Chiral oxazoline route to enantiomerically pure biphenyls: magnesio and copper mediated asymmetric hetero- and homo-coupling reactions

A series of chiral biphenyls were prepared via asymmetric reactions involving chiral oxazolines. One series of chiral biphenyls was reached by the magnesium mediated coupling of aryl bromides (via their Grignard reagents) with o-methoxyaryl oxazolines. In this case only the o-methoxy group was replaced by the ArMgBr. The initially formed biphenyl adducts were obtained in de's as high as 92:8. These adducts could be manipulated to various other chiral biphenyls. Another series of chiral biphenyls were obtained via an asymmetric Ullmann reaction, which was shown to be thermodynamically controlled. The de's of this copper mediated process were also in the range of 90% and could be utilized to reach various derivatives. Racemization, thermal stability, and atropisomerization characteristics were also studied.     

Pd/MCM-41催化碘苯Ullmann偶合制备联苯

联苯是一种重要的有机合成中间体,广泛应用于超分子、高性能染料和药物活性剂以及有机导体和半导体的生产中。目前,联苯的合成方法主要有Ullmann偶合反应、Stille反应、Heek反应、Suzuk反应和Sonogashira反应等。其中,Ullmann偶合反应由于成本低且简单易操作而倍受青睐。最早采用Cu-基催化剂,但需要在高温下进行,反应条件相当苛刻。采用Pd-基均相催化剂可大大降低反应温度,     

以空气为氧化剂Pd(OAc)2/HPMo/AcOH催化苯液相氧化偶联合成联苯

 研究了以Pd(OAc)2为催化剂,H3PMo12O40为助催化剂,空气为氧化剂,在乙酸溶液中于373 K条件下,在500 ml高压釜中由苯液相氧化偶联合成联苯. 结果表明,反应产物中联苯的选择性高达92%以上,并且只有少量的三联苯副产物生成. 分别考察了H3PMo12O40的加入量和O2分压对以空气或纯O2为氧化剂时Pd/HPMo/AcOH催化苯液相氧化偶联合成联苯反应催化性能的影响. 根据反应液颜色的变化以及文献结果推测,在反应过程中通过钯和钼物种的氧化和还原作用使苯氧化生成联苯.     

The synthesis and resolution of 2,2'-, 4,4'-, and 6,6'-substituted chiral biphenyl derivatives for application in the preparation of chiral materials

Various routes were examined for the synthesis of chiral biphenyl species that are substituted at the 2,2', 4,4' and 6,6' positions. Because the biaryl bond is tetrasubstituted, many coupling reactions were not suitable. The most reliable coupling reaction proved to be the Ullmann, which gave the desired product in 82% yield. The products were required as the starting point for the preparation of chiral materials using these as the monomer. For this reason, a route was required that produced large quantities of both enantiomers. The two enantiomers were resolved at the penultimate step by the use of chiral HPLC. A complicating feature proved to be the necessity to have a reactive group at the 4,4' positions, which would permit polymerization though this point. Ultimately, we employed an Ullmann coupling on a dibrominated arene, which occurred selectively at the more hindered bromine by virtue of the directing effect of an ortho ester substituent.     

Reductiveversus coupling pathways in the reactions of nickel and copper vapours with the mono-halobenzenes

Summary The reactions of nickel and copper vapours with mono-halobenzenes to form benzene and biphenyl are reported. Benzene formation apparently proceeds through the intermediacy of the phenyl radical, which is produced when metal clusters abstract halogen from the halobenzene. Biphenyl formation proceedsvia an oxidative insertion/disproportionation/reductive elimination sequence, and requires that metal atoms, rather than metal clusters, initiate the reaction sequence. The concentration of the metal in the matrix determines the pathway of the reaction. Cluster formation and benzene production are favouted by high metal concentrations, while low metal concentrations in the matrix favour biphenyl production. Copper vapours are anomalously less reactive than nickel vapours, even though copper reagents are used in the Ullmann reaction to produce biaryls through the coupling of haloarenes. This result appears to be due to the preferential formation of atoms or very small clusters over large clusters or crystallites under the conditions of the metal vapour synthesis technique.     

联苯类化合物的合成

联苯类化合物是一类极为重要的有机合成中间体,在有机合成中往往通过有机金属偶联反应构建此类化合物.以反应底物分类综述了近年来通过偶联反应合成此类化合物的方法,详细介绍了以卤代芳烃与芳基金属化合物为底物的反应.     

Microwave-assisted synthesis of macrocycles via intramolecular and/or bimolecular Ullmann coupling

Microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling is described. Using the optimized conditions, a panel of macrocycles, with different substitution patterns, ring sizes, and linkers, has been successfully synthesized using microwave irradiation. To the best of our knowledge, this work represents the first examples of the microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling.     

Ullmann‐Ma Reaction: Development,Scope and Applications in Organic Synthesis†

Copper‐catalyzed cross‐couplings of aryl halides and nucleophiles, traditionally called Ullmann‐type coupling reactions, were initially reported by Ullmann et al. from 1901—1929. A seminal report in 1998 by Ma et al. from Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences revealed an accelerating effect caused by amino acids, which brought Ullmann‐type coupling reactions into a ligand‐accelerating era. From 1999 to the first 10 years of 2000s, the first‐generation ligands were developed by many researchers and promoted Ullmann‐type coupling reactions of aryl iodides and bromides under relatively mild conditions. Amino acid ligands, developed by Ma and coworkers, are one class of the most important first‐generation ligands. In the second 10 years of 2000s, Ma et al. led the discovery of second‐generation ligands for copper‐catalyzed cross‐coupling reactions. Two great breakthroughs have been realized by using second‐generation oxalic diamide and related amide ligands, with aryl chlorides as general coupling partner and with low catalyst loadings. Now copper‐catalyzed cross coupling reactions of aryl halides and nucleophiles with amino acids or oxalic diamides and related amides as ligands are recognized as Ullmann‐Ma reactions and have found extensive applications in organic synthesis.     

Synthesis and Characteristics of Hole-transporting Materials Based on Biphenyl Diamine Derivatives with Carbazole Groups

IntroductionThe development of organic light-emitting diodes(OLEDs)has been the subject of intensive academicand industrial research that is directed toward the fabri-cation of large-area,monocolor and full color flat-paneldisplays[1].Ever since Tanget al…     

Synthesis of Methylene‐Bridged Biscarbazole Alkaloids by using an Ullmann‐type Coupling: First Total Synthesis of Murrastifoline‐C and Murrafoline‐E

We describe the total synthesis of methylene‐bridged biscarbazole alkaloids by using a late‐stage Ullmann‐type coupling of fully functionalised carbazole subunits. The carbazole derivatives were synthesised via a sequence of palladium(0)‐ and palladium(II)‐catalysed coupling reactions. Our approach has provided bismurrayafoline‐A, bismurrayafolinol, chrestifolines B–D, and the first total synthesis of murrastifoline‐C and murrafoline‐E.     

Poly(dimethyl biphenylene)

Two methods were investigated for the preparation of poly(dimethyl biphenylene) in a search for polymers combining good solubility with sufficiently high chain extension to produce a lyotropic nematic phase. The Ullmann reaction was used to condense 4,4′-diiodo-3,3′-dimethyl biphenyl and the corresponding 2,2′-dimethyl derivative with copper, and 4,4′-dibromo-2,2′-dimethyl biphenyl was polymerized using the coupling reagent, bis(1,5-cyclooctadiene)nickel(0), developed by Semmelhack. The Ullmann polymers were completely soluble in CHCl₃ but only partially soluble in toluene, whereas earlier work had indicated similar polymers of higher molecular weight to be completely soluble in toluene. All the polymers produced were of low molecular weight and no evidence of the nematic phase was found by polarized light microscopy for CHCl₃ solutions over the concentration range 6.8–25% by weight.     

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons and its application for the synthesis of diaryl ethers

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons support for the synthesis of diaryl ethers via Ullmann type coupling is reported. The catalyst showed excellent performance for C–O cross coupling reactions under ligand free condition. The catalyst was characterized by various techniques such as SEM, TEM, XRD, EDX, BET, TGA, and UV spectrophotometry. It was recycled several times without significant loss in its catalytic activity.     

A General, Highly Efficient Ullmann C-O Coupling Reaction under Microwave Irradiation and the Effects of Water

A general, rapid and highly efficient method for the synthesis of diaryl ethers under the assistance of microwave irradiation was described. A series of diaryl ethers were prepared by direct coupling of phenols and aryl halides in good to excellent yields in anhydrous DMF or NMP at 150 ℃ within 20 rain. The presence of water was found to have a significant impact on the Ullmann C-O coupling reaction between aryl halides and phenols under microwave irradiation.     

Synthesis-in-place of highly-conjugated oligothiophene micropatterns via photo-activated Ullmann coupling on copper surface

In contrast to the traditional thermally-activated Ullmann coupling, a photo-activated Ullmann coupling for facile synthesis of oligothiophene and polythiophene films and micropatterns is reported.     

New regiospecific isothiazole C-C coupling chemistry

Regioselective palladium catalysed coupling reactions are achieved in good to high yields, starting from either 3,5-dichloro- or 3,5-dibromoisothiazole-4-carbonitriles 1 and 2, providing 3-halo-5-(hetero/aryl, alkenyl and alkynyl)isothiazoles 3, 4, 6-9 from Stille couplings, 3-halo-5-(hetero/arylethynyl)isothiazoles 14-19 from Sonogashira and 5,5'-bi(3-chloroisothiazole-4-carbonitrile) (13) from an Ullmann type coupling. 3,5-Dibromoisothiazole-4-carbonitrile 2 is more reactive than the dichloroisothiazole-4-carbonitrile 1 and effective enough for Stille, Negishi and Sonogashira couplings. 5,5-Bi(3-chloroisothiazole-4-carbonitrile) (13) is prepared by a palladium catalysed Ullmann coupling from 3-chloro-5-iodoisothiazole-4-carbonitrile (11). A variety of 3-substituted isothiazoles (3-substituents = Cl, Br, OMs, OTs and OTf) are less reactive and fail to give successful Suzuki couplings at the isothiazole C-3 position. The 3-iodo-5-phenyl-isothiazole-4-carbonitrile (28), prepared via Sandmeyer iodination, participates successfully in Suzuki, Ullmann type, Stille, Negishi and Sonogashira coupling reactions. All products are fully characterized.     

An efficient regioselective copper catalyzed multi-component synthesis of 1,3-disubstituted pyrazoles

An efficient synthesis of unsymmetrically substituted 1,3-pyrazole derivatives has been developed via three-component coupling reaction involving 3-(dimethylamino)-1-phenylprop-2-en-1-one, hydrazine, and aryl halides in one pot process exhibiting high regioselectivity. The pyrazole synthesis proceeds via a sequential series of reactions such as Michael addition, heterocyclization, dehydration, and Ullmann cross-coupling.     

Synthesis of biphenyl anilines using iodo phenylformamides via a one-pot Suzuki coupling reaction

We have developed a novel and economical synthesis of biphenyl anilines via a one-pot Suzuki coupling reaction with iodo phenylformamides. This literature is an unprecedented approach to biphenyl anilines replacing costly aminophenylboronic acids with economical iodo anilines for the preparation of biphenyl anilines. It also provides a viable synthesis toward substituted biphenyl anilines where the required aminophenylboronic acids are not readily available.     

Periodic Mesoporous Organosilicas: A Type of Hybrid Support for Water‐Mediated Reactions

Hybrid mesoporous periodic organosilicas (Ph‐PMOs) with phenylene moieties embedded inside the silica matrix were used as a heterogeneous catalyst for the Ullmann coupling reaction in water. XRD, N₂ sorption, TEM, and solid‐state NMR spectroscopy reveal that mesoporous Ph‐PMO supports and Pd/Ph‐PMO catalysts have highly ordered 2D hexagonal mesostructures and covalently bonded organic–inorganic (all Si atoms bonded with carbon) hybrid frameworks. In the Ullmann coupling reaction of iodobenzene in water, the yield of biphenyl was 94 %, 34 %, 74 % and for palladium‐supported Ph‐PMO, pure silica (MCM‐41), and phenyl‐group‐modified Ph‐MCM‐41 catalysts, respectively. The selectivity toward biphenyl reached 91 % for the coupling of boromobenzene on the Pd/Ph‐PMO catalyst. This value is much higher than that for Pd/Ph‐MCM‐41 (19 %) and Pd/MCM‐41 (0 %), although the conversion of bromobenzene for these two catalysts is similar to that for Pd/Ph‐PMO. The large difference in selectivity can be attributed to surface hydrophobicity, which was evaluated by the adsorption isotherms of water and toluene. Ph‐PMO has the most hydrophobic surface, and in turn selectively adsorbs the reactant haloaryls from aqueous solution. Water transfer inside the mesochannels is thus restricted, and the coupling reaction of bromobenzene is improved.     

Cu-nanoparticle catalyzed O-arylation of phenols with aryl halides via Ullmann coupling

Recyclable Cu-nanoparticles provide an efficient, economic, and novel method for the synthesis of diaryl ethers via Ullmann type coupling. This method provides a wide range of substrate applicability and avoids the use of a heavy metal co-catalyst and gives diaryl ethers in satisfactory yields.     

Nano ceria catalyzed Ullmann type coupling reactions

Ullmann type intermolecular coupling of aryl halide with hetero-aromatic compounds, such as phenols, amines, and thiophenols are key reactions for the formation of carbon-heteroatom bond in organic synthesis. We report a robust and novel method that provides an efficient and economic route for the synthesis of O, N, and S-arylation via Ullman coupling by using nano cerium oxide (ceria, CeO₂). CeO₂ is a cheaper catalyst compared to related copper based catalysts. This method provides a wide range of substrate applicability in the case of phenols and amines. Less reactive chlorobenzene substituted with strong electron withdrawing groups such as 4-nitrochlorobenzene and 4-cyanochlorobenzene favor the reaction. This protocol avoids the use of ligand and gives arylated product in satisfactory yields.