Recyclable CNT-chitosan nanohybrid film utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media

A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.     

Silica chloride: An efficient promoter for oxidation of arylboronic acids to phenols

This work reports simple, highly efficient protocol for the oxidation of arylboronic acids. Various arylboronic acids were selectively and completely converted into their corresponding oxidized phenols using H₂O₂ as an oxidant in presence of catalytic amount of silica chloride. The results show that silica chloride is a suitable and efficient promoter for the oxidation of arylboronic acids. Heterogeneous catalyst, mild reaction conditions, easy availability of the reagent, easy work-up, excellent yield of corresponding phenols, short reaction time and broad substrate scope makes this protocol attractive and a practical alternative to the existing methods.     

Cyclometalated Ir(III) complexes-catalyzed aerobic hydroxylation of arylboronic acids induced by visible-light

The cyclometalated Ir(III) complexes-catalyzed aerobic hydroxylation of arylboronic acids under visible-light has been successfully developed. This catalytic system has a broad substrate scope, affording a series of phenols smoothly with the highest isolated yield up to 95%. Moreover, this protocol is capable to synthesize several useful phenols containing bulky moieties, which are potential candidates or intermediates used as pharmaceuticals and functional materials. The Ir(III)-catalyzed hydroxylation of arylboronic acids could be applied in a one-pot synthesis of several important phenol derivatives, including 1,1′-methylene-bis(2-naphthol), 2,3-dihydro-1H-naphtho[2,1-e][1,3]oxazine and a bioactive compound LUF5771.     

A mild conversion of arylboronic acids and their pinacolyl boronate esters into phenols using hydroxylamine

Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields.     

Electrophilic ipso-iodination of silylated arylboronic acids

Silylated functionalized arylboronic acids were converted into corresponding iodinated arylboronic acids in good yields via the electrophilic ipso-desilylation effected with iodine chloride in refluxing CHCl₃. Disilylated arylboronic acids were susceptible to diiodination. In addition, the structural characterization and reactivity of a novel sterically hindered ortho-silylated diarylborinic ester were reported. The potential of selected iodinated phenylboronic acids as monomers for the Suzuki-Miyaura cross-coupling polymerization was demonstrated.     

A reusable polymer supported copper catalyst for the C–N and C–O bond cross-coupling reaction of aryl halides as well as arylboronic acids

A simple and industrially viable protocol for C–N and C–O coupling was reported here. The polymer supported heterogeneous copper catalyst was prepared from chloromethyl polystyrene using a simple procedure. O-Arylation of substituted phenols with various aryl halides was achieved using this copper catalyst in DMSO medium. This heterogeneous copper catalyst, also efficiently works for the N-arylation of N–H heterocycles with aryboronic acids in methanol. This catalyst was also effective in amination reaction of primary amines with aryl halides as well as arylboronic acids in DMSO medium. The effects of solvent, base and temperature for the O-Arylation and amination reactions were reported. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to several times without sufficient loss of its catalytic activity.     

A reusable polymer supported copper catalyst for the C–N and C–O bond cross-coupling reaction of aryl halides as well as arylboronic acids

A simple and industrially viable protocol for C–N and C–O coupling was reported here. The polymer supported heterogeneous copper catalyst was prepared from chloromethyl polystyrene using a simple procedure. O-Arylation of substituted phenols with various aryl halides was achieved using this copper catalyst in DMSO medium. This heterogeneous copper catalyst, also efficiently works for the N-arylation of N–H heterocycles with aryboronic acids in methanol. This catalyst was also effective in amination reaction of primary amines with aryl halides as well as arylboronic acids in DMSO medium. The effects of solvent, base and temperature for the O-Arylation and amination reactions were reported. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to several times without sufficient loss of its catalytic activity.     

Synthesis of symmetrical diaryl ethers from arylboronic acids mediated by copper(II) acetate

Copper promoted generation of phenols in situ through arylation of water and their subsequent arylation with arylboronic acids affords a wide range of symmetrical diaryl ethers in good to high yield. The reaction is rapid, mild, convenient and tolerant of a wide range of functionalities on the arylboronic acid.     

A novel sustainable strategy for the synthesis of phenols by magnetic CuFe2O4-catalyzed oxidative hydroxylation of arylboronic acids under mild conditions in water

A novel sustainable strategy for the synthesis of phenols has been developed using inexpensive, readily available, air-stable, and recyclable CuFe₂O₄ nanoparticles as the catalyst, and the corresponding substituted phenols were obtained in moderate to good yields by oxidative hydroxylation of arylboronic acids in water. Importantly, a ligand or an additive was not necessary. The catalyst was completely recoverable with an external magnet and could be reused six times without significant loss of catalytic activity.     

Microwave-assisted phase-transfer catalysis for the rapid one-pot methylation and gas chromatographic determination of phenolics

Microwave-assisted phase-transfer catalysis (PTC) is reported for the first time, for the one-step extraction–derivatization–preconcentration and gas chromatographic determination of twenty phenols and ten phenolic acids. The well established phase-transfer catalytic methylation is largely accelerated when heating is replaced with the “greener” microwave irradiation. The overall procedure was thoroughly optimized and the analytes were determined by GC/MS. The method presented adequate analytical characteristics being more sensitive in analyzing phenols than phenolic acids. The limits of detection without any additional preconcentration steps (e.g. solvent evaporation) were adequate and ranged from 0.4 to 15.8 ng/mL while limits of quantitation were between 1.2 and 33.3 ng/mL. The method was applied to the determination of phenols, in spiked environmental samples and phenolic acids in aqueous infusions of commercially available pharmaceutical dry plants. The recoveries of fortified composite lake water samples and Mentha spicata aqueous infusions ranged from 89.3% to 117.3% for phenols and 93.3% to 115.2% for phenolic acids.     

Nickel-catalyzed cross-coupling of phenols and arylboronic acids through an in situ phenol activation mediated by PyBroP

A new method for the Suzuki–Miyaura cross‐coupling of phenols and arylboronic acids through in situ phenol activation mediated by PyBroP is presented. The reaction proceeds efficiently by using cost‐effective, markedly stable [NiCl₂(dppp)] (dppp=1,3‐bis(diphenylphosphino)propane) as the catalyst in only 5 mol % loading, as well as in the absence of extra ligands. The method exhibits broad applicability and high efficiency towards a wide range of both phenols and boronic acids, including activated, nonactivated, deactivated, and heteroaromatic coupling partners. In addition, various functional groups, such as ether, amino, cyano, ester, and ketone groups, are compatible with this transformation. Notably, arylboronic acids containing an unprotected NH₂ group and 2‐heterocyclic boronic acids, which are generally problematic for coupling under conventional conditions, are also viable substrates, although moderate yields were obtained for sterically hindered substrates. Consequently, the in situ cross‐coupling methodology coupled with the use of an inexpensive and stable nickel catalyst provides a rapid and efficient pathway for the assembly of biaryls and heterobiaryls with structural diversity from readily available phenol compounds.     

A simple rhodium-catalyzed addition reaction of aldehydes with arylboronic acids in aqueous γ-valerolactone

A simple rhodium-catalyzed addition reaction of aldehydes with arylboronic acids in aqueous γ-valerolactone provides the corresponding benzylic alcohols in moderate to good yields. Other organoboron reagents (boronic esters, aryl-trifluoroborates, etc.) also showed good compatibilities, albeit with relatively lower yields.     

Reactions of diborane with organic derivatives of tin and lead

Diborane reacts with aryltin and aryllead compounds to give intermediates which on hydrolysis give arylboronic and arylborinic acids, and on oxidation give phenols.     

低温Suzuki反应合成联苯及三联苯化合物

发展了一个低温下无配体钯催化溴代芳烃与芳基硼酸的Suzuki反应体系。该体系以醋酸钯为催化剂,无水碳酸钾为碱,乙醇水溶液为溶剂,无需加入任何配体,在0oC下即可高效催化溴代芳烃与芳基硼酸的Suzuki反应;反应的底物容忍性好,产品分离收率最高达97%。以溴代芳基N-甲基亚氨基二乙酸硼酸酯为砌块分子,通过调控反应温度,实现了砌块分子选择性Suzuki反应,从而一锅合成了不对称三联苯化合物,产品收率最高为81%。     

Efficient, protection-free Suzuki-Miyaura synthesis of ortho-biphenyltetrazoles

We describe an efficient protocol for the Suzuki-Miyaura synthesis of ortho-biphenyltetrazoles from non-protected 2-bromophenyltetrazole and arylboronic acids. The optimised conditions were achieved using [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) as catalyst and Na₂CO₃ as base. A panel of structurally diverse arylboronic acids was used to demonstrate the scope of the coupling procedure.     

One-pot synthesis of fluorinated terphenyls by site-selective Suzuki-Miyaura reactions of 1,4-dibromo-2-fluorobenzene

The Suzuki-Miyaura reaction of 1,4-dibromo-2-fluorobenzene with two equivalents of arylboronic acids gave fluorinated para-terphenyls. The reaction with 1 equiv of arylboronic acid resulted in site-selective formation of biphenyls. The one-pot reaction of 1,4-dibromo-2-fluorobenzene with two different arylboronic acids afforded fluorinated para-terphenyls containing two different terminal aryl groups.     

First preparation of a novel polyol resin for purifying arylboronic acids

A novel polystyrene-supported triol resin was first prepared by reaction of the Merrifield resin with trometamol.Using this resin, arylboronic acids were efficiently isolated and purified through a "capture-release" procedure in organic solvents.However,in basic aqueous solvents arylboronic acids were immobilized on the resin only with low yield.     

Aqueous bile salt accelerated cascade synthesis of 1,2,3-triazoles from arylboronic acids

A facile, efficient and mild copper catalyzed strategy for cascade synthesis of various 1,4-disubstituted 1,2,3-triazoles from arylboronic acids, sodium azide and alkynes was developed by using aqueous bile salt NaDC solution as an accelerating medium. Low catalyst loading (only 1?mol% Cu source was sufficient for in situ generation of azide followed by azide–alkyne coupling), green solvent, use of bio-surfactant as additive and short reaction time make this protocol highly accessible and environment friendly.     

Metal-free synthesis of substituted phenols from arylboronic acids in water at room temperature

A convenient,efficient and practical metal-free method for the synthesis of substituted phenols from arylboronic acids has been developed.The protocol uses hydrogen peroxide as a hydroxylating agent ammonium bicarbonate as an additive,and the reactions were conveniently performed in water at room temperature.The method shows an excellent tolerance of functional groups,so it will find a wide variety of applications in academic and industrial research.     

In situ generated cationic Pd(II)/bipyridine-catalyzed addition of arylboronic acids to N-sulfonyl-arylaldimines

An in situ generated cationic Pd(II)/bipyridine-catalyzed nucleophilic addition of arylboronic acids to N-sulfonyl arylaldimines was developed and optimized, and the reaction was proceeded highly efficiently and conveniently in CH₃NO₂. A series of arylboronic acids and N-sulfonyl arylaldimines were surveyed, and 12 of 13 examples gave 90～96% yields.