Organoboronic Acids Research Articles

Photochemical Defluorinative Alkenylation of Trifluoromethyl Alkenes with Organoboronic Acids

AbstractWe have developed a photo‐catalyzed defluorinative two‐component coupling reaction of trifluoromethyl alkenes and organoboronic acids, providing a straightforward and efficient route for the synthesis of functionalized gem‐difluorinated 1,4‐dienes. Both the chemical yields and functional group tolerance are generally good.

Co-Catalyzed Suzuki-Miyaura Coupling of Organoboronic Acids and Alkynyl Chlorides Using Potassium Bicarbonate as Base.

Organoboronic acids, some of the most common and widely used organoboron compounds, have not yet been used in the cobalt-catalyzed cross coupling reactions, despite cobalt demonstrating good reactivity with zinc reagents, Grignard reagents, and metal organoborates that are formed by n-butyl lithium or alkaline metal alkoxide salts and organoboron esters. Herein, a highly efficient and practical cobalt-catalyzed coupling reaction of aryl/alkenyl boronic acids and alkynyl chloride under mild reaction conditions is reported. The advantages of the organoboronic acids, along with a broad functional group compatibility and the reaction's tolerance to moisture and air, enable this reaction to be a synthetically useful protocol for the construction of a C(sp2)-C(sp) bond. Lastly, the synthesis of two natural products and a key intermediate of roxadustat was effectively accomplished using the methodology to construct the critical alkynyl-aryl bond.

Cu(I)-Induced 'Click Reaction' Involving Coordination and Covalent Assembly of Hybrid Borates for the Electrocatalytic CO2 Reduction.

The design and synthesis of hybrid borates by the organic ligand modification method are urgent and undeveloped areas of research. It is difficult to directly integrate organoboronic acids within inorganic borate chemistry by adopting the traditional preparation approaches. This work reports a facile synthetic method to synthesize a large family of pyrazole molecule-protected borates in a rapid and precise manner under mild conditions. A unique cyclic eight-membered B4O4-ring has been identified as the cluster core for all these hybrid borates with two different conformations (boat and crown). This strategy can be applied to a system of pyrazolyl molecules to generate such hybrid borates in two independent routes from organoboronic or inorganic boric acids. Furtherly, the mechanism of 'click reaction' between boric acid and pyrazole induced by copper ions has been proposed based on the synthetic conditions and the structure of intermediate. Due to the bimetallic Cu sites and the functional surfaces, these materials can be used as electrocatalysts for CO2 reduction reaction and efficiently enhance the selectivity of HCOOH and C2H4. Our strategy can be regarded as a typical template technique for organic molecule-protected borates.

Cu(I)‐Induced ‘Click Reaction’ Involving Coordination and Covalent Assembly of Hybrid Borates for the Electrocatalytic CO2 Reduction

AbstractThe design and synthesis of hybrid borates by the organic ligand modification method are urgent and undeveloped areas of research. It is difficult to directly integrate organoboronic acids within inorganic borate chemistry by adopting the traditional preparation approaches. This work reports a facile synthetic method to synthesize a large family of pyrazole molecule‐protected borates in a rapid and precise manner under mild conditions. A unique cyclic eight‐membered B4O4‐ring has been identified as the cluster core for all these hybrid borates with two different conformations (boat and crown). This strategy can be applied to a system of pyrazolyl molecules to generate such hybrid borates in two independent routes from organoboronic or inorganic boric acids. Furtherly, the mechanism of ‘click reaction’ between boric acid and pyrazole induced by copper ions has been proposed based on the synthetic conditions and the structure of intermediate. Due to the bimetallic Cu sites and the functional surfaces, these materials can be used as electrocatalysts for CO2 reduction reaction and efficiently enhance the selectivity of HCOOH and C2H4. Our strategy can be regarded as a typical template technique for organic molecule‐protected borates.

Nickel-Catalyzed, Aminoquinoline-Directed Chemo- and Regioselective Carboamination of Unactivated Olefins with Organoboronic Acids and Anthranils.

A nickel-catalyzed three-component carboamination of unactivated alkenes with organoboronic acids and anthranils has been achieved for the expedient synthesis of δ-aryl and γ-amino acid derivatives. The 8-aminoquinoline (AQ) directing group is crucial for the success of the reaction, and anthranil serves as an arylnitrene precursor in this conversion. This method features mild reaction conditions, good chemo- and regioselectivity, and a broad substrate scope with good functional group tolerance.

Palladium‐Catalyzed Selective Syntheses of 2,3‐Allenyl Amines via Double Functionalization Coupling of 2‐Alkynyl‐1,4‐diol Dicarbonates

Comprehensive Summary2,3‐Allenyl amines have shown wide applicability in biomedical and synthetic applications. Due to their enormous potential for applications, researchers have been dedicated to the development of methods for synthesizing 2,3‐allenyl amines. Herein, a palladium‐catalyzed three‐component reaction of 2‐alkynyl‐1,4‐diol dicarbonates, organoboronic acids, and nitrogen nucleophiles forming 2,3‐allenyl amines with excellent regio‐ and chemo‐selectivity has been developed. Substrate compatibility and synthetic applications have been demonstrated. Control experiments supported a mechanism involving 1,2,3‐triene‐Pd species and methylene‐π‐allyl palladium species.

Dinuclear gold-catalyzed divergent dechlorinative radical borylation of gem-dichloroalkanes

The enormous and widespread use of organoboronic acids has prompted the development of innovative synthetic methodologies to meet the demands on structural diversity and functional group tolerance. The existing photoinduced defunctionalization radical borylation, typically focused on the conversion of one C-X bond (X= Br, I, or other leaving group) into only one C-B bond. Herein, we disclose a divergent radical dechloroborylation reaction enabled by dinuclear gold catalysis with visible light irradiation. A wide range of structurally diverse alkyl boronic, α-chloroboronic, and gem-diboronic esters can be synthesized in moderate to good yields (up to 92%). Its synthetic robustness is further demonstrated on a preparative scale and applied to late-stage diversification of complex molecules. The process hinges on a C-Cl bond relay activation in readily available gem-dichloroalkanes through inner-sphere electron transfer, overcoming the redox potential limits of unreactive alkyl chlorides.

A Synthesis of α-Alkyl Cycloenones by Pd-Catalyzed Suzuki-Miyaura Coupling with Cyclic Morita-Baylis-Hillman Adducts.

We herein disclose a Pd-catalyzed Suzuki-Miyaura coupling of cyclic Morita-Baylis-Hillman adducts with organoboronic acids under mild conditions, which allows for a rapid access to diverse α-alkyl substituted cycloenones. The advantage of this method resides in the employment of functionalized allyl alcohols as the unprecedented electrophilic partners in the absence of external activators.

Palladium-Catalyzed Heck/Suzuki Tandem Reaction of (Z)-1-Iodo-1,6-dienes and Organoboronic Acids.

The Heck/Suzuki tandem reaction has emerged as an essential strategy for the synthesis of complex molecules. Herein, an efficient palladium-catalyzed Heck/Suzuki tandem reaction of (Z)-1-iodo-1,6-dienes with organoboronic acids is described, providing various tetrahydropyridines in good to excellent yields under mild reaction conditions. The key to the success of this approach is the avoidance of the intramolecular second Heck insertion occurring prior to the transmetalation step. In addition, the asymmetric version of this reaction is investigated to deliver chiral tetrahydropyridine in excellent yield with promising enantioselectivity.

Rhodium-Catalyzed Asymmetric Addition to 4- or 5-Carbonyl-cycloenones through Dynamic Kinetic Resolution: Enantioselective Synthesis of (-)-Cannabidiol.

The reaction of 4/5-carbonyl-cycloalkenone 1 or its achiral isomer 1' with organoboronic acid 2 in the presence of a chiral diene (S,S)-Fc-tfb-rhodium catalyst gave disubstituted trans-cycloalkanone 3 with high diastereo- and enantioselectivity. This highly efficient dynamic kinetic resolution is achieved by fast racemization of 1 through the formation of a dienolate followed by kinetic resolution with the chiral catalyst. The utility is demonstrated by the synthesis of key intermediates en route to (-)-cannabidiol.

BIII-Subporphyrins Bearing Distorted Metal-Coordinating Straps: CuII-Assisted meso-Fabrications.

BIII-subporphyrins 4, 5, and 6 possessing metal-coordinating carbaporphyrin-like pockets were synthesized by Suzuki-Miyaura coupling reactions. Compounds 4 and 5 gave PdII complexes 4-Pd and 5-Pd upon metalation with Pd(OAc)2 but did not give either their NiII or CuII complexes. Conversely, 6 was expected to induce distorted square planar coordination because of its 2,5-di(pyrid-2-yl)pyrrole strap. Indeed reaction of 6 with Cu(OAc)2 did not give its CuII complex but produced meso-alkoxy and meso-phenoxy products in the presence of alcohols and phenol, possibly via CuII-mediated C-H bond functionalization, which was further extended to meso-C-C bond-forming fabrications by using organoboronic acids. These CuII-mediated C-H bond meso-fabrications are the first example for porphyrinoid substrates.

Nickel-catalysed C–N cross-coupling of organoboronic acids and isoxazoles

A nickel-catalyzed C–N cross-coupling of organoboronic acids and isoxazoles has been established for the efficient synthesis of (Z) N-aryl β-enamino esters.

Synthesis of allenynes via Pd-catalyzed coupling of 1,4-diyn-3-yl carbonates with boronic acids

A palladium-catalyzed cross-coupling reaction of 1,4-diyn-3-yl carbonates with organoboronic acids for a series of conjugated allenynes using S-phos or Gorlos-phos as the ligand under mild conditions has been developed.

Oxazaborolidinones: Steric Coverage Effect of Lewis Acidic Boron Center in Suzuki-Miyaura Coupling Reactions.

It was demonstrated that α-hydroxycarboxamide is an excellent boron-protecting group. The reaction between α-hydroxycarboxamide and organoboronic acids produced stable oxazaborolidinones (OxBs), in which the -hybridized boron atom was sterically protected by α-hydroxycarboxamide. The alkyl groups of the α-hydroxycarboxamide moiety can dynamically cover the p-orbital of the -hybridized boron center, creating a small space around the boron atom, allowing for smooth transmetalation by a Pd catalyst and easy deprotection by water. This protecting phenomenon is effective for readily purification, Suzuki-Miyaura coupling reactions with unstable boronic acids and iterative cross-couplings.

Synthesis of Skipped Aminodienes by a Ni‐Catalyzed Ring‐Opening/Cross‐Coupling Reaction of Vinylaziridines with Multifunctional Organoboronic Acids†

Comprehensive SummarySkipped dienes are of great importance but remain challenging to synthesize because of the presence of a sp3 hybrid carbon between the two alkenes. Herein, we have developed the first nickel‐catalyzed regio‐, (E)‐stereo‐ and linear‐selective ring‐opening/cross‐coupling reaction of vinylaziridines with organoboronic acids under mild conditions to construct various skipped aminodienes. The reaction exhibits wide functional‐group compatibility, and could be adapted for the introduction of skipped aminodiene functionality into bioactive molecules. In addition, the reaction could be carried out on a gram‐scale, delivering the ring‐opening products in high yields and with linear‐selectivity (90% yield, l : b >20 : 1). Furthermore, DFT calculations and mechanistic experiments provided detailed insights into the mechanism.

Silica-supported Schiff-based palladium nanocatalyzed cross-coupling reactions and its applications in the synthesis of antiplatelet and fungicidal

The readily available silica gel was converted into an amino functionalized silica by refluxing with 3-aminopropylthiethoxy silane. The amino functionalized silica was transformed into the respective Schiff-based ligand by the incorporation of [2,2′-bithiophene]-5,5′-dicarbaldehyde. The Pd(0) nanocatalyst on the silica gel support was developed by further processing the Schiff-based ligand with ammonium tetrachloropalladate and hydrazine. The Schiff-based Pd(0) nanocatalyst was extensively characterized using a range of spectroscopic techniques, including Raman, SEM, EDX, TEM, XRD, ICP, and XPS. Raman spectroscopy was used to confirm that the organic moietieshavebeen successfully incorporated, and XPS, XRD, and EDX analyses supported the existence of palladium species on the silicasurface. According to the TEM analysis,Pd-nanocomplexwith a size distribution of 5.3 ± 0.6 nm was found to be evenly distributed on the silica surface. Palladium was incorporated into the silica surface at a rate of 1.9 w%, according to ICP and EDX analysis. The Mizoroki-Heck and Suzuki-Miyaura coupling reactions were successfully catalyzed by the Schiff-based Pd(0) catalyst using a diverse range of aryl halides, olefines, and organoboronic acids. High yields were achieved in each example in the case for the coupling products. Despite being recoveredfrom the reaction medium and used multiple times, the catalyst still maintained the majority of its catalytic activity. Furthermore, this Schiff-based Pd(0) catalyst was used to produce biologically active molecules of Ozagrel, an antiplatelet agent and fungicidal Boscalid with high yield.

Transition-Metal-Free Insertion of Diazo Compounds, N-Arylsulfonylhydrazones or Ylides into Organoboronic Acids or Their Derivatives

AbstractInsertion reactions of carbenes or ylides with organoboronic acids or their derivatives have emerged as valuable methods for coupling or homologation of organoboron compounds under metal-free conditions. The crucial steps of these reactions are coordination of the electron-rich carbon centers of the carbene precursors or ylides to the electron-poor boron center, followed by 1,2-migration of the corresponding tetracoordinated boron intermediates. This type of unique transformation provides an efficient method for the construction of C–C or C–X (X = H, B) bonds. Moreover, the C–B bonds generated by such transformations can be utilized as a handle for further derivatization or iterative homologations. In this Account, we summarize the developments in this arena according to the reactive diazo compound, N-arylsulfonylhydrazone or ylide species involved.1 Introduction2 Reactions with Diazo Compounds3 Reactions with N-Arylsulfonylhydrazones4 Reactions with Ylides5 Conclusion

Air and moisture stable robust bio-polymeric palladium catalyzed C[sbnd]C bond formation and its application to the synthesis of fungicidal

Cellulose supported bio-heterogeneous polymeric Pd(II) catalyst, stable to air and moisture, was designed and characterized with different spectroscopic techniques including FESEM, TEM, XPS, XRD, ICP-AES and EDX. The Pd(II) catalyst showed high catalytic performance (0.2 to 0.0009 mol%) to the Suzuki-Miyaura CC cross-coupling reaction of aromatic halides and aryl diazonium salts with a range of organoboronic acids to produce the respective biaryl product in up to 97% yield. Biologically active Boscalid, a fungicide that effectively inhibits the growth of fungal pathogens like ascomycetes on fruits and plants, could also be constructed through using this catalyst. Additionally, it was possible to recover the Pd(II) catalyst from the reaction medium and reused it repeatedly without significantly degrading its catalytic efficiency.

The C-3 Functionalization of 1H-Indazole through Suzuki–Miyaura Cross-Coupling Catalyzed by a Ferrocene-Based Divalent Palladium Complex Immobilized over Ionic Liquid, as Well as Theoretical Insights into the Reaction Mechanism

The C-3 functionalization of 1H-indazole could produce a lot of highly valuable pharmaceutical precursors, which could be used for the treatment of cancer and many other inflammatory diseases. This work was focused on the C-3 functionalization of 1H-indazole through Suzuki–Miyaura cross-coupling of 3-iodo-1H-indazole with organoboronic acids, catalyzed by various palladium catalysts immobilized over imidazolium ionic liquids, as well as catalyst recycling. A series of reaction parameters, including the substrate, catalyst, and ionic liquid, were fully investigated. It is significant to note that the yields of the present Suzuki–Miyaura cross-coupling were mainly determined by the catalyst and the solvent used, more than the chemical structure of the substrate. Furthermore, ferrocene-based divalent palladium complexes showed better catalytic outputs compared to simple palladium salts. Moreover, using two imidazolium ionic liquids, BMImX (BMIm+ = 1-n-butyl-3-methylimidazolium, X− = BF4−, PF6−) not only improved the yields of cross-coupled products, but also avoided the formation of Pd(0) black, as compared to the non-ionic liquid facilitated reactions, and simultaneously making catalyst recycling more effective. On average, BMImBF4 performed better than BMImPF6. Additionally, scientific calculations revealed that 1,1′-bis(diphenylphosphino)ferrocene-palladium(II)dichloride dichloromethane complex (PdCl2(dppf)) showed a lower energy barrier in the formation of intermediates than [1,1′-bis(di-tert-butylphosphino)ferrocene]dichloropalladium(II) (PdCl2(dtbpf)), leading to higher catalytic outputs. This work may contribute to the development of 1H-indazole-derived new pharmaceuticals.

Innenrücktitelbild: Salt Metathesis: Tetrafluoroborate Anion Rapidly Fluoridates Organoboronic Acids to give Organotrifluoroborates (Angew. Chem. 16/2023)

Salt metathesis and BFX (boron–fluoride exchange) of BF4− with boronic acids generates RBF3− derivatives, thus showing the solvolytic lability of BF4− that enables its use as a fluorinating agent, even though many highly reactive reagents employ BF4− as a non-reactive counteranion. In their Research Article (e202215371), David M. Perrin and co-workers report the synthesis of RBF3− derivatives via a salt metathesis reaction using a series of MBF4 salts in methanol. This work highlights the proclivity of BF4−, generally considered weakly coordinating and unreactive, to rapidly fluorinate boronic acids.