,2 – trisubstituted aryl alkenes in excellent yields in very short reaction times.     

Polyacrylonitrile fiber mat‐supported palladium catalyst for Mizoroki–Heck reaction in aqueous solution

A novel palladium catalyst immobilized on polyacrylonitrile fiber mats (Pd/PAN) was prepared by electrospinning. The catalytic activity and recyclability of the microwave‐assisted Pd/PAN fiber mats were examined for the Mizoroki–Heck cross‐coupling of aryl iodides with three different acrylates in aqueous solution. The morphology of the prepared Pd/PAN fiber mats was characterized by scanning electron microscopy. The large size of the PAN fiber mat‐supported palladium catalyst enables much easier separation from the reaction mixture by simple filtration. Density functional theory calculation indicates that the chelation energy of palladium chloride (PdCl₂) with propionitrile (model of PAN) is considerable smaller than that of PdCl₂ with water, suggesting that the stability and reactivity of the Pd/PAN fiber mats catalyst could be improved through the surface derivatization with polar functional groups. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel hydrophobic fluorous ionic liquid for ligand-free Mizoroki–Heck reaction

Mizoroki–Heck reaction is carried out in a novel hydrophobic fluorous ionic liquid which was catalyzed by Pd-nanoparticles formed in situ from Pd(OAc)₂ used in the reaction. This reaction is operable under mild, aerobic, and ligand-free conditions in excellent yields. Aryl iodides, bromides as well as chlorides can be used showing its versatility. The key feature of the system is that catalyst along with ionic liquid can be reused at least five times with superior activity.     

Heck reaction catalyzed by Pd/C, in a triphasic-organic/Aliquat 336/aqueous-solvent system

The rate of the Pd/C catalyzed Heck coupling of Ar-I with CH(2)=CH-R is accelerated tenfold by the presence of Aliquat 336 (A336), a well known phase transfer catalyst, and an ionic liquid. Both when conducted in A336 as solvent, and in an isooctane/A336/aqueous triphasic mixture, the Heck reaction of aryl iodides with electron deficient olefins, catalyzed by Pd/C, proceeds with high yields and selectivity. When KOH is used instead of Et(3)N, selective formation of the biphenyl rather than the Heck product, is observed. Aryl bromides react more sluggishly, and only the more activated ones undergo the Heck reaction. In the absence of the olefin, aryl halides possessing an electron withdrawing group are reduced to the corresponding Ar-H.     

Kryptofix 5 as an inexpensive and efficient ligand for the palladium‐catalyzed Mizoroki‐Heck reaction

A novel complex of PdCl₂ with a multidentate cryptand ligand, Kryptofix 5, has been prepared and characterized by various techniques including ¹H‐ and ¹³C NMR spectroscopy, Fourier transform infrared (FT‐IR), Raman, ultraviolet and visible (UV‐VIS) spectroscopy, inductively coupled plasma (ICP), CHN elemental and energy dispersive X‐ray analysis (EDX). This heat‐ and air‐stable complex was utilized as a highly active catalyst for the Mizoroki‐Heck reaction of aryl halides with various olefins. Interestingly, it was found that aryl bromides as well as aryl iodides were efficiently cross‐coupled with terminal alkenes at 130 °C in 10 min. Furthermore, the least reactive aryl chlorides reacted with styrene to obtain the desired products in acceptable yields.     

A highly active palladium(II)–bis(oxazoline) catalyst for Suzuki–Miyaura,Mizoroki–Heck and sonogashira coupling reactions in aqueous dimethylformamide

An efficient catalytic system based on a new palladium–bis(oxazoline) ( Pd-BOX-1 ) complex has been developed. The complex Pd-BOX-1 adopts a legless chair‐type structure where the distorted square planar [PdN₂Cl₂] moiety and the benzene ring spacer represent the seat and the chair back, respectively. The catalytic activity of Pd-BOX-1 has been investigated in dimethylformamide–water under aerobic and mild conditions in Suzuki–Miyaura coupling reactions of arylboronic acids with aryl iodides, aryl bromides and aryl chlorides, Mizoroki–Heck coupling reactions of aryl halides with styrene derivatives, and Sonogashira coupling reactions of aryl halides with terminal alkynes. A wide range of functional groups as substituents on the arylboronic acids and aryl halides were considered. Pd-BOX-1 demonstrates exceptional air and moisture stability. Of note, the catalyst system based on Pd-BOX-1 shows high recycling ability in Suzuki–Miyaura coupling reactions in dimethylformamide–water without any loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

[Au]/[Pd] Multicatalytic Processes: Direct One‐Pot Access to Benzo[c]chromenes and Benzo[b]furans

A new synthetic protocol that combines the advantages offered by eco‐friendly solvent‐free reactions and sequential transformations is reported. This strategy offers straightforward access to benzo[c]chromenes and benzo[b]furans from commercially available starting materials. This two‐step, one‐pot strategy consists of an Au‐catalyzed hydrophenoxylation process followed by Pd‐catalyzed C?H activation or Mizoroki–Heck reactions. The selectivity of the process towards C?H activation or Mizoroki–Heck reaction can be easily tuned.     

18‐Crown‐6 promoting Pd/C‐catalyzed cross‐coupling reaction of aryl bromides and arylboronic acids in aqueous media

Pd/C‐catalyzed Suzuki–Miyaura cross‐coupling between aryl bromides and arylboronic acids in 50% methanol aqueous solution proceeded smoothly in the presence of 18‐crown‐6. Various aryl bromides bearing electron‐withdrawing groups and electron‐donating groups coupled with arylboronic acid in high yields. In addition, the catalyst could be recycled five times without loss of activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Ligand‐free palladium‐catalyzed tandem pathways for the synthesis of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐butenones under microwave conditions

Two efficient Pd‐catalyzed tandem pathways for the synthesis of 4,4‐diaryl‐2‐butanones and 4,4‐diaryl‐3‐buten‐2‐ones were elaborated. The first step in both procedures was the Heck coupling of methyl vinyl ketone (MVK) and various aryl iodides leading to 4‐aryl‐3‐buten‐2‐one with the yield of up to 92% in 1 hr. The second step performed with the same catalyst and a new portion of aryl iodide in the presence K₂CO₃ as a base produced 4,4‐diaryl‐3‐buten‐2‐ones in high yield. Reaction selectivity changed completely to saturated 4,4‐diaryl‐2‐butanones, reductive Heck products, when a tertiary amine was used instead of K₂CO₃. Due to the application of microwave irradiation (MW), the desired products were obtained in high yield in a short time (4 hr), using 0.5 mol% of the Pd (OAc)₂ catalyst without additional ligands.