A highly selective synthesis of 1‐substituted (E)‐buta‐1,3‐dienes with 4,4,5,5‐tetramethyl‐2‐vinyl‐1,3,2‐dioxaborolane as building block

Highly selective synthesis of 1‐substituted (E)‐buta‐1,3‐dienes via palladium‐catalyzed Suzuki–Miyaura cross‐coupling of (E)‐alkenyl iodides with 4,4,5,5‐tetramethyl‐2‐vinyl‐1,3,2‐dioxaborolane ( 1 ) is reported. The vinylboronate pinacol ester ( 1 ) acts as a vinyl building block to show high chemoselectivity for the Suzuki–Miyaura pathway versus Heck coupling in the presence of biphasic conditions (Pd(PPh₃)₄, aqueous K₂CO₃, toluene and ethanol). Copyright © 2014 John Wiley & Sons, Ltd.     

Palladium‐catalysed Suzuki reaction of aryl chlorides in aqueous media using 1,3‐dialkylimidazolidin‐2‐ylidene ligands

A highly effective, easy to handle and environmentally benign process for palladium‐mediated Suzuki cross‐coupling is developed. The in situ prepared three‐component system Pd(OAc)₂–1,3‐bis(alkyl)imidazolinium chlorides (2a–f) and Cs₂CO₃ catalyses quantitatively the Suzuki cross‐coupling of deactivated aryl chlorides. Copyright © 2005 John Wiley & Sons, Ltd.     

Application of Suzuki Cross‐Coupling Reaction Catalyzed by Ligandless Palladium Chloride in the Synthesis of Liquid Crystals

Palladium chloride–catalyzed Suzuki cross‐coupling reaction was applied to the preparation of highly pure multiring liquid crystals with a biphenyl unit. The optimal reaction condition is the combination of 0.5 mol% PdCl₂, pyridine, and K₃PO₄, which was able to catalyze the cross‐coupling of substituted aryl bromides with substituted trans‐cyclohexylphenylboronic acids to give pure products in 38–87% yields.     

Use of N‐methyliminodiacetic acid boronate esters in suzuki‐miyaura cross‐coupling polymerizations of triarylamine and fluorene monomers

Polytriarylamine copolymers can be prepared by Suzuki‐Miyaura cross‐coupling reactions of bis N‐methyliminodiacetic acid (MIDA) boronate ester substituted arylamines with dibromo arenes. The roles of solvent composition, temperature, reaction time, and co‐monomer structure were examined and (co)polymers prepared containing 9, 9‐dioctylfluorene (F8), 4‐sec‐butyl or 4‐octylphenyl diphenyl amine (TFB), and N, N′‐bis(4‐octylphenyl)‐N, N′‐diphenyl phenylenediamine (PTB) units, using a Pd(OAc)₂/2‐dicyclohexylphosphino‐2′,6′‐dimethoxybiphenyl (SPhos) catalyst system. The performance of a di‐functionalized MIDA boronate ester monomer was compared with that of an equivalent pinacol boronate ester. Higher molar mass polymers were produced from reactions starting with a difunctionalized pinacol boronate ester monomer than the equivalent difunctionalized MIDA boronate ester monomer in biphase solvent mixtures (toluene/dioxane/water). Matrix‐assisted laser desorption/ionization mass spectroscopic analysis revealed that polymeric structures rich in residues associated with the starting MIDA monomer were present, suggesting that homo‐coupling of the boronate ester must be occurring to the detriment of cross‐coupling in the step‐growth polymerization. However, when comparable reactions of the two boronate monomers with a dibromo fluorene monomer were completed in a single phase solvent mixture (dioxane + water), high molar mass polymers with relatively narrow distribution ranges were obtained after only 4 h of reaction. © 2017 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2798–2806     

Room temperature suzuki cross‐coupling polymerizations of aryl dihalides and aryldiboronic acid/acid esters with t‐Bu3P‐coordinated 2‐phenylaniline‐based palladacycle complex as the precatalyst

Room temperature Suzuki cross‐coupling polymerization of aryl dibromides/diiodides with aryldiboronic acids/acid esters with t‐Bu₃P‐coordinated 2‐phenylaniline‐based palladacycle complex, [2′‐(amino‐kN)[1,1′‐biphenyl]‐2‐yl‐kC]chloro(tri‐t‐butylphosphine)palladium, as a general precatalyst is described. Such room temperature Suzuki cross‐coupling polymerization is achieved by employing six equivalents or more of the base and affords polymers within an hour, with the yields and the molecular weights in general comparable to or higher than reported results that required higher reaction temperature and/or longer polymerization time. Our study provides a general catalyst system for the room temperature Suzuki cross‐coupling polymerization of aryl dibromides/diiodides with aryldiboronic acids/acid esters and paves the road for the investigation of employing other monodentate ligand‐coordinated palladacycle complexes including other electron‐rich monophosphine‐coordinated ones for room temperature cross‐coupling polymerizations. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1606–1611     

A simple,quick and novel protocol for biaryl synthesis using LiCl‐promoted in situ‐generated Pd nanoparticles

This paper describes a simple and a very quick protocol for biaryl synthesis using the Suzuki–Miyaura cross‐coupling reaction. A quintessential role of salting‐out agent LiCl was observed in the Suzuki–Miyaura cross‐coupling reaction that enhanced the reduction rate of Pd (II) to a considerable extent, resulting in the formation of nanosized palladium in a few seconds. The isolated Pd nanoparticles were characterized with X‐ray diffraction, dynamic light scattering, TGA, transmission electron microscopy and scanning electron microscopy‐dispersive X‐ray spectroscopy. The Suzuki–Miyaura cross‐coupling reaction proceeded very well with the in situ‐generated Pd nanocatalysts furnishing the desired biaryl adducts with excellent yields.     

Stereoselective Synthesis of Novel C-Disaccharides via Suzuki Cross-Coupling Reaction

Novel β-C-disaccharides containing a three carbon linkage using exo-glycal as the precursor were prepared stereoselectively. The synthesis was achieved by the tandem reactions of the stereoselective hydroboration of exo-glycal and Suzuki cross-coupling reaction with an iodovinyl sugar, and followed by hydrogenated deprotection under the catalysis of Pd（OH）2/C.     

Palladium(II)‐N‐heterocyclic carbene complexes: synthesis,characterization and catalytic application

N‐Heterocyclic carbenes (NHCs) are of great importance and are powerful ligands for transition metals. A new series of sterically hindered benzimidazole‐based NHC ligands (LHX) ( 2a , 2b , 2c , 2d , 2e , 2f ), silver–NHC complexes ( 3a , 3b , 3c , 3d , 3e , 3f ) and palladium–NHC complexes ( 4a , 4b , 4c , 4d , 4e , 4f ) have been synthesized and characterized using appropriate spectroscopic techniques. Studies have focused on the development of a more efficient catalytic system for the Suzuki coupling reaction of aryl chlorides. Catalytic performance of Pd–NHC complexes and in situ prepared Pd(OAc)₂/LHX catalysts has been investigated for the Suzuki cross‐coupling reaction under mild reaction conditions in aqueous N,N‐dimethylformamide (DMF). These complexes smoothly catalyzed the Suzuki–Miyaura reactions of electron‐rich and electron‐poor aryl chlorides. Copyright © 2014 John Wiley & Sons, Ltd.     

One‐Pot Halogen Dance/Negishi Coupling of Dibromothiophenes for Regiocontrolled Synthesis of Multiply Arylated Thiophenes

One‐pot halogen dance/Negishi cross‐coupling of readily available 2,5‐dibromothiophenes is described. A lithium diisopropylamide (LDA)‐mediated halogen dance reaction resulted in the formation of thermodynamically stable α‐lithiodibromothiophenes, which were transmetalated with ZnCl₂ and subjected to Negishi cross‐coupling to provide the corresponding arylated dibromothiophenes in one pot. The resultant β‐bromo group was much less reactive than the remaining α‐bromo group, which was used in a one‐pot double Suzuki–Miyaura cross‐coupling, enabling facile synthesis of multiply arylated thiophenes.     

Mechanistic Investigation of Catalyst‐Transfer Suzuki–Miyaura Condensation Polymerization of Thiophene–Pyridine Biaryl Monomers with the Aid of Model Reactions

We have investigated the requirements for efficient Pd‐catalyzed Suzuki–Miyaura catalyst‐transfer condensation polymerization (Pd‐CTCP) reactions of 2‐alkoxypropyl‐6‐(5‐bromothiophen‐2‐yl)‐3‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)pyridine ( 12 ) as a donor–acceptor (D –A) biaryl monomer. As model reactions, we first carried out the Suzuki–Miyaura coupling reaction of X–Py–Th–X′ (Th=thiophene, Py=pyridine, X, X′=Br or I) 1 with phenylboronic acid ester 2 by using tBu₃PPd⁰ as the catalyst. Monosubstitution with a phenyl group at Th‐I mainly took place in the reaction of Br–Py–Th–I ( 1 b ) with 2 , whereas disubstitution selectively occurred in the reaction of I–Py–Th–Br ( 1 c ) with 2 , indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the M_n of the obtained polymer, as well as the matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectra, indicated that Suzuki–Miyaura coupling polymerization of 12 with (o‐tolyl)tBu₃PPdBr initiator 13 proceeded in a step‐growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki–Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step‐growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th‐Pd‐Py complex formed by transmetalation of polymer Th–Br with (Pin)B–Py–Th–Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal–arene η²‐coordination for D and A monomers may be needed for CTCP reactions of biaryl D–A monomers.     

Optimization of the Suzuki coupling reaction in the synthesis of 2‐[(2‐substituted)phenyl]pyrrole derivatives

A facile three‐step synthesis of 2‐(2‐aminophenyl)pyrrole ( 1 ) and 2‐[(2‐aminomethyl)phenyl]pyrrole ( 2 ) is reported by use of Suzuki coupling of N‐Boc‐pyrrol‐2‐yl boronic acid ( 3 ) and o‐substituted aryl halogenides, followed by hydrogenation. The Pd‐catalyzed cross‐coupling reaction is optimized to be applicable to a wide range of substitued aryl halogenides, with electron‐donating and electron‐withdrawing substituents, 5a , 5b , 5c , 5d , 5e , 5f , 5g . Moreover, Pd‐catalyzed coupling of o‐bromoaniline and 3 could be applied for the one‐step preparation of pyrrolo[1,2‐c]quinazolin‐5(6H)‐one ( 8 ). J. Heterocyclic Chem., (2011).     

An Electron‐Poor C64 Nanographene by Palladium‐Catalyzed Cascade C−C Bond Formation: One‐Pot Synthesis and Single‐Crystal Structure Analysis

Herein, we report the one‐pot synthesis of an electron‐poor nanographene containing dicarboximide groups at the corners. We efficiently combined palladium‐catalyzed Suzuki–Miyaura cross‐coupling and dehydrohalogenation to synthesize an extended two‐dimensional π‐scaffold of defined size in a single chemical operation starting from N‐(2,6‐diisopropylphenyl)‐4,5‐dibromo‐1,8‐naphthalimide and a tetrasubstituted pyrene boronic acid ester as readily accessible starting materials. The reaction of these precursors under the conditions commonly used for Suzuki–Miyaura cross‐coupling afforded a C₆₄ nanographene through the formation of ten C?C bonds in a one‐pot process. Single‐crystal X‐ray analysis unequivocally confirmed the structure of this unique extended aromatic molecule with a planar geometry. The optical and electrochemical properties of this largest ever synthesized planar electron‐poor nanographene skeleton were also analyzed.     

Solid‐Phase Synthesis of Oligo(triacetylene)s and Oligo(phenylenetriacetylene)s Employing Sonogashira and Cadiot?Chodkiewicz‐Type Cross‐Coupling Reactions

We describe the first polymer‐supported synthesis of poly(triacetylene)‐derived monodisperse oligomers, utilizing Pd⁰‐catalyzed Sonogashira and Cadiot? Chodkiewicz‐type cross‐couplings as the key steps in the construction of the acetylenic scaffolds. For our investigations, Merrifield resin functionalized with a 1‐(4‐iodoaryl)triazene linker was chosen as the polymeric support ( R2 ; Figure and Scheme 3). The linker selection was made based on the results of several model studies in the liquid phase (Schemes 1 and 2). For the solid‐support synthesis of the oligo(phenylene triacetylene)s 7b – 7d , a set of only three reactions was required: i) Pd⁰‐catalyzed Sonogashira cross‐coupling, ii) Me₃Si? alkyne deprotection by protodesilylation, and iii) cleavage of the linker with liberation of the generated oligomers (Scheme 5). The longest‐wavelength absorption maxima of the oligo(phenylene triacetylene)s 7a – 7d shift bathochromically with increasing oligomeric length, from λ_max 337 nm (monomer 7a ) to 384 nm (tetramer 7d ; Table 2). Based on the electronic absorption data, the effective conjugation length (ECL) of the oligo(phenylene triacetylene)s is estimated to involve at least four monomer units and 40 C‐atoms. π‐Electron conjugation in these oligomers is less efficient than in the known oligo(triacetylene)s 14a – 14d (Table 2) due to poor transmittance of π‐electron delocalization by the phenyl rings inserted into the oligomeric backbone. Similar conclusions were drawn from the electrochemical properties of the two oligomeric series as determined by cyclic (CV) and rotating‐disk voltammetry (RDV; Table 3). In sharp contrast to 14b – 14d , the oligo(phenylene triacetylene)s 7b – 7d are strongly fluorescent, with the highest quantum yield Φ_F=0.69 measured for trimer 7c (Table 2). Whereas the Sonogashira cross‐coupling on solid support proceeded smoothly, optimal conditions for alkyne? alkyne cross‐coupling reactions employing Pd⁰‐catalyzed Cadiot? Chodkiewicz conditions still remain to be developed, despite extensive experimentation (Scheme 7 and Table 1).     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Modular Stereoselective Synthesis of (1→2)‐C‐Glycosides based on the sp2–sp3 Suzuki–Miyaura Reaction

This work reports a modular and rapid approach to the stereoselective synthesis of a variety of α‐ and β‐(1→2)‐linked C‐disaccharides. The key step is a Ni‐catalyzed cross‐coupling reaction of D ‐glucal pinacol boronate with alkyl halide glycoside easily prepared from commercially available D ‐glucal. The products of this sp²–sp³ cross‐coupling reaction can be converted to glucopyranosyl, mannopyranosyl, or 2‐deoxy‐glucopyranosyl C‐mannopyranosides by one‐ or two‐step stereoselective oxidative–reductive transformations. To the best of our knowledge, we demonstrated the first synthetic application of a challenging sp²–sp³ Suzuki‐Miyaura cross‐coupling reaction in carbohydrate chemistry.     

Suzuki Cross‐coupling Method to Prepare 4,4″‐Diamino‐p‐terphenyl

The synthesis of 4,4″‐dinitro‐p‐terphenyl is accomplished by double Suzuki cross‐coupling. The product was reduced catalytically to give 4,4″‐diamino‐p‐terphenyl in 75% overall yield.     

Preparation of phenyl‐modified natural rubber in latex stage

Phenyl‐modified natural rubber was prepared in latex stage by bromination of deproteinized natural rubber followed by Suzuki‐Miyaura cross‐coupling reaction. First, the bromination of natural rubber was carried out using N‐bromosuccinimide in latex stage. The bromine atom content increased as amount of N‐bromosuccinimide increased. Second, the allylic bromine atom was replaced with a phenyl group using phenyl boronic acid in the presence of a palladium catalyst, according to the Suzuki‐Miyaura cross‐coupling reaction in latex stage. The resulting products were characterized by nuclear magnetic resonance (NMR) spectroscopy. Signal at 7.13 ppm was assigned to the phenyl group of the product, while signals at 3.98, 4.14, and 4.44 ppm were assigned to the remaining allylic brominated cis‐1,4‐isoprene units. The estimated phenyl group content and the conversion of the Suzuki‐Miyaura cross‐coupling reaction were 1.32 and 23.7 mol%, respectively. Glass transition temperature (T_g) of deproteinized natural rubber increased from ?62°C to ?46.7°C, when the phenyl group was introduced into the rubber.     

Synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles by reductive cyclization of 6‐(2′‐Nitrophenyl)benzo[b]thiophenes obtained by palladium‐catalyzed cross‐coupling isabel

The synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles (5) (R=H) was achieved by a palladium‐catalyzed cross‐coupling, intramolecular reductive cyclization sequence of reactions. The cyclization precursors 6‐(2′‐nitrophenyl)benzo[b]thiophenes (3) were obtained by Suzuki cross‐coupling of 6‐boronated methylbenzo[b]thiophenes intermediates (2) with 2‐bromo or iodonitrobenzene. The boronated intermediates (2) were prepared via bromine‐lithium exchange followed by boron transmetalation and coupled in situ using Pd(OAc)₂ giving thus a “one‐pot” three steps reaction from the 6‐bromobenzo[b]thio‐phenes (1) to the cyclization precursors (3) . In the reductive cyclization step, N‐ethylthienocarbazoles (5) (R=Et) were also obtained. Several experiments have been made varying the amount of triethylphosphite and the time of reaction, to avoid their formation.     

Optimized Palladium(0)‐catalyzed Suzuki Cross‐coupling Reaction of Polystyrene‐supported Selenenyl Flavanones: A Convenient Preparation of Biaryl‐chromen‐4‐one

Application of the Suzuki cross‐coupling reaction for efficient synthesis of diverse substituted biaryl‐chromen‐4‐ones using an optimized palladium(0) catalyst system is reported. The coupling of arylboronic acids with the resin‐bound bromoflavanones which were prepared by organoselenium‐induced regioselective intramolecular cyclization of bromo‐2‐hydroxylchalcones proceeded smoothly. Biaryl‐chromen‐4‐ones were synthesized by subsequent selenoxide syn‐elimination in good total yields.     

Direct Cross‐Couplings of Propargylic Diols

[Pd(PPh₃)₄] catalyzes a Suzuki–Miyaura‐like twofold cross‐coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3‐dienes. Thus, 2,3‐diaryl‐1,3‐butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen‐free, single‐step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single‐ and twofold cross‐coupled products with acid leads to remarkably short syntheses of highly‐substituted benzofulvenes and aryl indenes, respectively.