- Isopropanol as a hydrogen source for single atom cobalt-catalyzed Wacker-type oxidation
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The first example of a heterogeneous cobalt catalytic system for Wacker-type oxidation catalyzed by a single atom dispersed Co-N/C catalyst using alcohol as the hydrogen source under an oxygen atmosphere is presented. By combining a well-designed, controlled experiment and various methods of characterization, we determined that single atom cobalt was the active center rather than nanoparticle or oxide counterparts.
- An, Yue,Chen, Bo,Gao, Shuang,Huang, Guanwang,Luo, Huihui,Shang, Sensen,Wang, Lianyue
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p. 2769 - 2773
(2020/06/17)
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- Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
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A general protocol for visible-light-induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α-aryl or methyl-substituted Michael acceptors and styrene derivatives, the unactivated 1,1-dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3-bis(1-arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late-stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.
- Luo, Wenping,Fang, Yewen,Zhang, Li,Xu, Tianhang,Liu, Yongjun,Li, Yan,Jin, Xiaoping,Bao, Jiakan,Wu, Xiaodong,Zhang, Zongyong
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supporting information
p. 1778 - 1781
(2020/03/11)
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- Scandium(III) Trifluoromethanesulfonate Catalyzed Selective Reactions of Donor–Acceptor Cyclopropanes with 1,1-Diphenylethanols: An Approach to Polysubstituted Olefins
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An unexpected synthetic approach to polysubstituted olefins through the scandium(III) trifluoromethanesulfonate catalyzed ring-opening reaction of donor–acceptor cyclopropanes with 1,1-diphenylethanols was developed. The reactions, which are experimentally easy to handle, feature tolerance of various functional groups and mild reaction conditions. On the basis of experimental evidence, a plausible mechanism was also proposed.
- Zhu, Xiaoyan,Hong, Gang,Hu, Chen,Wu, Shengying,Wang, Limin
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supporting information
p. 1547 - 1551
(2017/04/01)
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- Al(OTf)3: An efficient lewis acid additive for domino addition-elimination of Grignard reagents to activated ketones
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It has been demonstrated that aluminium triflate in either stoichiometric or catalytic quantities facilitates the addition-elimination of Grignard reagents to electron-rich ketones, such as methoxy substituted acetophenones, propiophenone and chromanone in a one-pot process, and that it has an enhancing effect on the addition of these reagents to the ketones. It has also been found that the reactions are highly stereoselective towards one regioisomer of the alkene in the case of oxygenated aryl-alkyl substituted substrates, but not when the elimination originates from a double benzylic alcohol intermediate.
- Pieterse, Tanya,Visser, Melanie,Marais, Charlene,Bezuidenhoudt, Barend C. B.
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supporting information
p. 1541 - 1546
(2016/06/14)
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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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- Rhodium(I)-n-heterocyclic carbene-catalyzed addition of sodium tetraphenylborate to ketones to form tertiary alcohols
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Rhodium complexes ([Rh(COD)(NHC)Cl]) were synthesized by the reaction of bis(1,3-dialkylperhydrobenzimidazolin-2-ylidene) with [RhClCOD]2 in toluene and characterized by elemental analysis, 1H NMR, 13C NMR and IR spectroscopy. These complexes were used as catalysts for the addition of sodium tetraphenylborate to aromatic ketones and corresponding tertiary alcohols were obtained in good yields.
- Yiit, Beyhan,Yiit, Murat,?zdemir, Ismail
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p. 2562 - 2571
(2015/01/09)
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- Reaction of Grignard reagents with carbonyl compounds under continuous flow conditions
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This contribution details how a continuous flow reactor was used to react carbonyl compounds with Grignard reagents at room temperature in an efficient and safe manner. Flow rate, residence time and temperature were optimized for the preparation of a small collection of secondary and tertiary alcohols. Excellent yields and general applicability were observed using the set-up protocol. The procedure was also applied for the preparation of Tramadol, an analgesic drug belonging to the opioid group. The developed conditions allowed the selective addition of Grignard reagents to aldehydes and ketones in the presence of a nitrile function.
- Riva,Gagliardi,Martinelli,Passarella,Vigo,Rencurosi
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experimental part
p. 3242 - 3247
(2010/05/19)
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- SUBSTITUTED BENZHYDRYLETHERS
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Disclosed herein are substituted benzhydrylethers of Formula I, processes of preparation thereof, pharmaceutical compositions thereof, and methods of their use thereof.
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Page/Page column 35
(2009/08/18)
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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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- Rhodium-catalyzed addition of arylboron compounds to nitriles, ketones, and imines
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The rhodium-catalyzed addition reactions of sodium tetraphenylborate and arylboronic acids to nitriles, ketones, and imines were examined. The reaction of nitriles could be carried out efficiently in the presence of a catalyst system of [RhCl(cod)]2-dppp and H2O to give the corresponding monoarylated products selectively. Although unactivated ketones and imines are known to be poor electrophiles for rhodium-catalyzed arylation, the phenylation of them with use of sodium tetraphenylborate proceeded smoothly in the presence of [RhCl(cod)]2 and Rh(acac)(cod) as catalysts, respectively. The addition of NH4Cl was found to be crucial to effectively conduct the reaction of ketones and imines.
- Ueura, Kenji,Miyamura, Sawako,Satoh, Tetsuya,Miura, Masahiro
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p. 2821 - 2826
(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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- Biomimetic oxidation of clemastine fumarate
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The reaction of clemastine fumarate (1) with the biomimetic system manganese(III)-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin chloride (MnTPFPPCl)/imidazole/hydrogen peroxide in a mixture of dichlormethane/methanol affords several metabolites. These compounds are products of O-dealkylation, N-demethylation, N-oxidation and separation of water. The reaction of 1 in aqueous solution with manganese(III)-5,10,15,20-tetrakis(pentafluorophenyl)-β-tetrasulfonat oporphyrin chloride (MnTPFPS4PCl) as catalyst additional generates products of aromatic hydroxylation. Products were identified by TLC, UV, and MS. Thereby we found a close conformity with rat metabolism.
- Froehlich,Pietzyk,Smolinka,Goeber
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p. 409 - 414
(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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- ORGANOMANGANESE (II) REAGENTS XIV: A SHORT AND EFFICIENT SYNTHESIS OF DIASTEREOISOMERIC (+/-)-α-BISABOLOLS AND (+/-)-CHLORPHENOXAMINE
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Diastereomeric (+/-)-α-bisabolols (7), a sesquiterpenoid alcohol, and (+/-)-chlorphenoxamine (12), an antihistamine, have been prepared in excellent yields.Both these short and convenient syntheses involve as a key step the one-pot elaboration of a dissymetrical tertiary alcohol via an organomanganese reagent (5 to 7 and 9 to 10 respectively).
- Cahiez, Gerard,Rivas-Enterrios, Jose,Clery, Patrick
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p. 3659 - 3662
(2007/10/02)
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- Amide derivatives and 5-lipoxygenase inhibitors containing the same as an active ingredient
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According to the invention, there are provided novel amide derivatives and 5-lipoxygenase inhibitors containing the same as an effective ingredient. The above-mentioned compounds of the invention have been demonstrated to posses 5-lipoxygenase-inhibiting activities. These compounds can inhibit the production of leucotrienes such as LTC4 and LTD4 which are allergy-inducing factors by inhibiting the activity of 5-lipoxygenase. Accordingly, the amide derivatives can be used as 5-lipoxygenase inhibitors effective for allergic asthma, allergic rhinitis and the like.
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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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