- Comments on a Conversion of Epoxides to Halohydrins with Elemental Halogen Catalyzed by Phenylhydrazine: Tandem Electrophilic Halogenation of Aromatic Compounds and Epoxide Ring Opening to Halohydrins
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The halogenation of aromatic compounds by bromine or chlorine in the presence of an epoxide gives the corresponding halogenated aromatics and 2-halohydrins, both with good yields.
- Soroka, Miroslaw,Goldeman, Waldemar,Malysa, Piotr,Stochaj, Monika
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- A convenient new method for the bromination of deactivated aromatic compounds
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Treatment of deactivated aromatic compounds with N-bromosuccinimide in trifluoroacetic acid solvent in the presence of sulfuric acid gave the corresponding monobromoaromatic compounds in good to excellent yields.
- Duan, Jianxin,Zhang, Lian Hao,Dolbier Jr., William R.
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- Photoelectrochemistry with Quinone Radical Anions-Photoassisted Reduction of Halobenzenes and Carbonyl Compounds
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Photoexcited electrochemically generated quinone radical anions reduced 1,2-dibromobenzene to bromobenzene, 1,4-dibromobenzene to bromobenzene and 4-chlorobenzonitrile to benzonitrile.In the presence of anthracene, 2-bromophenyl-, 4-bromophenyl- and 4-cyanophenyl-anthracenes were formed.With acetaldehyde, acetone, acetophenone, benzaldehyde and benzophenone, the major products were the corresponding pinacols, with small amounts of the two-electron secondary alcohols.In acetonitrile as solvent, cinnamonitriles, hydrocinnamonitriles and phenylglutaronitriles were formed in addition to the alcohols.Glyoxylic acid was reduced to tartaric, glycolic and malic acids.The reduction of CO2 was unsuccessful.
- Robertson, Peter K. J.,Eggins, Brian R.
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- C?I-Selective Cross-Coupling Enabled by a Cationic Palladium Trimer
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While there is a growing interest in harnessing synergistic effects of more than one metal in catalysis, relatively little is known beyond bimetallic systems. This report describes the straightforward access to an air-stable Pd trimer and presents unambiguous reactivity data of its privileged capability to differentiate C?I over C?Br bonds in C?C bond formations (arylation and alkylation) of polyhalogenated arenes, which typical Pd0 and PdI-PdI catalysts fail to deliver. Experimental and computational reactivity data, including the first location of a transition state for bond activation by the trimer, are presented, supporting direct trimer reactivity to be feasible.
- Diehl, Claudia J.,Scattolin, Thomas,Englert, Ulli,Schoenebeck, Franziska
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- Directly Observed Reductive Elimination of Aryl Halides from Monomeric Arylpalladium(II) Halide Complexes
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Monomeric, three-coordinate arylpalladium(II) halide complexes undergo reductive elimination of aryl halide to form free haloarene and Pd(0). Reductive elimination of aryl chlorides, bromides, and iodides were observed upon the addition of P(t-Bu)3/
- Roy, Amy H.,Hartwig, John F.
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- Vibrational Spectroscopy and Photodissociation Properties of Ions As Determined by Two-Laser Photodissociation Techniques.
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Iodobenzene, bromobenzene, and m-iodotoluene cations trapped in an ion cyclotron resonance (ICR) mass spectrometer undergo an enhanced visible photodissociation process in the presence of infrared irradiation.The infrared wavelength dependence in the 9.7-10.7-μm region for this effect exhibits features wich relate to the infrared spectroscopy of these ions.The variation in extent of the infrared enhancement with visible wavelength is interpreted as reflecting two different mechanisms: at short wavelengths the enhancement is attributed to changes invisible-absorption cross section with increasing internal energy and gives a useful means of observing such effects, while at long wavelengths the enhancement is attributed to a perturbation of the two-photon dissociation kinetics.The photodissociation rates of several other ions were shown not to undergo an enhancement effect when irradiated with the infrared laser.
- Honovich, Jeffrey P.,Dunbar, Robert C.
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- Effects of Solvent and Additives on the Rearrangement Pathway of the Seyferth Reaction
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The Seyferth reagent has dual reactivity with electron-deficient alkenes. trans-1,2-Dichloroethene reacts both with the free carbene to give cyclopropane stereospecifically and with a complex between carbene and a second molecule of Seyferth reagent (homogeneous catalysis) to give a rearranged propene.The addition of other materials to the reaction mixture can have a profound effect on the ratio of the two pathways.Good ? donors such as p-xylene decrease the pathway to rearranged propene via the complexed carbene.Such materials thus serve as inhibitors to the process of homogeneous catalysis by forming a competing complex that does not go on to propene but instead reverts to free carbene.The existence of the inhibitor-carbene complex is supported by concentration studies.The presence of insoluble materials such as zinc chloride, on the other hand , serves to decrease the pathway that leads through free carbene to the cyclopropane.Free carbene may react with the surface of the additive and be removed as a reactive species.This latter process would have no effect on carbene previously complexed with the homogeneous catalyst, the Seyferth reagent , which could still proceed to rearranged propene.
- Lambert, Joseph B.,Boch, Richard J.,Larson, Eric G.
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- A study on Zr-Ir multiple bonding active for C-H bond cleavage
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Zr-Ir hydrido complexes with ansa-(cyclopentadienyl)(amide) as the supporting ligand in the zirconium fragment, e.g., (L1ZrR) (Cp*Ir)(μ-H)3 [L1 = Me2Si(η 5-C5Me4)(NtBu), R = Cl (5), Ph (7), Me (10), alkyl, and aryl] were designed, synthesized, and isolated as tractable early-late heterodinuclear complexes. Despite the presence of the three supporting hydride ligands, Zr-Ir distances in the crystal structures of 5, alkyl, and aryl complexes [2.74-2.76 A] were slightly longer than the sum of the element radii of Zr and Ir [2.719 A]. These hydrocarbyl complexes displayed the thermolytic C-H activation of a variety of aromatic compounds and several organometallic compounds. Also, the substrate scope and limitation in the Zr-Ir system were studied. The regiochemical outcomes during the C-H activation of pyridine derivatives and methoxyarenes suggested the in situ generation of a Lewis acidic active intermediate, i.e., (L1Zr) (Cp*IrH2) (III). The existence of III and relevant σ-complex intermediates {L1Zr(η2-R-H)} (Cp*IrH2) (IIR) (R = Me, Ph) in the ligand exchange was demonstrated by the direct isolation of a Et3PO-adduct of III (39b) from 7 and kinetic studies. The structure of the direct Zr-Ir bonds in IIPh, IIMe, III, and 39b were probed using computational studies. The unprecedented strong M-M′ interactions in the early-late heterobimetallic (ELHB) complexes have been proposed herein.
- Oishi, Masataka,Oshima, Masato,Suzuki, Hiroharu
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- The Addition Reaction of Benzynes Generated Electrochemically from Dihalobenzenes with Tertiary Amines
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The electroreduction of dihalobenzenes was carried out in the presence of tertiary amines as benzyne acceptors in DMF-TBAP, giving the addition products in yields more than 10percent.For o-dibromobenzene, the yield of the addition product, N-phenylpiperidine, increased to 21percent in the presence of N-ethylpiperidine.
- Egashira, Naoyoshi,Takenga, Jun,Hori, Fumikai
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- ON THE ABSOLUTE REACTIVITY OF ARYL CATIONS: SELECTIVITY TOWARD HALIDE IONS AS A FUNCTION OF VISCOSITY
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The selectivities toward bromide and chloride ions observed in the dediazoniation of three arenediazonium salts are found to be independent of viscosity.It is inferred that the capture of aryl cations by these halide ions is diffusion controlled.
- Lorand, John P.
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- Generation, structure, and reactivity of o-iodobenzoyloxyl radicals. Pulsed laser photolysis of 1-(o-halobenzoyloxy)-2-pyridones
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The transient absorption spectrum of o-iodobenzoyloxyl radicals was observed for the first time in acetonitrile using 1-(o-iodobenzoyloxy)-2-pyridone as a precursor. On the basis of the comparison of the spectra of o-halobenzoyloxyl radicals, it is proposed that the o-iodobenzoyloxyl radicals take a planar structure with a strong interaction between the radical center oxygen atom and the neighboring iodine atom.
- Hashimoto, Ji-Ichiro,Segawa, Katsunori,Itoh, Hiroki,Sakuragi, Hirochika
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- Photochemically Switching Diamidocarbene Spin States Leads to Reversible Büchner Ring Expansions
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The discovery of thermal and photochemical control by Woodward and Hoffmann revolutionized how we understand chemical reactivity. Similarly, we now describe the first example of a carbene that exhibits differing thermal and photochemical reactivity. When a singlet ground-state N,N'-diamidocarbene 1 was photolyzed at 380 nm, excitation to a triplet state was observed. The triplet-state electronic structure was characteristic of the expected biradical σ1pπ1 spin configuration according to a combination of spectroscopic and computational methods. Surprisingly, the triplet state of 1 was found to engage a series of arenes in thermally reversible Büchner ring expansion reactions, marking the first examples where both cyclopropanation and ring expansion of arenes were rendered reversible. Not only are these photochemical reactions different from the known thermal chemistry of 1, but the reversibility enabled us to perform the first examples of photochemically induced arene exchange/expansion reactions at a single carbon center.
- Perera, Tharushi A.,Reinheimer, Eric W.,Hudnall, Todd W.
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- Nucleophilic substitution of hydrogen in naphthalene by chloride (Cl -) in ionic liquids
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Nucleophilic aromatic substitution of hydrogen in non-activated aromatic ring, a very rare phenomenon in organic chemistry, is found in ionic liquids containing Cl- as anion under mild reaction conditions. The reaction may be carried out by the addition of the halogen-bonding adduct (Br 2Cl-) as nucleophile to aromatic ring carbon atom, leading to the formation of the nucleophilic substitution product.
- Shi, Shen Yi,Kong, Ai Guo,Zhao, Xin Hua,Ding, Han Ming,Yang, Fan,Shan, Yong Kui
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- Hydroxyl radical induced reactions in aqueous solutions of halogenated benzenes: Effect of electronegativity of halogen
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The .OH radicals, generated by radiolysis, are found to react only in acidic conditions with halogenated benzenes by an electron transfer mechanism. The concentration of acid, at which solute radical cation of halogenated benzenes appear, is observed to depend strongly on the nature and number of halogen atoms in halogenated benzenes. A linear increase in the acid concentration required for solute radical cation formation is observed with electronegativity of halogen.
- Mohan, Hari,Mittal, Jai P.
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- Cope rearrangement versus a novel tandem retro-diels-alder-diels-alder reaction with role reversal
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A reinvestigation of the thermolysis of 4,4-dibromotetracyclo[6.2.1.0 2,7.03,5]undec-9-ene (2) affords diene 8 with a completely rearranged hydrocarbon skeleton via the isolable intermediate 4, along with cyclopentadiene and bromobenzene. DFT calculations show that the novel tandem retro-Diels-Alder-Diels-Alder reaction with role reversal is slightly less favored than the overall single-step Cope rearrangement. (Chemical Equation Presented)
- Su, Kuan-Jen,Mieusset, Jean-Luc,Arion, Vladimir B.,Brecker, Lothar,Brinker, Udo H.
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- REDUCTION BY A MODEL OF NAD(P)H. 42. DIRECT EVIDENCE FOR ONE ELECTRON TRANSFER MECHANISM IN THE REDUCTION OF ARENEDIAZONIUM SALTS.
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Arenediazonium salts are reduced by an NAD(P)H- model in methanol at room temperature to afford the corresponding reduction product, ArH.The reaction proceeds partially with a radical-chain mechanism involving initial one electron transfer from the NAD(P)H-model to the diazonium salt.
- Yasui, Shinro,Nakamura, Kaoru,Ohno, Atsuyoshi
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- Through-Space Activation Can Override Substituent Effects in Electrophilic Aromatic Substitution
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Electrophilic aromatic substitution (EAS) represents one of the most important classes of reactions in all of chemistry. One of the "iron laws" of EAS is that an electron-rich aromatic ring will react more rapidly than an electron-poor ring with suitable electrophiles. In this report, we present unique examples of electron-deficient arenes instead undergoing preferential substitution in intramolecular competition with more electron-rich rings. These results were made possible by exploiting the heretofore unknown propensity of a hydrogen-bonding OH-arene interaction to switch to the alternative HO-arene interaction in order to provide activation. In an extreme case, this through-space HO-arene activation is demonstrated to overcome the deactivating effect of a trifluoromethyl substituent, making an otherwise highly electron-deficient ring the site of exclusive reactivity in competition experiments. Additionally, the HO-arene activation promotes tetrabromination of an increasingly more electron-deficient arene before the unactivated "control" ring undergoes monobromination. It is our hope that these results will shed light on biological interactions as well as provide new strategies for the electrophilic substitution of aromatic rings.
- Guan, Liangyu,Holl, Maxwell Gargiulo,Pitts, Cody Ross,Struble, Mark D.,Siegler, Maxime A.,Lectka, Thomas
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- Pd-catalyzed reduction of aryl halides using dimethylformamide as the hydride source
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The Pd-catalyzed homocoupling of aryl halides in a basic DMF solution is often accompanied by the dehalogenation of the substrate as side reaction. When an inorganic base such as sodium bicarbonate is used, the reducing role of the solvent has been demonstrated using DMF-d7 and GC/MS analysis.
- Zawisza, Anna Maria,Muzart, Jacques
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- Properties of PTFE tape as a semipermeable membrane in fluorous reactions
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In a PTFE tape phase-vanishing reaction (PV-PTFE), a delivery tube sealed with PTFE tape is inserted into a vessel which contains the substrate. The reagent diffuses across the PTFE tape barrier into the reaction vessel. PTFE co-polymer films have been found to exhibit selective permeability towards organic compounds, which was affected by the presence of solvents. In this study, we attempted to establish general trends of permeability of PTFE tape to different compounds and to better describe the process of solvent transport in PV-PTFE bromination reactions. Though PTFE tape has been reported as impermeable to some compounds, such as dimethyl phthalate, solvent adsorption to the tape altered its permeability and allowed diffusion through channels of solvent within the PTFE tape. In this case, the solvent-filled pores of the PTFE tape are chemically more akin to the adsorbed solvent rather than to the PTFE fluorous structure. The solvent uptake effect, which was frequently observed in the course of PV-PTFE reactions, can be related to the surface tension of the solvent and the polarity of the solvent relative to the reagent. The lack of pores in bulk PTFE prevents solvents from altering its permeability and, therefore, bulk PTFE is impermeable to most solvents and reagents. However, bromine, which is soluble in liquid fluorous media, diffused through the bulk PTFE. A better understanding of the PTFE phase barrier will make it possible to further optimize the PV-PTFE reaction design.
- Parsons, Brendon A.,Smith, Olivia Lin,Chae, Myeong,Dragojlovic, Veljko
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- Bromine and iodine-cucurbit[6]uril complexes: Preparation and applications in synthetic organic chemistry
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Iodine and bromine inclusion compounds were easily prepared by gas diffusion of the halogens using finely powdered CB[6]. A brown powder consisting of I2-CB[6]·4H2O and an orange one of (Br 2)4-CB[6]·10H2O were employed in several different reactions. I2-CB[6] can be used in catalytic reactions giving yields comparable to those reported in the literature. Br 2-CB[6] was effectively applied in electrophilic bromination of benzene and formation of bromohydrin. However, the radical substitution at cyclohexene could not be performed. Overall, based on these results, several applications can be envisioned for these complexes. This journal is the Partner Organisations 2014.
- Reddy,Cavallini,Demets,Silva
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- Photochemical Decomposition of Dibenzoyl Peroxide and Phenyl Benzoate in Solid KBr Matrix
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Physical and photochemical properties of dibenzoyl peroxide (DBPO) and phenyl benzoate (PB) in a solid KBr matrix were investigated.The photoinduced decompositions of DBPO and PB were monitored with infrared spectroscopy and HPLC.The organic molecules at different locations in the matrix contribute to the overall IR absorption differently.Therefore, they are affected differently during a photochemical decomposition.The bromide ions in the matrix intercept some of the radical intermediates in the decomposition of DBPO but have no influence on the radical pair in the rearrangement of phenyl benzoate.
- Owen, David J.,O'Donnell, Jennifer,Schutt, Wendy,Morrow, Jeffrey,Li, Yuzhuo
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- Noncatalytic bromination of benzene: A combined computational and experimental study
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The noncatalytic bromination of benzene is shown experimentally to require high 5-14 M concentrations of bromine to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable (6-benzene of 0.97 ± 0.03 at 298 K. These results are rationalized using computed transition states models at the B3LYP+D3/6-311++G(2d,2p) level with an essential continuum solvent field for benzene applied. The model with the lowest predicted activation free energies agrees with the high experimental kinetic order in bromine and involves formation of an ionic, concerted, and asynchronous transition state with a Br8 cluster resembling the structure of the known Br9-. This cluster plays three roles; as a Br+ donor, as a proton base, and as a stabilizing arm forming weak interactions with two adjacent benzene C-H hydrogens, these aspects together combining to overcome the lack of reactivity of benzene induced by its aromaticity. The computed inverse kinetic isotope effect of 0.95 agrees with experiment, and arises because C-Br bond formation is essentially complete, whereas C-H cleavage has not yet commenced. The computed free energy barriers for the reaction with 4Br2 and 5Br2 for a standard state of 14.3 M in bromine are reasonable for an ambient temperature reaction, unlike previously reported theoretical models involving only one or two bromines.
- Shernyukov, Andrey V.,Genaev, Alexander M.,Salnikov, George E.,Rzepa, Henry S.,Shubin, Vyacheslav G.
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- Formation and Reactivity of the Radical Cation of Bromobenzene in Aqueous Solution: A Pulse Radiolysis Study
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A transient optical absorption band (λmax=325 nm) is formed upon reaction of . OH radical with bromobenzene in neutral aqueous solution and is assigned to the OH adduct.In strongly acidic solution (HClO4 > 3 mol dm3), the OH adduct undergoes H+-catalyzed dehydroxylation to form the bromobenzene radical cation.This radical cation absorbs at 550 nm and at 270-310 nm.Even at this high H+ concentration, only a fraction of the OH adduct is converted to the radical cation.SO4.- reacts with bromobenzene to form the hydroxycyclohexadienyl radical (λmax=325 nm) and the phenoxyl radical (λmax=400 nm).The bromobenzene radical cation is also observed in irradiated 1,2-dichloroethane solutions.C6H5Br.+ is a strong one-electron oxidant and oxidizes Br-, SCN-, and organic sulfides with high rate constants.C6H5Br.+ undergoes electron transfer reaction with Cl- to establish an equilibrium, from which a reduction potential value for C6H5Br.+/C6H5Br was determined to be 2.31+/-0.15 V versus NHE.
- Mohan, Hari,Mittal, Jai P.
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- Radical Rearrangements of Bicyclohexane: Homolytic Substitution of a Cyclobutane Ring
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Bromine atoms react with bicyclohexane in an SH2 reaction at the bridgehead carbon atoms; the bicyclohex-2-yl radical rearranges by β-scission of the inter-ring bond.
- Walton, John C.
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- Remarkably stable ortho-halophenylcopper reagents
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We wish to report the generation of remarkably stable o-halophenlycopper reagents at room temperature by the direct oxidative addition of activated copper to o-flouro-and o-choloriodobenzene. The reagents will undergo substitution reactions with suitable organic halides at 25°C.
- Ebert, Greg W.,Pfennig, Deborah R.,Suchan, Scott D.,Donovan Jr., Thomas A.
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- Reactivity of alkali and alkaline earth metal tetrafluorobromates towards aromatic compounds and pyridine
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The bromination activity of tetrafluorobromates of alkali and alkali-earth metals increases in the order KBrF4, CsBrF4, RbBrF4and Ba(BrF4)2. The most active tetrafluorobromate—Ba(BrF4)2is able to selectively brominate the deactivated aromatic compounds nitrobenzene and 4-nitrotoluene, but not the activated compounds benzene and toluene. In all cases bromination of methyl groups of methylbenzenes does not occur. Ba(BrF4)2forms the known complex C6H5N·BrF3when reacted with pyridine. Due to dilution by inert BaF2, this pyridine-based complex is air stable and can be considered as safer and more convenient reagent in comparison with the original fluorobromates; it can selectively brominate benzene and toluene in contrast with tetrafluorobromates.
- Sobolev, Vasily I.,Filimonov, Victor D.,Ostvald, Roman V.,Radchenko, Vyacheslav B.,Zherin, Ivan I.
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- Silk?Fibroin-Supported Palladium Catalyst for Suzuki-Miyaura and Ullmann Coupling Reactions of Aryl Chlorides
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Recently, we have reported the preparation of a silk fibroin-supported Palladium catalyst (Pd/SF) and its use in the Suzuki-Miyaura cross-coupling of aryl iodides. Since its synthetic applicability and structural features are still far from being fully ex
- Albano, Gianluigi,Farinola, Gianluca M.,Giannini, Cinzia,Musio, Roberta,Omenetto, Fiorenzo G.,Rizzo, Giorgio,Sibillano, Teresa
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supporting information
(2022/02/03)
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- Radical Hydrodehalogenation of Aryl Halides with H2 Catalyzed by a Phenanthroline-Based PNNP Cobalt(I) Complex
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Radical hydrodehalogenation of aryl halides (Ar-X; X = Cl, Br, I) is achieved in the presence of atmospheric pressure H2 as a H-atom donor using a Co(I) catalyst bearing a phenanthroline-based PNNP ligand (2,9-bis((diphenylphosphanyl)methyl)-1,10-phenanthroline). The reaction proceeds under mild conditions (1 atm H2) and is applicable to aryl bromides and aryl chlorides with various functional groups. A mechanistic study revealed that the PNNP-Co complex underwent facile H-H cleavage and facilitated a H-atom transfer. This process is mediated by a long-range metal-ligand cooperation of the PNNP-Co system, which includes the dearomatization/aromatization sequence of the phenanthroline ligand backbone. A radical clock experiment demonstrated the Ar-X bond cleavage via a radical mechanism. Further kinetic study supported that the rate-determining step includes electron transfer from the Co center to the substrate, affording a radical pair ArX?- and an odd-electron metal-halide complex [Co(II) + ArX?-]? as a transition state.
- Iizuka, Kosuke,Ishizaka, Yusuke,Jheng, Nai-Yuan,Minami, Yasunori,Naganawa, Yuki,Nakajima, Yumiko,Sekiguchi, Akira
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p. 2320 - 2329
(2022/02/16)
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- Poly-N-bromosulfonamide-melamine as a novel brominating reagent for regioselective ipso-bromination of arylboronic acids
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A practical synthetic method for the synthesis of aryl bromide was developed through regioselective bromination of boronic acid in the presence of poly-N-bromosulfonamide-melamine (PBBSM). In this regard, a novel heterogeneous support, cross-linked poly sulfonamide-melamine, has been successfully synthesized to stabilize bromine with high surface functional group density (6.6?mmol Br+/g). The prepared reagent is a novel brominating reagent that combines the effective functions of N-bromosulfonamide, N-bromosulfonamide-melamine, and melamine groups. The structure of PBBSM was characterized using XRD, FT–IR, 1H NMR, TGA, FE-SEM, EDX, and TGA analysis. Graphic abstract: [Figure not available: see fulltext.]
- Alavinia, Sedigheh,Ghorbani-Vaghei, Ramin
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p. 1269 - 1276
(2021/08/27)
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- The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
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An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
- Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
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p. 18040 - 18049
(2021/05/29)
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- METHOD FOR PRODUCING LITHIUM COMPOUND
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PROBLEM TO BE SOLVED: To provide a method capable of producing a lithium compound in a higher yield by lithiation reaction. SOLUTION: A method for producing a lithium compound includes a step (1) for mixing an organic lithium reagent with a reaction solvent species, and a step (2) for mixing the treated organic lithium reagent obtained by the step (1) with a raw material substrate. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0044; 0072-0092
(2021/01/29)
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- Alternative method for the synthesis of triazenes from aryl diazonium salts
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An alternative mild method for access to 1-aryl-3,3-dimethyl alkyl triazenes is described. This protocol employs the dropwise addition of a methanolic solution of a carboxylate (RCO2M) or carbonate (CO32?) to a gently heated DMF solution containing an aryl diazonium salt (ArN2+), that had been previously isolated. Presumably homolysis of the weak N–O bond of diazo ether adducts formed in this operation initiates radical pathways that lead to the generation of triazene product. DMF serves as not only a one-electron donor to the diazonium salts employed in this process, but also as a source of dimethylamine radicals that act as a nucleophilic coupling partner. The reaction provides modest yields (ca. 20–40%) across an array of aryl diazonium salts that contain various substitution. Furthermore this unique approach to triazenes contrasts with traditional methods that employ dimethyl amine in reagent form which directly couples with diazonium salts. Seemingly, only one other example employing somewhat similar reaction conditions to this current investigation en route to triazenes has been reported, albeit with lower yields and for one representative example furnished as a side-product. The current work here improves upon the efficiency of this reported result, and further expands the reaction scope.
- Abrams
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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supporting information
(2021/10/05)
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- Triptycenyl Sulfide: A Practical and Active Catalyst for Electrophilic Aromatic Halogenation Using N-Halosuccinimides
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A Lewis base catalyst Trip-SMe (Trip = triptycenyl) for electrophilic aromatic halogenation using N-halosuccinimides (NXS) is introduced. In the presence of an appropriate activator (as a noncoordinating-anion source), a series of unactivated aromatic compounds were halogenated at ambient temperature using NXS. This catalytic system was applicable to transformations that are currently unachievable except for the use of Br2 or Cl2: e.g., multihalogenation of naphthalene, regioselective bromination of BINOL, etc. Controlled experiments revealed that the triptycenyl substituent exerts a crucial role for the catalytic activity, and kinetic experiments implied the occurrence of a sulfonium salt [Trip-S(Me)Br][SbF6] as an active species. Compared to simple dialkyl sulfides, Trip-SMe exhibited a significant charge-separated ion pair character within the halonium complex whose structural information was obtained by the single-crystal X-ray analysis. A preliminary computational study disclosed that the πsystem of the triptycenyl functionality is a key motif to consolidate the enhancement of electrophilicity.
- Nishii, Yuji,Ikeda, Mitsuhiro,Hayashi, Yoshihiro,Kawauchi, Susumu,Miura, Masahiro
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supporting information
p. 1621 - 1629
(2020/02/04)
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- Controllable synthesis of ultrasmall Pd nanocatalysts templated by supramolecular coordination cages for highly efficient reductive dehalogenation
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Supported ultrasmall noble metal nanocatalysts (UNMNs) are one of the most important classes of solid materials for heterogeneous catalysis. Herein, a simple and efficient supramolecular coordination cage (SCC) template-strategy has been developed to synthesize UNMNs with controllable size and size distribution. A series of SCCs, including M2L4, M4L2, M6L4 and M12L24, with well-defined sizes and shapes as well as different numbers of Pd ions were designed and synthesized as templates. Subsequently, the corresponding Pd nanocatalysts M2&at;CMC, M4&at;CMC, M6&at;CMC and M12&at;CMC were prepared by an impregnation-reduction method on carboxymethylcellulose (CMC) hydrogel supports. It was found that the employment of SCCs as templates could not only significantly reduce the aggregation tendency of Pd nanoparticles but also play an important role in regulating their size and size distribution. For example, the analysis of the catalyst size distribution indicated that the greater the number of Pd ions the cage possesses, the bigger the size of the catalyst. Moreover, with the decrease of the concentration of the template, the size of the Pd nanocatalyst also decreased obviously. Particularly, the resultant catalyst with a nano-Pd loading as high as 12.63percent could still maintain a narrow size distribution. Furthermore, the as-prepared Pd nanocatalyst could serve as a highly efficient polychlorinated biphenyl (PCB) degrader both in a stirred vessel and a continuous flow reactor because of its excellent catalytic efficiency in the reductive dehalogenation reaction under mild conditions. In a word, the SCC template-strategy employed in this study provides new guidelines for the preparation of size-controllable UNMNs on a variety of supports, along with high noble metal loading and catalytic activity. This journal is
- Jiang, Wei-Ling,Peng, Zhiyong,Shen, Ji-Chuang,Shi, Xueliang,Wu, Gui-Yuan,Yang, Hai-Bo,Yin, Guang-Qiang
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supporting information
p. 12097 - 12105
(2020/07/09)
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- Effects of Ligand Substitution on the Optical and Electrochemical Properties of (Pyridinedipyrrolide)zirconium Photosensitizers
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A series of seven bis(pyridinedipyrrolide)zirconium complexes, Zr(R1PDPR2)2, where [R1PDPR2]2- is the doubly deprotonated form of [2,6-bis(5-R1-3-R2-1H-pyrrol-2-yl)pyridine], were prepared and characterized in solution by NMR, UV/vis absorption, and emission spectroscopy and cyclic voltammetry. The molecular structures were determined by single-crystal X-ray crystallography. All complexes exhibit remarkably long emission lifetimes (τ = 190-576 μs) with high quantum efficiencies (φPL = 0.10-0.38) upon excitation with visible light in a benzene solution. The substituents on the pyrrolide rings were shown to have significant effects on the photoluminescence and electrochemical properties of these compounds. The R2 substituents (R2 = H, Me, Ph, or C6F5) show only limited effects on the absorption and emission profiles of the complexes but allow systematic tuning of the ground- and excited-state redox potentials over a range of almost 600 mV. The R1 substituents (R1 = H, Me, Ph, or 2,4,6-Me3Ph) influence both the optical and electrochemical properties through electronic effects. Additionally, the R1 substituents have profound consequences for the structural flexibility and overall stability of the compounds. Distortions of the Zr(PDP)2 core from idealized D2d symmetry in the solid state can be traced to the steric profiles of the R1 substituents and correlate with the observed Stokes shifts for each compound. The complex with the smallest ligand system, Zr(HPDPH)2, coordinates two additional solvent molecules in a tetrahydrofuran (THF) solution, which allowed the isolation of photoluminescent, eight-coordinate Zr(HPDPH)2(THF)2. The photoredox catalytic dehalogenation of aryl iodides and aryl chlorides using the most reducing derivative, Zr(MePDPMe)2, highlights the potential of Zr(PDP)2 photosensitizers to promote challenging reductive transformations under mild conditions upon excitation with green light.
- Belldina, Anne M.,Leary, Dylan C.,Milsmann, Carsten,Petersen, Jeffrey L.,Zhang, Yu
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supporting information
p. 14716 - 14730
(2020/11/02)
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- COMPOUND FOR ORGANIC ELECTRIC ELEMENT, ORGANIC ELECTRIC ELEMENT COMPRISING THE SAME AND ELECTRONIC DEVICE THEREOF
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The present invention relates to: a compound for an organic electric element; the organic electric element using the same; and an electronic device thereof. According to the present invention, it is possible to achieve high luminous efficiency, low driving voltage, and high heat resistance of an element, and to improve color purity and lifespan of the element. By using the compound according to the present invention, it is possible to achieve high luminous efficiency, low driving voltage, and high heat resistance of the element, and to provide an effect of improving color purity and lifespan of the element.(110) Substrate(120) Positive electrode(130) Hole injection layer(140) Hole transfer layer(141) Buffer layer(150) Light emitting layer(151) Light emitting auxiliary layer(160) Electron transfer layer(170) Electron injection layer(180) Negative electrodeCOPYRIGHT KIPO 2020
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Paragraph 0263-0267; 0288-0289; 0291
(2020/04/30)
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- A General Photocatalytic Route to Prenylation
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Prenylation is an essential reaction on which nature relies to modify properties of molecules and build terpenoids, but remains a challenging chemical reaction. Aiming to capitalize on recent advances in photocatalysis to easily and cleanly generate a broad range of carbon based radicals, we have developed a prenyl transfer reagent that is captured by transiently generated radicals. The reagent can be made in bulk, is bench stable, and broadly applicable such that it can be used with existing photocatalytic methods with very few changes to reaction conditions. Ultimately, this provides a true drop-in solution for prenylation, expanding the scope of substrates that can be readily prenylated.
- Rathnayake, Manjula D.,Weaver, Jimmie D.
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supporting information
p. 1433 - 1438
(2019/06/13)
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- Oxidative bromination of non-activated aromatic compounds with AlBr3/KNO3 mixture
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Bromination of non-activated aromatic compounds with reaction mixture containing KNO3 and AlBr3 was studied in liquid substrates and in solvent. Aluminium bromide has three different roles in this reaction mixture. First, it is a source of bromide ions, which are essential in oxidative bromination application. Second, it acts as a catalyst, and lastly, it forms acidic environment via its hydrolysis, which is necessary for enhancement of the oxidising properties of nitrate ions. It was shown that when changing the reaction conditions, different side reactions (like nitration or Friedel–Crafts type arylation) can occur. However, it is possible to guide the reaction path and receive the desired outcome by choosing the suitable reaction conditions. In addition, it was shown that there has to be water content in this reaction mixture as the bromine formation rate depends on it, while there exists an optimal volume of water, where bromine formation is the fastest.
- Rahu, Ida,J?rv, Jaak
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p. 1219 - 1227
(2019/11/13)
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- A Nickel-Doped Dehydrobenzoannulene-Based Two-Dimensional Covalent Organic Framework for the Reductive Cleavage of Inert Aryl C-S Bonds
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The development of metalated covalent organic frameworks (COFs) is useful for generating recyclable catalytic systems for practical applications. Herein, we report the synthesis, characterization, and catalytic properties of an azine-linked two-dimensional (2D) COF containing nickel-doped dehydrobenzoannulene (DBA) units. We demonstrate that Ni-DBA-2D-COF can be used to reductively cleave the aryl C-S bonds of several organosulfur compounds utilizing dimethylethylsilane as the reducing agent. The Ni-DBA-2D-COF catalytic system displays excellent recyclability and good yields. This work highlights a rare example of utilizing metalated DBA complexes to perform catalytic transformations.
- Haug, W. Karl,McGrier, Psaras L.,Morman, Blake T.,Thomas, Christine M.,Wolfson, Eric R.
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supporting information
p. 5521 - 5525
(2020/04/09)
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- Metal- and base-free synthesis of aryl bromides from arylhydrazines
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An efficient method was developed to synthesize brominated aromatic compounds from arylhydrazine hydrochlorides by using BBr3 in DMSO/CPME (cyclopentyl methyl ether) under air at 80 °C for 1 h without the use of bases or metal catalysts. In particular, this method could be carried out satisfactorily using electron-withdrawing groups to afford aryl bromides in a moderate to excellent yields.
- Phuc Tran, Dat,Nomoto, Akihiro,Mita, Soichiro,Dong, Chun-ping,Kodama, Shintaro,Mizuno, Takumi,Ogawa, Akiya
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supporting information
(2020/05/08)
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- Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
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While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
- Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
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supporting information
p. 18717 - 18722
(2020/08/25)
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- Grignard-Reagent-Promoted Desulfonylation/Intramolecular Coupling for the Synthesis of 2-(1-Fluorovinyl)pyridines
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A novel process involving Grignard-reagent-promoted desulfonylation/intramolecular coupling of readily available α-fluoro-α,β-unsaturated-(2-pyridyl)sulfones was realized that provided a series of polysubstituted 2-(1-fluorovinyl)pyridines in good yields. The intrinsic coordination between pyridine and Mg(II) along with the "negative fluorine effect"of the substrates should play the key role for the smooth transformation in the absence of transition-metal catalysts.
- Jiang, Gaoxi,Kang, Lei,Qian, Jinlong,Yang, Huameng,Zhang, Jinlong
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supporting information
p. 9118 - 9122
(2020/12/02)
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- Regioselective arene homologation through rhenium-catalyzed deoxygenative aromatization of 7-oxabicyclo[2.2.1]hepta-2,5-dienes
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Combined use of oxorhenium catalysts with triphenyl phosphite as an oxygen acceptor allowed efficient deoxygenative aromatization of oxabicyclic dienes. The reaction proceeded under neutral conditions and was compatible with various functional groups. Combining this deoxygenation with regioselective bromination and trapping of the generated aryne with furan resulted in benzannulative π-extension at the periphery of the PAHs. This enabled direct use of unfunctionalized PAHs for extension of π-conjugation. Iteration of the transformations increased the number of fused-benzene rings one at a time, which has the potential to alter the properties of PAHs by fine-tuning the degree of π-conjugation, shape, and edge topology.
- Murai, Masahito,Ogita, Takuya,Takai, Kazuhiko
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supporting information
p. 2332 - 2335
(2019/02/27)
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- Maximizing Property Tuning of Phosphorus Corrole Photocatalysts through a Trifluoromethylation Approach
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An eight-member series of CF3-substituted difluorophosphorus corroles was prepared for establishing a structure-activity profile of these high-potential photosensitizers. It consisted of preparing all four possible isomers of the monosubstituted corrole and complexes with 2-, 3-, 4-, and 5-CF3 groups on the macrocycle's periphery. The synthetic pathway to these CF3-substituted derivatives, beginning with (tpfc)PF2, involves two different initial routes: (i) direct electrophilic CF3 incorporation using FSO2CF2CO2Me and copper iodide, or (ii) bromination to achieve the 2,3,8,17,18-pentabrominated compound using excess bromine in methanol. Crystallographic investigations revealed that distortion of the original planar macrocycle is evident even in the monosubstituted case and that it becomes truly severe for the penta-CF3-substituted derivative 5. There is a shift in redox potentials of about 193 mV per -CF3 group, which decreases to only 120 mV for the fifth one in 5. Differences in the electronic spectra suggest that the Gouterman four orbital model decreases in relevance upon gradual -CF3 substitution, a conclusion that was corroborated by DFT calculations. The very significant energy lowering of the frontier orbitals suggested that photoexcitation should lead to a highly oxidizing photocatalyst. This hypothesis was proven true by finding that the most synthetically accessible CF3-substituted derivative is an excellent catalyst for the photoinduced conversion of bromide to bromine (phenol, toluene, and benzene assay).
- Zhan, Xuan,Teplitzky, Peter,Diskin-Posner, Yael,Sundararajan, Mahesh,Ullah, Zakir,Chen, Qiu-Cheng,Shimon, Linda J. W.,Saltsman, Irena,Mahammed, Atif,Kosa, Monica,Baik, Mu-Hyun,Churchill, David G.,Gross, Zeev
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p. 6184 - 6198
(2019/05/08)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- The Tandem Photoredox Catalysis Mechanism of [Ir(ppy)2(dtb-bpy)]+ Enabling Access to Energy Demanding Organic Substrates
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We report the discovery of a tandem catalytic process to reduce energy demanding substrates, using the [Ir(ppy)2(dtb-bpy)]+ (1+) photocatalyst. The immediate products of photoinitiated electron transfer (PET) between 1+ and triethylamine (TEA) undergo subsequent reactions to generate a previously unknown, highly reducing species (2). Formation of 2 occurs via reduction and semisaturation of the ancillary dtb-bpy ligand, where the TEA radical cation serves as an effective hydrogen atom donor, confirmed by nuclear magnetic resonance, mass spectrometry, and deuterium labeling experiments. Steady-state and time-resolved luminescence and absorption studies reveal that upon irradiation, 2 undergoes electron transfer or proton-coupled electron transfer (PCET) with a representative acceptor (N-(diphenylmethylene)-1-phenylmethanamine; S). Turnover of this new photocatalytic cycle occurs along with the reformation of 1+. We rationalize our observations by proposing the first example of a mechanistic pathway where two distinct yet interconnected photoredox cycles provide access to an extended reduction potential window capable of engaging a wide range of energy demanding and synthetically relevant organic substrates including aryl halides.
- Connell, Timothy U.,Fraser, Catherine L.,Czyz, Milena L.,Smith, Zoe M.,Hayne, David J.,Doeven, Egan H.,Agugiaro, Johnny,Wilson, David J. D.,Adcock, Jacqui L.,Scully, Andrew D.,Gómez, Daniel E.,Barnett, Neil W.,Polyzos, Anastasios,Francis, Paul S.
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p. 17646 - 17658
(2019/11/11)
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- Nickel-catalysed C–O bond reduction of 2,4,6-triaryloxy-1,3,5-triazines in 2-methyltetrahydrofuran
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A nickel-catalysed reduction of phenol derivatives activated by 2,4,6-trichloro-1,3,5-triazine (TCT) in ecofriendly 2-methyltetrahydrofuran (2-MeTHF) is described. The phenol-TCT derivatives were readily prepared using grinding method in short time without further purification. This catalytic system allowed the facile C–O cleavage of phenol-TCT derivatives under mild reaction conditions with high efficiency and good functional group tolerance. Gram-scale reaction was also achieved. Particularly, sequential functionalization of phenol-TCT derivatives followed by C–O bond reduction could also be realized, affording the high value-added products in moderate to good yields.
- Wang, Yaoyao,Shen, Jun,Chen, Qun,Wang, Liang,He, Mingyang
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p. 409 - 412
(2018/10/02)
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- Transition-State Interactions in a Promiscuous Enzyme: Sulfate and Phosphate Monoester Hydrolysis by Pseudomonas aeruginosa Arylsulfatase
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Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyzes sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and analyses of active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs PASWT has a much less negative Br?nsted coefficient (βleaving groupobs-Enz = 0.33) than the uncatalyzed reaction (βleaving groupobs = 1.81). This situation is diminished when cationic active site groups are exchanged for alanine. The considerable degree of bond breaking during the transition state (TS) is evidenced by an 18Obridge KIE of 1.0088. LFER and KIE data for several active site mutants point to leaving group stabilization by active site K375, in cooperation with H211. 15N KIEs and the increased sensitivity to leaving group ability of the sulfatase activity in neat D2O (βleaving groupH-D = +0.06) suggest that the mechanism for S-Obridge bond fission shifts, with decreasing leaving group ability, from charge compensation via Lewis acid interactions toward direct proton donation. 18Ononbridge KIEs indicate that the TS for PAS-catalyzed sulfate monoester hydrolysis has a significantly more associative character compared to the uncatalyzed reaction, while PAS-catalyzed phosphate monoester hydrolysis does not show this shift. This difference in enzyme-catalyzed TSs appears to be the major factor favoring specificity toward sulfate over phosphate esters by this promiscuous hydrolase, since other features are either too similar (uncatalyzed TS) or inherently favor phosphate (charge).
- Van Loo, Bert,Berry, Ryan,Boonyuen, Usa,Mohamed, Mark F.,Golicnik, Marko,Hengge, AlVan C.,Hollfelder, Florian
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p. 1363 - 1378
(2019/03/11)
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- Hydro/deutero deamination of arylazo sulfones under metal and (photo)catalyst-free conditions
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Hydrodeaminated and monodeuterated aromatics were obtained via a visible-light driven reaction of arylazo sulfones. Deuteration occurs efficiently in deuterated media such as isopropanol-d8 or in THF-d8/water mixtures and exhibits a high tolerance to the nature and the position of the aromatic substituents.
- Amin, Hawraz I.M.,Raviola, Carlotta,Amin, Ahmed A.,Mannucci, Barbara,Protti, Stefano,Fagnoni, Maurizio
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- 2-Bromo-2-chloro-3-arylpropanenitriles as C-3 Synthons for the Synthesis of Functionalized 3-Aminothiophenes
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2-Bromo-2-chloro-3-arylpropanenitriles can be prepared by Meerwein reaction from 2-chloroacrylonitrile and various aryldiazonium salts under copper(II) bromide catalysis. They proved to be stable compounds which form 2-chlorocinnnamonitriles upon treatment with bases. Reaction of the title compounds with substituted thioglycolates gave substituted 3-aminothiophenes which have not yet been accessible by other routes. Three-component reactions with the title compound, sodium sulfide and bromonitromethane, chloroacetonitrile, or ethyl 4-chloroacetoacetate gave 2-nitro- and 2-cyano-substituted 3-aminothiophenes, and thienopyridinediones in high yields and in one single step, respectively.
- Batsyts, Sviatoslav,Shehedyn, Maksym,Goreshnik, Evgeny A.,Obushak, Mykola D.,Schmidt, Andreas,Ostapiuk, Yurii V.
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p. 7842 - 7856
(2019/12/24)
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- Polymer-anchored [Fe(III)Azo] complex: An efficient reusable catalyst for oxidative bromination and multi-components reaction for the synthesis of spiropiperidine derivatives
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A heterogeneous catalyst was prepared by attaching Fe(III) into organically modified chloromethylated polytstyrene and characterized by AAS, IR, PXRD, TG-DTA, UV–Vis, and SEM studies. In presence of H2O2 and KBr as bromine source, the catalyst showed remarkably high conversion with para-selectivity towards the oxidative bromination reaction in acetic acid medium. The catalyst was also very active and highly efficient for the production of spiropiperidine derivatives through multi-component reaction in isopropyl alcohol at room temperature. The catalyst was not leached during the catalytic reactions, moreover, after five cycles the catalytic activity and selectivity of the catalyst were not decreased very significantly.
- Khatun, Resmin,Biswas, Surajit,Ghosh, Swarbhanu,Islam, Sk. Manirul
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- Green halogenation reactions for (hetero)aromatic ring systems in alcohol, water, or no solvent
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A new method of brominating aromatic and heteroaromatic ring systems is investigated. The combination of hydrobromic acid as the halogen source, hydrogen peroxide as the oxidant, and ethanol, water, or no solvent are evaluated as greener conditions than those that have been previously published. The new conditions give high yields and good regioselectivity for a variety of substrates when the ring is activated by electron-donating groups or heteroatoms. Phenols, anisole, thiophenes, and pyrrole give comparable or superior results when compared to a traditional bromination by N-bromosuccinimide in tetrahydrofuran. Other nitrogen-containing heterocycles do not react under the conditions because they are protonated and hence deactivated; similarly, substrates with electron-withdrawing groups are not brominated. The reaction is very tolerant of a variety of functional groups.
- Kajorinne, Jessie K.,Steers, Jennifer C.M.,Merchant, Marnie E.,MacKinnon, Craig D.
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p. 1087 - 1091
(2018/11/25)
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- Synthesis of NHC Pincer Hydrido Nickel Complexes and Their Catalytic Applications in Hydrodehalogenation
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The C(carbene)N(amino)N(amine)-pincer nickel(II) bromides 1a-c were hydrogenated to the corresponding nickel(II) hydrides 2a-c by (EtO)3SiH/NaOtBu or NaBH4. These nickel(II) hydrides 2a-c were characterized by NMR and IR spectroscopy as well as X-ray diffraction. The catalytic performance of complex 2b for hydrodehalogenation reactions was explored. With a combination of 3 mol % catalyst loading, (EtO)3SiH/NaOtBu/toluene/80 °C and different reaction times, organic halides were successfully reduced to the related alkanes. A catalytic radical mechanism is proposed and partially verified by experiments.
- Wang, Zijing,Li, Xiaoyan,Sun, Hongjian,Fuhr, Olaf,Fenske, Dieter
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p. 539 - 544
(2018/03/08)
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- A general electrochemical strategy for the Sandmeyer reaction
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Herein we report a general electrochemical strategy for the Sandmeyer reaction. Using electricity as the driving force, this protocol employs a simple and inexpensive halogen source, such as NBS, CBrCl3, CH2I2, CCl4, LiCl and NaBr for the halogenation of aryl diazonium salts. In addition, we found that these electrochemical reactions could be performed using anilines as the starting material in a one-pot fashion. Furthermore, the practicality of this process was demonstrated in the multigram scale synthesis of aryl halides using highly inexpensive graphite as the electrode. A series of detailed mechanism studies have been performed, including radical clock and radical scavenger study, cyclic voltammetry analysis and in situ electron paramagnetic resonance (EPR) analysis.
- Liu, Qianyi,Sun, Beiqi,Liu, Zheng,Kao, Yi,Dong, Bo-Wei,Jiang, Shang-Da,Li, Feng,Liu, Guoquan,Yang, Yang,Mo, Fanyang
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p. 8731 - 8737
(2018/12/10)
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- Dimethyl sulfoxide-accelerated reductive deamination of aromatic amines with t-BuONO in tetrahydrofuran
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An efficient method for the conversion of aryl amines into arenes by a one-pot reductive deamination has been achieved. It was found the reductive deamination using t-BuONO in tetrahydrofuran could be accelerated by dimethyl sulfoxide and provided the deamination products with good yields under mild conditions. A plausible mechanism is discussed.
- Fang, Lu,Qi, Liang,Ye, Longfei,Pan, Zhentao,Luo, Wenjun,Ling, Fei,Zhong, Weihui
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p. 579 - 583
(2018/11/27)
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- An Additive-Free, Base-Catalyzed Protodesilylation of Organosilanes
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We report an additive-free, base-catalyzed C-, N-, O-, and S-Si bond cleavage of various organosilanes in mild conditions. The novel catalyst system exhibits high efficiency and good functional group compatibility, providing the corresponding products in good to excellent yields with low catalyst loadings. Overall, this transition-metal-free process may offer a convenient and general alternative to current employing excess bases, strong acids, or metal-catalyzed systems for the protodesilylation of organosilanes.
- Yao, Wubing,Li, Rongrong,Jiang, Huajiang,Han, Deman
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p. 2250 - 2255
(2018/02/23)
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- Pd-PEPPSI complexes based on 1,2,4-triazol-3-ylidene ligands as efficient catalysts in the Suzuki—Miyaura reaction
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The palladium complexes of the Pd-PEPPSI type with N-heterocyclic carbenes of the 1,2,4-triazole series were synthesized in 76—99% yields by the reactions of PdCl2 with 1,4-di- alkyl-1,2,4-triazolium salts in pyridine in the presence of KBr or KI as sources of halide ions and tetrabutylammonium salts as phase-transfer catalysts. The obtained complexes can be used as efficient catalysts for the Suzuki—Miyaura cross-coupling and are not inferior to the commercially available Pd-PEPPSI catalysts in activity.
- Chernenko, A. Yu.,Astakhov,Pasyukov,Dorovatovskii,Zubavichus, Ya. V.,Khrustalev,Chernyshev
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- Synthesis of Polyfunctionalized Triaryllanthanum Reagents by Using Ph3La and Related Species as Exchange Reagents
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Ph3La?5 LiCl and the related (m-xylyl)3La?5 LiCl were used as Hal/La exchange reagents (Hal=Br, I) for the preparation of various triaryl- and triheteroaryl-lanthanum derivatives. These new exchange reagents are compatible with isoquinolines and some functional groups such as a nitrile or an ester. The reactivity of the resulting lanthanum compounds towards electrophiles, such as ketones, aldehydes, N,N-dimethylamides, and primary alkyl halides was investigated. Additionally, a Pd-catalyzed cross-coupling procedure with aryl bromides was developed.
- Benischke, Andreas D.,Anthore-Dalion, Lucile,Kohl, Fabien,Knochel, Paul
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supporting information
p. 11103 - 11109
(2018/08/09)
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- "naked" Lithium Cation: Strongly Activated Metal Cations Facilitated by Carborane Anions
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Experimental and spectroscopic studies revealed unprecedented reactivity of a "naked" lithium cation with very weakly coordinating anions, including carborane anions. The superactivated lithium cation has greatly enhanced Lewis acidic character and mediates various organic reactions such as carbonyl-ene reaction, NBS-bromination of unactivated aromatics, and Friedel-Crafts alkylation, which are not promoted by conventional lithium salts. Chemical robustness of the counteranion also plays an important role in the chemistry of the strongly activated lithium cation.
- Kitazawa, Yu,Takita, Ryo,Yoshida, Kengo,Muranaka, Atsuya,Matsubara, Seijiro,Uchiyama, Masanobu
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p. 1931 - 1935
(2017/02/26)
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- Transition-metal-free dehalogenation of aryl halides promoted by phenanthroline/potassium tert-butoxide
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Transition-metal-free dehalogenation of various aryl halides (iodides and bromides) can take place efficiently at 70–110?°C in the presence of a catalytic amount of 1, 10-phenanthroline and t-BuOK using THF or Dioxane as solvent. Control experiments indicated that radical transfer occurred between aryl radical and alkyl C[sbnd]H bond to generate alkyl radical.
- Liu, Wei,Hou, Fanyi
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p. 931 - 937
(2017/01/25)
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- Enhanced photocatalytic dehalogenation of aryl halides by combined poly-p-phenylene (PPP) and TiO2 photocatalysts
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The abundant energy provided by sunlight makes visible-light driven photoredox catalysis an attractive means of performing chemical transformations. Titanium dioxide (TiO2) and conjugated polymers are semiconducting materials that have been used as photoredox catalysts. Driving electron transfer process with photoredox catalysts and visible light has become a powerful method for achieving efficient chemical transformations. However, titanium dioxide does not readily absorb visible light, and conjugated polymers have not been extensively studied as photoredox catalysts for organic transformations. In this work, TiO2 and the conjugated polymer poly-p-phenylene (PPP) were successfully used as heterogeneous co-catalysts for the dehalogenation of some simple aryl halides using triethylamine as a sacrificial electron donor. While PPP alone exhibited some photocatalytic activity upon irradiation with visible light, the efficiency of dehalogenation was enhanced by the addition of titanium dioxide. No reaction was observed in the absence of both photocatalysts or when TiO2 was used as the sole photocatalyst. The optimum operating parameters were examined.
- Petroff II, John T.,Nguyen, Anh H.,Porter, Alex J.,Morales, Fraisher D.,Kennedy, Michael P.,Weinstein, David,Nazer, Hossam El,McCulla, Ryan D.
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p. 149 - 154
(2016/12/07)
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- Quantum Dots in Visible-Light Photoredox Catalysis: Reductive Dehalogenations and C-H Arylation Reactions Using Aryl Bromides
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In the recent past, visible-light-mediated photoredox catalysis has made a huge impact on the development of new synthetic methods under very mild and ecologically benign conditions. Although semiconductor nanocrystals or quantum dots (QDs) possess suitable optoelectronic and redox properties for photoredox catalytic applications, surprisingly, their use for the activation of challenging chemical bonds in the synthesis of organic molecules is little explored. We report here the application of ZnSe/CdS core/shell QDs for the synthetically important photoredox catalytic activation of carbon-halogen bonds in dehalogenation and C-H arylation reactions using (hetero)aryl halides as bench-stable inexpensive bulk starting materials, under very mild reaction conditions. The outstanding catalytic activity of ZnSe/CdS core/shell QDs is a direct consequence of the high specific surface area and homogeneity of QDs in solution and their high photostability toward oxidation.
- Pal, Anuushka,Ghosh, Indrajit,Sapra, Sameer,K?nig, Burkhard
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p. 5225 - 5231
(2017/07/04)
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- One-Pot, Metal-Free Conversion of Anilines to Aryl Bromides and Iodides
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A metal-free synthesis of aryl bromides and iodides from anilines via halogen abstraction from bromotrichloromethane and diiodomethane is described. This one-pot reaction affords aryl halides from the corresponding anilines in moderate to excellent yields without isolation of diazonium salts. The transformation has short reaction times, a simple workup, and insensitivity to moisture and air and avoids excess halogenation. DFT calculations support a SRN1 mechanism. This method represents a convenient alternative to the classic Sandmeyer reaction.
- Leas, Derek A.,Dong, Yuxiang,Vennerstrom, Jonathan L.,Stack, Douglas E.
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supporting information
p. 2518 - 2521
(2017/05/24)
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- Salicylic Acid-Catalyzed One-Pot Hydrodeamination of Aromatic Amines by tert-Butyl Nitrite in Tetrahydrofuran
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A significant acceleration in the hydrodeamination of in situ formed diazonium salts (from aromatic amines) has been observed in the presence of 10-mol% salicylic acid, using tetrahydrofuran as the hydrogen donor. The reaction proceeds efficiently at 20 °C for a wide range of substituted anilines, even at 10-mmol scale, without any other additive. The same protocol has been adapted to the selective deuterodeamination of some aromatic amines. Control experiments clearly show that aryl radicals are involved in the reaction mechanism. (Figure presented.).
- Felipe-Blanco, Diego,Alonso, Francisco,Gonzalez-Gomez, Jose C.
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supporting information
p. 2857 - 2863
(2017/08/23)
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- Acid-promoted metal-free protodeboronation of arylboronic acids
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A facile acid-promoted protodeboronation of arylboronic acids in the absence of metal catalysts or any other additives is described. This protodeboronation is general for a range of arylboronic acids with both electron-donating and electron-withdrawing groups in good to excellent yields under air atmosphere. Density functional theory mechanistic studies showed that the protodeboronation of arylboronic acids followed an intermolecular metathesis via a four-membered ring transition state. The effect of the substituent of arylboronic acids in protodeboronation is also theoretically studied.
- Zhang, Guoqing,Li, Yang,Liu, Jianhui
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p. 34959 - 34962
(2017/07/25)
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- A green organic boron reagent carbon boron key cracking hydrogenation of the new method (by machine translation)
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The invention relates to a kind of green, efficient organic boron reagent carbon boron key cracking hydrogenation of the new method. The method uses a cheap and easily obtained inorganic base as catalyst, common organic alcohol as the reaction solvent and a hydrogen source, is placed under the environment of air can be conveniently catalytic organic boric acid or borate generating carbon boron key cracking hydrogenation reaction, the reaction substrate universality is wide, functional group compatibility outstanding. System realizing metallic catalytic various boric acid and boric acid ester in the fracture of the carbon boron key reaction, also overcome the traditional method requires the use of greatly excessive inorganic alkali, organic acid in great harm to the environment or complex metal catalyst to the limitations of the b-hydrogenation, laboratory preparation and industrial production organoboron reagent of the b-hydrogenation reaction provides a completely new strategy. (by machine translation)
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Paragraph 0024; 0025
(2017/10/09)
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- PROCESS FOR THE PREPARATION OF ORGANIC HALIDES
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The present invention provides a halo-de-carboxylation process for the preparation of organic chlorides, organic bromides and mixtures thereof, from their corresponding carboxylic acids, using a chlorinating agent selected from trichloroisocyanuric acid (TCCA), dichloroisocyanuric acid (DCCA), or combination thereof, and a brominating agent.
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Paragraph 00145
(2017/08/01)
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- Ruthenium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols
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Dehydrogenative decarbonylation of a primary alcohol involves the release of both dihydrogen and carbon monoxide to afford the by one carbon unit shorter product. The transformation has now been achieved with a ruthenium-catalyzed protocol by using the complex Ru(COD)Cl2 and the hindered monodentate ligand P(o-tolyl)3 in refluxing p-cymene. The reaction can be applied to both benzylic and long-chain linear aliphatic alcohols. The intermediate aldehyde can be observed during the transformation, which is therefore believed to proceed through two separate catalytic cycles involving first dehydrogenation of the alcohol and then decarbonylation of the resulting aldehyde.
- Mazziotta, Andrea,Madsen, Robert
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p. 5417 - 5420
(2017/10/06)
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