20532-03-0Relevant articles and documents
Pd-catalyzed oxidative homocoupling of arylboronic acids in WEPA: A sustainable access to symmetrical biaryls under added base and ligand-free ambient conditions
Appa, Rama Moorthy,Lakshmidevi, Jangam,Naidu, Bandameeda Ramesh,Venkateswarlu, Katta
, (2021/01/11)
Symmetrical and unsymmetrical biaryls comprises a diverse class of biologically eloquent organic compounds. We herein report, a quick and eco-friendly protocol for the synthesis of biaryls by an oxidative (aerobic) homocoupling of arylboronic acids (ABAs) using Pd(OAc)2 in water extract of pomogranate ash (WEPA) as an efficient agro-waste(bio)-derived aqueous (basic) media. The reactions were executed at ambient aerobic conditions in the absence of external base and ligand to result symmetrical biaryls in excellent yields. The use of renewable media with an effective exploitation of waste, short reaction times, excellent yields of products, easy separation of the products, unnecessating the external base, oxidant, ligand or volatile organic solvents and ambient reaction conditions are the vital insights of the present protocol.
Fine Tuning of Chiral Bis(N-heterocyclic carbene) Palladium Catalysts for Asymmetric Suzuki-Miyaura Cross-Coupling Reactions: Exploring the Ligand Modification
Zhang, Dao,Yu, Jueqin
, p. 1269 - 1280 (2020/05/05)
Novel chiral N,N′-bisaryl bis(NHC) ligand precursors H2[(S)-2]Cl2 on a spiro scaffold and H2[(S)-3b-g]Cl2 with a binaphthyl linkage were rationally designed and their cyclometalated cis-chelated NHC palladium complexes (S)-5, (S)-6, and (S)-7b-g have been synthesized and fully characterized. Complexes 6 and 7b were further confirmed by X-ray single-crystal analysis. Both complexes adopted a slightly distorted square planar geometry around the Pd(II) center. The structure of 6 consists of a rare dimeric arrangement incorporating two palladium(II) centers bonded through a short metal-metal bond (2.853(2) ?), indicating a PdII-PdII intramolecular interaction (?). These N,N′-bisaryl-bis(NHC)-Pd complexes together with N,N′-bisalkyl analogues {[(S)-1a-d]PdX2} (X = I, (S)-4a; X = Br, (S)-4b-d) have been used in the asymmetric aryl-aryl cross-coupling reactions of arylboronic acids and aryl halides. The enantioselectivity of the biaryl products was greatly improved within 24 h (up to 74% ee) when complexes 7a-g were used as catalysts. The results show that for these types of bis(NHC) palladium catalysts the structural characters of the chiral scaffolds play a decisive role in the enantioselectivities of cross-coupling reactions.
A Copper-Based Metal-Organic Framework Acts as a Bifunctional Catalyst for the Homocoupling of Arylboronic Acids and Epoxidation of Olefins
Parshamoni, Srinivasulu,Telangae, Jyothi,Sanda, Suresh,Konar, Sanjit
, p. 540 - 547 (2016/03/12)
A copper(I)-based metal-organic framework ({[Cu2Br2(pypz)]na.nH2O} (Cu-Br-MOF) [pypz=bis[3,5-dimethyl-4-(4'-pyridyl)pyrazol-1-yl] methane] has been synthesized by using an elongated and flexible bridging ligand. The structure analysis reveals that each pypz ligand acts as a tritopic ligand connected to two Cu2Br2 dimeric units, forming a one-dimensional zig-zag chain, and these chains further connected by a Cu2Br2 unit, give a two-dimensional framework on the bc-plane. In the Cu2Br2 dimeric unit, the copper ions are four coordinated, thereby possessing a tetrahedral geometry; this proves to be an excellent heterogeneous catalyst for the aerobic homocoupling of arylboronic acids under mild reaction conditions. This method requires only 3 mol % of catalyst and it does not require any base or oxidant-compared to other conventional (Cu, Pd, Fe, and Au) catalysts-for the transformation of arylboronic acids in very good yields (98 %). The shape and size selectivity of the catalyst in the homocoupling was investigated. The use of the catalyst was further extended to the epoxidation of olefins. Moreover, the catalyst can be easily separated by simple filtration and reused efficiently up to 5 cycles without major loss of reactivity.
Palladacycles promote the base-free homocoupling of arylboronic acids in air at room temperature
Kapdi, Anant R.,Dhangar, Gopal,Serrano, Jose Luis,De Haro, Jose A.,Lozano, Pedro,Fairlamb, Ian J. S.
, p. 55305 - 55312 (2015/02/18)
Homocoupling of arylboronic acids can be successfully achieved in commercial grade THF using [Pd(Phbz)(X)(PPh3)] palladacycles as catalysts (Phbz = N-phenylbenzaldimine; X = imidate or acetate). Symmetric biaryls were obtained in good yields working under mild conditions in an air atmosphere at room temperature. The reaction occurs without the addition of an exogenous base. The reaction conditions were optimized to provide the homocoupled products in excellent yield. Evidence for the transmetallation step being important for precatalyst activation has been gathered. The influence of electronic properties of the arylboronic acids on the outcome of the homocoupling reaction has been assessed through competition experiments. This journal is
CN-Dimeric ortho-palladated complex catalyzed cyanation of aryl halides under microwave irradiation
Hajipour, Abdol Reza,Rafiee, Fatemeh
, p. 1391 - 1395 (2014/11/07)
The catalytic activity of dimeric [Pd{C6H2(CH 2CH2NH2)-(OMe)2,2,3}(m-Br)] 2 complex was investigated in the synthesis of benzonitriles under microwave irradiation conditions. The substituted benzonitriles were produced from various aryl halides in excellent yields and short reaction times using a catalytic amount of this complex as efficient, stable and air- and moisture-tolerant catalyst, and K4[Fe(CN)6] as a green cyanide source in DMF at 130 °C.
Amine-bridged bis(phenol) ligands for efficient Pd-catalyzed aqueous C-C coupling reactions
Zhou, Zhonggao,Liu, Minyan,Wu, Xiaoli,Yu, Hongwei,Xu, Guohai,Xie, Yongrong
, p. 562 - 569 (2013/10/21)
The influence of ring size (5 or 6), chain length (1, 2 or 3) and bulkiness of N-aryl substituents in amine-bridged bis(phenol) ligands (1, 2, 3) on palladium-catalyzed aqueous C-C coupling reactions were revealed. The homocoupling of arylboronic acid can be completed in neat water with the aid of a catalytic amount of p-toluenesulfonyl chloride (TsCl) in a very short time under anaerobic or aerobic conditions. Interestingly, the same catalytic system was efficient for Suzuki-Miyaura reaction in aqueous acetone under aerobic conditions in the absence of TsCl. The crystal structures of ligand 1 and three unsymmetrical fluorine-substituted biaryl derivatives were also reported. Copyright
Microwave-enhanced synthesis of aryl nitriles using dimeric orthopalladated complex of tribenzylamine and K4[Fe(CN)6]
Hajipour, Abdol Reza,Rafiee, Fatemeh,Ruoho, Arnold E.
experimental part, p. 526 - 529 (2012/02/01)
The activity of palladacycle [Pd{C6H4(CH 2N(CH2Ph)2)} (μ-Br)]2 complex was investigated in the synthesis of benzonitriles under both conventional and microwave irradiation conditions and their results were compared together. This complex is an efficient, stable, and non-sensitive to air and moisture catalyst for the cyanation reaction. The substituted benzonitriles were produced of various aryl halides in excellent yields and short reaction times using a catalytic amount of [Pd{C6H4(CH2N(CH 2Ph)2)} (μ-Br)]2 complex and K 4[Fe(CN)6] in DMF at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave higher yields in shorter reaction times.
Homocoupling of arylboronic acids catalyzed by CuCl in air at room temperature
Cheng, Guanjun,Luo, Meiming
experimental part, p. 2519 - 2523 (2011/06/10)
Homocoupling of arylboronic acids has been successfully carried out by using the inexpensive simple copper salt CuCl as the catalyst in methanol to obtain symmetric biaryls in good to excellent yields. The reaction proceeds with a CuCl loading of 2 mol-% under extremely mild conditions: in air, at room temperature, without the need of any additives such as base, oxidant, or ligand. A simple and efficient CuCl-catalyzed homocoupling of arylboronic acids for the synthesis of symmetrical biaryls is described. The homocoupling reaction takes place with a catalyst loading of at 2 mol-% in economical and easily handled methanol and under extremely mild conditions: in air, at room temperature, without any additives such as base, oxidant, or ligand. Copyright
The Reaction of Iodine Monochloride with Polycyclic Aromatic Compounds: Polar and Electron Transfer Pathways
Turner, Dean E.,O'Malley, Robert F.,Sardella, Dennis J.,Barinelli, Lucio S.,Kaul, Pushkar
, p. 7335 - 7340 (2007/10/02)
Several polycyclic aromatic hydrocarbons were treated with iodine monochloride.Although iodination is the predominant reaction of benzenoid arenes, chlorination is the sole reaction with anthracene, phenanthrene and naphthalene compounds (except for 5), whose oxidation half-wave potentials are less than 1.58 V vs Ag/Ag(+) (0.1 M).Arenes with higher potentials are unreactive.Naphthalene (9) and its derivatives with mild electron-withdrawing substituents are chlorinated; the exception (5) yields the 1-iodo product (21).The reaction is first order in substrate and second order in ICl.An electron transfer pathway involving radical cation intermediates is assumed.Ion-pair collapse of the radical cation-ICl intermediates is proposed for the chlorinations and radical-pair collapse for the iodination.
