Copper salt catalyzed addition of arylboronic acids to azodicarboxylates

The addition of arylboronic acids 1 to azodicarboxylates 2 in the presence of a catalytic amount of a copper salt under mild reaction conditions gives aryl-substituted hydrazines 3 in high yields. The reaction is tolerant of a wide variety of functional groups.     

Suzuki-Miyaura cross-coupling of α-phosphoryloxy enol ethers with arylboronic acids

The Suzuki-Miyaura cross-coupling reaction of cyclic ketene acetal phosphates with arylboronic acids was found to be a convenient and highly efficient method for the construction of aryl vinyl ethers. A wide variety of differentially substituted electron-poor and electron-rich arylboronic acids smoothly underwent the coupling process to provide the desired dihydropyrans in moderate to excellent yields.     

Palladium(II) catalyst systems for the addition of boronic acids to bicyclic alkenes: new scope and reactivity

[reaction: see text] The palladium-catalyzed ring-opening addition of arylboronic acids to heterobicyclic alkenes is reported. Excellent yields are obtained for the addition of a wide variety of arylboronic acids to aza- and oxabicyclic alkenes. This methodology is especially useful in the synthesis of 1-amino-2-aryldihydronaphthalene scaffolds, for which rhodium catalysts are currently unreactive or give complex mixtures. Asymmetric versions of these reactions are under development, and preliminary results are reported.     

Suzuki-type cross-coupling reaction of pentavalent triarylantimony diacetates with arylboronic acids without a base

Novel base-free Suzuki-type cross-coupling reaction by the use of triarylantimony diacetates and arylboronic acids in the presence of Pd(PPh₃)₄ catalyst led to the formation of biaryl derivatives in moderate to excellent yields. The reaction is applicable to a variety of arylboronic acids bearing base-sensitive functional groups.     

Direct C-H bond arylation of 2-hydroxybenzaldehydes with arylboronic acids via ligand-free palladium catalysis

A mild and efficient ligand-free palladium-catalyzed direct C-H bond arylation reaction was developed to afford 2-hydroxybenzophenones in good to excellent yields from easily available 2-hydroxybenzaldehydes and arylboronic acids. The given reaction provided one of the easiest pathways for accessing 2-hydroxybenzophenones, and a variety of functional groups could be tolerated in this process.     

Cross-coupling of organoboronic acids and sulfinate salts using catalytic copper(II) acetate and 1,10-phenanthroline: synthesis of aryl and alkenylsulfones

A mild method for the preparation of aryl and alkenylsulfones from the cross-coupling reaction of organoboronic acids and sodium sulfinate salts is described. Optimized conditions utilize a catalytic amount of copper(II) acetate monohydrate with 1,10-phenanthroline as ligand in the presence of 4 Å molecular sieves. A co-solvent mixture of dichloromethane/DMSO was used, with reactions occurring at 40 °C under an atmosphere of oxygen. Reaction at room temperature also yields sulfone product, but in lower yields. The method tolerates a variety of substituents on the organoboronic acid, including amide, aldehyde, halide and nitro functionalities, as well as ortho-substituents. In general, the reaction is found to be less efficient using arylboronic acids bearing electron-withdrawing substituents, or using aryltrifluoroborate salts.     

A ruthenium-catalyzed reaction of aromatic ketones with arylboronates: a new method for the arylation of aromatic compounds via C-H bond cleavage

The ruthenium-catalyzed reaction of aromatic ketones with arylboronic acid esters (arylboronates) gave the ortho arylation product. For this coupling reaction, a RuH2(CO)(PPh3)3 complex exhibited the highest catalytic activity among the complexes screened. Several aromatic ketones, for example, acetophenones, acetonaphthone, alpha-tetralone, and benzosuberone, can be used in this coupling reaction. A variety of arylboronates containing electron-donating (OMe and NMe2) and -withdrawing (F and CF3) groups were found to react with aromatic ketones to give the corresponding aylation products. The corresponding arylboronic acids could be used in this coupling reaction, but the yields were slightly lower, as compared to those of the reaction using the corresponding arylboronates.     

Copper-catalyzed halogenation of arylboronic acids

In this Letter, a copper-catalyzed halogenation of arylboronic acids was described. This reaction tolerates a variety of functional groups, providing aromatic halides with good yields. It represents a facile and mild procedure to aryl halides.     

Palladium-catalyzed domino protodecarboxylation/oxidative Heck reaction: regioselective arylation of coumarin-3-carboxylic acids

A protocol for straightforward and step-economical synthesis of neoflavones from coumarin-3-carboxylic acids is developed. This approach enables controlled protodecarboxylation/regioselective C–H arylation of coumain-3-carboxylic acids in one-pot using a monometallic catalytic system. A wide variety of electron-donating and -withdrawing substituents on both coumarins and arylboronic acid are tolerated under the reaction conditions and 4-aryl coumarins are constructed in high yields.     

Base-free Pd-MOF catalyzed the Suzuki-Miyaura cross-coupling reaction of arenediazonium tetrafluoroborate salts with arylboronic acids

A convenient and environmental benign synthesis of biaryls has been demonstrated by a straightforward reaction catalyzed by the palladium-containing metal-organic framework (Pd-MOF) [Pd (2-pymo)₂]_n (2-pymo = 2-pyrimidinolate). A series of functionalized biaryl derivatives have been synthesized in good to excellent yields by the Suzuki-miyaura cross-couplings of sustainable arenediazonium salts with a variety of arylboronic acids and the reactions were catalyzed by the Pd-MOF using methanol as a benign solvent. Those base- and additive-free catalytic reactions proceeded smoothly under non-anhydrous and non-degassed condition. Such transformation avoided high reaction temperature, tolerated many functional groups and presented a wide substrate scope. The catalyst could be recovered by filtration and reused for four successive cycles before collapse of the MOF structure.     

Synthetic approach to flavanones and flavones via ligand-free palladium(ii)-catalyzed conjugate addition of arylboronic acids to chromones

The remarkable catalytic effects of Fe(OTf)(3) in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO(2) to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.     

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.     

Palladium-catalyzed synthesis of arylacetamides from arylboronic acids

Aryl amides were synthesized by the palladium catalyzed cross-coupling reaction of α-bromoacetamides with arylboronic acids in good yields. Both electron-donating and electron-withdrawing substituents on the aromatic ring are found to be compatible. The addition of Cu₂O and PPh₃ was found to be essential for good reaction yields.     

Synthesis of Aryl Ketones by Cross-Coupling Reaction of Arylboronic Acids with Carboxylic Anhydrides in Aqueous Phase

A highly efficient aqueous system of PdCl₂-catalyzed cross-coupling reaction of arylboronic acid with carboxylic anhydride (Suzuki-type reaction) without the use of phosphine ligands was developed. The reactions went smoothly in acetone/H₂O phase to give good yields of aryl ketones in short reaction times (1–3 h) at room temperature in air and were unaffected by the presence of electron-releasing and electron-withdrawing substituents in both the arylboronic acids and carboxylic anhydrides.     

Synthesis of tetrasubstituted olefins by Pd-catalyzed addition of arylboronic acids to internal alkynes

[Reaction: see text] Tetrasubstituted olefins are readily prepared by the Pd-catalyzed cis addition of two aryl groups from an arylboronic acid to opposite ends of the triple bond of internal alkynes. The synthesis proceeds under very mild reaction conditions and tolerates a wide variety of functional groups, including alcohol, aldehyde, ester, TMS, and acetal groups.     

Nickel and Copper Catalyzed ipso-Phosphonodifluoromethylation of Arylboronic Acids with BrCF2P(O)(OEt)2 for the Synthesis of Phosphonodifluoromethylarenes

A convenient method for the direct ipso-phosphonodifluoromethylation of arylboronic acids via nickel-copper co-catalysis is disclosed. This work, which utilizes inexpensive first row transition metals, represents a facile alternative to the traditional palladium catalyzed approach. The method utilizes inexpensive commodity chemicals and substrates while tolerating a variety of biologically relevant functional groups. Structurally diverse phosphonodifluoromethylarenes are furnished in good yields under short reaction times. Control experiments to probe possible reaction pathways are also included.     

Suzuki reaction of vinyl triflates from six- and seven-membered N-alkoxycarbonyl lactams with boronic acids and esters

The Pd(0)-catalyzed reaction of vinyl triflates from N-alkoxycarbonyl lactams with different boron compounds has been studied. The coupling reaction of alkenylboronates and arylboronic acids with six- and seven-membered lactam-derived N-alkoxycarbonyl vinyl triflates was feasible under very mild conditions in THF-water employing (Ph3P)2PdCl2 as a catalyst and Na2CO3 as a base, which provided in high yields the corresponding 6- or 7-substituted N-alkoxycarbonyl-3,4-dihydro-2H-pyridines and N-alkoxycarbonyl-2,3,4,5-tetrahydroazepines. Allylboronates reacted slower but, with vinyl triflates from delta-valerolactam, still gave acceptable yields of the coupling product. Alkylboronic acids required different reaction conditions, in particular the presence of Ag2O together with a base in anhydrous toluene and (dppf)PdCl2 as a catalyst, affording the corresponding 6-alkyl-N-alkoxycarbonyl-3,4-dihydro-2H-pyridines in high yields.     

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.     

SiO2-NHC-CuI–Catalyzed N-Arylation of Imidazoles with Arylboronic Acids Under Base-Free Reaction Conditions

N-Arylation of imidazoles with arylboronic acids was efficiently carried out in the presence of a catalytic amount of SiO₂-NHC-Cu^I in methanol at room temperature under base-free reaction conditions. The reactions of a variety of arylboronic acids with imidazoles generated the corresponding products N-arylimidazoles in good to excellent yields. In addition, SiO₂-NHC-Cu^I could be recovered and recycled for six consecutive trials without significant loss of its reactivity.     

Palladium-catalyzed oxidative carbocyclization/arylation of enallenes

A stereoselective palladium-catalyzed oxidative carbocyclization/arylation of enallenes is described. The reaction shows wide tolerance toward highly functionalized arylboronic acids and results in a cis addition of two carbon moieties to an olefin in good to excellent yields.