Synthesis and microwave‐assisted catalytic activity of novel bis‐benzimidazole salts bearing furfuryl and thenyl moieties in Heck and Suzuki cross‐coupling reactions

A mixture of bis‐benzimidazole salts ( 1–7 ), Pd(OAc)₂ and K₂CO₃ in DMF ? H₂O catalyzes, in high yield, the Suzuki and Heck cross‐coupling reactions assisted by microwave irradiation in a short time. In particular, the yields of the Heck and Suzuki reactions with aryl bromides were found to be nearly quantative. The synthesized bis‐benzimidazole salts ( 1 – 7 ) were identified by ¹H? ¹³C NMR, IR spectroscopic methods and micro analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,microwave‐promoted catalytic activity in Suzuki–Miyaura cross‐coupling reactions and antimicrobial properties of novel benzimidazole salts bearing trimethylsilyl group

A mixture of benzimidazole salts (2–7), Pd(OAc)₂ and K₂CO₃ in DMF–H₂O catalyzes the Suzuki–Miyaura cross‐coupling reactions promoted by microwave irradiation resulting in high yield within a short time. In particular, the yield of the Suzuki–Miyaura reactions with aryl bromides was found to be nearly quantitative. The synthesized benzimidazole salts (2–7) were identified by ¹H‐¹³C, NMR, IR spectroscopic methods and microanalysis. The molecular structure of 1 was determined by X‐ray crystallography. The antibacterial and antifungal activities of the novel benzimidazole derivatives (1–7) were also tested against standard strains. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and catalytic activity of novel xylyl‐linked benzimidazolium salts

The reaction of 1‐alkylbenzimidazole derivatives with o‐/p‐di(chloromethyl)benzene results in the formation of the new o‐/p‐xylyl‐linked bis(benzimidazolium) salts, 1 and 2, respectively. The salts were characterized by NMR spectroscopy and elemental analysis. The in situ prepared complexes derived from Pd(OAc)₂–1 and 2 exhibit catalytic activity (61–98%), to give the Heck coupling products of aryl bromides and styrene. Copyright © 2009 John Wiley & Sons, Ltd.     

New route to synthesis of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Heck and Suzuki cross‐coupling reactions

Herein we report a new method for the synthesis and characterization of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Suzuki coupling and Heck reactions of aryl bromides with phenylboronic acid and styrene, respectively, under mild conditions. The PVP‐stabilized palladium(0) nanoclusters with a particle size of 4.5 ± 1.1 nm were prepared using a new method: refluxing a mixture of potassium tetrachloropalladate(II) and PVP in methanol at 80 °C for 1 h followed by reduction with sodium borohydride. Palladium(0) nanoclusters prepared in this way were stable in solution for weeks, could be isolated as solid materials and were characterized by TEM, XPS, UV–vis, and XRD techniques. The PVP‐stabilized palladium(0) nanoclusters were active catalysts in Heck and Suzuki coupling reactions of arylbromides with styrene and phenylboronic acid affording stilbenes and biphenyls, respectively, in high yield. Recycling experiments showed that PVP‐stabilized palladium(0) nanoclusters could be used five times with essentially no loss in activity in the Heck and Suzuki coupling reactions. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of novel palladium N‐heterocyclic‐carbene complexes as catalysts for Heck and Suzuki cross‐coupling reactions

Novel palladium‐1,3‐dialkylperhydrobenzimidazolin‐2‐ylidene (2a–c) and palladium‐1,3‐dialkylimidazolin‐2‐ylidene complexes (4a,b) have been prepared and characterized by C, H, N analysis, ¹H‐NMR and ¹³C‐NMR. Styrene or phenylboronic acid reacts with aryl halide derivatives in the presence of catalytic amounts of the new palladium‐carbene complexes, PdCl₂(1,3‐dialkylperhydrobenzimidazolin‐2‐ylidene) or PdCl₂(1,3‐dialkylimidazolin‐2‐ylidene) to give the corresponding C? C coupling products in good yields. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis,structural characterization and catalytic activity of benzimidazole‐functionalized Pd(II) N‐heterocyclic carbene complexes

Two Pd(II)–NHC complexes bearing benzimidazole and pyridine groups have been successfully prepared and fully characterized by NMR and X‐ray diffraction analysis. The structure of palladium complexes are a typical square‐planar with palladium surrounded by two pairs of trans‐arranged benzimidazole and carbene ligands. The Pd–NHC complexes have been proved to be a highly efficient catalyst for the Mizoroki–Heck coupling reaction of aryl halides with various substituted acrylates under mild conditions in excellent yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Iminophosphine palladium(II) complexes: synthesis,characterization, and application in Heck cross‐coupling reaction of aryl bromides

Palladium(II) complexes containing phosphorus and nitrogen donor atoms (iminophosphine), dichlorido{N‐[2‐(diphenylphosphino)benzylidene]‐2‐trifluoromethylaniline}palladium(II) 1 , dichlorido{N‐[2‐(diphenylphosphino)benzylidene]‐3‐trifluoromethylaniline}palladium(II) 2 , dichlorido{N‐[2‐(diphenylphosphino)benzylidene]‐2‐methylaniline}palladium(II) 3 , dichlorido{N‐[2‐(diphenylphosphino)benzylidene]‐3‐methylaniline}palladium(II) 4 have been successfully synthesized and fully characterized by FT‐IR and NMR (¹H, ³¹P, ¹⁹F, and ¹³C) spectroscopy techniques. These complexes were first step tested in the reaction of bromobenzene and styrene to determine the optimal coupling reaction conditions and then successfully applied as catalysts for Heck cross‐coupling reactions of activated and deactivated aryl bromides with styrene derivatives and several acrylates. Copyright © 2014 John Wiley & Sons, Ltd.     

Ligand effects in palladium‐catalyzed Suzuki and Heck coupling reactions

A range of sterically hindered diimine ligands and their palladium (II) complexes were synthesized. These compounds were fully characterized by elemental analysis, ¹H and ¹³C‐NMR spectroscopy. The use of the palladium complexes as catalysts for Suzuki and Heck coupling has been studied in an attempt to demonstrate the effect of side groups on catalytic activity. It was clearly seen that the location of side ? CH₃ groups which bound to benzene ring had little effect on catalytic activity. Interestingly when we changed these ? CH₃ groups with ? Cl groups the activity of the complexes increased. On the other hand, side groups which bound to imine nitrogen also had a large effect on catalytic activity. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficient and green catalytic system incorporating new benzimidazolium salts for the Sonogashira cross‐coupling reaction

A number of novel benzimidazole salts were synthesized and their structures were determined using ¹H NMR, ¹³C NMR and infrared spectroscopic techniques and elemental analysis. A catalyst system consisting of Pd(OAc)₂ and copper nanoparticles in the presence of Cs₂CO₃ and incorporating the novel benzimidazole salts in poly(ethylene glycol) solvent significantly improved the yields of Sonogashira reactions between aryl halides and phenylacetylene under microwave irradiation in 10 min.     

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.     

Synthesis,characterization and catalytic activity of new aminomethyldiphosphine–Pd(II) complexes for Suzuki cross‐coupling reaction

A new range of CF₃‐substituted aminomethyldiphosphine (P―C―N) ligands ((C₆H₅)₂PCH₂)₂NR (R = ―C₆H₄(2‐CF₃) ( 1 ), ―C₆H₄(3‐CF₃) ( 1b ) has been synthesized from 2‐(trifluoromethyl)aniline and 3‐(trifluoromethyl)aniline with diphenylphosphine. The aminomethyldiphosphine ligands were reacted with Pd(cod)Cl₂ to give corresponding metal complexes, PdLCl₂ ( 2a , 2b ). The aminomethyldiphosphine–palladium compounds were characterized by utilizing several methods including NMR (¹H, ¹³C, ³¹P) and elemental analysis. These compounds were used as catalysts in Suzuki cross‐coupling reaction of aryl chlorides and bromides. The effect of base was also investigated in this current project. CF₃‐substituted aminomethyldiphosphine–palladium complexes were found to be efficient catalysts in Suzuki cross‐coupling reaction of activated and deactivated aryl boronic acids. Copyright © 2013 John Wiley & Sons, Ltd.     

Heck and oxidative boron Heck reactions employing Pd(II) supported amphiphilized polyethyleneimine‐functionalized MCM‐41 (MCM‐41@aPEI‐Pd) as an efficient and recyclable nanocatalyst

A novel nanocatalyst was developed based on covalent surface functionalization of MCM‐41 with polyethyleneimine (PEI) using [3‐(2,3‐Epoxypropoxy)propyl] trimethoxysilane (EPO) as a cross‐linker. Amine functional groups on the surface of MCM‐41 were then conjugated with iodododecane to render an amphiphilic property to the catalyst. Palladium (II) was finally immobilized onto the MCM‐41@PEI‐dodecane and the resulted MCM‐41@aPEI‐Pd nanocatalyst was characterized by FT‐IR, TEM, ICP‐AES and XPS. Our designed nanocatalyst with a distinguished core‐shell structure and Pd²⁺ ions as catalytic centers was explored as an efficient and recyclable catalyst for Heck and oxidative boron Heck coupling reactions. In Heck coupling reaction, the catalytic activity of MCM‐41@aPEI‐Pd in the presence of triethylamine as base led to very high yields and selectivity. Meanwhile, the MCM‐41@aPEI‐Pd as the first semi‐heterogeneous palladium catalyst was examined in the C‐4 regioselective arylation of coumarin via the direct C‐H activation and the moderate to excellent yields were obtained toward different functional groups. Leaching test indicated the high stability of palladium on the surface of MCM‐41@aPEI‐Pd as it could be recycled for several runs without significant loss of its catalytic activity.     

Threonine stabilizer‐controlled well‐dispersed small palladium nanoparticles on modified magnetic nanocatalyst for Heck cross‐coupling process in water

We report the synthesis of magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ magnetic nanoparticles with a core–shell structure. After synthesis of Fe₃O₄@Silica, threonine as an efficient stabilizer/ligand was bonded to the surface of Fe₃O₄@Silica. Then, palladium nanoparticles were generated on the threonine‐modified catalyst. The threonine stabilizer helps to generate palladium nanoparticles of small size (less than 4 nm) with high dispersity and uniformity. Magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ nanocatalyst was fully characterized using various techniques. This nanocatalyst efficiently catalysed the Heck cross‐coupling reaction of a variety of substrates in water medium as a green, safe and inexpensive solvent at 80°C. The Fe₃O₄@Silica‐Threonine‐Pd⁰ catalyst was used for at least eight successful consecutive runs with palladium leaching of only 0.05%.     

Palladium nanoparticles supported on modified hollow Fe3O4@TiO2: Preparation,characterization, and catalytic activity in Suzuki cross‐coupling reactions

Hollow Fe₃O₄@TiO₂‐NH₂/Pd as a light‐weight, magnetically heterogeneous catalyst was successfully prepared, and characterized by using different techniques including X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), vibrating sample magnetometer (VSM) measurements, and thermogravimetric analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross‐coupling reaction, and the results confirmed the success of this method. The catalyst could be separated easily using an external magnet and reused at least in five runs successfully without any appreciable loss in its catalytic activity.     

Synthesis and characterization of transition metal complexes of thiophene‐2‐methylamine: X‐ray crystal structure of palladium (II) and platinum (II) complexes and use of palladium(II) complexes as pre‐catalyst in Heck and Suzuki cross‐coupling reactions

The reactions of thiophene‐2‐(N‐diphenylphosphino)methylamine, Ph₂PNHCH₂‐C₄H₃S, 1 and thiophene‐2‐[N,N‐bis(diphenylphosphino)methylamine], (Ph₂P)₂NCH₂‐C₄H₃S, 2, with MCl₂(cod) (M = Pd, Pt; cod = 1,5‐cyclooctadiene) or [Cu(CH₃CN)₄]PF₆ yields the new complexes [M(Ph₂PNHCH₂‐C₄H₃S)₂Cl₂], M = Pd 1a, Pt 1b, [Cu(Ph₂PNHCH₂‐C₄H₃S)₄]PF₆, 1c, and [M(Ph₂P)₂NCH₂‐C₄H₃S)Cl₂], M = Pd 2a, Pt 2b, {Cu[(Ph₂P)₂NCH₂‐C₄H₃S]₂}PF₆, 2c, respectively. The new compounds were isolated as analytically pure crystalline solids and characterized by ³¹P‐, ¹³C‐, ¹H‐NMR and IR spectroscopy and elemental analysis. Furthermore, the solid‐state molecular structures of representative palladium and platinum complexes of bis(phosphine)amine, 2a and 2b, respectively, were determined using single crystal X‐ray diffraction analysis. The palladium complexes were tested as potential catalysts in the Heck and Suzuki cross‐coupling reactions. Copyright © 2009 John Wiley & Sons, Ltd.     

Silica‐supported 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) complex: Heck and Suzuki cross‐coupling reactions

A novel mesoporous silica‐nanotube‐supported 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) complex was prepared and characterized. 3‐4,5‐Dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) and mesoporous silica‐supported 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) were tested for catalytic activity for Heck coupling reactions between styrene and several aryl halides and Suzuki coupling reactions between phenylboronic acid and several aryl halides. Copyright © 2003 John Wiley & Sons, Ltd.     

Pd(II) complexes of novel phosphine ligands: Synthesis,characterization, and catalytic activities on Heck reaction

Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH₃, monitored by ³¹P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.     

A General Synthesis of Alkenyl‐Substituted Benzofurans,Indoles, and Isoquinolones by Cascade Palladium‐Catalyzed Heterocyclization/Oxidative Heck Coupling

Structurally diverse C3‐alkenylbenzofurans, C3‐alkenylindoles, and C4‐alkenylisoquinolones are efficiently prepared by using consecutive Sonogashira and cascade Pd‐catalyzed heterocyclization/oxidative Heck couplings from readily available ortho‐iodosubstituted phenol, aniline, and benzamide substrates, alkynes, and functionalized olefins. The cyclization of O‐ and N‐heteronucleophiles follows regioselective 5‐endo‐dig‐ or 6‐endo‐dig‐cyclization modes, whereas the subsequent Heck‐type coupling with both mono‐ and disubstituted olefins takes place stereoselectively with exclusive formation of the E isomers in most cases.     

Enantioselective Synthesis of Chromenes via a Palladium‐Catalyzed Asymmetric Redox‐Relay Heck Reaction

A palladium‐catalyzed asymmetric redox‐relay Heck reaction of 4H ‐chromenes and arylboronic acids has been successfully developed. The reaction proceeded in moderate to good yields with good to high enantioselectivities. The resulting product is an advanced intermediate of bio‐active compound BW683C.     

Immobilized Pd on (S)‐methyl histidinate‐modified multi‐walled carbon nanotubes: a powerful and recyclable catalyst for Mizoroki–Heck and Suzuki–Miyaura C–C cross‐coupling reactions in green solvents and under mild conditions

A stable and powerful heterogeneous palladium catalyst was synthesized using immobilized palladium on (S)‐methyl histidinate bonded onto the surface of multi‐walled carbon nanotubes. The catalyst was characterized using a combination of Fourier transform infrared and X‐ray photoelectron spectroscopies, transmission electron microscopy, X‐ray powder diffraction and inductively coupled plasma, thermogravimetric and elemental analyses. This new air‐ and moisture‐stable phosphine‐free palladium catalyst was found to be highly active and reusable in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions in poly(ethylene glycol) and aqueous ethanol as green solvents using an extremely small amount of palladium under mild conditions. Copyright © 2016 John Wiley & Sons, Ltd.