Potassium Aryltrifluoroborates Research Articles

Suzuki-Miyaura cross-coupling of arenediazonium salts catalyzed by alginate/gellan-stabilized palladium nanoparticles under aerobic conditions in water

The use of palladium nanoparticles stabilized by natural beads made of an alginate/gellan mixture in the Suzuki-Miyaura cross-coupling reaction of arenediazonium tetrafluoroborates with potassium aryltrifluoroborates (1 : 1 molar ratio) with loading as low as 0.01–0.002 mol% under aerobic, phosphine-, and base-free conditions in water is described. The catalyst system can be reused several times without significant loss of activity.

Palladium(II)-exchanged hydroxyapatite-catalyzed Suzuki–Miyaura-type cross-coupling reactions with potassium aryltrifluoroborates

Palladium(II)-exchanged hydroxyapatite (PdHAP; Pd/Ca ratio = ca. 1/200) was prepared by ion-exchanging with Ca 2+ from calcined hydroxyapatite (2.0 mmol) and Pd(NO 3) 2 (0.10 mmol) in water (150 mL) at 70 °C for 24 h. The PdHAP (1 mol% Pd to aryl bromides) functioned as a catalyst for the Suzuki–Miyaura-type cross-coupling reaction of aryl bromides and potassium aryltrifluoroborates with triphenylphosphine (1 mol%) and excess potassium carbonate at 50 °C in methanol under air. This cross-coupling reaction was found to proceed in water, while the rate was slow compared with that in methanol. The heterogeneous PdHAP catalyst was used ten times repeatedly at 50 °C in methanol under air, though its catalytic activity gradually declined. XRD and XRF analyses and TEM images revealed that most of palladium species would still be supported as isolated ions on the repeatedly used PdHAP, in spite of the changes of the structure and composition of PdHAP surface at the late stages in the repetitive uses and the partial leaching of Pd species at the initial stages in the repetitive uses. The gradual decline of the catalytic activity might be dependent on either the changes of PdHAP surface at the late stages or the partial leaching of Pd species at the initial stages. Still, heterogeneous PdHAP served as a reusable catalyst for Suzuki–Miyaura-type cross-coupling reaction with potassium aryltrifluoroborates.

Palladium(II)‐Catalyzed One‐Pot Syntheses of 9‐(Pyridin‐2‐yl)‐9H‐carbazoles through a Tandem CH Activation/CX (X=C or N) Formation Process

A new one-pot synthesis of 9-(pyridin-2-yl)-9H-carbazoles through the simultaneous C-H activation and palladium(II)-catalyzed cross-coupling of N-phenylpyridin-2-amines with potassium aryltrifluoroborates is presented. Silver acetate and 1,4-dioxane proved to be the best oxidant and solvent, respectively. The product yields fluctuated from modest to excellent and the reaction showed sufficient functional group tolerance. p-Benzoquinone served as an important ligand for the transmetalation and reductive elimination steps in the catalytic process. The kinetic isotope effects (k(H)/k(D)) for the first and second C-H activation/C-C or C-N formation steps were measured as 2.14 and 1.18, respectively. Finally, a rational catalytic mechanism is presented based on all experimental evidence.

Expedient synthesis of 4- O-methylhonokiol via Suzuki–Miyaura cross-coupling

Concise and practical synthesis of 4- O-methylhonokiol was achieved in 34% overall yield. The key features of our synthesis include chemoselective ortho-mono bromination of phenol as well as biaryl formation via Suzuki–Miyaura cross-coupling, in which bromophenol was reacted with potassium aryltrifluoroborate using Pd(OAc) 2 and RuPhos under microwave conditions.

ChemInform Abstract: CuI‐Catalyzed Suzuki Coupling Reaction of Organoboronic Acids with Alkynyl Bromides.

Abstract A CuI-catalyzed Suzuki cross-coupling reaction of organoboron derivatives with alkynyl bromides has been developed. In the presence of CuI (10 mol %) and 8-hydroxyquinoline (20 mol %), organoboron derivatives including aromatic and alkenyl boronic acids, potassium aryltrifluoroborates, and sodium tetraphenylborate reacted smoothly with 1-bromo-2-substituted acetylene to generate the corresponding cross-coupling products in good to excellent yields in C2H5OH. It is important to note that aromatic N,O-ligand 8-hydroxyquinoline is the most effective ligand for the reaction.

Phosphane-free Suzuki–Miyaura Coupling of Aryl Imidazolesulfonates with Arylboronic Acids and Potassium Aryltrifluoroborates under Aqueous Conditions

Abstract Aryl imidazole-1-sulfonates are efficiently cross-coupled with arylboronic acids and potassium aryltrifluoroborates using only 0.5 mol % of oxime palladacycles 1 under aqueous conditions at 110 °C. Under these simple phosphane-free reaction conditions a wide array of biaryl derivatives has been prepared in high yields. This methodology allows in situ phenol sulfonation and one-pot Suzuki arylation as well as the employment of microwave irradiation conditions.

Expanded Substrate Scope and Improved Reactivity of Ether-Forming Cross-Coupling Reactions of Organotrifluoroborates and Acetals

Mixed acetals and organotrifluoroborates undergo BF(3)·OEt(2)-promoted cross-couplings to give dialkyl ethers under simple, mild conditions. A survey of reaction partners identified a hydroxamate leaving group that improves the regioselectivity and product yield in the BF(3)·OEt(2)-promoted coupling reaction of mixed acetals and potassium alkynyl-, alkenyl-, aryl- and heteroaryltrifluoroborates to access substituted dialkyl ethers. This leaving group enables the reaction to proceed rapidly under mild conditions (0 °C, 5-60 min) and permits reactions with electron-deficient potassium aryltrifluoroborates that are less reactive with other acetal substrates. A study of the reaction mechanism and characterization of key intermediates by NMR spectroscopy and X-ray crystallography identified a role for the hydroxamate moiety as a reversible leaving group that serves to stabilize the key oxocarbenium intermediate and the need for a slight excess of organodifluoroborane to serve as a catalyst. A secondary role for the boron nucleophile as an activating ligand was also considered. These studies provide the basis for a general class of reagents that lead to dialkyl ethers by a simple, predictable cross-coupling reaction.

Environmentally friendly homocoupling reaction of functionalized potassium aryl trifluoroborates salts in aqueous media

The homocoupling reaction between potassium aryl trifluoroborates containing different functionalities promoted by a catalytic amount of Pd(OAc)2 is described. The methodology uses water as a solvent under aerobic conditions to give the corresponding biaryl compounds in good yields.

An Efficient and Recyclable Magnetic-Nanoparticle-Supported Palladium Catalyst for the Suzuki Coupling Reactions of Organoboronic Acids with Alkynyl Bromides

A highly active, air- and moisture-stable and easily recoverable magnetic-nanoparticle-supported palladium catalyst has been developed for the Suzuki cross-coupling reaction of organoboron derivatives with alkynyl bromides. In the presence of palladium catalyst (0.5 mol%), organoboron derivatives including aromatic and aliphatic boronic acids, potassium aryltrifluoroborates, and sodium tetraphenylborate reacted smoothly with 1-bromo-2-substituted acetylenes to generate the corresponding cross-coupling products in good to excellent yields in ethanol. In addition, it is possible to recover and reuse the supported palladium catalyst at least 16 times without significant loss of its catalytic activity.

ChemInform Abstract: Pd(II)‐Catalyzed Decarboxylative Cross‐Coupling of Potassium Aryltrifluoroborates with α‐Oxocarboxylic Acids at Room Temperature.

A novel Pd-catalyzed decarboxylative cross-coupling of potassium aryltrifluoroborates with α-oxocarboxylic acids is performed at room temperature. This reaction provides an efficient access to aryl ketones under mild conditions.

ChemInform Abstract: Palladium‐Catalyzed Carbonylative Suzuki Coupling of Benzyl Halides with Potassium Aryltrifluoroborates in Aqueous Media.

AbstractVarious benzyl halides are converted into diarylethanones in the presence of carbon monoxide using different aryl trifluoroborates.

CuI-catalyzed Suzuki coupling reaction of organoboronic acids with alkynyl bromides

A CuI-catalyzed Suzuki cross-coupling reaction of organoboron derivatives with alkynyl bromides has been developed. In the presence of CuI (10 mol %) and 8-hydroxyquinoline (20 mol %), organoboron derivatives including aromatic and alkenyl boronic acids, potassium aryltrifluoroborates, and sodium tetraphenylborate reacted smoothly with 1-bromo-2-substituted acetylene to generate the corresponding cross-coupling products in good to excellent yields in C 2H 5OH. It is important to note that aromatic N, O-ligand 8-hydroxyquinoline is the most effective ligand for the reaction.

ChemInform Abstract: Functionalization of (2S)‐Isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐ones by a Suzuki—Miyaura Cross‐Coupling Reaction Using Aryltrifluoroborate Salts: Convenient Enantioselective Preparation of α‐Substituted β‐Amino Acids.

AbstractA large variety of groups present in the potassium aryltrifluoroborates (‐CF3, ‐OMe, ‐SEt, ‐CN, ‐CHO, ‐Cl, ‐Cbz, ‐OH) are tolerated in the title reaction.

Palladium‐Catalyzed Carbonylative Suzuki Coupling of Benzyl Halides with Potassium Aryltrifluoroborates in Aqueous Media

AbstractA general palladium‐catalyzed carbonylative cross‐coupling reaction of benzyl chlorides with potassium aryltrifluoroborates in water has been developed. Applying this improved methodology 16 different 1,2‐diarylethanones have been synthesized in 40–89% yield.

Pd(II)-Catalyzed Decarboxylative Cross-Coupling of Potassium Aryltrifluoroborates with α-Oxocarboxylic Acids at Room Temperature

A novel Pd-catalyzed decarboxylative cross-coupling of potassium aryltrifluoroborates with α-oxocarboxylic acids is performed at room temperature. This reaction provides an efficient access to aryl ketones under mild conditions.

Synthesis of diaryl selenides using electrophilic selenium species and nucleophilic boron reagents in ionic liquids

We described herein the use of imidazolium ionic liquids [bmim]PF6 and [bmim]BF4 in the selective, metal and catalyst-free synthesis of unsymmetrical diaryl selenides by electrophilic substitution in arylboron reagents with arylselenium halides (Cl and Br) at room temperature. This is a general substitution reaction and it was performed with arylboronic acids or potassium aryltrifluoroborates bearing electron-withdrawing or electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The ionic liquid [bmim][PF6] was easily recovered and utilized for further substitution reactions.

Functionalization of (2S)‐Isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐ones by a Suzuki–Miyaura Cross‐Coupling Reaction Using Aryltrifluoroborate Salts: Convenient Enantioselective Preparation of α‐Substituted β‐Amino Acids

AbstractA simple protocol for the Pd(OAc)2‐catalyzed cross‐coupling reaction of 1‐benzoyl‐(2S)‐isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐ones with potassium aryltrifluoroborates was developed. The reaction is performed at 110 °C with a ligand‐free catalyst. In all cases, complete conversion of the 1‐benzoyl‐(2S)‐isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐onesand aryltrifluoroborates into the C–C coupling products was observed within 30–360 min. It is noteworthy that a largevariety of groups present in the potassium aryltrifluoroborates (–CF3, –OMe, –SEt, –CN, –CHO, –Cl, –Cbz, –NCbz,–OH, –CO2H) could be tolerated. Hydrogenation of the endocyclic double bonds in the Suzuki–Miyaura products followed by acid hydrolysis afforded highly enantioenrichedα‐aryl‐substituted β‐amino acids.

Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization

An efficient synthesis of ortho-arylated 2-phenoxypyridines catalyzed by palladium acetate is described. Treatment of 2-phenoxypyridines with two and a half equivalents of potassium aryltrifluoroborate and 10 mol % of Pd(OAc)2 in the presence of two equivalents of Ag2CO3, one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H2O at 130−140 °C for 48 h in dried CH2Cl2 gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. p-Benzoquinone is found to be an important ligand and co-oxidant for the transmetalation reductive elimination step in the catalytic reaction. The investigation of kinetic isotope effect (kH/kD) is determined to be 5.25, which indicates that C−H bond cleavage occurs in the rate-determining step. One of the arylated compounds, 2-(4′-nitrobiphenyl-2-yloxy)pyridine, was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-(4-nitrophenyl)phenol in 79% yield, demonstrating that pyridine is a removable d...

Nickel-Catalyzed C−O Activation of Phenol Derivatives with Potassium Heteroaryltrifluoroborates

A general method based on nickel-catalyzed C-O activation of various phenol derivatives with potassium (hetero)aryltrifluoroborates has been developed. A large number of heterobiaryls can be easily obtained with yields up to 99% using methanesulfonate cross-coupling partners.

ChemInform Abstract: Homocoupling of Arylboronic Acids and Potassium Aryltrifluoroborates Catalyzed by Protein‐Stabilized Palladium Nanoparticles under Air in Water.

AbstractThe palladium nanoparticles are stabilized primarily within the protein cavity of a highly thermostable Dps protein from the thermophilic bacterium Thermosynechoccus elongatus.