A practical method for preparation of phenols from arylboronic acids catalyzed by iodopovidone in aqueous medium

A novel and efficient strategy for the ipso-hydroxylation of arylboronic acids to phenols has been developed using inexpensive, readily available, air-stable water-soluble povidone iodine as catalyst and aqueous hydrogen peroxide as oxidizing agent. The reactions were performed at room temperature under metal-, ligand- and base-free condition in a short reaction time. The corresponding substituted phenols were obtained in moderate to good yields by oxidative hydroxylation of arylboronic acids in aqueous medium.     

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.     

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.     

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.     

Visible Light Induced Copper-Catalyzed Enantioselective Deaminative Arylation of Amino Acid Derivatives Assisted by Phenol

The exploration of value-added conversions of naturally abundant amino acids has received considerable attention from the synthetic community. Compared with the well-established asymmetric decarboxylative transformation, the asymmetric deaminative transformation of amino acids still remains a formidable challenge, mainly due to the lack of effective strategies for the C−N bond activation and the potential incompatibility with chiral catalysts. Here, we disclose a photoinduced Cu-catalyzed asymmetric deaminative coupling reaction of amino acids with arylboronic acids. This new protocol provides a series of significant chiral phenylacetamides in generally good yields and excellent stereoselectivity under mild and green conditions (42–85 % yields, up to 97 % ee). Experimental investigations and theoretical calculations were performed to reveal the crucial role of additional phenols in improving catalytic efficiency and enantiocontrol.     

Nucleophilic substitution of alkyl halides by zinc salts-32 preparation of tertiary alkyl esters and ethers under non-solvolytic conditions

Zinc salts of carboxylic acids, phenols and alcohols are found to react with tertiary alkyl halides in nonpolar solvents and in presence of a base yielding the corresponding esters and ethers in moderate to good yields.     

Copper-mediated C-H bond arylation of arenes with arylboronic acids

A new copper-mediated cross-coupling of arenes and arylboronic acids is described. Under the influence of Cu(OCOCF 3) 2, the C-H bond arylation of electron-rich arenes with arylboronic acids takes place to afford a range of biaryls in good yields. The reaction is selective for cross-coupling; no homocoupling product arising from arenes or arylboronic acids is detected. Multiple C-H bond arylation is possible with indoles and pyrroles furnishing interesting extended pi-systems.     

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.     

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.     

An efficient base-free N-arylation of imidazoles and amines with arylboronic acids using copper-exchanged fluorapatite

N-Arylation of imidazoles and amines with arylboronic acids was accomplished with copper-exchanged fluorapatite (CuFAP) in methanol at room temperature. The products N-arylimidazoles and N-arylamines were isolated in good to excellent yields. A variety of arylboronic acids were converted to the corresponding N-arylimidazoles and N-arylamines, demonstrating the versatility of the reaction.     

Tetrasubstituted olefin synthesis via Pd-catalyzed addition of arylboronic acids to internal alkynes using O2 as an oxidant

The Pd(II)-catalyzed reaction of arylboronic acids and internal alkynes provides a convenient route to a wide variety of tetrasubstituted olefins. The reaction is conducted in DMSO using molecular O2 as an oxidant in the absence of any base. The reaction involves the cis addition of two aryl groups from the arylboronic acid to opposite ends of the triple bond of the internal alkyne. The synthesis tolerates a wide variety of functional groups, including alcohol, aldehyde, ester, TMS, and acetal groups. Electron-rich dialkylacetylenes, such as 4-octyne, provide highly substituted 1,3-dienes in moderate yields. The very mild O2/DMSO conditions also afford good to excellent yields of biaryls by the homocoupling of arylboronic acids.     

N-Heterocyclic Carbene-Palladium(II)-1-Methylimidazole Complex-Catalyzed Suzuki-Miyaura Coupling of Aryl Sulfonates with Arylboronic Acids

A well-defined NHC-Pd(II)-Im complex 1 was found to be an effective catalyst for the Suzuki-Miyaura coupling of aryl sulfonates including tosylates and phenylsulfonates with arylboronic acids, giving the desired coupling products in good to high yields. Acceptable yields can also be achieved even by using the less reactive mesylates as the substrates. It is worthy of noting here that this is the first example of NHC-Pd(II) complex-catalyzed Suzuki-Miyaura coupling of aryl sulfonates with arylboronic acids, enriching an inexpensive, convenient, and alternative method for the synthesis of biaryl compounds.     

Iridium-catalyzed C-H activation/borylation/oxidation for the preparation of bis-protected phloroglucinol derivatives

The preparation of bis-protected phloroglucinol derivatives from a range of protected resorcinol substrates is presented. Functionalization was achieved via a two-step, one-pot iridium-catalyzed C-H activation/borylation/oxidation protocol. Our system gave high conversions to the arylboronic esters and good yields of the desired phenols following subsequent oxidation. A range of common protecting group categories was studied including alkyl, silyl, ether and ester.     

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.     

Highly efficient nitration of phenolic compounds by zirconyl nitrate

Zirconyl nitrate was found to be an excellent reagent in the nitration of phenol and substituted phenols to give nitrated phenols. This procedure works efficiently on most of the examples at room temperature yielding nitro derivatives in fair to good yields with high regioselectivity.     

Convenient synthesis of α,β-unsaturated phosphonates via a Mizoroki-Heck reaction of arylboronic acids with diethyl vinylphosphonate

Palladium acetate catalyzed Mizoroki-Heck reactions of arylboronic acids with diethyl vinylphosphonates afford α,β-unsaturated phosphonates in good yields.     

Convenient synthesis of α,β-unsaturated sulfones via a Mizoroki-Heck reaction of arylboronic acids with phenyl vinyl sulfones

Palladium acetate catalyzed Mizoroki-Heck reaction of arylboronic acids with phenyl vinyl sulfones afford α,β-unsaturated sulfones in good yields.     

Asymmetric nitroallylation of arylboronic acids with nitroallyl acetates catalyzed by chiral rhodium complexes and its application in a concise total synthesis of optically pure (+)-gamma-lycorane

[reaction: see text]A new rhodium-catalyzed highly enantioselective nitroallylation of 2-nitrocyclohex-2-enol esters with arylboronic acids is described. A rhodium complex of [RhOH(COD)]2 and optically pure BINAP is the optimal catalyst that provides good yields and high enantioselectivities ranging from 90 to 99% ee for various arylboronic acids at 50 degrees C. A concise total synthesis of optically pure (+)-gamma-lycorane in overall 38% yield was achieved on the basis of this new method.     

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.