Palladium-catalyzed Suzuki Cross-coupling Reaction Research Articles

Synthesis of 2,2‘-Biimidazolium-Based Ionic Liquids: Use as a New Reaction Medium and Ligand for Palladium-Catalyzed Suzuki Cross-Coupling Reactions

Neat reactions of 2,2'-biimidazole with an excess of alkyl or polyfluoroalkyl iodides at 140 degrees C, followed by anion exchange with LiN(SO(2)CF(3))(2) or KPF(6), gave the diquaternary salts 3a-k in >80% yields. However, by controlling the reaction stoichiometry, 2,2'-biimidazole can also be monoquaternized with the same electrophiles at 100 degrees C under similar conditions. Subsequent metathesis reactions with LiN(SO(2)CF(3))(2) or KPF(6) resulted in the ionic liquids 4a-m in high yields. Thermal properties were determined with a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA). Most of the monoquaternary salts are room-temperature ionic liquids. 1,3,1'-Tributyl-2,2'-biimidazolium hexafluorophosphate was demonstrated to be an excellent solvent and ligand for palladium-catalyzed Suzuki cross-coupling reactions. The catalytic ionic liquid system may be recycled at least 14 times without a significant decrease in catalytic performance.

Formal Total Syntheses of Crocacin A-D

A concise route to the common polyketide fragment5of crocacin A-D (1-4) is presented which has previously been converted into all members of this fungicidal and cytotoxic family of dipeptidic natural products by various means. Our synthesis features asyn-selective titanium aldol reaction controlled by a valinol-derived auxiliary, a zinc-mediated, palladium-catalyzedanti-selective addition of propargyl mesylate10to the chiral aldehyde9, as well as a comparison of palladium-catalyzed Stille and Suzuki cross-coupling reactions for the formation of the diene moiety of the target.

Dye-functionalized head-to-tail coupled oligo(3-hexylthiophenes)—perylene–oligothiophene dyads for photovoltaic applications

A series of novel donor-acceptor systems, consisting of head-to-tail coupled oligo(3-hexylthiophene)s covalently linked to perylenemonoimide, is described. These hybrid molecules, which differ by the length of the oligothiophene units from a monothiophene up to an octathiophene, were created via effective palladium-catalyzed Negishi and Suzuki cross-coupling reactions in good to excellent yields. The optical and electrochemical properties of these compounds were determined and based on this series structure-property relationships have been established which give vital information for the fabrication of photovoltaic devices. Because the synthesized perylenyl-oligothiophenes distinguish themselves by a high absorption between 300 and 550 nm and an almost complete fluorescence quenching of the perylene acceptor, they meet the requirements for organic solar cells.

Novel fluorene–pyridine-based alternating copolymers: syntheis, characterization and optical properties

A novel series of well-defined soluble poly[2,7-(9,9-dialkyfluorenyl)-alt-pyridinyl] (except for PDHFP-25, a polymer with same composition but different weight-average molecular mass ( M w) was reported in reference [B. Liu, W.L. Yu, Y.H. Lai, W. Huang, Chem. Mater. 13 (2001), 1984–1991] were synthesized using palladium-catalyzed Suzuki cross-coupling reactions in good to high yields. In the series of alternating copolymers, 2,7-(9,9-dialkylfluorenyl) was used as the light emitting unit and the electron deficient pyridinyl unit was employed to provide improved electron transportation. All these polymers were characterized by 1H NMR, 13C NMR, GPC, thermal analyses, UV–vis and fluorescence spectroscopy. The shorter pendant 9,9-dihexyl at fluorenyl unit is better to polymer for higher thermal stability and higher T g than 9,9-dioctyl at fluorenyl unit. The meta-linkage (3,5- or 2,6-linkage) of pyridinyl units in the polymer backbone is more favourable to polymer for pure blue emission and prevention of aggregation of polymer chain than the para-linkage (2,5-linkage) of the pyridinyl units.

Rhenium-Containing Phosphorus Donor Ligands for Palladium-Catalyzed Suzuki Cross-Coupling Reactions: A New Strategy for High-Activity Systems

The chiral racemic methyl complex (η5-C5H5)Re(NO)(PPh3)(CH3) is converted to the rhenium-containing phosphorus donor ligands (η5-C5H5)Re(NO)(PPh3)((CH2)nPR2) (n/R = 3a, 0/Ph; 3b, 0/t-Bu; 3c, 0/Me; 5a, 1/Ph; 5b, 1/t-Bu) and (η5-C5H4PR2)Re(NO)(PPh3)(CH3) (7; R = a, Ph; b, t-Bu) via standard reactions (3, TfOH/CH2Cl2 or HBF4/chlorobenzene, then PR2H, then t-BuOK; 5, Ph3C+X-, then PR2H, then t-BuOK; 7, n-BuLi, then PR2Cl). (η5-C5H4PR2)Re(CO)3 (R = Ph, t-Bu) is prepared from (η5-C5H5)Re(CO)3 analogously to 7. Most of these species are effective ligands for palladium-catalyzed Suzuki couplings. Typical conditions involve toluene solvent, an aryl bromide (1.0 equiv), phenylboronic acid (1.5 equiv), K3PO4 (2.0 equiv), Pd(OAc)2 (1 mol %), the rhenium/PR2 species (4 mol %), and 60−100 °C. In the cases of 3 and 5, the rhenium/PR2 species are generated in situ from indefinitely stable conjugate acids [rhenium/PR2H]+ and t-BuOK (2 equiv or 8 mol %). The bulkier and more electron-rich rhenium/P(t-Bu)2 systems generally...

Pyrrolodiazines. 6. Palladium-Catalyzed Arylation, Heteroarylation, and Amination of 3,4-Dihydropyrrolo[1,2-a]pyrazines

The palladium-catalyzed Suzuki cross-coupling reaction of arylboronic acids and 6-bromo- and 6,8-dibromo-3,4-dihydropyrrolo[1,2-a]pyrazines afforded 6-substituted and 6,8-disubstituted 3,4-dihydropyrrolo[1,2-a]pyrazines in good yields. Stille and Negishi coupling reactions have been used to prepare 6-heteroaryl-substituted derivatives in moderate yields by employing heteroaryl halides and 6-metalated 3,4-dihydropyrrolo[1,2-a]pyrazines as reaction partners. A variety of cyclic secondary amines have also been incorporated at position C-6 of 6-bromo-1-phenyl-3,4-dihydropyrrolo[1,2-a]pyrazine in the presence of the palladium catalyst Pd(2)(dba)(3) in conjunction with BINAP as ligand. This amination reaction is one of the few reported examples of such a palladium-catalyzed transformation on a pyrrole ring, although the reaction could not be extended to less nucleophilic amines.

Generation of 3‐Pyridyl Biaryl Systems via Palladium‐Catalyzed Suzuki Cross‐Couplings of Aryl Halides with 3‐Pyridylboroxin.

The synthesis of 3-pyridyl biaryl systems can be readily achieved by means of palladium-catalyzed Suzuki cross-coupling reactions between aryl halides and 3-pyridylboroxin. A series of cross-couplings were conducted in order to investigate the scope and limitations of this protocol.

Synthesis of Aryl‐ and Heteroaryl‐Substituted 3‐Benzyloxyisothiazoles via Suzuki and Negishi Cross‐Coupling Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Phosphorus—Nitrogen—Phosphorus Ligands: Cooperative Effects Between Nitrogen and Phosphorus Substituents on Catalytic Activity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Generation of 3-pyridyl biaryl systems via palladium-catalyzed Suzuki cross-couplings of aryl halides with 3-pyridylboroxin.

The synthesis of 3-pyridyl biaryl systems can be readily achieved by means of palladium-catalyzed Suzuki cross-coupling reactions between aryl halides and 3-pyridylboroxin. A series of cross-couplings were conducted in order to investigate the scope and limitations of this protocol.

Palladium Catalyzed Suzuki Cross‐coupling Reaction in Molten Tetra‐r)‐butylammonium Bromide

AbstractA practical procedure for palladium catalyzed Suzuki cross‐coupling reaction of arylboronic acids with aryl halides, including aryl chlorides in molten tetra‐n‐butylammonium bromide (TBAB) was developed. The reaction exhibits high efficiency and functional group tolerance. The recovery of the catalyst and molten n‐Bu4NBr was also investigated.

Synthesis of aryl- and heteroaryl-substituted 3-benzyloxyisothiazoles via Suzuki and Negishi cross-coupling reactions.

Introduction of aryl and heteroaryl substituents into the 5-position of 3-benzyloxyisothiazole (1) using palladium-catalyzed Suzuki and Negishi cross-coupling reactions was investigated. Attempts to generate synthetically viable nucleophilic species from 1 for Suzuki- or Negishi-type cross-couplings were unsuccessful. However, using 3-benzyloxy-5-iodoisothiazole 2 as an intermediate, a range of aromatic and heteroaromatic substituents were successfully introduced under Suzuki or Negishi cross-coupling conditions in good to excellent yields.

Phosphorus-nitrogen-phosphorus ligands: cooperative effects between nitrogen and phosphorus substituents on catalytic activity.

A new generation of PNP compounds bearing different diarylphosphine groups were prepared and used as ligands in palladium-catalysed Suzuki cross-coupling reactions. Rates of oxidative addition of iodobenzene to (PNP)Pd[0] complexes were measured using UV spectroscopy. Synergistic effects between the N- and P- substituents were identified and correlated in redox and catalytic chemistry.

1,3-Phenylene-bis-(1H)-tetrazole Pincer Ligand for Palladium-Catalyzed Suzuki Cross-Coupling Reactions of Arylhalides with Arylboronic Acids

1,3-Phenylene-bis-(1H)-tetrazole pincer ligand was ­synthesized by the reaction of 1, 3-phenylenediamine, sodium azide and triethyl orthoformate in acetic acid and successfully used in ­Suzuki cross coupling reactions of aryl halides with aryl boronic ­acids.

Palladium-Catalyzed Suzuki Cross-Coupling Reactions in Ambient Temperature Ionic Liquids: Evidence for the Importance of Palladium Imidazolylidene Complexes

Palladium-catalyzed Suzuki cross-coupling reactions have been conducted in a range of ambient temperature ionic liquids. The ionic liquids give excellent reactivities for bromoarenes in addition to easy product isolation. The preferred reaction conditions are explored and the effect of changing the ionic liquid components is investigated. The in situ formation of mixed phosphine/imidazolylidene palladium complexes is demonstrated in all of the catalytically active solutions, but in none of the inactive solutions. Formation of 1,3-dialkyl-2-arylimidazolium salts is demonstrated, but it is also shown that these salts can act as a source of arene for the reaction; that is, both reductive elimination and oxidative addition of 1,3-dialkyl-2-arylimidazolium salts from/to the palladium are occurring. The implications of this for the use of ionic liquids as solvents for Suzuki reactions are discussed.

The First Total Synthesis of Dragmacidin D.

The first total synthesis of the biologically significant bis-indole alkaloid dragmacidin D (5) has been achieved. Thermal and electronic modulation provides the key for a series of palladium-catalyzed Suzuki cross-coupling reactions that furnished the core structure of the complex guanidine- and aminoimidazole-containing dragmacidins. Following this crucial sequence, a succession of meticulously controlled final events was developed leading to the completion of the natural product.

Synthesis and Derivatization of Ethynyl α,α-Dibromomethyl Ketones: Formation of Highly Functionalized Vinyl Triflates

[reaction: see text] We describe the synthesis of alpha,alpha-dibromomethyl ynones (8) and their subsequent derivatization to vinyl acetates (10). These vinyl acetates feature a 1,1-dibromo-olefin moiety, which is readily exploited in palladium-catalyzed Sonogashira, Stille, and Suzuki cross-coupling reactions with alkynes, stannanes, and boronic acids, respectively. A novel one-pot process then directly converts the resulting vinyl acetates 11-13 to the vinyl triflate derivatives 14a-j.

Efficient Ligandless Palladium‐Catalyzed Suzuki Reactions of Potassium Aryltrifluoroborates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The first total synthesis of dragmacidin d.

The first total synthesis of the biologically significant bis-indole alkaloid dragmacidin D (5) has been achieved. Thermal and electronic modulation provides the key for a series of palladium-catalyzed Suzuki cross-coupling reactions that furnished the core structure of the complex guanidine- and aminoimidazole-containing dragmacidins. Following this crucial sequence, a succession of meticulously controlled final events was developed leading to the completion of the natural product.

Efficient ligandless palladium-catalyzed Suzuki reactions of potassium aryltrifluoroborates.

[reaction: see text] The ligandless palladium-catalyzed Suzuki cross-coupling reaction of potassium aryl- and heteroaryltrifluoroborates with aryl- or heteroaryl halides or triflates proceeds readily with very good yields. The cross coupling can be effected in methanol or water, in the open air, using Pd(OAc)(2) as a catalyst in the presence of K(2)CO(3). A variety of functional groups are tolerated.