- Regioselective Silylations of Propargyl and Allyl Pivalates through Ca-Promoted Reductive C(sp3)-O Bond Cleavage
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A practical protocol for the regioselective preparation of 3-phenylpropargylsilanes and 3-phenylallylsilanes in yields of 36-77 and 48-86%, respectively, from readily accessible 3-phenylpropargyl and 1-phenylallyl pivalates was developed through reductive C(sp3)-O bond cleavage. This method represents the first example of the direct application of vastly abundant calcium granules to a reductive coupling reaction. A broad range of propargylsilanes and allylsilanes are simply prepared using easy-to-handle pivalates and chlorotrimethylsilane under mild catalyst-free and additive-free conditions.
- Zhang, Tianyuan,Zheng, Suhua,Kobayashi, Taro,Maekawa, Hirofumi
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p. 7129 - 7133
(2021/09/18)
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- Nickel-Mediated Enantiospecific Silylation via Benzylic C-OMe Bond Cleavage
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Benzylic stereocenters are found in bioactive and drug molecules, as enantiopure benzylic alcohols have been used to build such a stereogenic center, but are limited to the construction of a C-C bond. Silylation of alkyl alcohols has the potential to build bioactive molecules and building blocks; however, the development of such a process is challenging and unknown. Herein, we describe an unprecedented AgF-assisted nickel catalysis in the enantiospecific silylation of benzylic ethers.
- Balakrishnan, Venkadesh,Murugesan, Vetrivelan,Chindan, Bincy,Rasappan, Ramesh
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supporting information
p. 1333 - 1338
(2021/02/20)
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- Fluoroalkylselenolation of Alkyl Silanes/Trifluoroborates under Metal-Free Visible-Light Photoredox Catalysis
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Herein a metal-free fluoroalkylselenolation of alkylsilanes as well as potassium alkyltrifluoroborates under visible light photocatalysis is disclosed. The developed methodologies are performed under mild conditions, room temperature in the presence of an organic photocatalyst and blue LED irradiation. Mechanistic investigations including luminescence and EPR spectroscopy allow us to shed light on both mechanisms.
- Ghiazza, Clément,Khrouz, Lhoussain,Billard, Thierry,Monnereau, Cyrille,Tlili, Anis
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supporting information
p. 1559 - 1566
(2019/11/03)
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- METALLATED BENZYLSILANES AND THEIR USE AS POLYMERIZATION INITIATORS
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The invention relates to novel compounds useful as polymerization initiators or precursors for polymerization initiators. The invention further relates to a method of making the polymerization initiators and resulting polymers. The invention also relates
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Page/Page column 32
(2018/09/12)
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- Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional iridium catalyst
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Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded, resulting in the formation of chlorohydrosilanes (R2SiHCl or RSiHCl2) as synthetically important building blocks for various organosilicon compounds. A mechanistic study supported the in-situ formation of an iridium hydride species as a key intermediate, which could transfer the hydride to the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from Me3SiCl.
- Beppu, Teruo,Sakamoto, Kei,Nakajima, Yumiko,Matsumoto, Kazuhiro,Sato, Kazuhiko,Shimada, Shigeru
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- Broad scope hydrofunctionalization of styrene derivatives using iron-catalyzed hydromagnesiation
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The highly regioselective iron-catalyzed formal hydrofunctionalization of styrene derivatives with a diverse range of electrophiles has been developed using a single, operationally simple hydromagnesiation procedure and only commercially available, bench-stable reagents. Using just 0.5 mol % FeCl2·4H2O and N,N,N',N'-tetramethylethylenediamine, hydromagnesiation and electrophilic trapping have been used to form new carbon-carbon bonds (13 examples) and carbon-heteroatom bonds (5 examples) including the products of formal cross-coupling reactions, hydroboration, hydroamination, hydrosilylation, and hydrofluorination.
- Jones, Alison S.,Paliga, James F.,Greenhalgh, Mark D.,Quibell, Jacob M.,Steven, Alan,Thomas, Stephen P.
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supporting information
p. 5964 - 5967
(2015/01/08)
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- Iron-catalyzed hydromagnesiation: Synthesis and characterization of benzylic grignard reagent intermediate and application in the synthesis of ibuprofen
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Iron-catalyzed hydromagnesiation of styrene derivatives using ethylmagnesium bromide has been investigated for the synthesis of benzylic Grignard reagents. The benzylic Grignard reagent formed in the reaction was observed directly and its conformation in solution characterized by multinuclear and variable-temperature NMR spectroscopy. The Grignard reagent could be stored for at least 2 weeks without significant loss in activity. Hydromagnesiation of styrene in tetrahydrofuran gave a mixture of monoalkyl- and dialkylmagnesium species, (1-phenylethyl)magnesium bromide (2; RMgBr) and bis(1-phenylethyl)magnesium (3; R2Mg), with the equilibrium between these species lying in favor of the dialkylmagnesium species. The thermodynamic parameters of alkyl exchange for the reaction MgBr2 + R2Mg (3) 2RMgBr (2) were quantified, with the enthalpy and entropy of formation of 2 from MgBr2 and 3 calculated as 32 ± 7 and 0.10 ± 0.03 kJ mol-1, respectively. This methodology was applied, on a 10 mmol scale, as the key step in the synthesis of ibuprofen, using sequential iron-catalyzed alkyl-aryl and aryl-vinyl cross-coupling reactions to give 4-isobutylstyrene, which following hydromagnesiation and reaction with CO2 gave ibuprofen. Each step proceeded in excellent yield, at temperatures between 0 °C and room temperature, at atmospheric pressure. Inexpensive, nontoxic, and air- and moisture-stable iron(III) acetylacetonate was used as the precatalyst in each step in combination with inexpensive amine ligands.
- Greenhalgh, Mark D.,Kolodziej, Adam,Sinclair, Fern,Thomas, Stephen P.
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supporting information
p. 5811 - 5819
(2015/02/19)
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- Friedel-Crafts acetylation and benzoylation of benzylsilanes and xanthenes
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The synthesis of p-acetyl and p-benzoyl derivatives of various benzylsilanes (p-R1CO-C6H4-CR2R3- SiMe3: R1, R2, R3=Me, H, H; Me, H, Ph; Me, H, Me; Me, Me, M
- Georgakilas, Vasilios,Perdikomatis, Gerasimos P.,Triantafyllou, Anastasios S.,Siskos, Michael G.,Zarkadis, Antonios K.
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p. 2441 - 2447
(2007/10/03)
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- Generation of allylic and benzylic organolithium compounds by fluorine-lithium exchange: Reaction with electrophiles
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The application of the naphthalene-catalysed lithiation methodology to allylic and benzylic fluorides 1 led to the corresponding allylic and benzylic organolithium reagents, which, in the presence of different electrophiles (Barbier-type reaction conditions), afforded the expected products 2 in moderate yields. The procedure was useful for the transformation of primary, secondary and tertiary benzylic fluorides into the corresponding lithium derivatives. When a two-step lithiation process was used (treatment of fluoride 1 with lithium and a catalytic amount of naphthalene, followed by addition of the electrophilic reagent), only Wurtz-type coupling products were formed.
- Guijarro, David,Yus, Miguel
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- Generation of allylic and benzylic organolithium reagents from the corresponding ester, amide, carbonate, carbamate and urea derivatives
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The reaction of different allylic and benzylic non-enolisable esters or amides (1), carbonates (4), carbamates (6, 7) and ureas (8) with an excess of lithium powder and a catalytic amount of naphthalene (10%) in the presence of an electrophile [(i)PrCHO, (t)BuCHO, PhCHO, Me2CO, Et2CO, (CH2)5CO, Ph2CO, Me3SiCl] in THF at different temperatures (-78, -30 or 0°C) leads, after hydrolysis with water to the corresponding allylated or benzylated products (2).
- Alonso, Emma,Guijarro, David,Martinez, Pedro,Ramon, Diego J.,Yus, Miguel
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p. 11027 - 11038
(2007/10/03)
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- Direct Transformation of Allylic and Benzylic Alcohols or Their Silylated Derivatives into Orgnolithium Compounds
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The reaction of allylic or benzylic alcohols 1 with n-butyllithium followed by treatment with lithium powder and a catalytic amount of DTBB (5 mol percent) in THF at room temperature gives a solution of the corresponding alkyllithium reagent, which reacts in situ with different electrophiles to yield the expected products 2.Alternatively, the O-silylated derivatives of the same alcohols are lithiated under Barbier-type reaction conditions to afford the same reaction products with better yields.
- Alonso, Emma,Guijarro, David,Yus, Miguel
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p. 11457 - 11464
(2007/10/02)
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- The Mechanism of the Petersen Reaction. Part 2. The Effect of Reaction Conditions, and a New Model for the Addition of Carbanions to Carbonyl Derivatives in the Absence of Chelation Control
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The stereochemistry of the Petersen olefination reaction between PhHSiMe3 and PhCHO has been studied under a wide variety of conditions with excellent reproducibility and extremely high yields.The effects of counterion, solvent, added salts, variation of the carbanion-forming base, and temperature have been investigated.The product stereochemistry is remarkably insensitive to the reaction conditions.The results lead to a new method of analysis of steric approach control based on the angle of approach as defined by Dunitz and Baldwin.The method involves analysis of 'primary' and 'secondary' transition-state interactions.This analysis should be generally applicable to carbanion additions in which chelation is insignificant.
- Bassindale, Allan R.,Ellis, Richard J.,Lau, Juliana C.-Y.,Taylor, Peter G.
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p. 593 - 598
(2007/10/02)
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- AN ELECTROREDUCTIVE SYNTHESIS OF ALLYLSILANES AND BENZYLSILANES
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The electrochemical reduction of benzyl and allyl halides carried out in the presence of chlorotrimethylsilane afforded the corresponding benzylsilanes and allylsilanes in satisfactory yields.
- Shono, Tatsuya,Matsumura, Yoshihiro,Katoh, Susumu,Kise, Naoki
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p. 463 - 466
(2007/10/02)
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- Carbanion Rearrangements by Intramolecular 1,ω Proton Shifts, III. The Reaction of 2-, 3-, 4-, and 5-Phenylalkyllithium Compounds
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Upon addition of THF to a solution of 4-phenylbutyllithium (2) in diethyl ether a rapid intramolecular 1,4 proton shift takes place with the formation of 1-phenylbutyllithium (5).Similarly, although somewhat more slowly, 5-phenylpentyllithium (82) rearranges to 1-phenylpentyllithium (83) via 1,5 proton transfer.The corresponding rearrangements by 1,2 or 1,3 hydrogen shifts, however, starting with 2-phenylethyllithium (1) and 3-phenylpropyllithium (54), respectively, were not detected.With 3-phenylpropyllithium (54) a slow intramolecular 1,5 transfer an ortho proton is observed instead, yielding o-propylphenyllithium (100).The corresponding 1,6 shift with 4-phenylbutyllithium (2) was also detected in a minor amount in addition to the 1,4 proton shift already mentioned.There is no indication, however, for a 1,4 transfer of an ortho proton in 2-phenylethyllithium (1).The reaction products in this case can be exclusively explained by intermolecular transmetallation reactions.All ω-phenylalkyllithium compounds under investigation show interesting side and secondary reactions being rather different in deuterated solvents and in deuteriumfree solvents, respectively, due to the isotope effects.The analysis of the products is accomplished by 1H-NMR spectroscopy and, after derivatization, with the help of a GC-MS-combination.Stereoelectronic reasons are made responsible for the failure of the intramolecular 1,2 and 1,3 proton shift in these systems.
- Maercker, Adalbert,Passlack, Michael
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p. 540 - 577
(2007/10/02)
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