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Dearomative bis-functionalization of quinoxalines and bis-N-arylation of (benz)imidazoles via Cu(II) mediated addition of boronic acids
Abstract
A Cu(OTf)2 mediated regioselective de-aromatized aryl-hydroxylation across C(sp2)N bond of 2-aryl quinoxalines and bis-N-arylation of (benz)imidazoles is developed using aryl boronic acids. For dearomative aryl-hydroxylation, the C-center should be electrophilic...
... There has been extensive focus on the CÀ H functionalization of aromatic compounds in organic synthesis because of their ability to facilitate the construction of complex molecules. [6][7][8] Selectively constructed new CÀ C bonds using aromatic compounds are stable and electron-rich, making them suitable for further functionalization. By introducing new CÀ C bonds at specific positions on an aromatic ring, a wide range of functionalized aromatic derivatives with altered properties can be obtained. ...
... Among these solvents, ACN, dioxane, and THF were incompatible with this transformation. However, toluene, nitromethane, and DCM afforded the desired product 3a in moderate yields (55%, 58%, and 48%, respectively; Table 1, entries [8][9][10][11][12][13]. To maintain the sustainability profile of the current protocol, we examined some greener solvents such as ethyl acetate, methanol, ethanol, tertiary butanol, DMSO, DMF, and 2-methyl THF; among these, only ethyl acetate provided a considerable yield (26%) of the desired product 3a at 100°C and a higher (30%) yield at 120°C (Table 1, entries [14][15][16][17][18][19]. ...
Functionalized naphthols are prominent scaffolds in organic synthesis and materials chemistry. Herein, we demonstrated continuous flow alkylation of α‐ and β‐naphthols by using various primary and secondary benzylic alcohols in the presence of environmentally benign granular β‐zeolite as a reusable catalyst. For a variety of β‐naphthols, the respective alkylated products with good regioselectivity were obtained in high yields under mild reaction conditions. This protocol proceeded via the classical Friedel‐Crafts type alkylation process and generated stable carbocations as intermediates. Applying this protocol, versatile naphthol derivatives have been synthesized using primary and secondary benzylic alcohols (50 and 44 examples in batch and continuous flow process, respectively), with good yields. Key advantages of this process includes rapid and efficient transformation, facilitates gram‐scale synthesis, and generates water as the sole by‐product. The most significant advantage is the continuous reusability of granular β‐zeolite, which further emphasizes the sustainability of the method. The application of alkylated naphthols for quaternary functionalization was demonstrated through peroxidation, azidation, and halogenation reactions under the continuous flow module, which yielded the respective peroxynaphthalen‐2(1H)‐one, azidonaphthalen‐2(1H)‐one and fluoronaphthalen2(1H)‐one derivatives.
Carbon–carbon (C–C) bond formation reactions have contributed significantly to the construction of numerous important molecules that have contributed in various dimensions. Heterogeneous catalysts that are recyclable and can convert a chemical reaction with the same affinity as that of the homogeneous counterpart provide an economically viable path. This account, therefore, focuses on different types of C–C bond formation reactions triggered by transition metal catalysts supported mostly on zeolite-Y and a few metal oxide nanocatalysts. The account comprises our recent works devoted to various C–C bond formation reactions performed by such heterogeneous catalysts including photocatalysts.
1 Introduction
2 Biaryl Synthesis by C–Cl Bond Activation
3 Synthesis of 3,3′-Bis(indolyl)methanes
4 C2 Trimerization of Indoles
5 Cross-Aldol Condensation Reaction
6 Friedel–Crafts Benzylation of Naphthol and Phenol
7 Oxidative C–C Coupling of Naphthols
8 Conclusion
Solvent plays an important role in many chemical reactions. The C−H activation has been one of the most powerful tools in organic synthesis. These reactions are often assisted by solvents which not only provide a medium for the chemical reactions but also facilitate reaching to the product stage. The solvent helps the reaction profile both chemically and energetically to reach the targeted product. Organic transformations via C−H activation from the solvent assistance perspective has been discussed in this review. Various solvents such as tetrahydrofuran (THF), MeCN, dichloromethane (DCM), dimethoxyethane (DME), 1,2‐dichloroethane (1,2‐DCE), dimethylformamide (DMF), dimethylsulfoxide (DMSO), isopropyl nitrile (ⁱPrCN), 1,4‐dioxane, AcOH, trifluoroacetic acid (TFA), Ac2O, PhCF3, chloroform (CHCl3), H2O, N‐methylpyrrolidone (NMP), acetone, methyl tert‐butyl ether (MTBE), toluene, p‐xylene, alcohols, MeOH, 1,1,1‐trifluoroethanol (TFE), 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP), tert‐amyl alcohol and their roles are discussed. The exclusive role of the solvent in various transformations has been deliberated by highlighting the substrate scope, along with the proposed mechanisms. For easy classification, the review has been divided into three parts: (i) solvent‐switched divergent C−H activation; (ii) C−H bond activation with solvent as the coupling reagent, and (iii) C−H activation with solvent caging and solvent‐assisted electron donor acceptor (EDA) complex formation and autocatalysis.
A variety of α‐benzotriazinium ketones were prepared in 38%–89% yields through a copper(II)‐catalyzed Chan‐Lam reaction and [2,3]‐rearrangement in a one pot reaction open to air from N‐hydroxybenzotriazin‐4‐ones and alkenyl boronic acids at room temperature. Experimental results showed that the copper catalyst not only played as cross‐coupling catalyst but also served as Lewis acid catalyst to control the chemoselectivity of [2,3]‐rearrangement. The reaction tolerated various linear and cyclic disubstituted alkenyl boronic acids. Moreover, α‐benzotriazinium ketone could be easily prepared in gram scales. The present method highlights dual roles of copper catalyst and [2,3]‐rearrangement of N,O‐vinyl moiety.
A visible light-driven di-functionalization of maleimide with disulfide and in situ-generated singlet oxygen offers selective 1,2-thiohydroxylation under additive-free conditions. Here the disulfide plays the dual role of photo catalyst and...
A Ru(II) catalyzed regioselective Heck-type C-H olefination of isoxazole with unactivated allyl phenyl sulfone is revealed. The solvent DCM offers dual sp2-sp2 C-H activation via an N-directed strategy, leading to ortho-olefinated isoxazoles with exclusive E-selectivity. On the other hand, in DCE solvent, isoxazole serves as the nitrile synthon and leads to o-olefinated benzonitrile. At a higher temperature (110 °C) in DCE, after the ortho-olefination Ru(II) mediated cleavage of isoxazoles delivered the nitrile functionality.
A Mn(I)-catalyzed site-selective nondirected C3-maleimidation of quinoxaline is established. Herein, the electrophilic C3-metalation precedes over the o-directed strategy to access diversely substituted quinoxaline-appended succinimides. The products undergo PIFA-promoted C(sp2)-C(sp3) spirocyclization via π-electrons drifting from aryls and Selectfluor-mediated dehydrogenation of succinimide at room temperature.
An efficient and practical N-arylation of hydantoins with substituted aryl/heteroaryl boronic acids has been established, assisted by CuF2/MeOH under the base and ligand-free conditions at room temperature and open air. The protocol is general, and various N-arylated hydantoins have been prepared in excellent yields with exclusive regioselectivity. The CuF2/MeOH combination was explored further to furnish selective N3-arylation of 5-fluorouracil nucleosides. The efficiency of the protocol was also demonstrated with the gram-scale synthesis of the marketed drug, Nilutamide. A mechanistic study based on density functional theory calculations revealed that both hydantoin and MeOH are crucial for the generation of catalytically active copper species in the reaction process, in addition to their role as a reactant and solvent, respectively. The proposed reaction mechanism indicated that selective N3-arylation of hydantoin is favorable in MeOH, which helps initiate the catalytic cycle by forming a square-planner Cu(II) complex where strong hydrogen-bond interactions are observed. This study is expected to improve the understanding of Cu(II)-catalyzed oxidative N-arylation reactions and for the de novo design and development of Cu-catalyzed coupling reactions.
Despite the widespread applications of 2-(hetero)aryl N-heteroarenes in numerous fields of science and technology, universal access to such compounds is hampered due to the lack of a general method for their synthesis. Herein, by a H2O-mediated H2-evolution cross-coupling strategy, we report an iridium(III)-catalyzed facile method to direct α-arylation of N-heteroarenes with both aryl and heteroaryl boronic acids, proceeding with broad substrate scope and excellent functional compatibility, oxidant and reductant-free conditions, operational simplicity, easy scalability, and no need for prefunctionalization of N-heteroarenes. This method is applicable for structural modification of biomedical molecules, and offers a practical route for direct access to 2-(hetero)aryl N-heteroarenes, a class of potential cyclometalated C^N ligands and N^N bidentate ligands that are difficult to prepare with the existing α-C-H arylation methods, thus filling an important gap in the capabilities of synthetic organic chemistry. 2-(hetero)aryl N-heteroarenes are ubiquitously applied in numerous fields of science and useful for the development of bioactive molecules and drugs, but there is a lack of general methods for their synthesis. Here, the authors report an iridium(III)-catalyzed method for direct α-arylation of N-heteroarenes with aryl and heteroaryl boronic acids, by a H2O-mediated H2-evolution cross-coupling strategy.
Metal‐catalyzed C–N cross‐coupling generally forms C−N bonds by reductive elimination from metal complexes bearing covalent C‐ and N‐ligands. We have identified a Cu‐mediated C–N cross‐coupling that uses a dative N‐ligand in the bond‐forming event, which, in contrast to conventional methods, generates reactive cationic products. Mechanistic studies suggest the process operates via transmetalation of an aryl organoboron to a CuII complex bearing neutral N‐ligands, such as nitriles or N‐heterocycles. Subsequent generation of a putative CuIII complex enables the oxidative C–N coupling to take place, delivering nitrilium intermediates and pyridinium products. The reaction is general for a range of N(sp) and N(sp²) precursors and can be applied to drug synthesis and late‐stage N‐arylation, and the limitations in the methodology are mechanistically evidenced.
Multifaceted application potential of AEEgens in bioimaging, theranostics, chemo/biosensors, mechanochromics, solar cells, and organic photoelectronics opens up a new research paradigm to develop and design more such compounds. Herein, quinoxaline N-directed Ru(II)-catalyzed oxidative annulation of 2-arylquinoxalines with internal alkynes leads to the formation of highly luminescent annulated quaternary ammonium salts in the presence of a Cu(OAc) 2 ·H 2 O oxidant. While the synthesized compounds exhibit emissions in the green-to-yellow region with large Stokes shifts and reasonable quantum yields, their DFT calculations display a 3D twisted conformation bearing a donor-acceptor (D-A) configuration where the two phenyl moieties could serve as the donors and the extended quinoxaline core as the acceptor. Single-crystal analysis of the quaternary salt 3aa depicts the presence of multiple intermolecular noncovalent and weak interactions that are possibly responsible for the luminescence behavior in crystalline and solid states. The advent of aggregation-enhanced emission in quinoxalinium salt 3aa in DMF/water is due to the restriction of intramolecular motion and suppression of intermolecular charge transfer in the aggregated state. AEEgen 3aa unveils reversible mechanochromism on changing from crystalline to the amorphous state upon grinding and returning back to the crystalline state upon DCM fuming, where a few of such compounds are utilized for development of latent fingerprints on adhesive tape. Furthermore, a representative group of synthesized luminescent quinoxalinium salts portrays dose-dependent cell growth inhibition of HeLa cells with concomitant cell arrest in G1 phases. Hence, these AEE luminogens are not only attractive as luminescent "light-up" probes for cell imaging but also important as anticancer agents.
We report an enantioselective Ni-catalyzed cross coupling of arylzinc reagents with pyridinium ions formed in situ from pyridine and a chloroformate. This reaction provides enantioenriched 2-aryl-1,2-dihydropyridine products that can be elaborated to numerous piperidine derivatives with little or no loss in ee. This method is notable for its use of pyridine, a feedstock chemical, to build a versatile, chiral heterocycle in a single synthetic step.
Cu-catalysed arylation reactions devoted to the formation of C-C and C-heteroatom bonds (Ullmann-type couplings) have acquired great importance in the last decade. This review discusses the history and development of coupling reactions between aryl halides and various classes of nucleophiles, focusing mostly on the different mechanisms proposed through the years. Selected mechanistic investigations are treated more in depth than others. For example, evidence in favour or against radical mechanisms is discussed. Cu(i) and Cu(iii) complexes involved in the Ullmann reaction and N/O selectivity in aminoalcohol arylation are discussed. A separate section has been dedicated to the synthesis of heterocyclic rings through intramolecular couplings. Finally, recent developments in green chemistry for these reactions, such as reactions in aqueous media and heterogeneous catalysis, have also been reviewed.
The direct functionalization of heterocyclic compounds has emerged as one of the most important topics in the field of metal-catalyzed C-H bond activation due to the fact that products are an important synthetic motif in organic synthesis, the pharmaceutical industry, and materials science. This critical review covers the recent progresses on the regioselective dehydrogenative direct coupling reaction of heteroarenes, including arylation, olefination, alkynylation, and amination/amidation mainly utilizing transition metal catalysts (113 references).
A direct arylation of a variety of electron-deficient heterocycles with arylboronic acids has been developed. This new reaction proceeds readily at room temperature using inexpensive reagents: catalytic silver(I) nitrate in the presence of persulfate co-oxidant. The scope with respect to heterocycle and boronic acid coupling partner is broad, and sensitive functional groups are tolerated. This method allows for rapid access to a variety of arylated heterocycles that would be more difficult to access with traditional methods.
Herein, we report a Co(III)-catalysed regioselective C8 linear olefination of isoquinoline-1H-2-one with terminal (aromatic and aliphatic) alkynes. This is an exclusive report for the C8 functionalization of isoquinolone using non-noble...
Quinoxaline has become a subject of extensive research due to its emergence as an important chemical moiety, demonstrating a wide range of physicochemical and biological activities. The last few decades have witnessed several publications utilizing quinoxaline scaffolds for the design and development of numerous bioactive molecules, dyes, fluorescent materials, electroluminescent materials and organic sensitizers for solar cell applications and polymeric optoelectronic materials. Therefore, to fulfill the need of the scientific community, tremendous effort has been observed in the development of newer synthetic strategies as well as novel methodologies to decorate the quinoxaline scaffold with proper functional groups. Hence, to provide an updated comprehensive account of the diverse synthetic routes to access quinoxaline as well as approaches for structural diversifications, we have attempted to document the synthetic strategies and their functionalization with possible mechanistic rationalization. This will no doubt be helpful for the readers who are anticipating a comprehensive overview on quinoxaline as well as benefitting researchers for future development.
The radical-involved 1,2-difunctionalization of alkenes has developed into a robust tool for preparation of complex organic molecules. Despite significant advances in this area, the catalytic asymmetric version still remains a challenging task mainly due to the difficulty in the stereocontrol of the highly reactive radical intermediates. Recently, owing to the good single-electron transfer ability and coordination with chiral ligands of copper catalysts, remarkable achievements in radical-involved asymmetric alkene difunctionalization have been made via synergistic combination of copper and chiral ligands. This tutorial review highlights the recent progress in copper-catalysed radical-involved asymmetric 1,2-difunctionalization of alkenes and the mechanistic scenarios governing the stereocontrol, with an emphasis on utilization of chiral ligands.
Transition metal-mediated formation of C-N bonds is an essential synthetic methodology. The discovery of the Chan-Lam amination provided a C-N bond forming process that was mild, convenient, and inexpensive, offering an alternative to complementary methods using other transition metals (TMs). Over the past 20 years, this reaction has seen considerable development in its scope of application, uptake into industry, and understanding of its mechanism. This review provides an account of the development of the Chan-Lam amination, highlighting progress and notable examples of application since 2011. Focus is given to evolution in mechanistic understanding and selected applications of the methodology within medicinal and process chemistry.
C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.
Transition metal (TM)-catalyzed difunctionalization of unactivated olefins with two carbon-based entities is a powerful method to construct complex molecular architectures rapidly from simple and readily available feedstock chemicals. While dicarbofunctionalization of unactivated olefins has a long history typically with the use of either carbon monoxide to intercept C(sp3)-[M] (alkyl-TM) species or substrates lacking in β-hydrogen (β-Hs), development of this class of reaction still remains seriously limited due to complications of β-H elimination arising from the in situ-generated C(sp3)-[M] intermediates. Over the years, different approaches have been harnessed to suppress β-H elimination, which have led to the development of various types of olefin dicarbofunctionalization reactions even in substrates that generate C(sp3)-[M] intermediates bearing β-Hs with a wide range of electrophiles and nucleophiles. In this review, these developments will be discussed both through the lens of historical perspectives as well as the strategies scrutinized over the years to address the issue of β-H elimination. However, this review article by no means is designed to be exhaustive in the field, and is merely presented to provide the readers an overview of the key reaction developments.
Metal catalyzed reactions for the formation of C-O bonds have had a dramatic impact in natural product synthesis over the past few decades. Various metals have been reported to efficiently catalyze cross-coupling reactions for the formation of various C(sp²)-O bonds from aryl/alkenyl halides or synthetic equivalents and phenols, aliphatic alcohols and water. The implementation of such reactions in natural product synthesis enabled the emergence of new bond disconnections, which notably resulted in remarkably efficient and short synthetic pathways. The use of these reactions for the formation of C-O bonds in natural product synthesis is overviewed in this critical review, with an emphasis on copper and palladium catalysts which are the most efficient ones to date.
We report an investigation of the Chan-Lam amination reaction. A combination of spectroscopy, computational modeling, and crystallography has identified the structures of key intermediates and allowed a complete mechanistic description to be presented, including off-cycle inhibitory processes, the source of amine and organoboron reactivity issues, and the origin of competing oxidation/protodeboronation side reactions. Identification of key mechanistic events has allowed the development of a simple solution to these issues: manipulating the Cu(I)->Cu(II) oxidation and exploiting three synergistic roles of boric acid has allowed the development of a general catalytic Chan-Lam amination, overcoming long-standing and unsolved amine and organoboron limitations of this valuable transformation.
Photoredox catalysis has emerged as a strong synthetic tool for radical reactions. In particular, a variety of regioselective difunctionalizations of carbon-carbon multiple bonds through SET photoredox processes (oxidative quenching cycle) have been accomplished by an appropriate choice of an electrophilic radical precursor and a nucleophile. The basic concept, representative results and future prospect are the topics of this article.
We report a concise, versatile, and practical method for PhI(OCOCF3)2 mediated direct ortho C–H monoarylation of 2-phenylpyridine and its derivatives and 1-phenyl-1H-pyrazoles via Ru catalyzed reaction. The significant advantage of this transformation is the creation of highly site selective C–C bond by using arylboronic acids as arylating agent under mild reaction conditions.
A study was conducted to investigate the use of copper (Cu)-catalyzed C-H functionalization reactions for efficient synthesis of heterocycles. Copper-catalyzed C-H functionalization reaction methods provided significant benefits toward the synthesis of a variety of heterocycles. The use of Cu-catalyzed C-H functionalization reactions had gained significant traction, and a range of these methodologies relating to the construction of heterocycles were successfully developed. A series of important structural motifs including N-heterocycles, N,Oheterocycles, O-heterocycles, and N,S-heterocycles were synthesized using a number of Cu-catalyzed C-H functionalization reactions.
A copper-catalyzed oxidative coupling of 2-carbonyl substituted phenols and 1,3-dicarbonyl compounds with a wide range of dibenzyl or dialkyl ethers is described. This protocol provides an efficient preparation of phenol esters and enol esters in good yields with high chemoselectivity. This method represents an alternative protocol for classical esterification reactions.
Imidazolium salts were conveniently prepared by direct aryl quaternization using arylboronic acids. This process features the tolerance of a broad range of functional groups and excellent chemoselectivity, and is especially effective for the synthesis of unsymmetrical imidazolium salts.
Nitrogen containing compounds are of great importance because of their interesting and diverse biological activities. The construction of the C-N bond is of significant importance as it opens avenues for the introduction of nitrogen in organic molecules. Despite significant advancements in this field, the construction of the C-N bond is still a major challenge for organic chemists, due to the involvement of harsh reaction conditions or the use of expensive catalysts in many cases. Thus, it is a challenge to develop alternative, milder and cheaper methodologies for the construction of C-N bonds. Herein, we have selected some prime literature reports that may serve this purpose.
A new aryl/heteroaryl CN bond cross-coupling reaction via the arylboronic acid/cupric acetate arylation of NH containing heteroarenes has been discovered. This new methodology is mild, proceeds at room temperature exposed to air, and works for many heteroarenes and arylboronic acids providing good yields of N-arylated heteroarenes.
Diaryl ethers are readily synthesized in high yield at room temperature through the copper(II)-promoted coupling of arylboronic acids and phenols. The reaction is tolerant of a wide range of substituents on both coupling partners. These reaction conditions permit the racemization-free arylation of phenolic amino acids, methodology that has been applied to an efficient synthesis of thyroxine.
A new method of arylating NH and OH containing compounds at room temperature with phenylboronic acids and cupric acetate in the presence of a tertiary amine promoter is described. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides.
An analysis of the chemical environment of the oxygen atoms in the DNP database compared to the CMC and SCD databases was performed. Some structural clusters were identified which are predominant among the natural products and can be considered as distinctive features of NPs. Fifty-three oxygen-containing structural fragments that are distinctive for the DNP (distinctive set of fragments DSF) in comparison with the SCD have been identified. A new descriptor Mc was introduced for describing the ratio of atoms involved in the DSF to the total number of heavy atoms. A significant difference in the Mc values among the reference databases allowed the use of a specific cluster of the DSF as a tool for performing similarity searches for oxygen-containing NP molecules, or for evaluation or comparison of databases according to their NP-likeness. An example illustrating that the suggested approach could allow not only estimating the NP-likeness, but also serve as a tool for designing new NP-like compounds is provided. The suggested approach for NP-likeness evaluation moves away from the traditional ideas of scaffolds, cycles, linkers and substituents.
Functionalized dihydrobenzofuran derivatives can be obtained by intramolecular alkoxycyanation and alkoxyacylation of alkenes. In both transformations, selective activation of an OFG bond is accomplished by using a transition-metal catalyst. These transformations represent a conceptually new approach to metal-catalyzed alkene difunctionalization.
Nearly a century after the first report of the Reissert reaction the first catalytic, asymmetric example was published. Since then there have been a small number of reports of similar reaction types: activation of nitrogen-containing aromatic rings through alkylation or acylation, followed by the addition of a carbon-centered nucleophile to the ring. These reactions place great demands on catalyst design; many of the catalysts are bifunctional, simultaneously activating both nucleophiles and electrophiles. The structures obtained from such reactions may easily be derivatized into natural products or drug-like structures. Despite the elegance of the known examples, there are still many reaction types that have not been reported.
A Ru-catalyzed oxidative coupling of arenes with boronic acids using molecular oxygen via direct C-H activation is reported. Both the scope and the mechanism of the process are discussed.
The first Suzuki-Miyaura cross-coupling of an aryl O-carbamate, a versatile and powerful directed metalation group (DMG) in directed ortho metalation (DoM) chemistry, is described using the inexpensive, bench-stable catalyst NiCl(2)(PCy(3))(2). Broad synthetic scope and good efficiency are demonstrated for aryl and heteroaryl O-carbamates. The role of water and hydrolysis equilibrium between free boronic acid and boroxine was established to be a crucial parameter for this transformation. When combined with DoM and traditional Pd-catalyzed Suzuki-Miyaura strategies, the methodology offers concise routes to uniquely substituted molecules, avoiding the need for protection/deprotection of the phenol and the use of strongly nucleophilic cross-coupling partners.
. ‥ und eine Prise Salz: Die erste katalytische Addition von Dialkylzinkreagentien an N-Acylpyridinium-Salze mit guten Ausbeuten und ausgezeichneten Enantioselektivitäten nutzt einen Kupferkomplex von (S)-L als Katalysator. Als Anwendungsbeispiel wird eine formale Synthese des Alkaloids (R)-Coniin präsentiert. Bn=Benzyl, Tf=Trifluormethansulfonyl.
Copper-catalyzed Ullmann condensations are key reactions for the formation of carbon-heteroatom and carbon-carbon bonds in organic synthesis. These reactions can lead to structural moieties that are prevalent in building blocks of active molecules in the life sciences and in many material precursors. An increasing number of publications have appeared concerning Ullmann-type intermolecular reactions for the coupling of aryl and vinyl halides with N, O, and C nucleophiles, and this Minireview highlights recent and major developments in this topic since 2004.
At one time the synthetic chemist's last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been supported by the discovery of new elementary reactions that occur at metal-heteroatom bonds and by the identification of factors that control these reactions. Together, these findings have led to new synthetic processes that are in daily use and have formed a foundation for the development of processes that are likely to be central to synthetic chemistry in the future.
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IR (neat, cm -1 ) 3074
- Hz
Hz),115.3, 76.2. 19 F NMR (471 MHz, CDCl3) δ -120.20. IR (neat, cm -1 ) 3074, 1611, 1502, 1338, 1288, 1158, 1104, 974, 836, 750, 695.
DMSO-d6) δ 10.38 (s, 1H
- Mhz
MHz, DMSO-d6) δ 10.38 (s, 1H), 7.85-7.82 (m, 4H), 7.73 (d, J = 8.5
DMSO-d6) δ -72.99. IR (neat, cm -1 ) 3138, 1579
- F Nmr
F NMR (471 MHz, DMSO-d6) δ -72.99. IR (neat, cm -1 ) 3138, 1579,
1248, 1211, 1169, 1144, 1023, 1007, 813, 758. HRMS (ESI) [M -
DMSO-d6) δ -77.97. IR (neat, cm -1 ) 3128, 1552
- Mhz
MHz, DMSO-d6) δ 10.28 (t, J = 1.7 Hz, 1H), 8.52 (d, J = 1.6 Hz, 2H),
7.88-7.85 (m, 4H), 7.68-7.63 (m, 4H), 7.60-7.55 (m, 2H).; 13 C{ 1 H}
NMR (101 MHz, DMSO-d6) δ 134.7, 134.6, 130.2, 130.1, 122.1,
122.0. 19 F NMR (471 MHz, DMSO-d6) δ -77.97. IR (neat, cm -1 ) 3128,
1552, 1285, 1257, 1147, 1120, 1067, 1060, 849, 755. HRMS (ESI) [M
-OTf] + calcd for C15H13N2 + 221.1079, found 221.1091.
DMSO-d6) δ -77.76. IR (neat, cm -1 ) 3133, 1569
- Mhz
MHz, DMSO-d6) δ 135.1, 134.7, 133.5, 130.2, 124.0, 122.0. 19 F NMR
(471 MHz, DMSO-d6) δ -77.76. IR (neat, cm -1 ) 3133, 1569, 1247,
1213, 1149, 1147, 1023, 1017, 812, 759. HRMS (ESI) [M -OTf] +
calcd for C15H11Cl2N2 + 289.0299, found 289.0356.