- Synthesis of B,O,N-Doped Adamantanes and Diamantanes by Condensation of Oximes with Boronic Acids
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Condensation of oximes with boronic acids RB(OH)2 or B(OH)3 affords remarkably stable 2,4,10-trioxa-1,5,7-triaza-3-boroadamantanes via an unprecedented multicomponent process. The mechanism involves the reversible generation of unstable oxime cyclotrimers, which are readily intercepted by boronic acids.
- Golovanov, Ivan S.,Sukhorukov, Alexey Yu.,Nelyubina, Yulia V.,Khomutova, Yulia A.,Ioffe, Sema L.,Tartakovsky, Vladimir A.
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- Structural Induction via Solvent Variation in Assemblies of Triphenylboroxine and Piperazine - Potential Application as Self-Assembly Molecular Sponge
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This study examined the direct effect of solvent on the chemical composition and structure of supramolecular assemblies formed from triphenylboroxine ((PhBO)3) and piperazine (ppz) through N→B bonds. Oxygen-containing solvents with a molecular size smaller than 4.1 ? produce 1D polymeric structures (1:1 boroxine/piperazine) of compositions {(PhBO)3(ppz)}n·nTHF (1a·THF) and {(PhBO)3(ppz)}n·nAcetone (1a·Acetone), in which the boroxine B3O3 rings are linked through N→B bonded piperazine molecules in a cis-conformation. In both cases, a pseudocavity is generated between two polymer chains, which is occupied by a solvent molecule interacting through bifurcated N-H···O···H-N hydrogen bonds with one of the chains. In contrast, oxygen-based solvents with a size larger than 6.3 ? give rise to discrete 2:1 assemblies, {(PhBO)3}2(ppz)·2Ethyl acetate (2·AcOEt) and {(PhBO)3}2(ppz)·2Pentanone (2·Pentanone), with the piperazine molecule bridging two B3O3 rings and interacting with two solvent molecules via N-H···O hydrogen bonds. In chloroform or dichloromethane 2:3 adducts, {(PhBO)3}2(ppz)3·4CHCl3 (3·CHCl3) and {(PhBO)3}2(ppz)3·2.09CH2Cl2 (3·CH2Cl2), were obtained, with N-H···N interactions formed between the piperazine molecules directing the crystal lattice. Finally, unlike with THF and acetone, the presence of two coordination sites in dioxane gives rise to a 1D polymeric 1:1 clathrate-type assembly with trans-conformation, {(PhBO)3(ppz)}n·3.5nDioxane (1b·Dioxane). In accordance with the structural characterization, the thermogravimetric analysis of compounds 1-2 evidenced relatively high decomposition (solvent elimination) temperatures for the inclusion complexes derived from oxygen-containing solvents (Tpeak = 76.4 to 145.4 °C). On the contrary, solvates based on halogenated solvents (3·CHCl3 and 3·CH2Cl2) or 1,4-dioxane started to decompose already at room temperature. In view of potential applications for the storage and structural characterization of volatile or highly reactive reagents, a final inclusion experiment was carried out with racemic 1,2-epoxybutane. As expected, the resulting N→B bonded inclusion complex exhibited a 1:1 cis-polymeric structure, in which the guest molecules were bonded by bifurcated Npip-H···Oepoxy···H-Npip hydrogen bonds.
- Torres-Huerta, Aaron,Velásquez-Hernández, Miriam De Jesús,Martínez-Otero, Diego,H?pfl, Herbert,Jancik, Vojtech
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- Ring expansion reactions of pentaphenylborole with dipolar molecules as a route to seven-membered boron heterocycles
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Reactions of pentaphenylborole with isocyanates, benzophenone, and benzaldehyde produced new seven-membered heterocycles in high yields. For 1-adamantyl isocyanate, a BNC5 heterocycle was obtained from the insertion of the C-N moiety into the five-membered borole, whereas for 4-methoxyphenyl isocyanate, a BOC5 heterocycle was generated from the insertion of the C-O unit. These reactions are believed to occur via a mechanism wherein coordination of the nucleophile to the borole (1-adamantyl, N-coordination or O-coordination for 4-methoxyphenyl) is followed by ring expansion to afford the observed seven-membered heterocycles. The selectivity to form B-O- or B-N-containing heterocycles is based on the polarization of the isocyanate implying tunable reactivity for the system. Having observed that isocyanates react as 1,2-dipoles with pentaphenylborole, we examined benzophenone and benzaldehyde, which both reacted to insert C-O units into the ring. This represents a new efficient method for preparing rare seven-membered boracycles.
- Huang, Kexuan,Martin, Caleb D.
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- Solubility of Phenylboronic Acid and its Cyclic Esters in Organic Solvents
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The solubilities of phenylboronic acid, its pinacol ester and azaester in organic solvents (chloroform, 3-pentanone, acetone, dipropyl ether and methylcyclohexane) have been determined experimentally by a dynamic method, in which the disappearance of turbidity was determined by measuring of light intensity using a luminance probe. Phenylboronic acid has high solubility in ether and ketones, moderate in chloroform and very low in hydrocarbon. Pinacol ester and azaester show better solubility than the parent acid in all tested solvents. For pinacol ester differences between particular solvents are small, while for azaester the differences are significant. For both esters the highest solubility is observed in chloroform and the lowest in the hydrocarbon. The results have been correlated by the Wilson, NRTL and Redlich–Kister equations. For the phenylboronic acid better correlation of the data is obtained by polynomials in comparison with the above equations. It is connected with additional acid-anhydride equilibrium in the system. The influence of polarity of the solvents on the solubility is discussed.
- Leszczyński, Pawe?,Hofman, Tadeusz,Sporzyński, Andrzej
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- Reversible formation of organyl(oxo)boranes (RBO) (R = C6H 5 or CH3) from boroxins ((RBO)3): A matrix isolation study
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Flash vacuum pyrolysis of triphenyl- and trimethylboroxin and subsequent trapping of the gas phase products in a large excess of argon at T 3BO, 1:1 dimer complex of CH3BO, (CH3BO)2, and (CH3BO)3, depends strongly on the trapping temperature and matrix host gas (Ar vs Xe) with the boroxin dominating at 30 K (Ar) or 55 K (Xe). An ab initio investigation (second-order Moller - Plesset perturbation theory) of the potential energy surface for trimerization of CH3BO is in agreement with the experimental observations.
- Bettinger, Holger F.
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- Can triorganoboroxins exist in a "monomeric" R-B=O form? MNDO calculations and ebulliometric molecular weight determination
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MNDO calculations were made for triethylboroxin (EtBO)3 and triphenylboroxin (PhBO)3 using both X-ray determined and optimized geometry of these molecules.The results were compared with hypothetical "monomeric" molecules R-B-O.Calculated energies of trimerization are about -200 kJ mol-1 for both compounds and confirm the much higher stability of the "trimer".Ebulliometric determination of molecular weight of triphenylboroxin in 2-pentanone confirms its trimeric character. Key words: Boroxin; MNDO calculations
- Sporzynski, Andrzej,Szatylowicz, Halina
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- Bimetallic zirconium heterocycles supported by boron-oxygen ligands
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Reaction between bis(cyclopentadienyl)dimethylzirconium, ZrCp2(CH3)2, and phenylboronic anhydride, (PhBO)3, resulted in the formation of the heterocyclic dimer [ZrCp2{μ-O2BPh}]2 (1); no reaction was observed with the mesityl derivative, (mesBO)3. Compound 1 was also synthesized from the protonolysis reaction between ZrCp2-(CH3)2 and in situ generated phenylboronic acid, PhB(OH)2. This approach was extended to afford the analogous complexes [ZrCp2{μ-O2BAr}]2 (2, Ar = mes; 3, Ar = C6F5) from the corresponding isolable arylboronic acids, ArB(OH)2. The molecular structures of 1-3, determined by X-ray diffraction techniques, revealed a common, dimeric motif consisting of a central "Zr2B2O4" metallacycle. Variations in the bond parameters within the heterocycle are attributed to the differing steric and electronic properties of the aryl substituents at boron.
- Balkwill, Jessica E.,Cole, Sarah C.,Coles, Martyn P.,Hitchcock, Peter B.
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- Dehydration of phenylboronic acid to boroxine catalyzed by Aun nanoclusters with atom packing core-shell structure
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Atomically precise Aun nanoclusters (n = number of gold atom in cluster) ideally composed of an exact number of gold atoms have unique core-shell structure and non-metallic electronic properties. The extremely small size of Au25 and Au38 nanoclusters induces a large energy gap in their electronic structures, which gives rise to unprecedented catalytic activity in some chemical reactions. Here we report dehydration of phenylboronic acid to boroxine with small Au25 and Au38 nanocluster catalysts, respectively. Especially, Au25 nanocluster is arranged with Au13 icosahedral core capped by twelve gold atoms as an exterior shell. Au38 nanocluster is a face-fused biicosahedral Au 23 core encapsulated by a shell comprised of fifteen gold atoms. Au38 nanoclusters exhibit higher activity than Au25 nanoclusters. This study is an attempt to provide a powerful tool for the catalyst design and to gain a further insight into the correlation of structural properties with catalytic properties. Copyright
- Huang, Ping,Jiang, Zhi,Chen, Guoxiang,Zhu, Yan,Sun, Yuhan
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- Increments for 1H and 13C NMR chemical shifts in areneboronic acids
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A series of areneboronic acids were studied by NMR spectroscopy. Increments for the 1H and 13C chemical shifts caused by the boronic acid substituent B(OH)2 in areneboronic acids were determined. Copyright
- Bruns, Stefan,Sinnwell, Volker,Voss, Juergen
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- Reductive Alkylation of Quinolines to N-Alkyl Tetrahydroquinolines Catalyzed by Arylboronic Acid
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A boronic acid catalyzed one-pot tandem reduction of quinolines to tetrahydroquinolines followed by reductive alkylation by the aldehyde has been demonstrated. This step-economcial synthesis of N-alkyl tetrahydroquinolines has been achieved directly from readily available quinolines, aldehydes, and Hantzsch ester under mild reaction conditions. The mechanistic study demonstrates the unique behavior of organoboron catalysts as both Lewis acids and hydrogen-bond donors.
- Adhikari, Priyanka,Bhattacharyya, Dipanjan,Nandi, Sekhar,Kancharla, Pavan K.,Das, Animesh
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supporting information
p. 2437 - 2442
(2021/04/05)
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- METHOD FOR SYNTHESIZING ORGANIC MAGNESIUM COMPOUND, METHOD FOR SYNTHESIZING ORGANIC BORONIC ACID COMPOUND, AND COUPLING METHOD
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An object is to establish a technology with which an organic magnesium compound can be easily and efficiently synthesized at a low cost with few steps that do not involve a complex chemical method. A method for synthesizing an organic magnesium compound includes, in a reaction solvent, reacting an organic halide represented by General Formula I (Ra—Xa) with a dispersion product obtained by dispersing sodium in a dispersion solvent to obtain an organic sodium compound represented by General Formula II (Ra—Na), and reacting the obtained organic sodium compound with a magnesium halide represented by General Formula III (Mg—(Xb)2) to obtain an organic magnesium compound represented by General Formula IV (Ra—Mg—Xb).
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Paragraph 0016; 0085-0087
(2021/03/13)
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- Structural requirements of 1-(2-pyridinyl)-5-pyrazolones for disproportionation of boronic acids
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We observed an unusual formation of four-coordinate boron(III) complexes from the reaction of 1-(2-pyridinyl)-5-pyrazolone derivatives with arylboronic acids in the basic media. The exact mechanism is not clear; however, the use of unprotected boronic acid and the presence of a bidentate ligand appeared to be the key structural requirements for the transformation. The results suggest that base-promoted disproportionation of arylboronic acid with the assistance of the [N,O]-bidentate ligation of 1-(2-pyridinyl)-5-pyrazolone should take place and facilitate the formation of pyrazole di-arylborinate. Experiments to obtain a deeper understanding of its mechanism are currently underway.
- Bae, Yunsoo,Cho, Joungmo,Han, Yohan,Lee, Hwajeong,Lee, Kee-In,Sadu, Venkata Subbaiah
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- Synthesis of Boroxine and Dioxaborole Covalent Organic Frameworks via Transesterification and Metathesis of Pinacol Boronates
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Boroxine and dioxaborole are the first and some of the most studied synthons of covalent organic frameworks (COFs). Despite their wide application in the design of functional COFs over the last 15 years, their synthesis still relies on the original Yaghi's condensation of boronic acids (with itself or with polyfunctional catechols), some of which are difficult to prepare, poorly soluble, or unstable in the presence of water. Here, we propose a new synthetic approach to boroxine COFs (on the basis of the transesterification of pinacol aryl boronates (aryl-Bpins) with methyl boronic acid (MBA) and dioxaborole COFs (through the metathesis of pinacol boronates with MBA-protected catechols). The aryl-Bpin and MBA-protected catechols are easy to purify, highly soluble, and bench-stable. Furthermore, the kinetic analysis of the two model reactions reveals high reversibility (Keq ~1) and facile control over the equilibrium. Unlike the conventional condensation, which forms water as a byproduct, the byproduct of the metathesis (MBA pinacolate) allows for easy kinetic measurements of the COF formation by conventional 1H NMR. We show the generality of this approach by the synthesis of seven known boroxine/dioxaborole COFs whose crystallinity is better or equal to those reported by conventional condensation. We also apply metathesis polymerization to obtain two new COFs, Py4THB and B2HHTP, whose synthesis was previously precluded by the insolubility and hydrolytic instability, respectively, of the boronic acid precursors.
- Hamzehpoor, Ehsan,Jonderian, Antranik,McCalla, Eric,Perepichka, Dmitrii F.
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supporting information
p. 13274 - 13280
(2021/09/07)
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- Room Temperature Coupling of Aryldiazoacetates with Boronic Acids Enhanced by Blue Light Irradiation
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A visible-light-promoted photochemical protocol is reported for the coupling of aryldiazoacetates with boronic acids. This photochemical reaction shows great enhancement compared to the same protocol performed in the absence of light. Except for a few cases, the room temperature coupling in the dark (thermal process) generally does not work. When it does, it is likely to also involve free carbenes as key intermediates. Alternatively, photochemical reactions show a broad scope, can be performed under air and tolerate a wide variety of functional groups. Reaction-evolution monitoring, DFT calculations and control experiments have been used to evaluate the main aspects of this intricate mechanistic scenario. Biologically active molecules Adiphenine, Benactyzine and Aprophen have been prepared as examples of synthetic applications.
- da Silva, Amanda F.,Afonso, Marco A. S.,Cormanich, Rodrigo A.,Jurberg, Igor D.
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supporting information
p. 5648 - 5653
(2020/04/22)
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- Synthesis method of triphenoxycyclotritriboroxane
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The invention relates to a synthesis method of triphenoxycyclotritriboroxane, belonging to the technical field of additives for battery electrolytes. The synthesis method comprises the following steps: with phenol and borane dimethyl sulfide as raw materials, adding borane dimethyl sulfide into tetrahydrofuran, and adding phenol and water in an argon atmosphere; then adding anhydrous toluene and 2-methylpyridine mesylate into a mixture obtained in the previous step under the condition of argon flow; conducting mixing for 5 to 10 min, and performing reacting for 30 to 40 min at a temperature of70 to 90 DEG C under a hermetic condition; then performing vacuumizing to a vacuum degree of 0.5 to 0.6 mmHg, and removing volatile matters; conducting complete vacuumization, and carrying out reacting for 10 to 15 min at a temperature of 70 to 90 DEG C under a vacuum state; and performing concentrating, drying, and cooling to room temperature so as to obtain the triphenoxycyclotritriboroxane. The synthesis method is simple, used raw materials are easy to obtain, synthesis time is greatly shortened, industrial production efficiency is improved, the synthesized triphenoxycyclotritriboroxane ishigh in purity, and the yield of the triphenoxycyclotritriboroxane can reach 80%.
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Paragraph 0016-0028
(2020/11/22)
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- Functionalization of the Imidazole Backbone by Means of a Tailored and Optimized Oxidative Heck Cross-Coupling
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A general and selective Pd-catalyzed cross-coupling of aromatic boronic acids with vinyl-imidazoles is disclosed. Unlike most cross-coupling reactions, this method operates well in absence of bases avoiding the formation of by-products. The reactivity is highly enhanced by the presence of nitrogen-based ligands, in particular bathocuproine. The method involves MnO2 as oxidant for the oxidation Pd (0)→Pd (II), a much weaker oxidant than previously reported in the literature. This allows for the use of reactants that possess a multitude of functional groups. A scope and limitation study involving a series of 24 boronic acids, whereof 18 afforded TMs in yields in the range 41–95%. The disclosed method constitutes the first general method for the oxidative Heck cross-coupling on the imidazole scaffold, which moreover operates with a selection of other heterocycles. (Figure presented.).
- Cirillo, Davide,Angelucci, Francesco,Bj?rsvik, Hans-René
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p. 5079 - 5092
(2020/09/23)
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- Sequential C-S and S-N Coupling Approach to Sulfonamides
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A one-pot three-component reaction involving nitroarenes, (hetero)arylboronic acids, and potassium pyrosulfite leading to sulfonamides was described. A broad range of sulfonamides bearing different reactive functional groups were obtained in good to excellent yields through sequential C-S and S-N coupling that does not require metal catalysts.
- Chen, Kai,Chen, Wei,Han, Bing,Chen, Wanzhi,Liu, Miaochang,Wu, Huayue
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supporting information
p. 1841 - 1845
(2020/03/04)
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- A carrier-free and recyclable protocol for the cross-coupling of terminal alkynes with arylboronic acids in H2O/TBAB
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A new and recyclable protocol was developed for Pd(OAc)2-catalyzed the cross-coupling reaction of terminal alkynes with arylboronic acids using environmentally friendly H2O/TBAB as reaction medium. A series of cross-coupling products containing internal acetylenic bond can be obtained with good selectivity and yield. The Pd(OAc)2/H2O/TBAB system was stable in the Sonogashira-type cross-coupling reaction and could be used at least three cycles without considerable decrease in catalytic performance. The results suggest that the unsupported and recyclable systems can be extended to the other realm of C&C bond formation in synthetic organic chemistry.
- Tang, Bo-Xiao,Kuang, Ren-Yun,Wen, Ji-Wu,Huang,Zhang, Zhen-Xing,Shen, Yu-Jun,Chen, Jia-Ping,Wu, Wen-Ying
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p. 1975 - 1977
(2019/07/03)
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- Nickel-Catalyzed Directed Hydroarylation of Alkynes with Boronic Acids
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A regio- and stereoselective nickel-catalyzed hydroarylation of alkynes using propargylic carbamates as directing groups has been developed. The reaction proceeds under mild reaction conditions using arylboronic acids in the absence of base. A range of heterocycles and functional groups are tolerated under the reaction conditions, providing high yields of trisubstituted alkenes with control of olefin geometry.
- Hanna, Luke E.,Konev, Mikhail O.,Jarvo, Elizabeth R.
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supporting information
p. 184 - 187
(2018/12/05)
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- Copper-mediated anomeric: O -arylation with organoboron reagents
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Copper-mediated couplings of arylboroxines with glycosyl hemiacetals furnish O-aryl glycosides via Csp2-O bond formation. The method enables the anomeric O-arylation of protected pyranose and furanose derivatives, and is tolerant of functionalized arylboroxine partners. Whereas mixtures of anomers are formed from glucopyranose, galactopyranose and arabinofuranose hemiacetals, the α-anomer is generated selectively from mannopyranose and mannofuranose-derived substrates.
- Dimakos, Victoria,Liu, Jacklyn J. W.,Ge, Zhenlu,Taylor, Mark S.
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supporting information
p. 5671 - 5674
(2019/06/18)
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- A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations
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Background: Silicon rhodamines are of particular interest because of their advantageous dye properties (fluorescence- and biostability, quantum efficiency, tolerance to photobleaching). Therefore, silicon rhodamines find frequent application in STED (stimulated emission depletion) microscopy, as sensor molecules for, e.g., ions and as fluorophores for the optical imaging of tumors. Different strategies were already employed for their synthesis. Because of just three known literature examples in which Suzuki–Miyaura cross couplings gave access to silicon rhodamines in poor to moderate yields, we wanted to improve these first valuable experimental results. Results: The preparation of the xanthene triflate was enhanced and several boron sources were screened to find the optimal coupling partner. After optimization of the palladium catalyst, different substituted boroxines were assessed to explore the scope of the Pd-catalyzed cross-coupling reaction. Conclusions: A number of silicon rhodamines were synthesized under the optimized conditions in up to 91% yield without the necessity of HPLC purification. Moreover, silicon rhodamines functionalized with free acid moieties are directly accessible in contrast to previously described methods.
- Kanagasundaram, Thines,Timmermann, Antje,Kramer, Carsten S.,Kopka, Klaus
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supporting information
p. 2569 - 2576
(2019/12/11)
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- Asymmetric Catalysis in Liquid Confinement: Probing the Performance of Novel Chiral Rhodium–Diene Complexes in Microemulsions and Conventional Solvents
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The role of liquid confinement on the asymmetric Rh catalysis was studied using the 1,2-addition of phenylboroxine (2) to N-tosylimine 1 in the presence of [RhCl(C2H4)2]2 and chiral diene ligands as benchmark reaction. To get access to Rh complexes of different polarity, enantiomerically pure C2-symmetric p-substituted 3,6-diphenylbicyclo[3.3.0]octadienes 4 and diastereomerically enriched unsymmetric norbornadienes 5 and 6 carrying either the Evans or the SuperQuat auxiliary were synthesized. A microemulsion containing the equal amounts of H2O/KOH and toluene/reactants was formulated using the hydrophilic sugar surfactant n-octyl β-d-glucopyranoside (C8G1) to mediate the miscibility between the nonpolar reactants and KOH, needed to activate the Rh–diene complex. Prominent features of this organized reaction medium are its temperature insensitivity as well as the presence of water and toluene-rich compartments with a domain size of 55 ? confirmed by small-angle X-ray scattering (SAXS). Although bicyclooctadiene ligands 4 a,b,e performed equally well under homogeneous and microemulsion conditions, ligands 4 c,d gave a different chemoselectivity. For norbornadienes 5, 6, however, microemulsions markedly improved conversion and enantioselectivity as well as reaction rate, as was confirmed by kinetic studies using ligand 5 b.
- Deimling, Max,Kirchhof, Manuel,Schwager, Barbara,Qawasmi, Yaseen,Savin, Alex,Mühlh?user, Tina,Frey, Wolfgang,Claasen, Birgit,Baro, Angelika,Sottmann, Thomas,Laschat, Sabine
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p. 9464 - 9476
(2019/07/04)
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- Kinetics and Mechanism of the Palladium-Catalyzed Oxidative Arylating Carbocyclization of Allenynes
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Pd-catalyzed C-C bond-forming reactions under oxidative conditions constitute a class of important and widely used synthetic protocols. This Article describes a mechanistic investigation of the arylating carbocyclization of allenynes using boronic acids and focuses on the correlation between reaction conditions and product selectivity. Isotope effects confirm that either allenic or propargylic C-H activation occurs directly after substrate binding. With an excess of H2O, a triene product is selectively formed via allenic C-H activation. The latter C-H activation was found to be turnover-limiting and the reaction zeroth order in reactants as well as the oxidant. A dominant feature is continuous catalyst activation, which was shown to occur even in the absence of substrate. Smaller amounts of H2O lead to mixtures of triene and vinylallene products, where the latter is formed via propargylic C-H activation. The formation of triene occurs only in the presence of ArB(OH)2. Vinylallene, on the other hand, was shown to be formed by consumption of (ArBO)3 as a first-order reactant. Conditions with sub-stoichiometric BF3·OEt2 gave selectively the vinylallene product, and the reaction is first order in PhB(OH)2. Both C-H activation and transmetalation influence the reaction rate. However, with electron-deficient ArB(OH)2, C-H activation is turnover-limiting. It was difficult to establish the order of transmetalation vs C-H activation with certainty, but the results suggest that BF3·OEt2 promotes an early transmetalation. The catalytically active species were found to be dependent on the reaction conditions, and H2O is a crucial parameter in the control of selectivity.
- Bartholomeyzik, Teresa,Pendrill, Robert,Lihammar, Richard,Jiang, Tuo,Widmalm, G?ran,B?ckvall, Jan-E.
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supporting information
p. 298 - 309
(2018/01/17)
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- Rhodium-Catalyzed Enantioposition-Selective Hydroarylation of Divinylphosphine Oxides with Aryl Boroxines
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The rhodium-catalyzed hydroarylation of divinylphosphine oxides (RP(O)(CH=CH2)2) with aryl boroxines ((ArBO)3) gives the corresponding monoarylation products (RP(O)(CH=CHAr)CH2CH3) in high yields. One of the two vinyl groups in the phosphine oxide undergoes oxidative arylation while the other one is reduced to an ethyl moiety. These reactions proceed with high selectivity in terms of the enantiotopic vinyl groups in the presence of (R)-DTBM-segphos/Rh to give the P-stereogenic monoarylation products with high enantioselectivity.
- Wang, Zhe,Hayashi, Tamio
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supporting information
p. 1702 - 1706
(2018/02/06)
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- Catalytic and Enantioselective Diels-Alder Reactions of (E)-4-Oxopent-2-enoates
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Novel oxazaborolidines activated by the strong acid triflimide or AlBr3 form cationic chiral catalysts. These are effective catalysts for highly regio- and enantioselective Diels-Alder reactions using substituted (E)-4-oxopent-2-enoates as dienophiles.
- Zhang, Su-Lei,Lu, Yong,Li, Yuan-He,Wang, Kuang-Yu,Chen, Jia-Hua,Yang, Zhen
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supporting information
p. 3986 - 3989
(2017/08/14)
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- Highly Enantioselective Ferrocenyl Palladacycle-Acetate Catalysed Arylation of Aldimines and Ketimines with Arylboroxines
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Benzylic N-substituted stereocenters constitute a frequent structural motif in drugs. Their highly enantioselective generation is hence of technical importance. An attractive strategy is the arylation of imines with organoboron reagents. Chiral Rh complexes have reached a high level of productivity for this reaction type. In this article we describe that an electron rich PdIIcatalyst also performs well in the arylation of aldimines, comparable to the best Rh catalysts. The ferrocenyl palladacycle-acetate catalyst allows for a broad substrate scope and very high enantioselectivities. Commonly observed side reactions like aryl–aryl homocouplings and imine hydrolysis could be blocked. Mechanistic studies implicate that a) the acetate ligand is crucial for transmetallation, b) the active catalyst is most likely a palladacycle-OAc monomer, c) the rate limiting step is probably the product release. By added KOAc the arylation could also be applied to ketimines.
- Schrapel, Carmen,Frey, Wolfgang,Garnier, Delphine,Peters, René
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supporting information
p. 2448 - 2460
(2017/02/23)
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- Unveiling the role of boroxines in metal-free carbon-carbon homologations using diazo compounds and boronic acids
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By means of computational and experimental mechanistic studies the fundamental role of boroxines in the reaction between diazo compounds and boronic acids was elucidated. Consequently, a selective metal-free carbon-carbon homologation of aryl and vinyl boroxines using TMSCHN2, giving access to TMS-pinacol boronic ester products, was developed.
- Bomio, Claudio,Kabeshov, Mikhail A.,Lit, Arthur R.,Lau, Shing-Hing,Ehlert, Janna,Battilocchio, Claudio,Ley, Steven V.
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p. 6071 - 6075
(2017/08/29)
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- Palladium(II)-Catalyzed Enantioselective Synthesis of α-(Trifluoromethyl)arylmethylamines
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We describe a method for the synthesis of α-(trifluoromethyl)arylmethylamines that consists of the palladium(II)-catalyzed addition of arylboroxines to imines derived from trifluoroacetaldehyde. Palladium acetate is used as a catalyst with electron-neutral or electron-rich arylboroxines, and it was found that addition of an ammonium or silver salt was crucial to promote the reaction of electron-poor boroxines. With (S)-t-Bu-PyOX as the chiral ligand, this method delivers a variety of α-trifluoromethylated amines in 57-91% yield and with greater than 92% ee in most cases.
- Johnson, Thomas,Luo, Bo,Lautens, Mark
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p. 4923 - 4930
(2016/07/06)
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- Rhodium-Catalyzed Asymmetric Arylation/Defluorination of 1-(Trifluoromethyl)alkenes Forming Enantioenriched 1,1-Difluoroalkenes
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The reaction of 1-(trifluoromethyl)alkenes (CF3CH=CHR) with arylboroxines (ArBO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral 1,1-difluoroalkenes (CF2=CHC?HArR) with high enantioselectivity (≥95% ee). The reaction is assumed to proceed through β-fluoride elimination of a β,β,β-trifluoroalkylrhodium intermediate that is generated by arylrhodation of the 1-(trifluoromethyl)alkene.
- Huang, Yinhua,Hayashi, Tamio
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supporting information
p. 12340 - 12343
(2016/10/07)
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- Palladium Nanoparticles Supported on Zirconium Metal Organic Framework as an Efficient Heterogeneous Catalyst for the Suzuki-Miyaura Coupling Reaction
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Nanoparticles of zirconium metal organic framework UiO-66 (about 100 nm) have been used as proper supports for Pd nanoparticles. Highly dispersed Pd nanoparticles (about 3-15 nm) were deposed on activated UiO-66 metal organic framework using simple wet impregnation method at room temperature. UiO-66 and the supported Pd nanoparticles (Pd/UiO-66) were characterized by X-ray diffraction, N2 sorption, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy. Investigation of the catalytic performance of Pd/UiO-66 showed that the synthetic nanocomposites can effectively catalyze the Suzuki-Miyaura cross-coupling reaction of benzeneboronic acid with different aryl halides under mild reaction conditions using environmentally benign solvents. In addition, the stability and reusability of the catalyst were studied during the catalytic reaction and it is worth noting that the structure of Pd/UiO-66 catalyst remains intact during the catalytic reaction and the catalyst can be recycled four times without significant decrease in its catalytic activity.
- Pourkhosravani,Dehghanpour,Farzaneh
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p. 499 - 508
(2016/02/23)
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- The Influence of the Nature of the Support on the Copper-Palladium Catalysed Suzuki-Miyaura-Coupling
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Copper-palladium bimetallic catalysts supported on mixed oxides (MgO)0.75(Al2O3)0.25 (MgAlO) were prepared with two step impregnation (TSI) and co-impregnation (CI). These materials were studied to determine the effect of the support on the activity and stability in the Suzuki-Miyaura reaction and on the properties of a catalyst. The catalyst prepared by CI was active and selective during 6 catalytic cycles in Suzuki coupling, whereas the activity of the catalyst prepared with TSI dropped at the sixth use. The kinetics of the reaction was examined along with its scope. The relationship between the basic properties of the support and the catalytic performances were examined too. The importance of the nature of the support was also studied by catalyst characterization methods. (Chemical Equation Presented).
- Fodor, Anna,Hell, Zoltán,Pirault-Roy, Laurence
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p. 596 - 608
(2016/02/26)
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- Oxidative Heck desymmetrisation of 2,2-disubstituted cyclopentene-1,3-diones
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Oxidative Heck couplings have been successfully developed for 2,2-disubstituted cyclopentene-1,3-diones. The direct coupling onto the 2,2-disubstituted cyclopentene-1,3-dione core provides a novel expedient way of enantioselectively desymmetrising all-carbon quaternary centres. This journal is
- Walker,Lamb,Beattie,Nikodemiak,Lee
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supporting information
p. 4089 - 4092
(2015/03/30)
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- Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines
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The reaction of racemic diarylmethylamines, (Ar1Ar2CHNR2), where Ar1 is substituted with a 2-hydroxy group, with arylboroxines (Ar3BO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar1Ar2CH?Ar3) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through o-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents.
- Huang, Yinhua,Hayashi, Tamio
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supporting information
p. 7556 - 7559
(2015/07/01)
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- Direct Amidation of N-Boc- and N-Cbz-Protected Amines via Rhodium-Catalyzed Coupling of Arylboroxines and Carbamates
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N-Boc- and N-Cbz-protected amines are directly converted into amides by a novel rhodium-catalyzed coupling of arylboroxines and carbamates, replacing the traditional two-step deprotection-condensation sequence. Both protected anilines and aliphatic amines are efficiently transformed into a wide variety of secondary benzamides, including sterically hindered and electron-deficient amides, as well as in the presence of acid-labile and reducible functional groups.
- Lim, Diane S. W.,Lew, Tedrick T. S.,Zhang, Yugen
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supporting information
p. 6054 - 6057
(2016/01/09)
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- Vibrational properties of boroxine anhydride and boronate ester materials: Model systems for the diagnostic characterization of covalent organic frameworks
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The vibrational characteristics of 28 different boronic acid, boroxine anhydride, and boronate ester species have been systematically investigated using a combination of experimental infrared (IR) spectroscopy and computational modeling. IR bands characteristic to each boron-containing functionality have been categorized and assigned in conjunction with density functional theory (B3LYP/6-31G(d)), with the aim of better understanding and distinguishing the vibrational characteristics of covalent organic frameworks (COFs) built from boronic acids. In several cases, vibrational assignments differ from those previously reported in the literature on boronic acid-based COFs. Vibrations commonly regarded as diagnostic for one functionality are found in regions of the IR spectrum where other functionalities also show characteristic peaks. The collective experimental and computational results reveal that several alternative bands in the IR region can be used to more diagnostically distinguish between boronic acid, boroxine anhydride, and boronate ester species. The results presented herein provide the tools for straightforward characterization of boroxine anhydride and boronate ester species using IR spectroscopy. The results can be applied to additional theoretical studies of larger COF-like assemblies as well as the analysis of other boronic-acid-based materials.
- Smith, Merry K.,Northrop, Brian H.
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p. 3781 - 3795
(2014/07/08)
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- Enantioselective, nickel-catalyzed suzuki cross-coupling of quinolinium ions
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Quinolinium ions are engaged in an asymmetric, Ni-catalyzed Suzuki cross-coupling to yield 2-aryl- and 2-heteroaryl-1,2-dihydroquinolines. Key to the development of this method is the use of a Ni(II) precatalyst that activates without the need for strong reductants or high temperatures. The Ni-iminium activation mode is demonstrated as an exceptionally mild pathway to generate enantioenriched products from racemic starting materials.
- Shields, Jason D.,Ahneman, Derek T.,Graham, Thomas J. A.,Doyle, Abigail G.
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supporting information
p. 142 - 145
(2014/01/23)
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- Boroxine nanotubes: Moisture-sensitive morphological transformation and guest release
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Boroxines, (R-BO)3, which can be easily synthesized via a dehydration reaction of boronic acids, R-B(OH)2, selectively self-assemble in toluene into nanofibers, nanorods, nanotapes, and nanotubes, depending on the aromatic substituent (R). Spectroscopic measurements show that the nanotube consists of a J-aggregate of the boroxine. Humidification converts the morphology from the nanotube to a sheet as a result of the hydrolysis of the boroxine components and subsequent molecular-packing rearrangement from the J-aggregate to an H-aggregate. Such a transformation leads to the compulsive release of guest molecules encapsulated in the hollow cylinder of the nanotube. The hydrolysis and the molecular-packing rearrangement described above are suppressed by coordination of pyridine to the boron atom, with the resulting moiety acting as a Lewis acid of the boroxine component. The pyridine-coordinated nanotube is transformed into a helical coil by humidification. Guest release during the nanotube-to-helical-coil transformation is much slower than during the nanotube-to-sheet transformation, but faster than from a nanotube that did not undergo morphological transformation. The storage and release of guest molecules from the boroxine nanotubes can be precisely controlled by adjusting the moisture level and the concentration of Lewis bases, such as amines. Self-assembly of boroxines in toluene produce various nanostructures, including nanotubes, depending on the boroxines' aromatic substituents. Humidification-induced morphological transformations from nanotubes to sheets or helical coils are observed, accompanied by the hydrolysis of the boroxine components and a molecular-packing rearrangement from J- to H-aggregates. These morphological changes enable the precisely controlled release of guest molecules encapsulated in the nanotubes' hollow cylinders.
- Ishikawa, Kazuyuki,Kameta, Naohiro,Masuda, Mitsutoshi,Asakawa, Masumi,Shimizu, Toshimi
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p. 603 - 609
(2014/03/21)
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- Coupling of boronic acids with amines in the presence of a supported copper catalyst
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An efficient heterogeneous catalytic method was developed for Chan-Lam reaction, coupling of amines and boronic acid. Copper on 4 A molecular sieve provided yields comparable to the methods published. The method provides the main advantages of a heterogeneous catalytic procedure, the preparation of the catalyst is easy, the workup of the reaction mixture is simple. Graphical abstract: [Figure not available: see fulltext.]
- Debreczeni, Nora,Fodor, Anna,Hell, Zoltan
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p. 1547 - 1551,5
(2014/11/12)
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- Cu(I) metal organic framework catalyzed C-C and C-N coupling reactions
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DABCO (1,4-diazabicyclo[2.2.2]octane) based Cu(I) metal organic framework (here after represented as Cu(I)-MOF) catalyzed Sonogashira cross-coupling reaction of iodobenzene and phenylacetylene was conducted smoothly to afford diphenylacetylene in excellent yield under N2atmosphere. For comparative study, piperidine based Cu(I) clusters were also investigated. Among these catalysts, Cu(I)-MOF exhibited higher activity with good selectivity for the C-C cross-coupled product. Cu(I) catalysts investigated in this study exhibited similar activity in the C-C homo-coupling reaction of phenylacetylene in O2atmosphere. Application of these catalysts was extended in the C-N coupling reactions between phenylboronic acid and aromatic/aliphatic/heterocyclic amines. Cu(I)-MOF can be readily recovered from the reaction mixture and reused for several cycles without loss in the catalytic activity.
- Rani, Poonam,Srivastava, Rajendra
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p. 5256 - 5260
(2015/01/16)
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- Copper(II)- and palladium(II)-modified molecular sieve, a reusable catalyst for the Suzuki-Miyaura-coupling
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Copper-palladium bimetallic catalysts supported on 4 ? molecular sieve were prepared with two step impregnation (TSI) and co-impregnation (CI). These materials were studied to determine the importance of the preparation method, the interaction between the Cu-Pd particles, the activity, selectivity and stability in Suzuki-Miyaura reaction. The key-role of the preparation method in the composition of the metal species on the surface of the support was pointed out with catalyst characterisation methods (ICP, BET, XRD, TEM, EDS and TPR). The relationship between the properties of surface material and the catalytic performance and stability were examined too. The two metals (Cu, Pd) were brought to close interaction on the surface of the support. A correlation between these interactions and improvement of stability were found and proven with surface analysis methods. We found that a Cu-Pd alloy with atom ratio 1:1 is responsible for the catalytic activity. Our catalyst TSI was active and selective during six catalytic cycles in Suzuki coupling, whilst the activity of the catalyst prepared with CI dropped after the sixth use. This loss was due to the absence of Cu-Pd 1:1 alloy and the growth of the particle size.
- Fodor, Anna,Hell, Zoltán,Pirault-Roy, Laurence
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- Rhodium-catalyzed asymmetric hydroarylation of 3-pyrrolines giving 3-arylpyrrolidines: Protonation as a key step
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A hydroxorhodium complex coordinated with (R)-segphos was found to catalyze the hydroarylation of 3-pyrrolines with arylboroxines under neutral conditions to give 3-arylpyrrolidines with high enantioselectivity in high yields.
- So, Chau Ming,Kume, Satoshi,Hayashi, Tamio
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supporting information
p. 10990 - 10993
(2013/08/23)
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- Programmed selective sp2 C-O bond activation toward multiarylated benzenes
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A variety of important multiarylated benzenes were efficiently synthesized from phloroglucinol derivatives 1 through sequential cross-couplings via Pd-catalyzed C-OTs, Ni-catalyzed C-OC(O)NEt2, and C-OMe bond activation. High selectivity was achieved based on the rational design and inherent diversity in the reactivity of different C-O bonds.
- Zhao, Fei,Zhang, Yun-Fei,Wen, Jing,Yu, Da-Gang,Wei, Jiang-Bo,Xi, Zhenfeng,Shi, Zhang-Jie
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supporting information
p. 3230 - 3233
(2013/07/26)
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- Palladium(II)-catalyzed enantioselective synthesis of α- (trifluoromethyl)arylmethylamines
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Trifluoromethylacetaldimines, generated in situ from the corresponding N,O-acetals, undergo 1,2-addition of arylboroxines under palladium(II) catalysis to generate a variety of α-(trifluoromethyl)arylmethylamines with good to high enantioselectivity (up to 97% ee). The pyridine-oxazolidine (PyOX) class of ligands was found to be particularly suitable for this transformation, which proceeds without exclusion of ambient air and moisture.
- Johnson, Thomas,Lautens, Mark
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supporting information
p. 4043 - 4045
(2013/09/12)
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- Enantioselective one-pot catalytic synthesis of 4,5-epoxy-3-alkanols and 1-Phenyl-2,3-epoxy-1-alkanols from α,β-unsaturated aldehydes
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Conformationally restricted perhydrobenzoxazines have been demonstrated to be good chiral ligands for one-pot asymmetric ethylation/epoxidation, and the unprecedented arylation/epoxidation of trisubstituted α,β-unsaturated aldehydes. The scope of the reaction has been studied and a wide set of substrates with allylic strain of different nature has been explored, obtaining good or total diastereoselectivities in all cases. The enantiocontrol was good or high for the ethylation/epoxidation reaction, whereas it remained at moderate or good levels for the arylation/epoxidation. The reaction is general for trisubstituted enals, and alkylic and aromatic substituents are tolerated at both the α- and β-position of the unsaturated aldehyde; however, disubstituted enals remain challenging substrates. When the one-pot and two-pot protocols were compared, no significant differences concerning the stereocontrol were found, so the advantages of the one-pot procedure are clear. Copyright
- Infante, Rebeca,Hernandez, Yulan,Nieto, Javier,Andres, Celia
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p. 4863 - 4869
(2013/08/23)
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- Scalable synthesis of oxazolones from propargylic alcohols through multistep palladium(II) catalysis: β-selective oxidative heck coupling of cyclic sulfonyl enamides and aryl boroxines
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A whale of a scale: The title oxidative Heck coupling proceeded with unusual β selectivity to generate a variety of branched substituted oxazolones (see scheme; Ts=p-toluenesulfonyl). The three-step synthesis from readily available starting materials with a simple palladium catalyst and inexpensive reagents could be carried out in a single reaction vessel or scaled up for the preparation of large amounts of these amino acid precursors. Copyright
- Alamsetti, Santosh Kumar,Persson, Andreas K. A.,Jiang, Tuo,Baeckvall, Jan-E.
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supporting information
p. 13745 - 13750
(2014/01/06)
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- Synthesis of tellurasila cycles containing an annelated dicarba-closo-dodecaborane(12) unit: Structure of a 1,4-ditellura-2,3- disilacyclohexane derivative
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Insertion of tellurium into C-Li bonds of dilithiated 1,2-dicarba-closo- dodecaborane(12) gave 1,2-dicarba-closo-dodecaborano(12)-1,2-ditellurolate [(1,2-C2B10H10)Te2Li 2](Et2O) which, after reaction with 1,2- dichlorotetramethyldisilane, afforded a six-membered heterocycle containing the Te-Si-Si-Te unit with an annelated carborane moiety, characterized by multinuclear magnetic resonance and X-ray structural analysis. As a byproduct, a five-membered ring containing a Si-Si-Te unit was formed, which was obtained as a major product, using conditions favouring partial insertion of tellurium into C-Li bonds. Treatment of [(1,2-C2B10H10) Te2Li2](Et2O) with dichlorodimethylsilane led to a five-membered heterocycle as a major product containing a Te-Te-Si unit. Various decomposition/hydrolysis/oxidation products could be identified by multinuclear magnetic resonance, among them most notably 1,2-di(hydrotelluro)-1, 2-dicarba-closo-dodecaborane(12). The reactions of 1,2-dicarba-closo- dodecaborano(12)-1,2-ditellurolate with chlorosilanes afforded five-membered silatellura heterocyles containing the TeSiSi or TeTeSi moiety linked with the C2 unit of 1,2-dicarbadodecaborane(12) in addition to the six-membered heterocycle containing the TeSiSiTe fragment. Copyright
- Wrackmeyer, Bernd,Klimkina, Elena V.,Milius, Wolfgang
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p. 398 - 408
(2013/03/28)
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- Chiral diphosphane- and NHC-containing ruthenium catalysts for the catalytic asymmetric arylation of aldimines with organoboron reagents
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For the first time, we report the application of [RuCl2(η 6-p-cymene)]2 in the arylation of N-activated aldimines with boronic acids and its derivatives to afford chiral amines, which are important intermediates in the syntheses of key bioactive compounds. The behavior of the chiral ligands, the imine substrates, and the organoboron reagents were studied. Very good enantioselectivities were obtained. A new method is presented for the synthesis of chiral substituted amines by employing Ru catalysts along with known chiral phosphane ligands and a new NHC-type chiral ligand. Organoboron reagents were applied as the aryl transfer agents. High enantioselectivities were achieved with this new method, and some mechanistic insights are provided.
- Marques, Carolina S.,Burke, Anthony J.
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experimental part
p. 4232 - 4239
(2012/09/22)
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- Pd(η3-1-PhC3H4)(η5- C5H5), an unusually effective catalyst precursor for Suzuki-Miyaura cross-coupling reactions catalyzed by bis-phosphine palladium(0) compounds
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It has previously been shown that the easily handled, heat- and air-stable compound Pd(η3-1-PhC3H4)(η5- C5H5) (Vb) reacts rapidly with a wide variety of tertiary phosphines L to produce near-quantitative yields of the corresponding Pd(0) compounds PdL2, which are widely believed to be the active species in many often-used cross-coupling catalyst systems based on Pd(PPh 3)4 (I), Pd2(dba)3 (II), PdCl 2 (III), and Pd(OAc)2 (IV). However, catalyst precursors I-IV are in fact known to preferentially generate sterically hindered, three-coordinate Pd(0) species rather than two-coordinate PdL2, and thus Vb is hypothetically expected to be a better catalyst precursor for e.g. Suzuki-Miyaura cross-coupling reactions. Utilizing the conventional Suzuki-Miyaura cross-coupling reaction of phenylboronic acid with bromoanisole, comparisons are made of the efficacies of catalyst systems based on Vb with those based on compounds I-IV (L = the representative phosphines PPh 3, PCy3, PBut3). As anticipated, catalysts generated from Vb are significantly more competent and, as a bonus, Vb makes palladium(0) complexes PdL2 available under rigorously anhydrous conditions.
- Fraser, Andrew W.,Besaw, Jessica E.,Hull, Laura E.,Baird, Michael C.
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p. 2470 - 2475
(2012/06/04)
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- Rhodium(I)/diene-catalyzed addition reactions of arylborons with ketones
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Rh(I)/diene-catalyzed addition reactions of arylboroxines/arylboronic acids with unactivated ketones to form tertiary alcohols in good to excellent yields are described. By using C2-symmetric (3aR,6aR)-3,6-diaryl-1,3a,4,6a- tetrahydropentalenes as ligands, the asymmetric version of such an addition reaction, with up to 68% ee, was also realized.
- Liao, Yuan-Xi,Xing, Chun-Hui,Hu, Qiao-Sheng
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supporting information; experimental part
p. 1544 - 1547
(2012/06/05)
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- Mild and ligand-free Pd(II)-catalyzed conjugate additions to hindered γ-substituted cyclohexenones
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Ligand-free cationic Pd(II) catalyst with NaNO3 as an additive is a highly active catalytic system for conjugate additions to sterically hindered γ-substituted cyclohexenones. More challenging γγ- and βγ-substrates also react well to produce products with quaternary centers in good dr. The conjugate additions occur in a diastereoselective fashion under mild, practical and air-stable conditions, using readily available commercial reagents.
- Jordan-Hore, James A.,Sanderson, James N.,Lee, Ai-Lan
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supporting information; scheme or table
p. 2508 - 2511
(2012/07/03)
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- Solid-state 11B and 13C NMR, IR, and X-ray crystallographic characterization of selected arylboronic acids and their catechol cyclic esters
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Nine arylboronic acids, seven arylboronic catechol cyclic esters, and two trimeric arylboronic anhydrides (boroxines) are investigated using 11B solid-state NMR spectroscopy at three different magnetic field strengths (9.4, 11.7, and 21.1T). Through the analysis of spectra of static and magic-angle spinning samples, the 11B electric field gradient and chemical shift tensors are determined. The effects of relaxation anisotropy and nutation field strength on the 11B NMR line shapes are investigated. Infrared spectroscopy was also used to help identify peaks in the NMR spectra as being due to the anhydride form in some of the arylboronic acid samples. Seven new X-ray crystallographic structures are reported. Calculations of the 11B NMR parameters are performed using cluster model and periodic gauge-including projector-augmented wave (GIPAW) density functional theory (DFT) approaches, and the results are compared with the experimental values. Carbon-13 solid-state NMR experiments and spectral simulations are applied to determine the chemical shifts of the ipso carbons of the samples. One bond indirect 13C-11B spin-spin (J) coupling constants are also measured experimentally and compared with calculated values. The 11B/10B isotope effect on the 13C chemical shift of the ipso carbons of arylboronic acids and their catechol esters, as well as residual dipolar coupling, is discussed. Overall, this combined X-ray, NMR, IR, and computational study provides valuable new insights into the relationship between NMR parameters and the structure of boronic acids and esters. Copyright
- Oh, Se-Woung,Weiss, Joseph W. E.,Kerneghan, Phillip A.,Korobkov, Ilia,Maly, Kenneth E.,Bryce, David L.
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scheme or table
p. 388 - 401
(2012/08/13)
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- Rh-catalyzed addition of arylboroxines to cyclic N -(Isopropanesulfinyl) ketimines
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Arylboroxines, which are easily accessed by drying commercially available arylboronic acids, are added to N-(isopropanesulfinyl)ketimines derived from cyclohexanone, N-Boc-piperidin-4-one, and tetrahydropyran-4-one in high yields and with excellent functional group compatibility via rhodium catalysis. These results contrast with additions to the corresponding ketimines incorporating the larger N-tert-butanesulfinyl group, which give considerably lower yields. Efficient two-step preparation of racemic isopropanesulfinamide from inexpensive isopropyl disulfide and recycling of the isopropanesulfinyl group from the addition products are also described.
- Jung, Hyung Hoon,Buesking, Andrew W.,Ellman, Jonathan A.
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p. 9593 - 9600,8
(2012/12/12)
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- Rh-catalyzed addition of arylboroxines to cyclic N -(Isopropanesulfinyl) ketimines
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Arylboroxines, which are easily accessed by drying commercially available arylboronic acids, are added to N-(isopropanesulfinyl)ketimines derived from cyclohexanone, N-Boc-piperidin-4-one, and tetrahydropyran-4-one in high yields and with excellent functional group compatibility via rhodium catalysis. These results contrast with additions to the corresponding ketimines incorporating the larger N-tert-butanesulfinyl group, which give considerably lower yields. Efficient two-step preparation of racemic isopropanesulfinamide from inexpensive isopropyl disulfide and recycling of the isopropanesulfinyl group from the addition products are also described.
- Jung, Hyung Hoon,Buesking, Andrew W.,Ellman, Jonathan A.
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p. 9593 - 9600
(2013/01/15)
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- Selective consecutive insertion of alkynes into the B-Se bonds of 1,3,2-diselenaborolane derivatives: Synthesis and molecular structures of nine-membered rings
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Various alkynes have been inserted selectively and stepwise into the B-Se bond(s) of 1,3,2-diselenaboracyclopentanes {as the 4,5-[1,2-dicarba-closo- dodecaborano(12)] derivatives}. The B-phenyl derivative was much less reactive than the B-halogeno derivat
- Wrackmeyer, Bernd,Klimkina, Elena V.,Milius, Wolfgang
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p. 3909 - 3922
(2013/01/14)
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