1636-34-6Relevant articles and documents
New Generation Method for a Samarium(II) Equivalent: Me3SiX (X = Br and I)/Sm-Assisted Intermolecular Carbon-Carbon Bond Forming Reactions for Carbonyl Compounds
Akane, Noriyuki,Hatano, Tadashi,Kusui, Hiroko,Nishiyama, Yutaka,Ishii, Yasutaka
, p. 7902 - 7907 (1994)
Samarium(II) species can be efficiently generated in situ from a reaction between elemental samarium and chlorotrimethylsilane (Me3SiCl)/sodium iodide (NaI) reagent or bromotrimethylsilane (Me3SiBr) in acetonitrile.The reductive coupling reaction of carbonyl compounds was achieved by the action of Sm(II) reagent thus generated from Sm/Me3SiCl/NaI or Sm/Me3SiBr to give the corresponding pinacol products in moderate to high yields.The samarium(II) reagent induced the intermolecular coupling reaction of α,β-unsaturated esters with carbonyl compounds or imines followed by intramolecular cyclization to form the corresponding γ-lactones or γ-lactams in moderate yields.The reaction of α-bromo esters with carbonyl compounds using the Sm(II) species, generated from the Sm/Me3SiX system, led to the corresponding β-hydroxy esters in 52-95percent yields.
Intramolecular and intermolecular ketone-ester reductive coupling reactions promoted by samarium(II) iodide
Liu, Yunkui,Zhang, Yongmin
, p. 5745 - 5748 (2001)
Intramolecular and intermolecular ketone-ester reductive coupling reactions promoted by SmI2 have been studied. Substituted 2-hydroxy-5-ethoxycarbonylcyclopentanones, 5-ethoxycarbonylcyclopentenones and α-ketols were prepared in moderate to good yields at room temperature or under reflux under neutral conditions.
A Simple and Efficient New Synthesis of Vicinal Diols by Reductive Coupling of Carbonyl Compounds
Csuk, Rene,Fuerstner, Alois,Weidmann, Hans
, p. 1802 - 1803 (1986)
A universally applicable, new 'pinacolic reduction' for aldehydes and ketones is described.
A new preparation of samarium dibromide and its use in stoichiometric and catalytic pinacol coupling reactions
Hélion, Florence,Lannou, Marie-Isabelle,Namy, Jean-Louis
, p. 5507 - 5510 (2003)
A new convenient preparation of samarium dibromide in THF is reported. Pinacol coupling reactions using SmBr2 in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonyl compounds.
Radical pairs with rotational fluidity in the photochemical reaction of acetophenone and cyclohexane in the zeolite NAY: A 13C CPMAS NMR and product analysis study
Amboya, Ammee,Nguyen, Tina,Huynh, Hien T.,Brown, Ashley,Ratliff, Gretchen,Yonutas, Heather,Cizmeciyan, Deniz,Natarajan, Arunkumar,Garcia Garibay, Miguel A.
, p. 2322 - 2326 (2009)
The photochemical reaction of acetophenone and cyclohexane in the zeolite NaY occurs by combination of the geminate radical pairs to give products that reveal a significant amount of rotational fluidity, which was also documented by intermolecular nuclear dipolar interaction measurements using cross polarization 13C NMR (CPMAS) experiments. The Royal Society of Chemistry 2009.
Samarium(II) iodide promoted novel reductive coupling reactions of ketones and nitriles
Zhou, Longhu,Zhang, Yongmin,Shi, Daqing
, p. 8491 - 8494 (1998)
The intramolecular and intermolecular reductive coupling reaction of ketones-nitriles promoted by SmI2 were studied.
Diastereoselective pinacol coupling of alkyl aryl ketones with rare earth metals in the presence of chlorosilanes
Ogawa, Akiya,Takeuchi, Hiroki,Hirao, Toshikazu
, p. 7113 - 7114 (1999)
Rare earth metals (Ln) are found to act as useful reducing agents for the pinacol coupling reaction of alkyl aryl ketones in the presence of chlorosilanes. Although the hitherto known pinacol coupling reaction using rare earth reducing agents generally exhibits very low diastereoselectivities, the present pinacol coupling by use of a Ln/R3SiCl system usually indicates higher diastereoselectivities. In particular, a Yb/Me3SiCl system attains the diastereoselective pinacol coupling of primary alkyl aryl ketones with the dl/meso ratio of 8/2~9/1.
A convenient pinacol coupling of diaryl ketones with B2pin2viapyridine catalysis
Jo, Junhyuk,Kim, Seonyul,Choi, Jun-Ho,Chung, Won-Jin
supporting information, p. 1360 - 1363 (2021/02/22)
A convenient, pyridine-boryl radical-mediated pinacol coupling of diaryl ketones is developed. In contrast to the conventional pinacol coupling that requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed by DFT calculations, which suggests the necessity of both aromatic rings for the maximum stabilization of the transition states.
Thio-assisted reductive electrolytic cleavage of lignin β-O-4 models and authentic lignin
Fang, Zhen,Flynn, Michael G.,Jackson, James E.,Hegg, Eric L.
, p. 412 - 421 (2021/01/28)
Avoiding the use of expensive catalysts and harsh conditions such as elevated temperatures and high pressures is a critical goal in lignin depolymerization and valorization. In this study, we present a thio-assisted electrocatalytic reductive approach using inexpensive reticulated vitreous carbon (RVC) as the working cathode to cleave the β-O-4-type linkages in keto aryl ethers. In the presence of a pre-electrolyzed disulfide (2,2′-dithiodiethanol) and a radical inhibitor (BHT) at room temperature at a current density of 2.5 mA cm-2, cathodic reduction of nonphenolic β-O-4 dimers afforded over 90% of the corresponding monomeric C-O cleavage products in only 1.5 h. Extended to DDQ-oxidized poplar lignin, this combination of electric current and disulfide, applied over 6 h, released 36 wt% of ethyl acetate soluble fragments and 26 wt% of aqueous soluble fragments, leaving only 38 wt% of insoluble residue. These findings represent a significant improvement over the current alone values (24 wt% ethyl acetate soluble; 22 wt% aqueous soluble; 54 wt% insoluble residue) and represent an important next step in our efforts to develop a mild electrochemical method for reductive lignin deconstruction.
Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
, p. 4037 - 4050 (2020/03/10)
We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
