- Nickel-Catalyzed Defluorinative Coupling of Aliphatic Aldehydes with Trifluoromethyl Alkenes
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A simple procedure is reported for the nickel-catalyzed defluorinative alkylation of unactivated aliphatic aldehydes. The process involves the catalytic reductive union of trifluoromethyl alkenes with aldehydes using a nickel complex of a 6,6′-disubstituted bipyridine ligand with zinc metal as the terminal reductant. The protocol is distinguished by its broad substrate scope, mild conditions, and simple catalytic setup. Reaction outcomes are consistent with the intermediacy of an α-silyloxy(alkyl)nickel intermediate generated by a low-valent nickel catalyst, a silyl electrophile, and the aldehyde substrate. Mechanistic findings with cyclopropanecarboxaldehyde provide insights into the nature of the reactive intermediates and illustrate fundamental reactivity differences that are governed by subtle changes in the ligand and substrate structure.
- Montgomery, John,Xiao, Jichao
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p. 2463 - 2471
(2022/02/17)
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- Chemoselective Deoxygenation of 2° Benzylic Alcohols through a Sequence of Formylation and B(C6F5)3-Catalyzed Reduction
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A sequence of formylation and B(C6F5)3-catalyzed reduction of the resulting formate with Et3SiH enables the chemoselective deoxygenation of secondary benzylic alcohols. Primary benzylic and tertiary non-benzylic alcohols are not reduced by this protocol. The formyl group fulfills a double role as activator and self-sacrificing protecting group. The deoxygenation of these formates is fast and can be carried out in the presence of other potentially reducible groups. Neighboring-group participation was found in the deoxygenation of certain diol motifs.
- Oestreich, Martin,Richter, Sven C.
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supporting information
p. 2103 - 2106
(2021/07/22)
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- Cationic Dirhodium Complexes Bridged by 2-Phosphinopyridines Having an Exquisitely Positioned Axial Shielding Group: A Molecular Design for Enhancing the Catalytic Activity of the Dirhodium Core
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This report describes a strategy to create highly electrophilic dirhodium catalysts. The electrophilicity of lantern-Type dirhodium complexes is generally decreased by the coordination of a ligand to the axial site, which often causes a reduction in the catalytic activity. We designed and synthesized a series of cationic dirhodium complexes bridged by 2-diarylphosphinopyridines having a bulky 2,4,6-Triisopropylphenyl (Tip) group that can prevent the attack of external molecules to the closest axial site. Theoretical calculations indicated that the Tip group weakly interacts with the axial site but hardly reduces the electrophilicity of the dirhodium core. The complexes served as excellent catalyst precursors for the dehydrogenative silylation of alcohols using hydrosilanes under mild conditions and a low metal loading, producing the silyl ethers in higher yields in comparison to conventional dirhodium complexes.
- Ohnishi, Ryuhei,Ohta, Hidetoshi,Mori, Shigeki,Hayashi, Minoru
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p. 2678 - 2690
(2021/07/31)
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- Nickel-catalyzed reductive coupling of unactivated alkyl bromides and aliphatic aldehydes
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A mild, convenient coupling of aliphatic aldehydes and unactivated alkyl bromides has been developed. The catalytic system features the use of a common Ni(ii) precatalyst and a readily available bioxazoline ligand and affords silyl-protected secondary alcohols. The reaction is operationally simple, utilizing Mn as a stoichiometric reductant, and tolerates a wide range of functional groups. The use of 1,5-hexadiene as an additive is an important reaction parameter that provides significant benefits in yield optimizations. Initial mechanistic experiments support a mechanism featuring an alpha-silyloxy Ni species that undergoes formal oxidative addition to the alkyl bromideviaa reductive cross-coupling pathway.
- Cruz, Cole L.,Montgomery, John
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p. 11995 - 12000
(2021/09/28)
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- Pd catalysts supported on dual-pore monolithic silica beads for chemoselective hydrogenation under batch and flow reaction conditions
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Two different types of palladium catalysts supported on dual-pore monolithic silica beads [5% Pd/SM and 0.25% Pd/SM(sc)] for chemoselective hydrogenation were developed. Alkyne, alkene, azide, and nitro functionalities and the aromatic N-Cbz protecting group were chemoselectively hydrogenated using 5% Pd/SM. On the other hand, 0.25% Pd/SM(sc) showed unique and higher hydrogenation catalyst activity toward a wide variety of reducible functionalities. Furthermore, the catalyst activities of both 5% Pd/SM and 0.25% Pd/SM(sc) under flow hydrogenation conditions were also evaluated. A pre-packed 5% Pd/SM cartridge could be used continuously for at least 72 h without any loss of catalyst activity. The 0.2% Pd/SM(sc) catalyst prepacked in a cartridge showed high catalyst activity for the flow hydrogenation of trisubstituted alkenes under mild reaction conditions. This journal is
- Yamada, Tsuyoshi,Ogawa, Aya,Masuda, Hayato,Teranishi, Wataru,Fujii, Akiko,Park, Kwihwan,Ashikari, Yosuke,Tomiyasu, Noriyuki,Ichikawa, Tomohiro,Miyamoto, Riichi,Bai, Hongzhi,Matsuyama, Kiyoshi,Nagaki, Aiichiro,Sajiki, Hironao
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p. 6359 - 6367
(2020/11/03)
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- Rhenium-Catalyzed Reduction of Carboxylic Acids with Hydrosilanes
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Re2(CO)10 efficiently catalyzes the direct reduction of various carboxylic acids under mild conditions (rt, irradiation 350 or 395 nm). While aliphatic carboxylic acids were readily converted to the corresponding disilylacetals with low catalyst loading (0.5 mol %) in the presence of Et3SiH (2.2 equiv), aromatic analogues required more drastic conditions (Re2(CO)10 5 mol %, Ph2MeSiH 4.0 equiv) to afford the corresponding aldehydes after acid treatment.
- Wei, Duo,Buhaibeh, Ruqaya,Canac, Yves,Sortais, Jean-Baptiste
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supporting information
p. 7713 - 7716
(2019/10/10)
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- A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
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A versatile iridium(III) metallacycle catalysed rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. The reactions proceeded in high yields at room temperature by hydrosilylation followed by desilylation. Although the reactions of various aldehydes and ketones resulted exclusively in alcohols, the hydrosilylation of esters led to alcohols or ethers, depending on the type of substrate. Regarding the carboxylic acids, again the nature of the reagent controlled the outcome of the hydrosilylation reaction, either alcohols or aldehydes being formed.
- Corre, Yann,Rysak, Vincent,Trivelli, Xavier,Agbossou-Niedercorn, Francine,Michon, Christophe
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supporting information
p. 4820 - 4826
(2017/09/07)
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- Development of chelate resin-supported palladium catalysts for chemoselective hydrogenation
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Abstract Two kinds of palladium catalysts immobilized on a chelate resin bearing diiminoacetate or polyamine moieties on the polystyrene-divinylbenzene polymer were newly prepared by the adsorption of palladium (II) ions on these resins followed by the reduction to palladium (0) with hydrazine monohydrate. Both catalysts showed a similar activity for hydrogenation. A variety of reducible functionalities, except for benzylic alcohol, alkyl benzyl ether, silyl ether, and epoxide, could be reduced under the hydrogenation conditions using either catalyst. Since the palladium metal elution from the immobilized catalysts was never observed, the catalysts could be reused without any decrease in the catalyst activity for at least 5 runs.
- Monguchi, Yasunari,Ichikawa, Tomohiro,Nozaki, Kei,Kihara, Kensuke,Yamada, Yuuko,Miyake, Yutaka,Sawama, Yoshinari,Sajiki, Hironao
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supporting information
p. 6499 - 6505
(2015/08/18)
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- Unique Chemoselective Hydrogenation using a Palladium Catalyst Immobilized on Ceramic
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A heterogeneous palladium catalyst supported on a ceramic (5 % Pd/ceramic) was developed. The catalyst exhibited a specific chemoselectivity for hydrogenation that has never been achieved by other palladium-catalyzed methods. Either aliphatic or aromatic N-Cbz groups could be deprotected to the corresponding free-amines, while the hydrogenolysis of benzyl esters and ethers did not proceed. Furthermore, aryl chlorides and epoxides were tolerant under the Pd/ceramic-catalyzed hydrogenation conditions. 5 % Pd/ceramic could be reused without any loss of catalyst activity, as no palladium leaching was detected in the reaction media.
- Monguchi, Yasunari,Marumoto, Takahisa,Ichikawa, Tomohiro,Miyake, Yutaka,Nagae, Yoshiyuki,Yoshida, Michiyuki,Oumi, Yasunori,Sawama, Yoshinari,Sajiki, Hironao
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p. 2155 - 2160
(2015/11/24)
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- Indium(III)-catalyzed reductive bromination and iodination of carboxylic acids to alkyl bromides and iodides: Scope, mechanism, and one-pot transformation to alkyl halides and amine derivatives
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Highly effective indium(III)-catalyzed reductive bromination or iodination of a variety of carboxylic acids with 1,1,3,3-tetramethyldisiloxane (TMDS) and a source of bromine or iodine is described. This functional group interconversion has high tolerance for several functional groups, such as halogens, a hydroxy group, a nitro group, an olefin part, and a sulfide moiety. This indium catalytic system is also applicable to the reductive iodination of aldehyded, acyl chlorides, and esters. Furthermore, this reducing system can be applied to the one-pot synthesis of alkyl halides and amine derivatives via the addition of nucleophiles. Insight into the reaction mechanism was gained via the time course of 1H and 13C NMR monitoring experiments and the corresponding stepwise reactions.
- Moriya, Toshimitsu,Yoneda, Shinichiro,Kawana, Keita,Ikeda, Reiko,Konakahara, Takeo,Sakai, Norio
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p. 10642 - 10650
(2013/11/19)
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- Selective reduction of carboxylic acids to aldehydes catalyzed by B(C 6F5)3
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B(C6F5)3 efficiently catalyzes hydrosilylation of aliphatic and aromatic carboxylic acids to produce disilyl acetals under mild conditions. Catalyst loadings can be as low as 0.05 mol %, and bulky tertiary silanes are favored to give selectively the acetals. Acidic workup of the disilyl acetals results in the formation of aldehydes in good to excellent yields.
- Bezier, David,Park, Sehoon,Brookhart, Maurice
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supporting information
p. 496 - 499
(2013/03/29)
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- Indium-catalyzed reductive esterification of a carboxylic acid: Sequential preparation of an ester and symmetrical ether
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An unprecedented reductive dimerization of two carboxylic acids to produce ester derivatives by a combination catalyst involving InBr3 and sulfuric acid is described. A sequential conversion of the in-situ formed ester to a symmetrical ether by indium-catalyzed deoxygenation of the ester with a hydrosilane in the same pot was also demonstrated. Copyright
- Sakai, Norio,Usui, Yuta,Ikeda, Reiko,Konakahara, Takeo
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scheme or table
p. 3397 - 3401
(2012/02/02)
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- Rhodium-catalyzed, efficient deutero- and tritiosilylation of carbonyl compounds from hydrosilanes and deuterium or tritium
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A cationic rhodium compound which is an active catalyst for both the hydrogen isotope exchange in hydrosilanes and the hydrosilylation of carbonyl compounds permits, in a one-flask, two-step procedure, efficient deutero- and tritiosilylations using SiEt3H under D2 (0.5 bar) or T2, at low catalyst loadings (0.1-0.5 mol %).
- Rubio, Miguel,Campos, Jesuus,Carmona, Ernesto
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supporting information; experimental part
p. 5236 - 5239
(2011/12/15)
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- An efficient synthesis of silyl ethers of primary alcohols, secondary alcohols, phenols and oximes with a hydrosilane using InBr3 as a catalyst
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An efficient method for the preparation of silyl ethers by InBr3 catalyzed silylation of primary alcohols, secondary alcohols, phenols and oxime with a hydrosilane is described.
- Sridhar, Madabhushi,Raveendra, Jillella,China Ramanaiah, Beeram,Narsaiah, Chinthala
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experimental part
p. 5980 - 5982
(2011/12/02)
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- Highly efficient and chemoselective ruthenium-catalyzed hydrosilylation of aldehydes
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The highly chemoselective hydrosilylation of aldehydes was achieved using a ruthenium catalyst activated by a household fluorescent light (30 W) at or below room temperature. The hydrosilylation was almost exclusive to aldehydes over ketones and olefins.
- Do, Youngshil,Han, Junghoon,Rhee, Young Ho,Park, Jaiwook
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experimental part
p. 3363 - 3366
(2012/02/01)
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- Mechanistic study of nickel-catalyzed ynal reductive cyclizations through kinetic analysis
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The mechanism of nickel-catalyzed, silane-mediated reductive cyclization of ynals has been evaluated. The cyclizations are first-order in [Ni] and [ynal] and zeroth-order in [silane]. These results, in combination with the lack of rapid silane consumption
- Baxter, Ryan D.,Montgomery, John
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supporting information; experimental part
p. 5728 - 5731
(2011/06/18)
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- Reduction of esters to ethers utilizing the powerful lewis acid BF 2OTf·OEt2
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The direct reduction of esters to their corresponding ethers has been achieved using the Lewis acid BF2OTf·OEt2 generated via anionic redistribution between TMSOTf and BF3·OEt 2 with triethylsilane acting as the
- Morra, Nicholas A.,Pagenkopf, Brian L.
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p. 511 - 514
(2008/12/21)
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- Cationic Au(I)- and Pt(II)-catalyzed silylation of alcohols using allylsilanes
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The silylation of alcohols using allylsilanes was catalyzed by cationic Au(I) and Pt(II) species, which were prepared in situ from the metal chlorides ([AuCl(PPh3)], PtCl2) and a silver salt. TBS-, TES-, and TIPS-protections of vario
- Shibata, Takanori,Kanda, Kazumasa,Ueno, Yasunori,Fujiwara, Ryo
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p. 1146 - 1147
(2007/10/03)
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- Anilinosilanes/TBAF catalyst: Mild and powerful agent for the silylation of sterically hindered alcohols
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We developed an efficient method for the silylation of alcohols using anilinosilane with tetrabutylammonium fluoride (TBAF) catalyst, wherein TMS, TES and TBS groups were smoothly introduced into silylation-resistant hindered alcohols under mild condition
- Iida, Akira,Horii, Atsushi,Misaki, Tomonori,Tanabe, Yoo
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p. 2677 - 2682
(2007/10/03)
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- Solvent-modulated Pd/C-catalyzed deprotection of silyl ethers and chemoselective hydrogenation
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Recently we have reported undesirable and frequent deprotection of the TBDMS protective group of a variety of hydroxyl functions occurred under neutral and mild hydrogenation conditions using 10% Pd/C in MeOH. The deprotection of silyl ethers is susceptible to significant solvent effect. TBDMS and TES protecting groups were selectively cleaved in the presence of acid-sensitive functional groups such as TIPS ether, TBDPS ether and dimethyl acetal under hydrogenation condition using 10% Pd/C in MeOH. In contrast, chemoselective hydrogenation of reducible functional groups such as acetylene, olefin and benzyl ether, proceeds in the presence of TBDMS or TES ethers in AcOEt or MeCN.
- Ikawa, Takashi,Hattori, Kazuyuki,Sajiki, Hironao,Hirota, Kosaku
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p. 6901 - 6911
(2007/10/03)
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- Activation of silylphosphines by diethyl azodicarboxylate: Novel silylation of alcohols
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A novel activation mode of silylphosphines and an application of that to silylation of alcohols were described. Silylphosphines were found to be instantly activated by means of DEAD and PPTS to form reactive silyl cation equivalents. By using the activate
- Hayashi, Minoru,Matsuura, Yutaka,Watanabe, Yutaka
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p. 1409 - 1411
(2007/10/03)
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- A remarkable solvent effect toward the Pd/C-catalyzed cleavage of silyl ethers
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Selective hydrogenation conditions of olefin, benzyl ether and acetylene functionalities in the presence of TBDMS or TES ether have been developed.
- Sajiki, Hironao,Ikawa, Takashi,Hattori, Kazuyuki,Hirota, Kosaku
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p. 654 - 655
(2007/10/03)
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- A novel and efficient method for the silylation of alcohols with methallylsilanes catalyzed by Sc(OTf)3
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Reaction of alcohols with methallylsilanes in the presence of a catalytic amount of Sc(OTf)3 provides efficiently the corresponding alkyl silyl ethers. By using microencapsulated (MC) Sc(OTf)3, which can be easily recovered and reused, yields of alkyl silyl ethers are improved and the work-up process after completion of the reaction is considerably simplified. (C) 2000 Elsevier Science Ltd.
- Suzuki,Watahiki,Oriyama
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p. 8903 - 8906
(2007/10/03)
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- One-step conversion of formate esters to O-silyl ethers by means of samarium diiodide in the presence of chlorosilane reagents
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One-step conversion of various types of formate esters into the corresponding O-silyl ethers under neutral reaction conditions was established by employing samarium diiodide in the presence of chlorosilane reagents.
- Honda, Toshio,Ishikawa, Fumihiro
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p. 3323 - 3328
(2007/10/03)
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- Hydrosilylation of unsaturated (hetero)aromatic aldehydes and related compounds catalyzed by transition metal complexes
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[Rh(COD)CI]2 has been found to be a more active catalyst than Ir, Ru, Pt and Pd complexes for the hydrosilylation of unsaturated furan and aromatic aldehydes with HSiEt3. 1,4- and 1,2-addition reactions giving unsaturated silyl ethers in cis- and trans-configurations occurred as well as the hydrogenation reactions which produce the corresponding saturated silyl ethers. The migration of the ethyl group was observed in the hydrosilylation of 3-ethyl-3-(5-nitrofuryl)acrolein. The dehydrogenative silylation occurred in the reactions of cinnamyl alcohol and furan-2-acrylic acid.
- Iovel, Irina,Popelis, Juris,Gaukhman, Alexander,Lukevics, Edmunds
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p. 123 - 130
(2007/10/03)
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- Rhodium(II) Perfluorobutyrate Catalyzed Silane Alcoholysis. A Highly Selective Route to Silyl Ethers
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Rhodium(II) perfluorobutyrate, Rh2(pfb)4, is an effective catalyst for the alcoholysis of trialkylsilanes at room temperature.Primary alcohols react with triethylsilane approximately 5 times faster than do secondary alcohols, and tertiary alcohols are virtually inert.Enhanced selectivity is achieved with tert-butyldimethylsilane.Hydrosilylation of olefinic alcohols is relatively unimportant even with terminal alkenes, but Rh2(pfb)4 does promote hydrogenation of 3-phenyl-2-propen-1-ol.Selected diols have been silylated with complete regioselectivity in Rh2(pfb)4-catalyzed reactions with either triethylsilane or tert-butyldimethylsilane.Methanolysis of (S)-(-)-1-naphthylphenylmethylsilane occurs with nearly complete inversion of configuration at silicon, and spectral analysis of the catalytic reaction suggests a mechanism for silane alcoholysis in which the rhodium(II) catalyst coordinates with the silicon hydride to activate silicon for backside nucleophilic attack by the alcohol.
- Doyle, Michael P.,High, Kenneth G.,Bagheri, Vahid,Pieters, Roland J.,Lewis, Patricia J.,Pearson, Matthew M.
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p. 6082 - 6086
(2007/10/02)
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