Heteroaryl Boronic Acids Research Articles

ChemInform Abstract: Synthesis of 1,3‐Dienes via a Sequential Suzuki—Miyaura Coupling/Palladium‐Mediated Allene Isomerization Sequence.

We report a facile method for the synthesis of 1,3-dienes by a sequential process consisting of a palladium-catalyzed, base-free, Suzuki-Miyaura coupling/isomerization sequence. This sequence couples boronic acids with propargyl alcohols, generating the requisite allene in situ, followed by conversion of the unactivated allene to its 1,3-diene via a hydro-palladation/dehydro-palladation process. This process is general for a range of boronic acids, including boronic acids with electron-donating and -withdrawing groups, as well as heteroarylboronic acids. Key to this process is the boric acid byproduct of the base-free Suzuki-Miyauru coupling, which generates the required palladium-hydrido complex [H-Pd(II)-OB(OH)2] required for the isomerization.

ChemInform Abstract: Pd‐Catalyzed C—P Coupling of Heteroaryl Boronic Acid with H‐Phosphonate Diester.

AbstractA novel route to heteroaryl phosphonates (III) using a Pd/Ag‐catalyst system without addition of a base is described.

Grafting of Ru(III) complex onto nanosilica and its implication as heterogeneous catalyst for aerobic oxidative hydroxylation of arylboronic acids

An ecofriendly and highly efficient protocol for aerobic oxidative hydroxylation of aryl and heteroaryl boronic acids catalyzed by Ru(III) imine complex immobilized on nanosilica, derived from rice husk, has been developed. The main significance of this protocol is the base free and aerobic reaction condition at room temperature, short reaction time, aqueous reaction medium, and excellent yield of the product. This heterogeneous catalyst is reusable up to sixth cycle without loss in activity.

Copper-catalyzed oxidative trifluoroethoxylation of aryl boronic acids with CF3CH2OH

A mild and efficient copper-catalyzed oxidative trifluoroethoxylation of aryl and heteroaryl boronic acids with CF3CH2OH has been developed. This protocol tolerates a range of functional groups, allowing access to a variety of aryl and heteroaryl trifluoroethyl ethers.

ChemInform Abstract: Metal‐Free Allylation of Electron‐Rich Heteroaryl Boronic Acids with Allylic Alcohols.

AbstractThe regioselective cross‐coupling of heteroaryl boronic acids with allylic alcohols works under external oxidant‐ and metal‐free conditions, and proves to be very general with an unprecedented selectivity for ortho‐functionalization of the boronic acids.

Synthesis of 1,3-Dienes via a Sequential Suzuki-Miyaura Coupling/Palladium-Mediated Allene Isomerization Sequence.

We report a facile method for the synthesis of 1,3-dienes by a sequential process consisting of a palladium-catalyzed, base-free, Suzuki-Miyaura coupling/isomerization sequence. This sequence couples boronic acids with propargyl alcohols, generating the requisite allene in situ, followed by conversion of the unactivated allene to its 1,3-diene via a hydro-palladation/dehydro-palladation process. This process is general for a range of boronic acids, including boronic acids with electron-donating and -withdrawing groups, as well as heteroarylboronic acids. Key to this process is the boric acid byproduct of the base-free Suzuki-Miyauru coupling, which generates the required palladium-hydrido complex [H-Pd(II)-OB(OH)2] required for the isomerization.

Ligand Free Palladium Catalyzed Synthesis of 3‐Aryl/heteroaryl‐4‐Indolylmaleimide and its Antimicrobial Activity.

AbstractHere we have developed ligand free palladium catalyzed Suzuki coupling of 3‐bromo‐1‐methyl‐4‐indolylmaleimide under room temperature condition. Twenty unsymmetrical indolylmaleimide derivatives (4 a‐4 t) were synthesised using various aryl‐ and heteroarylboronic acids in good to excellent yields. Synthesised compounds were further screened for its antimicrobial activity. Compounds 4 q displayed significant minimum inhibitory concentration (MIC) value of 2.3µM toward S. aureus. 4 q was also found to be bactericidal in nature with minimum bactericidal concentration (MBC) value of 4.6 µM. The selective index calculated for compounds 4 q was 38.84 towards S. aureus. Compound 4 s was found to be active against M. Tuberculosis and 3.5 times more efficacious than standard drug rifampicin against multidrug‐resistant Mycobacterium tuberculosis (MDR‐MT) strain. In mechanistic study, we identified that 4 s is active in Shikimate kinase enzyme inhibition assay.

ChemInform Abstract: Copper‐Mediated Aerobic (Phenylsulfonyl)difluoromethylation of Arylboronic Acids with Difluoromethyl Phenyl Sulfone.

AbstractThe reagent “PhSO2CF2Cu” is generated in the reaction from sulfone (I) and it further reacts with aryl‐ and heteroarylboronic acids to afford the desired products.

Pd-catalyzed C–P coupling of heteroaryl boronic acid with H-phosphonate diester

We report herein a novel protocol to construct C–P bond from heteroaryl boronic acid with H-phosphonate diester under Pd–Ag catalyzed system without addition of base. This method, directly using commercial available heteroaryl boronic acid as the starting material, provides a new way to synthesize a variety of useful heteroaryl phosphonates.

Metal-free allylation of electron-rich heteroaryl boronic acids with allylic alcohols

A convenient and regioselective cross-coupling of heteroaryl boronic acids with allylic alcohols under catalyst-free reaction conditions is described. The developed procedure is simple, works under external oxidant- and metal-free conditions, and proves to be very general with an unprecedented ortho-selectivity. This approach represents one of the very few examples of ortho-functionalization of boronic acids.

ChemInform Abstract: Alkylations of Arylboronic Acids Including Difluoroethylation/Trifluoroethylation via Nickel‐Catalyzed Suzuki Cross‐Coupling Reaction.

An efficient alkylation method of functionalized alkyl halides under mild nickel-catalyzed C(sp3)C(sp2) Suzuki cross-coupling conditions is described. The features of this approach are excellent functional group compatibility, low cost nickel catalyst, and the use of a mild base. This is also the first successful example of the nickel-catalyzed direct 2,2-difluoroethylation or 2,2,2-trifluoroethylation of aryl-/heteroarylboronic acids.

Palladium(II)‐Catalyzed Synthesis of Sulfinates from Boronic Acids and DABSO: A Redox‐Neutral, Phosphine‐Free Transformation

AbstractA redox‐neutral palladium(II)‐catalyzed conversion of aryl, heteroaryl, and alkenyl boronic acids into sulfinate intermediates, and onwards to sulfones and sulfonamides, has been realized. A simple Pd(OAc)2 catalyst, in combination with the sulfur dioxide surrogate 1,4‐diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO), is sufficient to achieve rapid and high‐yielding conversion of the boronic acids into the corresponding sulfinates. Addition of C‐ or N‐based electrophiles then allows conversion into sulfones and sulfonamides, respectively, in a one‐pot, two‐step process.

Palladium(II)-Catalyzed Synthesis of Sulfinates from Boronic Acids and DABSO: A Redox-Neutral, Phosphine-Free Transformation.

A redox‐neutral palladium(II)‐catalyzed conversion of aryl, heteroaryl, and alkenyl boronic acids into sulfinate intermediates, and onwards to sulfones and sulfonamides, has been realized. A simple Pd(OAc)2 catalyst, in combination with the sulfur dioxide surrogate 1,4‐diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO), is sufficient to achieve rapid and high‐yielding conversion of the boronic acids into the corresponding sulfinates. Addition of C‐ or N‐based electrophiles then allows conversion into sulfones and sulfonamides, respectively, in a one‐pot, two‐step process.

Enantioselective Rh(I)-Catalyzed Addition of Arylboronic Acids to Cyclic Ketimines.

A method for the enantioselective synthesis of chiral α-tertiary amines via Rh-catalyzed 1,2-addition of arylboronic acids to cyclic ketimines is described. The products are efficiently accessed in good yields and excellent enantioselectivities using a commercially available chiral ligand. The reaction scope includes vinyl, aryl, and heteroarylboronic acids with yields ranging from 40% to 99% and enantiomeric excesses from 88% to 99%. Conversion of an addition product into an α,α-diaryl-substituted amino acid is also demonstrated.

ChemInform Abstract: Facile Synthesis of Trifluoroethyl Aryl Ethers Through Copper‐Catalyzed Coupling of CF3CH2OH with Aryl‐ and Heteroaryl Boronic Acids.

Abstract An efficient copper-catalyzed Chan–Lam reaction of trifluoroethanol with a variety of aryl- and heteroaryl boronic acids has been developed. This research provides a practical method to synthesize trifluoroethyl aryl ethers in moderate to good yields under mild conditions.

ChemInform Abstract: Simple Aminobenzoic Acid Promoted Palladium Catalyzed Room Temperature Suzuki—Miyaura Cross‐Coupling Reaction in Aqueous Media.

Abstract A highly efficient catalytic system based on Pd(OAc)2 and 4-aminobenzoic acid has been developed for the room temperature Suzuki–Miyaura cross-coupling reaction in aqueous media. The system can tolerate a wide range of functionalized arylboronic acids and aryl halides. Furthermore, this protocol is also applicable for hetero-aryl bromides and hetero-arylboronic acids.

Facile synthesis of trifluoroethyl aryl ethers through copper-catalyzed coupling of CF3CH2OH with aryl- and heteroaryl boronic acids

An efficient copper-catalyzed Chan–Lam reaction of trifluoroethanol with a variety of aryl- and heteroaryl boronic acids has been developed. This research provides a practical method to synthesize trifluoroethyl aryl ethers in moderate to good yields under mild conditions.

ChemInform Abstract: Practical and Efficient ipso‐Iodination of Arylboronic Acids via KF/I2 System.

Abstract A facile and effective iododeboronation of variously substituted aryl and heteroarylboronic acids through activation and subsequent ipso -introduction of iodine is presented. The use of KF and I 2 at 80 °C in 1,4-dioxane furnishes iodinated compounds in high yields.

Scope and Limitations of the Liebeskind-Srogl Cross-Coupling Reactions Involving the Biellmann BODIPY.

Several new examples of meso-(het)arylBODIPY were prepared via the Liebeskind-Srogl (L-S) cross-coupling reaction of the Biellmann BODIPYs (1a,b) and aryl- and heteroarylboronic acids in good to excellent yield. It was shown that this reaction could be carried out under microwave heating to shorten reaction times and/or increase the yield. It was illustrated that organostannanes also participate in the L-S reaction to give the corresponding BODIPY analogues in short reaction times and also with good to excellent yields. We analyze the role of the substituent at the sensitive meso position in the photophysical signatures of these compounds. In particular, the rotational motion of the aryl ring and the electron donor ability of the anchored moieties rule the nonradiative pathways and, hence, have a deep impact in the fluorescence efficiency.

Simple aminobenzoic acid promoted palladium catalyzed room temperature Suzuki–Miyaura cross-coupling reaction in aqueous media

A highly efficient catalytic system based on Pd(OAc)2 and 4-aminobenzoic acid has been developed for the room temperature Suzuki–Miyaura cross-coupling reaction in aqueous media. The system can tolerate a wide range of functionalized arylboronic acids and aryl halides. Furthermore, this protocol is also applicable for hetero-aryl bromides and hetero-arylboronic acids.