57807-91-7Relevant articles and documents
Designed electron-deficient gold nanoparticles for a room-temperature Csp3-Csp3coupling reaction
Yu, Qiu-Ying,Su, Hui,Zhai, Guang-Yao,Zhang, Shi-Nan,Sun, Lu-Han,Chen, Jie-Sheng,Li, Xin-Hao
supporting information, p. 741 - 744 (2021/02/06)
Stille cross-coupling reactions catalysed by an ideal catalyst combining the high activity of homogeneous catalysts and the reusability of heterogeneous catalysts are of great interest for C-C bond formation, which is a widely used reaction in fine chemistry. Despite great effort to increase the utilization ratio of surface metal atoms, the activity of heterogeneous catalysts under mild conditions remains unsatisfactory. Herein, we design a proof-of-concept strategy to trigger the room-temperature activity of heterogeneous Au catalysts by decreasing the electron density at the interface of a rationally designed Schottky heterojunction of Au metals and boron-doped carbons. The electron-deficient Au nanoparticles formed as a result of the rectifying contact with boron-doped carbons facilitate the autocleavage of C-Br bonds for highly efficient C-C coupling reactions of alkylbromides and allylstannanes with a TOF value of 5199 h-1 at room temperature, surpassing that of the state-of-the-art homogeneous catalyst. This journal is
Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
supporting information, p. 14806 - 14813 (2021/09/18)
We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
Fiorio, Jhonatan L.,Rossi, Liane M.
, p. 312 - 318 (2021/01/29)
The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
, p. 3685 - 3690 (2021/05/31)
Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
Cobalt-Catalyzed Kumada Coupling Forming Sterically Encumbered C-C Bonds
Brennan, Marshall R.,Darrow, William T.,Fout, Alison R.,Killion, Jack A.,Leahy, Clare A.
, (2021/12/02)
A Co(acac)3/PN precatalyst was developed and optimized for catalytic Kumada coupling of aryl Grignard reagents to sterically encumbered alkyl halides. The substrate scope demonstrates excellent yields for primary alkyl chlorides and bromides, including good performance using neopentyl chloride and neophyl chloride. Secondary alkyl halides were also successfully arylated in good yields, and the presence of β-hydrogen atoms in a substrate did not inhibit product formation. An intermolecular functional group tolerance screen was conducted which indicates that ester and amide functionality are well tolerated by the reaction conditions. Electrophiles containing ester, pyridine, and nitrile functionality were all coupled with 2-mesitylmagnesium bromide in good yields, supporting tolerance screen results. The intermolecular screen also showed that functional groups which are typically reactive with Grignard reagents such as alcohols and terminal alkynes were not well-tolerated by the reaction.
Mild olefin formationviabio-inspired vitamin B12photocatalysis
Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
, p. 1736 - 1744 (2021/02/22)
Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
Selective reduction of alkynes to alkenes with hydrogen or formic acid catalyzed by cis,mer-[IrH2Cl(mtppms)3]
Hankó, Gy?rgy,Márton, Richárd,Udvardy, Antal,Purgel, Mihály,Kathó, ágnes,Joó, Ferenc,Papp, Gábor
supporting information, (2021/04/09)
In this work we have found, that the water-soluble cis,mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine Na-salt) was an excellent catalyst for reduction of terminal alkynes by hydrogen transfer from aqueous HCOOH/HCOONa mixtures. The conversions strongly depended on the pH of the reaction mixtures, and the highest rate of phenylacetylene transfer hydrogenation was observed at pH 3. The same dihydrido-Ir(III) complex actively catalyzed also the hydrogenation of terminal alkynes under mild conditions (T = 50 °C; P(H2) = 2–10 bar). Importantly, both the hydrogenation and hydrogen transfer reductions afforded exclusively the corresponding alkenes as products. Phenylacetylene and its substituted derivatives reacted smoothly, while benzylic and aliphatic alkynes were less reactive or did not react at all. It was also found, that an excess of the mtppms ligand inhibited the reaction. This was rationalized by formation of cisz-[IrH2(mtppms)4]+ which was also confirmed with multinuclear NMR spectroscopy. On the basis of the experimental results, a joint mechanism was suggested for both the hydrogenation and transfer hydrogenation pathways. The mechanism of hydrogenation and transfer hydrogenation of phenylacetylene was also studied by DFT calculations, which revealed several possibilities for protonation of a vinyl intermediate as the crucial step in formation of the styrene product.
Controlling the performance of a silver co-catalyst by a palladium core in TiO2-photocatalyzed alkyne semihydrogenation and H2 production
Fudo, Eri,Imai, Shota,Kojima, Yasumi,Kominami, Hiroshi,Tanaka, Atsuhiro
, (2021/08/24)
Titanium (IV) oxide (TiO2) having palladium (Pd) core-silver (Ag) shell nanoparticles (Pd@Ag/TiO2) was prepared by using a two-step (Pd first and then Ag) photodeposition method. The core-shell structure of the nanoparticles having various Ag contents (shell thicknesses) and the electron states of Pd and Ag were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd core and the Ag shell was evaluated by hydrogenation of 4-octyne in alcohol suspensions of a photocatalyst under argon and light irradiation. 4-Octyne was fully hydrogenated to 4-octane over Pd/TiO2, whereas 4-octyne was selectively hydrogenated to cis-4-octene over Pd(0.2)@Ag(0.5)/TiO2. Further increase in the Ag content resulted in a decrease in the conversion of 4-octyne. Pd-free Ag/TiO2 was inactive for hydrogenation of alkyne and induced coupling of active hydrogen species (H2 production). Photocatalytic reactions at various temperatures revealed that the change in selectivity (semihydrogenation or H2 production) can be explained by the difference in values of activation energy of the two reactions. An applicability test showed that the Pd@Ag/TiO2 photocatalyst can be used for hydrogenation of various alkynes to alkenes.
Merging Pd0/PdII Redox and PdII/PdII Non-redox Catalytic Cycles for the Allylarylation of Electron-Deficient Alkenes
Semba, Kazuhiko,Ohta, Naoki,Paulus, Fritz,Ohata, Masaki,Nakao, Yoshiaki
supporting information, p. 5035 - 5040 (2021/02/26)
An allylarylation of electron-deficient alkenes with aryl boronates and allylic carbonates has been developed. This method allows access to a wide variety of carbon skeletons from readily available starting materials. Mechanistic studies indicate that this reaction is enabled by a cooperative catalysis based on merging Pd0/PdII redox and PdII/PdII non-redox catalytic cycles.
Properties and Reactivities of Zwitterionic Platinum(II)-ate Complexes Generated by Transforming Coordination of an Alkyne-Bisphosphine Ligand
Okamoto, Kazuhiro,Sasakura, Kohei,Funasaka, Satoshi,Watanabe, Hiiro,Suezaki, Masahiro,Ohe, Kouichi
, p. 848 - 856 (2021/05/04)
Coordination of an alkyne-bisphosphine ligand with platinum(II) precursors produced a structural reorganization in the ligand backbone to form stable zwitterionic platinum(II) complexes bearing an anionic platinum center. The structural properties and reactivities of these complexes were investigated using X-ray crystallographic analyses, computational studies, and stoichiometric reactions involving oxidative addition and reductive elimination. These studies have shown that the enhanced nucleophilicity of the platinum center to alkyl halides promotes smooth oxidative addition and that the charge rebalance accelerates the dissociation of the halide anion from the platinum(IV) intermediate, which is essential in the carbon-carbon bond-forming step.
