Coupling Of Aryl Bromides Research Articles

Synthesis of Symmetrical and Unsymmetrical N-Aryl-Substituted Cyclic Ureas through Copper(I) Iodide Catalyzed Goldberg-Buchwald-Nandakumar C-N Coupling Reactions

The catalytic conditions of copper(I) iodide/potassium carbonate/ TRANS- N, N′-dimethylcyclohexane-1,2-diamine, either in toluene at reflux temperature, or by heating neat at 150 °C effectively promoted the C-N coupling of aryl bromides with cyclic ureas. By employing a protection-deprotection strategy, unsymmetrical diaryl-substituted cyclic ureas could also be synthesized.

Water‐soluble 2‐arylnaphthoxazole‐derived palladium (II) complexes as phosphine‐free catalysts for the Suzuki reaction in aqueous solvent

AbstractTwo water‐soluble palladium (II) complexes 2 and 4 have been synthesized from easily available 2‐arylnaphthoxazole derivatives. They were successfully applied to the Suzuki coupling of aryl bromides with phenylboronic acid in water at 100 °C under phosphine‐free conditions. Copyright © 2008 John Wiley & Sons, Ltd.

Neopentylphosphines as effective ligands in palladium-catalyzed cross-couplings of aryl bromides and chlorides

The use of neopentylphosphine ligands in the palladium-catalyzed Suzuki, Sonogashira, Heck, and Hartwig–Buchwald couplings of aryl bromides and chlorides are reported. Di- tert-butylneopentylphosphine (DTBNpP) provided highly active catalysts for the coupling of aryl bromides at mild temperatures. Trineopentylphosphine, an air-stable trialkylphosphine, gave inactive catalysts at room temperature, but showed good activity in the H–B amination of aryl chlorides at elevated temperatures.

Sterically Demanding, Sulfonated, Triarylphosphines: Application to Palladium-Catalyzed Cross-Coupling, Steric and Electronic Properties, and Coordination Chemistry

Tri(2,4-dimethyl-5-sulfonatophenyl)phosphine trisodium (TXPTS·Na3) and tri(4-methoxy-2-methyl-5-sulfonatophenyl)phosphine trisodium (TMAPTS·Na3) both provide more active catalysts for Suzuki and Sonogashira couplings of aryl bromides in aqueous solvents than tri(3-sulfonatophenyl)phosphine trisodium (TPPTS·Na3). In the Heck coupling, TXPTS·Na3 provides the most effective catalyst system. Cone angles determined from DFT-optimized structures show that both TXPTS·Na3 (206°) and TMAPTS·Na3 (208°) are significantly larger than TPPTS·Na3 (165°). The identity of the counterion had a significant effect on the calculated cone angles for these ligands. The electronic properties of these ligands determined by the CO stretching frequencies of trans-RhL2(Cl)CO complexes were identical, although calculated electronic parameters suggest subtle differences between these ligands. Similar to TPPTS·Na3, both TXPTS·Na3 and TMAPTS·Na3 react with Pd(OAc)2 in aqueous solvents to give LnPd0 complexes and the corresponding phosph...

Rh(I)-catalyzed arylation of heterocycles via C-H bond activation: expanded scope through mechanistic insight.

A practical, functional group tolerant method for the Rh-catalyzed direct arylation of a variety of pharmaceutically important azoles with aryl bromides is described. Many of the successful azole and aryl bromide coupling partners are not compatible with methods for the direct arylation of heterocycles using Pd(0) or Cu(I) catalysts. The readily prepared, low molecular weight ligand, Z-1-tert-butyl-2,3,6,7-tetrahydrophosphepine, which coordinates to Rh in a bidentate P-olefin fashion to provide a highly active yet thermally stable arylation catalyst, is essential to the success of this method. By using the tetrafluoroborate salt of the corresponding phosphonium, the reactions can be assembled outside of a glovebox without purification of reagents or solvent. The reactions are also conducted in THF or dioxane, which greatly simplifies product isolation relative to most other methods for direct arylation of azoles employing high-boiling amide solvents. The reactions are performed with heating in a microwave reactor to obtain excellent product yields in 2 h.

Benzenimidazole-Functionalized Imidazolium-Based N-Heterocyclic Carbene Complexes of Silver(I) and Palladium(II): Isolation of a Ag3 Intermediate toward a Facile Transmetalation and Suzuki Coupling

A new benzenimidazole-functionalized imidazolium-based N-heterocyclic carbene complex of Pd(II) has been prepared from facile transmetalation via a Ag(I) precursor. The latter was obtained from a condensation reaction between Ag2O and benzenimidazolium salt. Single-crystal X-ray crystallography revealed an unusual trinuclear Ag3Cl2(μ-Cl)(μ-N-C)2 (N-C = 3-methyl-1-(1-ethyl-2-methylbenzoyl)imidazolin-2-ylidene) intermediate in which the central carbene-supported Ag(I) is flanked by two imidazole-coordinated Ag(I). The hybrid ligand (N-C), carrying two heterodonors of benzenimidazole and carbene, is bridging in Ag(I) but chelating in Pd(II). The latter mononuclear PdCl2(η-N-C) is active toward Suzuki−Miyaura coupling of aryl bromides and boronic acids, giving a TON up to 11 750 within 4 h at rt.

Palladium-Catalyzed Three-Component Arylcyanation of Internal Alkynes with Aryl Bromides and K4[Fe(CN)6

The one-pot, palladium-catalyzed, three-component coupling of aryl bromides, internal alkynes, and environmentally friendly K4[Fe(CN)6] provides an efficient and direct method for the preparation of beta-arylalkenylnitriles.

ChemInform Abstract: Unexpected Formation of Aryl Ketones by Palladium‐Catalyzed Coupling of Aryl Bromides with Vinylic Acetates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Design and Synthesis of Thioether‐Imidazolium Chlorides as Efficient Ligands for Palladium‐Catalyzed Suzuki—Miyaura Coupling of Aryl Bromides with Arylboronic Acids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Aryl Ketones by Palladium-Catalyzed Coupling of Aryl Bromides with Enol Acetates

Aryl Ketones by Palladium-Catalyzed Coupling of Aryl Bromides with Enol Acetates

Unexpected Formation of Aryl Ketones by Palladium-Catalyzed Coupling of Aryl Bromides with Vinylic Acetates

A palladium-catalyzed coupling reaction of aryl bromides with vinylic acetates in the presence of tributyltin methoxide has been described. Unexpected formation of aryl ketones was obtained. Preliminary mechanistic studies indicated that the reaction proceeded by the addition of the aryl moiety in the coordination sphere of palladium to a ketene.

Design and synthesis of thioether-imidazolium chlorides as efficient ligands for palladium-catalyzed Suzuki–Miyaura coupling of aryl bromides with arylboronic acids

The catalyst composed of 0.25–0.025 mol % of [Pd(allyl)Cl] 2 and 0.5–0.05 mol % of the thioether-imidazolium chloride 3c was proven to be efficient in the Suzuki–Miyaura cross-coupling reactions of aryl bromides with arylboronic acids.

An Efficient Heterogeneous Pd Catalyst for the Suzuki Coupling: Pd/Al2O3

Abstract PdII-loading alumina catalyst, which is simply prepared through impregnation of γ–alumina with Pd(OAc)2 followed by calcination in the air, shows a high catalytic activity for the Suzuki coupling of aryl bromides with arylboronic acids under phosphine ligand-free conditions. Only 0.25 mol % of palladium is sufficient for the promotion of the couplings in ethanol.

Pd(II) complexes of a sterically bulky, benzannulated N-heterocyclic carbene and their catalytic activities in the Mizoroki–Heck reaction

The bis( N, N′-diisopropylbenzimidazolin-2-ylidene)Pd(II) complexes trans-[PdBr 2( i Pr 2-bimy) 2] ( trans- 1) and trans-[PdI 2( i Pr 2-bimy) 2] ( trans- 2) have been prepared in good yields by in situ deprotonation of the corresponding N, N′-diisopropylbenzimidazolium salt ( i Pr 2-bimyH +X −) ( A: X = Br, B: X = I) with Pd(OAc) 2 in DMSO at elevated temperature. Salt metathesis of trans- 1 or trans- 2 with AgO 2CCF 3 in refluxing CH 3CN afforded the novel mixed carbene–carboxylato complex cis-[Pd(O 2CCF 3) 2( i Pr 2-bimy) 2] ( cis- 3). This halo/trifluorocarboxylato ligand substitution can be regarded as a selective method for the synthesis of cis-configured bis(carbene) complexes. All compounds have been fully characterized by multinuclei NMR spectroscopies and ESI mass spectrometry. X-ray diffraction studies on single crystals of trans- 1, trans- 2 and cis- 3 revealed a square planar geometry and a fixed orientation of the N-isopropyl substituents with the C–H protons pointing to the metal center to maximize rare C–H⋯Pd preagostic interactions. These interactions are also retained in solution as indicated by the large downfield shift of the isopropyl C–H protons in the 1H NMR spectrum compared to those in precursor salts A or B. A preliminary catalytic study revealed that all complexes are highly active in the Mizoroki–Heck coupling of aryl bromides and chlorides. However, these complexes gave slower conversions as compared to catalysts with less bulky benzimidazolin-2-ylidenes. This is most likely due to the steric bulk of the ligands, which hamper a fast reductive formation of catalytically active Pd(0) species.

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

The lithiation/alkylation of fluorene leads to various 9-alkyl-fluorenes (alkyl=Me, Et, iPr, -Pr, -C18H25) in>95% yields, for which lithiation and reaction with R2PCl (R=Cy, iPr, tBu) generates 9-alkyl, 9-PR2-fluorenes which constitute electron-rich and bulky phosphine ligands. The in-situ-formed palladium-phosphine complexes ([Na2PdCl4], phosphonium salt, base, substrates) were tested in the Sonogashira, Suzuki, and Buchwald-Hartwig reactions of aryl chlorides and aryl bromides in organic solvents. The Sonogashira coupling of aryl chlorides at 100-120 degrees C leads to>90% yields with 1 mol% of Pd catalyst. The Suzuki coupling of aryl chlorides typically requires 0.05 mol% of Pd catalyst at 100 degrees C in dioxane for quantitative product formation. To carry out "green" cross-coupling reactions in water, 9-ethylfluorenyldicyclohexylphosphine was reacted in sulphuric acid to generate the respective 2-sulfonated phosphonium salt. The Suzuki coupling of activated aryl chlorides by using this water-soluble catalyst requires only 0.01 mol% of Pd catalyst, while a wide range of aryl chlorides can be quantitatively converted into the respective coupling products by using 0.1-0.5 mol% of catalyst in pure water at 100 degrees C. Difficult substrate combinations, such as naphthylboronic acid or 3-pyridylboronic acid and aryl chlorides are coupled at 100 degrees C by using 0.1-0.5 mol% of catalyst in pure water to obtain the respective N-heterocycles in quantitative yields. The copper-free aqueous Sonogashira coupling of aryl bromides generates the respective tolane derivatives in>95% yield.

Efficient preparation of S-aryl thioacetates from aryl halides and potassium thioacetate

A method for the preparation of S-aryl thioacetates using palladium-mediated couplings of aryl bromides and aryl triflates with potassium thioacetate as an inexpensive thiol source was developed. Electron withdrawing groups, electron donating groups and heterocyclic substrates were tolerated in the reaction conditions, affording the corresponding products in good to excellent yields. This method was applied to the preparation of novel sulfone-containing DPP-IV inhibitors.

Palladium‐Catalyzed Synthesis of Aryl Ketones by Coupling of Aryl Bromides with an Acyl Anion Equivalent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of Aryl Ketones by Coupling of Aryl Bromides with an Acyl Equivalent

Synthesis of Aryl Ketones by Coupling of Aryl Bromides with an Acyl Equivalent

AlAr3(THF): highly efficient reagents for cross-couplings with aryl bromides and chlorides catalyzed by the economic palladium complex of PCy3

Novel and highly efficient cross couplings of aryl bromides and chlorides with AlAr3(THF) (Ar = Ph, 2,4,6-Me3C6H2, 2-naphthyl or 4-Me3SiC6H4) catalyzed by the economic palladium catalyst of PCy3 are reported without the use of a base and under mild reaction conditions at room temperature or temperatures < or = 60 degrees C even for couplings of bulky aryl halides and the Al(2,4,6-Me3C6H2)3(THF) reagent.

Pd(ii) complexes of N,S-heterocyclic carbenes with pendant and coordinated allyl function and their Suzuki coupling activities

3-(2-Propenyl)benzothiazolium bromide (A) provides a direct and simple entry to Pd(II) complexes with N,S-heterocyclic carbene (NSHC) ligands functionalized with an allyl pendant with hemilabile potential. Addition of salt A to Pd(OAc)2 eliminates HOAc and affords the bis(carbene) complexes cis-[PdBr2(NHSC)2] (cis-1, NSHC = 3-(2-propenyl)benzothiazolin-2-ylidene) and trans-[PdBr2(NHSC)2] (trans-1) along with the monocarbene complexes [PdBr2(NSHC)] (2) and trans-[PdBr2(benzothiazole-kappaN)(NSHC)] (3) as minor side products. Salt-metathesis of cis-1 with AgO2CCF3 yields the mixed dicarboxylato-bis(carbene) complex cis-[Pd(O2CCF3)2(NSHC)2] (4). Complexes cis-1, trans-1 and 4 were characterized by multinuclear NMR spectroscopies, ESI mass spectrometry and elemental analysis. The molecular structures of complexes cis-1, 2 and 3 have been determined by X-ray single crystal diffraction. Complexes cis-1 and 4 as well as an in situ mixture of Pd(OAc)2 and salt A are active toward Suzuki-Miyaura coupling of aryl bromides and activated aryl chlorides giving good conversions.