- A one-pot two-step synthesis of tertiary alcohols combining the biocatalytic laccase/TEMPO oxidation system with organolithium reagents in aerobic aqueous media at room temperature
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The one-pot/two-step combination of enzymes and polar organometallic chemistry in aqueous media is for the first time presented as a proof-of-concept study. The unprecedented combination of the catalytic oxidation of secondary alcohols by the system laccase/TEMPO with the ultrafast addition (3 s reaction time) of polar organometallic reagents (RLi/RMgX) to thein situformed ketones, run under air at room temperature, allows the straightforward and chemoselective synthesis of tertiary alcohols with broad substrate scope and excellent conversions (up to 96%).
- Capriati, Vito,Cicco, Luciana,García-álvarez, Joaquín,González-Sabín, Javier,Lecuna, Ramón,Presa Soto, Alejandro,Ríos-Lombardía, Nicolás,Ramos-Martín, Marina,Vitale, Paola
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supporting information
p. 13534 - 13537
(2021/12/23)
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- Catalyst-Free Enantiospecific Olefination with In Situ Generated Organocerium Species
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Described is the in situ formation of triorganocerium reagents and their application in catalyst-free Zweifel olefinations. These unique cerium species were generated through novel exchange reactions of organohalides with n-Bu3Ce reagents. The adequate electronegativity of cerium allowed for compensating the disadvantages of both usually functional-group-sensitive organolithium species and less reactive organomagnesium reagents. Exchange reactions were performed on aryl and alkenyl bromides, enabling enantiospecific transformations of chiral boron pinacol esters. Finally, these new organocerium species were engaged in selective 1,2-additions onto enolisable and sterically hindered ketones.
- Music, Arif,Hoarau, Clément,Hilgert, Nicolas,Zischka, Florian,Didier, Dorian
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supporting information
p. 1188 - 1192
(2019/01/04)
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- Preparation of Functionalized Diaryl- and Diheteroaryllanthanum Reagents by Fast Halogen–Lanthanum Exchange
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Aryl and heteroaryl halides (X=Br, I) undergo a fast and convenient halogen–lanthanum exchange with nBu2LaMe, which leads to functionalized diaryl- and diheteroaryllanthanum derivatives. Subsequent trapping reactions with selected electrophiles, such as ketones, aldehydes, or amides, proceeded smoothly at ?50 °C in THF, affording polyfunctionalized alcohols and carbonyl derivatives. Kinetic competition experiments revealed a similar reactivity trend as for Br/Mg exchange, but 106-times higher rates, making it comparable to Br/Li exchange.
- Benischke, Andreas D.,Anthore-Dalion, Lucile,Berionni, Guillaume,Knochel, Paul
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p. 16390 - 16394
(2017/11/28)
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- Enantioselective α-arylation of O-carbamates via sparteine-mediated lithiation and Negishi cross-coupling
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A general and highly enantioselective arylation of carbamates derived from primary alcohols was developed by combining Hoppe's sparteine-mediated asymmetric lithiation with Negishi cross-coupling. Coupled with Aggarwal's lithiation-borylation sequence, the current method provides a short and divergent access to a variety of enantioenriched secondary and tertiary benzylic alcohols.
- Royal, Titouan,Baumgartner, Yann,Baudoin, Olivier
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p. 166 - 169
(2017/11/27)
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- Iodine-catalyzed transformation of aryl-substituted alcohols under solvent-free and highly concentrated reaction conditions
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Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols. The relative reactivity of substituted 1-phenylethanols in I2-catalyzed dimerization under SFRC provided a good Hammett plot ρ+ = -2.8 (r2 = 0.98), suggesting the presence of electron-deficient intermediates with a certain degree of developed charge in the rate-determining step.
- Jereb, Marjan,Vra?i?, Dejan
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p. 747 - 762
(2018/01/17)
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- Catalytic Enantioselective Addition of Aryl Grignard Reagents to Ketones
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We report a catalytic system for the challenging enantioselective addition of aryl Grignard reagents to ketones. Using a simple, one-pot procedure under mild conditions, a wide range of aromatic ketones are converted into diaryl alcohols in good yields and with good enantioselectivities. The catalytic enantioselective addition of aryl Grignard reagents to ketones is now possible. Using a readily available Ar-BINMOL ligand and titanium(IV) isopropoxide in a simple, one-pot procedure under mild conditions, a wide range of aromatic ketones are converted into diaryl alcohols in good yields and with good enantioselectivities.
- Fernández-Mateos, Emilio,Maciá, Beatriz,Yus, Miguel
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p. 6519 - 6526
(2016/02/18)
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- Distinctive meta-directing group effect for iridium-catalyzed 1,1-diarylalkene enantioselective hydrogenation
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An iridium-catalyzed asymmetric hydrogenation of 1,1-diarylkenes is described. Employing a novel, modular phosphoramidite ligand, PhosPrOx, in this transformation affords biologically relevant 1,1-diarylmethine products in good enantiomeric ratios (96.5:3
- Bess, Elizabeth N.,Sigman, Matthew S.
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supporting information
p. 646 - 649
(2013/04/10)
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- Ni-catalysed, domino synthesis of tertiary alcohols from secondary alcohols
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The use of in situ generated (NHC)-Ni catalytic species (NHC = N-heterocyclic carbene) allows for the synthesis, in short reaction times, of a variety of tertiary alcohols from secondary alcohols through a domino oxidation-addition protocol.
- Berini, Christophe,Navarro, Oscar
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p. 1538 - 1540
(2012/02/16)
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- A nickel catalyst for the addition of organoboronate esters to ketones and aldehydes
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A Ni(cod)2/IPr catalyst promotes the intermolecular 1,2-addition of arylboronate esters to unactivated aldehydes and ketones. Dlaryl, alkyl aryl, and dialkyl ketones show good reactivity under mild reaction conditions (3) with aryl ether substrates. A Ni(0)/Ni(II) catalytic cycle initiated by the oxidative cyclization of the carbonyl substrate Is proposed.
- Bouffard, Jean,Itami, Kenichiro
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supporting information; scheme or table
p. 4410 - 4413
(2009/12/26)
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- Highly enantioselective arylation of aldehydes and ketones using AlArEt2(THF) as aryl sources
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A series of AlArEt2(THF) (Ar = Ph (la), 4-MeC6H 4 (1b), 4-MeOC6H 4 (1c), 4-Me 3SiC6H4 (1d), 2-naphthyl (le)) were synthesized from reactions of AlEt2Br(THF) with ArMgBr. In CDC13 solution, the 1H NMR spectra showed that AlArEt2(THF) compounds exist as a mixture of four species of formulas of AlAr xEt3-x (THF) (x = 0, 1, 2, or 3). AlArEt2(THF) compounds were found to be superior and atom-economic reagents for asymmetric aryl additions to organic carbonyls. Aryl additions of AlArEt2(THF) to aldehydes catalyzed by the titanium(IV) complex of (R)-H8-BINOL were efficient with a short reaction time of 1 h, affording aryl addition products as exclusive or main products in high yields and excellent enantioselectivities of up to 98% ee. Although ethyl additions to aldehydes occurred in minor extent, this study demonstrates that increasing the amount of AlArEt2(THF) from 1.2 to 1.4 or to 1.6 equiv significantly improved the aryl addition products of up to >99%. On the other hand, asymmetric arylations of AlArEt2(THF) to ketones employing a titanium(IV) catalyst of (S)-BINOL produced optically active tertiary alcohols exclusively in excellent enantioselectivities of up to 94% ee.
- Zhou, Shuangliu,Wu, Kuo-Hui,Chen, Chien-An,Gau, Han-Mou
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supporting information; experimental part
p. 3500 - 3505
(2009/09/30)
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- Selective one-pot synthesis of various phenols from diarylethanes
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Various substituted phenols were selectively synthesized by a one-pot reaction through the NHPI-catalyzed aerobic oxidation of 1,1-diarylethanes followed by treatment with dilute sulfuric acid. The Royal Society of Chemistry.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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supporting information; experimental part
p. 3417 - 3419
(2009/02/05)
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- Gold(I)-catalyzed oxidative cleavage of a C-C double bond in water
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Oxidative cleavage of the C=C bond to afford ketone or aldehyde products with tert-butyl hydrogenperoxide (TBHP) as the oxidant can be catalyzed by AuCl with neocuproine (1) in water.
- Xing, Dong,Guan, Bingtao,Cai, Guixin,Fang, Zhao,Yang, Liping,Shi, Zhangjie
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p. 693 - 696
(2007/10/03)
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- Charge-transfer interactions in 4-donor 4′-acceptor substituted 1,1-diphenylethenes
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Two 1,1-diphenylethenes bearing either a 4-dimethylamino or 4-methoxy group as electron donor and a 4′-cyano group as electron acceptor, as well as compounds containing only a donor or acceptor functionality, were synthesized. The observation of strong fl
- Van Walree, Cornelis A.,Kaats-Richters, Veronica E. M.,Veen, Sandra J.,Wieczorek, Birgit,Van Der Wiel, Johanna H.,Van Der Wiel, Bas C.
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p. 3046 - 3056
(2007/10/03)
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- Hammett ρ of reactions of MeLi with benzophenones
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Relative rates of reactions of MeLi with benzophenones in diethyl ether at 0 °C that furnish methyldiaryl-methanols were determined using slow addition of a MeLi solution to solutions containing an excess of two benzophenones. The additions exhibit a Hammett p of 0.94.
- Maclin, Keith M.,Richey Jr., Herman G.
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p. 4370 - 4371
(2007/10/03)
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- Activation conditions play a key role in the activity of zeolite CaY: NMR and product studies of Bronsted acidity
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CaY, activated under different conditions, was characterized with 1H, 31P, and 1H/27A] double resonance MAS NMR. The 1H MAS NMR spectra of CaY, calcined in an oven at 500 °C, shows resonances from H2O (bound to Ca2+ and the zeolite framework), CaOH+, aluminum hydroxides, silanols, and Bronsted acid sites. No evidence for Lewis acidity is observed on adsorption of trimethylphosphine, and an estimate of ≈16 Bronsted acid sites per unit cell is obtained for this sample. CaY activated in an oven at higher temperatures contains less water, but all the other species are still present. In contrast, CaY activated by slow ramping of the temperature under vacuum to 500 or 600 °C shows a much lower concentration of Bronsted acid sites (1/unit cell). Again, no evidence for Lewis acidity was observed. These NMR results have been utilized to understand the very different product distributions that are observed for reactions of 1,1- and 1,2-diarylethylenes in zeolite CaY activated in an oven (in air) and under vacuum. Samples with high concentrations of Bronsted acid sites react stoichiometrically with these sites, yielding diarylalkanes. At low concentrations, the Bronsted acid sites can act catalytically resulting in isomerization reactions.
- Kao, Hsien-Ming,Grey, Clare P.,Pitchumani, Kasi,Lakshminarasimhan,Ramamurthy
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p. 5627 - 5638
(2007/10/03)
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- Preparation of 1,1-diphenylethanols by addition of organotitanium compounds to substituted aceto- and benzophenones
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The 1,1-diphenylethanols 5a-h were prepared by the addition of phenyltitanium triisopropoxide (3) to 4-substituted acetophenones 1a-h. The titanium tetraalkoxide 7, formed in situ from 3 and 1a, forms complexes with up to two molecules of 1a, this was established by 13C-NMR. Preparation of the alcohols 5a-f was also carried out by the reaction of methyltitanium triisopropoxide (4) with 4-substituted benzophenones 2a-f.
- Dimitrov,Stanchev,Milenkov,Nikiforov,Demirev
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p. 228 - 232
(2007/10/02)
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- Electron Transfer in Reactions of Ketones with Organolithium Reagents. A Carbon-14 Kinetic Isotope Effect Probe
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Kinetic isotope effects have been determined for reactions of ketones labeled with carbon-14 at the carbonyl carbon with MeLi and Me2CuLi in diethyl ether at 0 deg C.Observed isotope effects were as follows: (C6H5)2C=O + MeLi, 12k/14k = 1.000 +/- 0.002; (C6H5)2C=O + Me2CuLi, 1.029 +/- 0.005; 2,4,6-Me3C6H2COC6H5 + MeLi, 1.023 +/- 0.004.The relative reactivities of ortho-, meta-, and para-substituted benzophenones with these reagents were also determined by the competition experiments.These results are consistent with an electron transfer step which is followed by a carbon-carbon bond-formimg step that is or is not rate determining depending on the structure of ketones and reagents.The reaction of benzophenone with MeLi proceeds via rate-determining electron transfer; the change in nucleophile from MeLi to Me2CuLi shifts the rate-determining step from electron-transfer to recombination; the change in ketone from benzophenone to 2,4,6-trimethylbenzophenone also shifts the rate-determining step from electron transfer to recombination because the latter step becomes slower for the more hindered ketone.The extent of the geometrical change of the substrate at the electron-transfer transition state of the reaction of benzophenone with MeLi was estimated to be small on the basis of the magnitude of the KIE and teh ρ value of the Hammett correlation.
- Yamataka, Hiroshi,Fujimura, Naoya,Kawafuji, Yukie,Hanafusa, Terukiyo
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p. 4305 - 4308
(2007/10/02)
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