Palladium-Catalyzed Suzuki-Miyaura Reactions Research Articles

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki-Miyaura reactions: relative reactivity of K[4-RC6F4BF3] and the role of silver-assistance in acceleration of transmetallation.

Small differences in the reactivity of weakly nucleophilic potassium aryltrifluoroborates are revealed in the silver-assisted Pd-catalyzed cross-coupling of K[4-RC6F4BF3] (R = H, Bu, MeO, EtO, PrO, iPrO, BuO, t-BuO, CH2=CHCH2O, PhCH2O, PhCH2CH2O, PhO, F, pyrazol-1-yl, pyrrol-1-yl, and indol-1-yl) with ArX (4-BrC6H4CH3, 4-IC6H4F and 3-IC6H4F). An assumed role of silver(I) compounds AgmY (Y = O, NO3, SO4, BF4, F) consists in polarization of the Pd–X bond in neutral complex ArPdLnX with the generation of the related transition state or formation of [ArPdLn][XAgmY] with a highly electrophilic cation and subsequent transmetallation with the weakly nucleophilic borate. Efficiency of AgmY as a polarizing agent decreases in order Ag2O > AgNO3 ≈ Ag2SO4 > Ag[BF4] > AgF. No clear correlation between the reactivity of K[4-RC6F4BF3] and substituent electron parameters, σI and σR°, of the aryl group 4-RC6F4 was found.

Palladium-catalyzed ligand-free and efficient Suzuki–Miyaura reaction of heteroaryl halides with MIDA boronates in water

A simple and environment-friendly protocol for the palladium-catalyzed Suzuki–Miyaura reaction of heteroaryl halides with N-methyliminodiacetic acid (MIDA) boronates in pure water is developed.

Carbohydrate-based phosphines as supporting ligand for palladium-catalyzed Suzuki–Miyaura cross-coupling reaction

Carbohydrate-based mono-phosphines (1 and 2) derived from glucose have been explored as supporting ligand for palladium-catalyzed Suzuki–Miyaura reaction. The combination of phosphine to palladium in a ratio of 2:1 resulted in a longer-living system than that in a ratio of 1:1. Using K2CO3 as base, aryl bromides as well as active aryl chlorides can be coupled nearly quantitatively by 0.1–0.2mol% of 1/Pd(OAc)2 with 95–99% of isolated yields. The amount of the catalyst could be lowered to 0.01mol% under the optimized condition with 80% yield at room temperature. The carbohydrate hydroxyl group in 1 was found to contribute to catalytic activity.

N-Hetercocyclic carbene metallacrown ethers based on 1,8-dihydroxy-9,10-anthraquinone: Synthesis, structures and application in situ palladium-catalyzed Suzuki–Miyaura reaction

N-Hetercocyclic carbene precursors containing 1,8-dihydroxy-9,10-anthraquinone derivative: 1,8-bis(3-(N-R-imidazole)propoxy)-9,10-anthraquinone 2X (L1H2: R = PhCH2, X = Br, L3H2: R = nBu, X = PF6, L4H2: R = PhCH2, X = PF6, L5H2: R = PyCH2, X = PF6), 1,8-bis(2-(N-R-imidazole)ethoxy)-9,10-anthraquinone 2X (L2H2: R = PhCH2, X = PF6) and 1,8-bis(3-(N-R-imidazole)propoxy)anthracene 2X (L6H2: R = PhCH2, X = PF6) were synthesized. N-Heterocyclic carbene metallacrown ethers: L1AgBr (1), L2AgPF6 (2), L3AgPF6 (3), L4AgPF6 (4), L6AgPF6 (5), L4AuPF6 (6), L5Hg(PF6)2 (7) have been prepared. Complexes 1–7 were characterized by elemental analysis, NMR spectroscopy and single crystal X-ray diffraction. Particularly, complex 4 and PdCl2(CH3CN)2 synergetically and efficiently catalyzed in situ Suzuki–Miyaura cross-coupling reaction in 100% aqua-phase.

Efficient Palladium-catalyzed Suzuki–Miyaura reactions using phenolic Schiff base ligands under ambient conditions in aqueous media

The palladium complexes of a series of simple Schiff base ligands with or without phenolic hydroxyl groups have been found to be the excellent catalysts for the Suzuki–Miyaura reactions of aryl iodides, aryl bromides and activated aryl chlorides under ambient conditions in aqueous ethanol media. The introduction of phenolic hydroxyl and/or pyridine groups to the ligands increased the catalytic activity. Under optimal reaction conditions, satisfactory to excellent yields of biaryls were obtained with a wide range of substrates for relatively low loadings of catalyst. Phenolic hydroxyl group and N4-type Schiff base ligands (L1-2) have been proven to be the excellent catalysts for the Suzuki–Miyaura reactions of aryl iodides, aryl bromides and activated aryl chlorides in aqueous ethanol under ambient. Furthermore, a diverse choice of functionalized arylboronic acids bearing difluoro, trifluoro and trifluoromethyl substituents were successfully coupled (>97 %) .

Novel bisimidazolium pincers as low loading ligands for in situ palladium-catalyzed Suzuki–Miyaura reaction in the ambient atmosphere

A series of novel triazinonide-bridged bisimidazolium pincers were easily synthesized by quaternization of functionalized N-phenylimidazoles with highly reactive cyanuric chloride under mild conditions. The pincer was proven to be a very efficient ligand for in situ Pd-catalyzed Suzuki-Miyaura reaction with ppm-level catalyst loading.

Stereospecific cross-coupling of secondary organotrifluoroborates: potassium 1-(benzyloxy)alkyltrifluoroborates.

Potassium 1-(alkoxy/acyloxy)alkyltrifluoroborates have been synthesized through a copper-catalyzed diboration of aldehydes and subsequent conversion of the resulting potassium 1-(hydroxy)alkyltrifluoroborates. The palladium-catalyzed Suzuki-Miyaura reaction employing the potassium 1-(benzyloxy)alkyltrifluoroborates with aryl and heteroaryl chlorides provides access to protected secondary alcohols in high yields. The β-hydride elimination pathway is avoided through use of the benzyl protecting group, which is proposed to stabilize the diorganopalladium intermediate by coordination of the arene to the metal center. This cross-coupling is stereospecific with complete retention of stereochemistry.

General and highly efficient fluorinated-N-heterocyclic carbene–based catalysts for the palladium-catalyzed Suzuki–Miyaura reaction

A general and highly efficient trifluoromethylated-N-heterocyclic carbene (NHC)-based catalyst for the palladium-catalyzed Suzuki–Miyaura reaction was reported. In the presence of the catalyst, reactions of non-activated aryl chlorides and triflates with aryl boronic acids occurred at room temperature with good to excellent yields (63–98%). In addition, catalysts generated from a combination of Pd(OAc)2/imidazolium salt 6a is not only effective for the coupling of heteroaryl boronic acid with aryl halides and heteroaryl halides, but also efficient for coupling of other heteroaryl halides and heteroaryl boronic acids. Finally, the catalyst is highly effective for Suzuki–Miyaura reaction of aryl bromides and chlorides with 0.01–0.1mol% loading if the temperature was raised at refluxed THF/H2O.

A highly active and stable imidazolidine-bridged N,O-donor ligand for efficient palladium catalyzed Suzuki–Miyaura reactions in water

We have used the sterically hindered N,O-donor ligand 1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)-imidazolidine with various Pd salts as a catalyst for the Suzuki reaction. This system exhibited excellent catalytic activity in Suzuki reactions of arylboronic acids with aryl halides, including aryl iodides, aryl bromides and activated aryl chlorides, using aqueous methanol as solvent under mild conditions. The catalytic system can be reused once without significant loss of activity. The sterically hindered imidazolidine-bridged mixed nitrogen, oxygen ligand 1 was efficient for Pd-catalyzed Suzuki reactions involving aryl iodides, aryl bromides and activated aryl chlorides with arylboronic acid in aqueous methanol with K2CO3 as a base the high catalytic activity and oxygen or moisture stable of palladium complexes maybe distribute to the bulky tert-butyl effect.

Iron carbonyl complex containing bis[2‐(diphenylphosphino)phenyl]ether enhancing efficiency in the palladium‐catalyzed Suzuki–Miyaura reaction

The reaction of [Fe3(CO)12] with bis[2‐(diphenylphosphino)phenyl]ether (DPEphos) in refluxing THF afforded a mononuclear complex, [Fe(CO)4(η1‐P‐DPEphos)] (1), as major product and a binuclear complex, [Fe2(CO)6(μ‐CO)(μ‐P,P‐DPEphos)] (2), as minor product respectively. The DPEphos ligand acts as a terminal P‐donor in complex 1 and a bridging P,P‐donor in complex 2. Complexes 1 and 2 were characterized by elemental analysis, fast atom bombardment mass spectrometry, FT‐IR, 1H and 31P{1H} NMR spectroscopy. The structure of complex 1 has been tentatively assigned by density functional theory calculations and its analogy with reported complexes. Combination of complex 1 and PdCl2 furnished an active catalyst for the Suzuki–Miyaura cross‐coupling reactions of various aryl halides with arylboronic acids. Interestingly, under the same experimental condition, complex 1/PdCl2 as catalyst showed superior activity over the DPEphos/PdCl2 system. Copyright © 2012 John Wiley & Sons, Ltd.

Phosphonate substituted 4,4′-bis(N-carbazolyl)biphenyl with dominant electron injection/transport ability for tuning the single-layer device performance of self-host phosphorescent dendrimer

A novel phosphonate substituted 4,4′-bis(N-carbazolyl)biphenyl (CBP), namely PCBP, has been designed and successfully synthesized by an indirect palladium catalyzed Suzuki–Miyaura reaction. X-Ray crystallography analysis from a PCBP single crystal demonstrates that there is a hydrogen bond interaction between the two adjacent molecules due to the presence of phosphonate, which promotes their one-dimensional line arrangement along the c-axis. Compared with the prototype CBP (−5.55 eV), in addition, the highest occupied molecular orbital (HOMO) level of PCBP is reduced to −6.00 eV, leading to a large hole injection barrier. On the other hand, the introduction of phosphonate substitutes can endow PCBP with excellent electron injection/transport ability. As a result, PCBP shows an electron-dominated behaviour observed in single carrier devices, which is different from the hole-dominated one for CBP. Such a transition is then used to tune the single-layer device performance of a self-host phosphorescent dendrimer, and the peak luminous efficiency significantly increases from 1.7 cd A−1 of CBP to 31.4 cd A−1 of PCBP.

Synthesis, Characterization, and OFET and OLED Properties of π-Extended Ladder-Type Heteroacenes Based on Indolodibenzothiophene

Abstract Ladder-type heteroacenes based on indolodibenzothiophene have been synthesized. The route involved a regioselective twofold intramolecular acid-induced cyclization of the central bis(butylsulfinyl)phenyl unit onto the adjacent carbazole units, followed by dealkylation to give diindolobenzobisbenzothiophene (DIBBBT) derivatives. Importantly, this sequence proceeded efficiently in the presence of the chloro substituents which provided reactive sites for further π-extension of the DIBBBT core. The chloro derivative underwent twofold palladium-catalyzed Suzuki–Miyaura reactions with phenylboronic acid or 4-n-octylphenylboronic acid. Compounds have been characterized by 1H NMR spectroscopy, mass spectrometry, elemental analysis, optical spectroscopy, and solution electrochemical studies. Organic field-effect transistors (OFETs) have been constructed based on drop-cast thin films and the performances as p-type semiconductor are presented. The chloro derivative was also copolymerized with 9,9-dioctyl-2,7-fluorenylenediboronic acid bis(1,3-propanediol) ester to give the alternating copolymer which exhibits blue photoluminescence in solution and blue-green electroluminescence in a solution processed organic light-emitting diode (OLED).

Benzotriazole : An efficient, inexpensive and phosphine-free ligand for the palladium-catalyzed Suzuki-Miyaura reaction

Benzotriazole : An efficient, inexpensive and phosphine-free ligand for the palladium-catalyzed Suzuki-Miyaura reaction

Pyrano[4,3-b]quinolines Library Generation via Iodocyclization and Palladium-Catalyzed Coupling Reactions

Synthesis of a 80-member library of novel pyrano[4,3-b]quinolines in solution-phase is reported. The key intermediate, 4-iodopyrano[4,3-b]quinolines were synthesized by the electrophilic iodocyclization of corresponding ortho-alkynyl aldehydes in good to excellent yields under mild reaction conditions. Subsequently a diverse set of libraries was generated by employing palladium-catalyzed Suzuki-Miyaura, Heck, and Sonogashira coupling reactions on 4-iodopyrano[4,3-b]quinolines. In this way, a series of structurally different and biologically interesting molecules were obtained. Some of the selected compounds were screened against 3D7 strains of Plasmodium falciparum for antimalarial activity. Suzuki coupling products 6{3} and 6{21} and Heck coupling product 8{12} exhibit promising antimalarial activity.

Bulky N-acyl-pyridylbenzamidine Ligands for Palladium Catalyzed Suzuki–Miyaura Reaction

In this letter, a series of bulky N-acyl-pyridylbenzamidine ligands were synthesized and characterized. Under the optimized reaction conditions, these bulky ligands were applied to catalyze Suzuki–Miyaura reactions of various aryl bromides and chlorides. The desired biaryl products were obtained in good to high yields. A series of bulky N-acyl-pyridylbenzamidine ligands were synthesized and employed in palladium catalyzed Suzuki–Miyaura reactions. This catalytic system showed effective catalytic efficiency towards an array of various aryl bromides and chlorides under aerobic conditions.

Kinetic Data for the Transmetalation/Reductive Elimination in Palladium‐Catalyzed Suzuki–Miyaura Reactions: Unexpected Triple Role of Hydroxide Ions Used as Base

The mechanism of the reaction of trans-[ArPdX(PPh(3))(2)] (Ar=p-Z-C(6)H(4); Z=CN, F, H; X=I, Br, Cl) with Ar'B(OH)(2) (Ar'=p-Z'-C(6)H(4); Z'=CN, H, OMe) has been established in DMF in the presence of the base OH(-) in the context of real palladium-catalyzed Suzuki-Miyaura reactions. The formation of the cross-coupling product ArAr' and [Pd(0)(PPh(3))(3)] has been followed through the application of electrochemical techniques. Kinetic data have been obtained for the first time, with determination of the observed rate constant, k(obs), of the overall reaction. trans-[ArPdX(PPh(3))(2)] is not reactive in the absence of the base. The base OH(-) plays three roles. It favors the reaction: 1) by formation of trans-[ArPd(OH)(PPh(3))(2)], a key complex which, in contrast to trans-[ArPdX(PPh(3))(2)], reacts with Ar'B(OH)(2) (rate-determining transmetalation), and 2) by unexpected promotion of the reductive elimination from the intermediate trans-[ArPdAr'(PPh(3))(2)], which generates ArAr' and a Pd(0) species. Conversely, the base OH(-) disfavors the reaction by formation of the unreactive anionic Ar'B(OH)(3)(-). As a consequence of these antagonistic effects of OH(-), the overall reactivity is controlled by the concentration of OH(-) and passes through a maximum as the concentration of OH(-) is increased. Therefore, the base favors the rate-determining transmetalation and unexpectedly also the reductive elimination.

Palladium Membrane‐Installed Microchannel Devices for Instantaneous Suzuki–Miyaura Cross‐Coupling

Instantaneous catalytic carbon-carbon bond-forming reactions were achieved in catalytic membrane-installed microchannel devices that have a polymeric palladium-complex membrane. The catalytic membrane-installed microchannel devices were provided inside the microchannels by means of coordinative and ionic molecular convolution at the interface between the organic and aqueous phases flowing laminarly, in which both non-crosslinked linear polymer ligands and palladium species dissolved. The palladium-catalyzed Suzuki-Miyaura reaction of aryl, heteroaryl, and alkenyl halides with arylboronic acids and sodium tetraarylborates was performed with the catalytic membrane-installed microchannel devices to give quantitative yields of biaryls, heterobiaryls, and aryl alkenes within 5 s of residence time in the defined channel region. These microchannel devices were applied to the instantaneous allylic arylation reaction of allylic esters with arylboron reagents under microflow conditions to afford the corresponding coupling products within 1 s of residence time.

Synthesis and photophysical properties of oligoarylenes with a pyrrolo[2,3-d]pyrimidine core

The palladium-catalyzed Suzuki–Miyaura reaction of 2,4-dichloropyrrolo[2,3-d]pyrimidine with aryl boronic acids has been studied. Pd(OAc)2/dicyclohexyl(2-biphenyl)phosphine/K3PO4 was found to be an efficient catalyst system to prepare 4-aryl-2-chloro- and 2,4-diarylpyrrolo[2,3-d]pyrimidines. Novel non-linear molecules consisting of a pyrrolo[2,3-d]pyrimidine core and aryl branches have been elucidated as blue light-emitters with fluorescence quantum yields ranging from 4% to 67% in THF solution. The impact of an electron-withdrawing t-BuOCO group attached to the pyrrole ring of pyrrolopyrimidine derivatives on optical properties is discussed.

2-Aminophenyl diphenylphosphinite as an easily accessible ligand for heterogeneous palladium-catalyzed Suzuki–Miyaura reaction in water in the absence of any organic co-solvent

In this article, we have introduced application of 2-aminophenyl diphenylphosphinite as an easily accessible ligand for heterogeneous palladium-catalyzed Suzuki–Miyaura reaction in water in the absence of any organic co-solvent. By using 2-aminophenyl diphenylphosphinite as a ligand and Pd(OAc) 2 as the pre-catalyst, structurally different aryl halides (I, Br, Cl) were reacted efficiently with phenylboronic acid in water to produce their corresponding biphenyl products in good to excellent yields under heterogeneous conditions. The catalyst is recyclable and was recycled for seven runs for the reaction of bromobenzene with phenylboronic acid without appreciable loss of its catalytic activity.

Highly efficient palladium-catalyzed Suzuki–Miyaura reactions of potassium aryltrifluoroborates with 5-iodo-1,3-dioxin-4-ones in water: an approach to α-aryl-β-ketoesters

The high efficient palladium-catalyzed Suzuki–Miyaura reactions of potassium aryltrifluoroborates 3 with 5-iodo-1,3-dioxin-4-ones 2a–b in water as only solvent in the presence of n-Bu4NOH as base is reported. The respective 5-aryl-1,3-dioxin-4-ones 4a–n were obtained in good to excellent yields. The catalyst system provides high efficiency at low load using electronically diverse coupling partners. The obtained 2,2,6-trimethyl-5-aryl-1,3-dioxin-4-ones were transformed into corresponding α-aryl-β-ketoesters 6 by reaction with an alcohol in the absence of solvent.