Arylboric Acids Research Articles

Carbon dot-based type I photosensitizers for photocatalytic oxidation reaction of arylboric acid and N-phenyl tetrahydroisoquinoline

Carbon dots (CDs) have emerged as promising materials for photocatalytic organic transformations due to their excellent photostability, tunable electronic properties, and environmental friendliness; However, the ability of CDs to selectively generate reactive oxygen species (ROS) and its integration with organic photocatalytic synthesis applications has always been a long-term challenge. In this work, we synthesized a new nitrogen and phosphorus co-doped carbon dots (N,P-CDs) with enhanced light absorption and notable efficiency in generating superoxide anion (O2•−) selectively. Leveraging the selective generation of superoxide anions, we achieved highly efficient photooxidation of boronic acids and N-phenyl tetrahydroisoquinolines, demonstrating the practical applicability of N,P-CDs as photocatalysts and represents good functional-group tolerance as well as a broad substrate scope. This study provides valuable insights into the design of carbon-based photocatalysts with controlled ROS generation, opening new avenues for environmentally benign organic transformations.

Copper‐Catalyzed One‐Pot Synthesis of 1,3,4‐Oxadiazol‐2(3H)‐ones using DMF as the Carbonyl Source

AbstractA series of 1,3,4‐oxadiazol‐2(3H)‐ones were prepared by an efficient copper‐catalyzed one‐pot reaction of arylhydrazides, arylboronic acids and DMF. Moderate to good yield of 1,3,4‐oxadiazol‐2(3H)‐ones were obtained using DMF as the carbonyl source and arylboronic as the aryl source. This reaction involved ligand exchange and transmetalation of copper catalysts with arylhydrazides and arylboric acids. Compared to the previous work, this work employs the stable and readily available aryl hydrazide and arylboronic substrates that enhance the practicality of this strategy, and this strategy features a short reaction time, relatively low heating temperature, convenient and more secure. Further, this protocol has the features of high functional group tolerance and reaction scalability.

Synthesis of fluorescein-containing polymeric heterogeneous photocatalyst and its applications

A novel fluorescein-containing polymeric photosensitizer (FS-PHEMA) was successfully synthesized and used as an excellent heterogeneous photocatalyst for aerobic photooxidation of thioethers, hydroxylation of aryl boric acids, and oxidative self-coupling of amines. All the reactions could run smoothly upon irradiation of blue LED under aerobic conditions at room temperature. This heterogeneous photosensitizer can be easily separated, recovered, and reused at least 5 times without significant loss of catalytic activity, showing a good potential in practical applications.

Bispidine‐Based S,N‐Chiral Ligands for Palladium‐Catalyzed Asymmetric Arylation of Cyclic N‐Sulfonyl Ketimines

AbstractDevelopment of new chiral ligands is essentially important in the field of asymmetric metal catalysis. Bispidines, steming from natural alkaloids, represent an intriguing yet underexplored class of chiral ligands. In this article, we developed a series of bispidine‐based chiral ligands with chirality locked in the side chain, and explore their properties by applying in the palladium‐catalyzed asymmetric addition of arylboric acids to cyclic N‐sulfonyl ketimines. A S,N‐bispidine ligand was found especially efficient, affording a series of chiral benzosultams with a quaternary chiral center in excellent yields with excellent ee values. Density functional theory (DFT) calculations and crystal structure of catalyst helped to propose a reasonable mechanism including a possible transition state model to explain the origin of stereoselectivity.

Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids forming o-amino biaryls.

We report a Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids. Under the reaction conditions, a wide range of arylboric acids can couple with free anilines to produce the corresponding o-amino biaryls in moderate to good yields with good functional group tolerance. This reaction can be conducted on the gram scale. The products can be easily further functionalized via transformation of the free amino group. These results indicate the potential synthetic value of this new reaction in organic synthesis.

Copper-Catalyzed N-Arylation of Pyranoquinolinones with Boronic Acids at Room Temperature without Ligand

Pyranoquinolinones synthesized from citral were used for Cu-catalyzed N-arylation with a wide range of arylboric acids. The reaction proceeded well with a broad substrate scope, providing a direct way to access highly functional pyranoquinolinone core structure derivatives in yields of up to 80%. Compared to citral, the compounds we obtained have a much better inhibitory effect on HeLa cervical cancer cells, and compound 3p has an IC50 value of 4.6 μM, lower than cisplatin’s 5.9 μM.

A Novel Fluorescent Probe for the Detection of Hydrogen Peroxide.

Hydrogen peroxide (H2O2) is one of the important reactive oxygen species (ROS), which is closely related to many pathological and physiological processes in living organisms. Excessive H2O2 can lead to cancer, diabetes, cardiovascular diseases, and other diseases, so it is necessary to detect H2O2 in living cells. Since this work designed a novel fluorescent probe to detect the concentration of H2O2, the H2O2 reaction group arylboric acid was attached to the fluorescein 3-Acetyl-7-hydroxycoumarin as a specific recognition group for the selective detection of hydrogen peroxide. The experimental results show that the probe can effectively detect H2O2 with high selectivity and measure cellular ROS levels. Therefore, this novel fluorescent probe provides a potential monitoring tool for a variety of diseases caused by H2O2 excess.

Highly dispersed, subnano Mo-catalyzed reductive C–N coupling of aryl boric acids and aromatic nitro compounds

Zeolitic imidazolate framework (ZIF)-derived CN-20@Mo catalyst has been successfully prepared by a simple and scalable strategy with high specific surface area and highly dispersed, subnano Mo species. Mo species of this catalyst exist in form of MoN4 single atom sites and MoOx subnanometer clusters, both of which exhibits excellent performance in C–N coupling reactions between arylboronic acids and aromatic nitro compounds. This catalyst is easy to recycle and can be reused for at least 6 times without significant decrease in activity. To the best of our knowledge, there is the first example on the heterogeneous Mo-catalyzed reductive C–N coupling of aryl boric acids and aromatic nitro compounds.

Nickel-Catalyzed Three-Component Tandem Radical Cyclization 1,5-Difunctionalization of 1,3-Enynes and Alkyl Bromide.

A nickel-catalyzed three-component tandem radical cyclization reaction of aryl bromides with 1,3-enynes and aryl boric acids to construct γ-lactam-substituted allene derivatives has been described. This protocol provides lactam alkyl radicals through the free radical cyclization process, which can be effectively used to participate in the subsequent multicomponent coupling reaction so that 1,3-enynes could directly convert into corresponding poly-substituted allene compounds. In addition, this efficient method enjoys a broad substrate scope and provides a series of 1,5-difunctionalized allenes in a one-pot reaction.

Boronic acid derived salicylidenehydrazinopyridine (BOSPY) complexes with aggregation-induced emission for fluorescence imaging of cellular organelles

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H-type aggregation to J-type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments.

1,2,3-Triazole-based conjugated porous polymers for visible light induced oxidative organic transformations

1,2,3-Triazole contained conjugated porous polymers (CPPs) have recently emerged as a new class of efficient photocatalysts. To gain more insight into the excellent photocatalytic activity of this kind of CPPs, herein, we report the design and preparation of a series of 1,2,3-triazole-based CPPs via oxidative coupling polymerization to study their photocatalytic performance. These CPPs have donor-acceptor properties and 1,2,3-triazole serves as an electron acceptor. The resulting CPPs with thiophene, carbazole and diphenylamine as electron donor units, respectively, have distinct porosities and optoelectronic properties, and showed effective photocatalytic performance towards oxidative hydroxylation of arylboric acids and alkylation of vinylarenes with diethyl bromomalonate or bromoacetonitrile. The thiophene contained CPP was a more efficient photocatalyst for the catalytic reactions, which can be attributed to its smaller optical band gap and greater charge separation efficiency. Furthermore, PTPT has shown reliable recyclability with no significant loss in its catalytic activity.

Base‐free Suzuki‐Miyaura Coupling of (Z)‐Trifluoromethyl Alkenyltriflates: An Efficient Approach to α‐Trifluoromethyl Arylenes

AbstractAn exogenous base is generally necessary for the traditional palladium‐catalyzed Suzuki‐Miyaura coupling reactions. We report a direct palladium‐catalyzed base‐free Suzuki‐Miyaura coupling reaction of α‐trifluoromethyl alkenyl triflates and aryl boric acids. Using Pd(OAc)2 (10 mol %) and PPh3 (40 mol %) as catalyst, this reaction proceeds smoothly without base or other additive. A variety of common functional groups, such as methyl, phenyl, naphthyl, fluoride, chloride, bromide, cyano, thienyl and alkyl, were well tolerated and a series of α‐trifluoromethyl arylenes were obtained in 84 %–100 % yields.

The Cascade C─H functionalization with sequential hydroxylation and oxidation through heterogeneous BINAP‐copper on hydrotalcite

AbstractBACKGROUNDAromatic thioether derivatives exist widely in natural products and have significant applications in modern synthesis and the pharmaceutical industry; for example, 2‐sulfanylphenols and arylthioquinones are important intermediates in the processing of anticancer, antibiotic, antivirus and antimalarial drugs. Direct C─H hydroxylation was considered as one of the efficient methods for the synthesis of these compounds. Homogeneous transition metal catalysts usually were used through a cross‐coupling of halogen‐substituted phenols with thiophenols. However, from the perspectives of sustainable development and easy recovery, it is necessary to develop an efficient and recoverable catalytic system to realize the synthesis of aromatic thioether derivatives with good efficiency and recyclability.RESULTSThe heterogeneous catalyst [Cu(binap)I]2@HT in the present work showed good catalytic activity for the C─H hydroxylation of benzenethiol and phenylboronic acid. The catalytic system was tolerant to various substituents including alkyl, alkoxy, ester, halogen or trifluoromethyl on the phenyl ring of the thiophenols or arylboric acids. In addition to electron‐donating groups, the products with strong electron‐withdrawing groups, such as methyl formylate and trifluoromethyl also were achieved with good yields at 90 °C for 12 h (68% and 66%, respectively). Repeated experiment results showed that the catalyst could be reused at least five times without obvious decrease in catalytic activity.CONCLUSIONA BINAP‐Cu complex supported on hydrotalcite was prepared and used as a heterogeneous catalyst for the C─H activation of thiophenol under mild reaction conditions. Through a cascade C─H hydroxylation and further oxidation process, 2‐Sulfanylphenols and arylthioquinones could be obtained with moderate‐to‐good yields for a series of 2‐(phenylthio)phenol derivatives using the heterogeneous catalyst [Cu(binap)I]2@HT. In addition, this heterogeneous catalyst showed good recylbility. © 2020 Society of Chemical Industry

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).

Design and fabrication of the Fe/Cl-doped Al foil-supported copper nano-material as the high turnover number catalyst for Suzuki coupling

Cu@Al nano-materials were easily fabricated by immersing Al foil in related metal salt solutions. Although simple Cu@Al was a poor catalyst, after Fe and Cl doping, it became highly active in Suzuki coupling reactions of aryl iodides with aryl boric acids and led to very high product yields (up to 99%) with extremely high catalyst turnover numbers (TON up to 9.1 × 103 mol/mol). Fe/Cl doping affected the morphologies of the materials, endowing more active sites as well as facilitating better contact with the reaction substrates. This is the first report on cheap metal “tea bag” style catalyst, which can be easily removed, overcoming the interruptions by the generated insoluble by-products or tars during the reaction processes.

Bortezomib-catechol conjugated prodrug micelles: combining bone targeting and aryl boronate-based pH-responsive drug release for cancer bone-metastasis therapy.

The treatment of metastatic tumors is highly desirable in clinics, which has also increased the interest in the design of nanoscale drug delivery systems. Bone metastasis is one of the most common pathways in the metastasis of breast cancer, and it is also an important cause for tumor recurrence and death. The aryl boronate group, as an acid-labile linker, has been introduced into nano-assemblies in recent years. Especially, as a proteasome inhibitor anticancer drug with a boric acid group, bortezomib can facilitate the formation of pH-sensitive aryl boric acid ester linkage with the catecholic group. In this study, bortezomib-loaded micelles with bone targeting properties were constructed for the treatment of breast cancer bone metastasis. The mixed micelles employed alendronate (ALN) as the bone-targeting ligand and encapsulated bortezomib-catechol conjugates as the cargo. In vitro and in vivo studies showed that compared with free drugs or control micelles, these prodrug micelles (ALN-NP) exhibited many favorable properties such as reduced systemic toxicity and improved therapeutic effects. Therefore, ALN-NP is promising as a nanovehicle for bone-targeting delivery of chemotherapeutic drugs. Furthermore, this study offers a novel strategy combining bone targeting and aryl boronate-based pH-responsive drug release for anti-metastasis therapy.

Design and fabrication of low-loading palladium nano particles on polyaniline (nano Pd@PANI): An effective catalyst for Suzuki cross-coupling with high TON

By using H2O2 as clean oxidant instead of air in previous fabrication process, a new nano palladium catalyst supported on polyaniline (nano Pd@PANI) with low Pd loading can be smoothly achieved by oxidative polymerization of the aniline with a reduced amount of PdCl2 (currently 0.12% Pd only vs. previously 2.5% Pd). Although this new catalyst contains much less amount of Pd in comparison with the old nano Pd@PANI catalyst (currently only 0.75% Pd vs. previously 10.0% Pd), it is still found to be an effective catalyst for the Suzuki coupling of aryl halides and aryl boric acids, affording biphenyl products in excellent yields with dramatically enhanced turnover numbers (TON, 4.7 × 103vs. 880).

Copper-Catalyzed Synthesis of Unsymmetrical Diorganyl Chalcogenides (Te/Se/S) from Boronic Acids under Solvent-Free Conditions.

The efficient and mild copper-catalyzed synthesis of unsymmetrical diorganyl chalcogenides under ligand- and solvent-free conditions is described. The cross-coupling reaction was performed using aryl boric acids and 0.5 equiv. of diorganyl dichalcogenides (Te/Se/S) in the presence of 3 mol % of CuI and 3 equiv. of DMSO, under microwave irradiation. This new protocol allowed the preparation of several unsymmetrical diorganyl chalcogenides in good to excellent yields.

Enantioselective synthesis of arylglycine derivatives by direct C-H oxidative cross-coupling.

A new method for the synthesis of chiral α-amino acid derivatives by enantioselective C-H arylation of N-aryl glycine esters with aryl boric acids in the presence of a chiral Pd(II)-catalyst has been developed. This work successfully integrates the direct C-H oxidation with asymmetric arylation and exhibits excellent enantioselectivity.

(2-Chlorobenzoyloxy)copper(i) catalyzed C–S cross-coupling of di(hetero)aryl disulfides with aryl boronic acids under base-free conditions

(2-Chlorobenzoyloxy)copper(i) exhibited high activity towards the challenging C–S cross-coupling of di(hetero)aryl disulfides with aryl boric acids with good to excellent yields under base-free conditions.