- Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
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Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
- Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
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p. 10964 - 10973
(2021/09/08)
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- Carbonyl 1,2-transposition through triflate-mediated a-amination
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To date, it remains challenging to selectively migrate a carbonyl oxygen within a given molecular scaffold, especially to an adjacent carbon. In this work, we describe a simple one- or two-pot protocol that transposes a ketone to the vicinal carbon. This approach first converts the ketone to the corresponding alkenyl triflate, which can then undergo the palladium- and norbornene-catalyzed regioselective a-amination and ipso-hydrogenation enabled by a bifunctional hydrogen and nitrogen donor. The resulting "transposed enamine" intermediate can subsequently be hydrolyzed to produce the 1,2-carbonyl-migrated product. This method allows rapid access to unusual bioactive analogs through late-stage functionalization.
- Wu, Zhao,Xu, Xiaolong,Wang, Jianchun,Dong, Guangbin
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p. 734 - 740
(2021/11/16)
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- Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
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A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
- Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
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supporting information
p. 9925 - 9937
(2021/06/30)
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- Lewis acid activation of fragment-coupling reactions of tertiary carbon radicals promoted by visible-light irradiation of EDA complexes
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The addition of tertiary carbon radicals generated from N-(acyloxy)phthalimide esters to cyclic α,β-unsaturated ketones and lactones is markedly enhanced by the addition of substoichiometric amounts of a Ln(OTf)3. The reaction is accomplished by irradiation with visible light in the absence of a photosensitizer and is suggested to proceed by excitation of a ternary electron donor?acceptor complex between the NHPI ester, Hantzsch ester, and a Ln(OTf)3
- Pitre, Spencer P.,Allred, Tyler K.,Overman, Larry E.
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supporting information
p. 1103 - 1106
(2021/02/16)
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- Sonochemical Preparation of Dipicolinamide Mn-complexes and Their Application as Catalysts Towards Sono-synthesis of Ketones
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A series of non-heme Mn-complexes has been synthesized by the sonication of manganese (II)chloride and bis-amides (condensation products of 2-picolinic acid and o-phenylenediamines). The Mn-complexes effectively promote the oxidation of unactivated aliphatic and benzylic C─H and N-bearing heterocycles substrates with low catalyst loading using eco-friendly hydrogen peroxide in the presence of acetic acid as additive under ultrasonic irradiation. Chromatographic studies revealed that the corresponding ketones are the only detectable products. Noteworthy, the presence of electron donors in the catalyst structure significantly increased the reaction yields. The substantial lowering of the oxidation reaction yields by adding ionol (2,6-di-tert-butyl-4-methylphenol) as a free radical trap suggesting a free radical reaction pathway.
- Arafa, Wael A. A.
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p. 1403 - 1412
(2019/02/25)
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- Iron-catalyzed oxidative functionalization of C(sp3)-H bonds under bromide-synergized mild conditions
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An efficient oxidation and functionalization of C-H bonds with an inorganic-ligand supported iron catalyst and hydrogen peroxide to prepare the corresponding ketones was achieved using the bromide ion as a promoter. Preliminary mechanistic investigations indicated that the bromide ion can bind to FeMo6 to form a supramolecular species (FeMo6·2Br), which can effectively catalyze the reaction.
- Yu, Han,Zhao, Qixin,Wei, Zheyu,Wu, Zhikang,Li, Qi,Han, Sheng,Wei, Yongge
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supporting information
p. 7840 - 7843
(2019/07/12)
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- Selective C(sp3)?H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow
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A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.
- Laudadio, Gabriele,Govaerts, Sebastian,Wang, Ying,Ravelli, Davide,Koolman, Hannes F.,Fagnoni, Maurizio,Djuric, Stevan W.,No?l, Timothy
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supporting information
p. 4078 - 4082
(2018/03/21)
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- Efficient Aliphatic C?H Bond Oxidation Catalyzed by Manganese Complexes with Hydrogen Peroxide
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A tetradentate nitrogen ligand containing a benzimidazole ring and an electron-rich pyridine ring was developed, the resulting manganese complex exhibited good activity in the C?H oxidation of simple alkanes. In particular, cyclic aliphatic alkanes were transformed into ketones in very good yields (up to 89 %) by using environmentally benign H2O2 as the terminal oxidant. This protocol was also applied successfully in benzylic C?H oxidation, giving the corresponding ketones with very good selectivities. In addition, tertiary C?H bond oxidation of complex molecules by the manganese complex showed potential utility for assembling alcohols with good selectivity in late-stage chemical synthesis.
- Wang, Wenfang,Xu, Daqian,Sun, Qiangsheng,Sun, Wei
-
supporting information
p. 2458 - 2464
(2018/04/02)
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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supporting information
p. 2043 - 2046
(2016/02/05)
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- Efficient benzylic and aliphatic C-H oxidation with selectivity for methylenic sites catalyzed by a bioinspired manganese complex
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A benzimidazole-based nonheme manganese complex efficiently catalyzes benzylic, aliphatic C-H as well as tertiary C-H oxidation with hydrogen peroxide as the oxidant in the presence of acetic acid as additive. 18O labeling experiments suggest the reaction may proceed via a high-valent manganese-oxo intermediate.
- Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
-
supporting information
p. 1108 - 1111
(2014/03/21)
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- Site-selective oxidation of unactivated C sp 3-H bonds with hypervalent iodine(III) reagents
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By design: The site-selective oxidation of unactivated secondary C sp 3-H bonds was accomplished with hypervalent iodine(III) reagents and tert-butyl hydroperoxide (see scheme). The preparation and derivatization of the hypervalent iodine(III) reagent are simple, thus allowing the rational design of these reagents to optimize the site selectivity of the oxidation. Copyright
- Moteki, Shin A.,Usui, Asuka,Zhang, Tiexin,Solorio Alvarado, Cesar R.,Maruoka, Keiji
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supporting information
p. 8657 - 8660
(2013/09/12)
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- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
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In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
- Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
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p. 3267 - 3273
(2013/10/01)
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- C-H oxidation by H2O2 and O2 catalyzed by a non-heme iron complex with a sterically encumbered tetradentate N-donor ligand
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The compound N,N′-dineopentyl-N,N′-bis(2-pyridylmethyl)-1,2- ethanediamine (dnbpn) and its ferrous complex [Fe(dnbpn)(OTf)2] were synthesized. The Fe(II) complex was used to catalyze the oxidation of hydrocarbons by H2O2 and O2. Although the catalyzed alkane oxidation by H2O2 displays a higher preference for secondary over tertiary carbons than those associated with most previously reported nonheme iron catalysts, the catalytic activity is markedly inferior. In addition to directing the catalyzed oxidation toward the less sterically congested C-H bonds of the substrates, the neopentyl groups destabilize the metal-based oxidants generated from H2O2 and the Fe(II) complex. The presence of benzylic substrates with weak C-H bonds stabilizes an intermediate which we have tentatively assigned as a high-spin ferric hydroperoxide species. The oxidant generated from O2 reacts with allylic and benzylic C-H bonds in the absence of a sacrificial reductant; less substrate dehydrogenation is observed than with related previously described systems that use O2 as a terminal oxidant.
- Zhang, Qiao,Gorden, John D.,Goldsmith, Christian R.
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p. 13546 - 13554
(2014/01/06)
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- Forming tertiary organolithiums and organocuprates from nitrile precursors and their bimolecular reactions with carbon electrophiles to form quaternary carbon stereocenters
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Unstabilized tertiary organolithium intermediates are conveniently generated by reductive decyanation of nitriles, and these reagents and their derived cuprates couple in useful yields with carbon- centered electrophiles (see example). Chiral tertiary org
- Schnermann, Martin J.,Untiedt, Nicholas L.,Jiménez-Osés, Gonzalo,Houk, Kendall N.,Overman, Larry E.
-
supporting information
p. 9581 - 9586
(2012/11/14)
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- Combined effects on selectivity in Fe-catalyzed methylene oxidation
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Methylene C-H bonds are among the most difficult chemical bonds to selectively functionalize because of their abundance in organic structures and inertness to most chemical reagents. Their selective oxidations in biosynthetic pathways underscore the power of such reactions for streamlining the synthesis of molecules with complex oxygenation patterns. We report that an iron catalyst can achieve methylene C-H bond oxidations in diverse natural-product settings with predictable and high chemo-, site-, and even diastereoselectivities. Electronic, steric, and stereoelectronic factors, which individually promote selectivity with this catalyst, are demonstrated to be powerful control elements when operating in combination in complex molecules. This small-molecule catalyst displays site selectivities complementary to those attained through enzymatic catalysis.
- Chen, Mark S.,White, M. Christina
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scheme or table
p. 533 - 571
(2010/10/05)
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- Enders SAMP-hydrazone as traceless auxiliary in the asymmetric 1,4-addition of cuprates to enones
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Conjugate additions of Gilman cyanocuprates to (5)-N-amino-2- (methoxymethyl)pyrrolidine (SAMP)-hydrazones 4, 5 derived from cyclic and acyclic α,β-unsaturated ketones were investigated. A protocol utilizing copper(II) sulfate/ammonium chloride was evolved, which allowed cleavage of SAMP (S)-1 under the hydrolysis and work-up conditions, followed by recovery of the auxiliary with ethylenediaminetetraacetic acid (EDTA). The enantioselectivity of cuprate additions was dominated for cyclic SAMP-hydrazones 4 by the cuprate alkyl substituent and the ring size, in the case of acyclic arylidene SAMP-hydrazones 5, however, by the nature of the aryl substituent. Electron-donating substituents gave poor enantiomeric excesses, whereas electron-withdrawing groups provided excellent ee values of 98-99%. The configuration of the new stereocenter was determined to be (R). Moreover, a reaction sequence was developed which integrates a tandem 1,4-addition/ methylation and traceless hydrolytic cleavage of the auxiliary (S)-1 in a one-pot reaction, resulting in enantiomerically pure methyl ketones 11-13, each of them with > 99% ee.
- Sammet, Karsten,Gastl, Christoph,Baro, Angelika,Laschat, Sabine,Fischer, Peter,Fettig, Ina
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supporting information; experimental part
p. 2281 - 2290
(2010/12/29)
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- Efficient stereo- and regioselective hydroxylation of alkanes catalysed by a bulky polyoxometalate
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Direct functionalization of alkanes by oxidation of C-H bonds to form alcohols under mild conditions is a challenge for synthetic chemistry. Most alkanes contain a large number of C-H bonds that present difficulties for selectivity, and the oxidants employed often result in overoxidation. Here we describe a divanadium-substituted phosphotungstate that catalyses the stereo- and regioselective hydroxylation of alkanes with hydrogen peroxide as the sole oxidant. Both cyclic and acyclic alkanes were oxidized to form alcohols with greater than 96% selectivity. The bulky polyoxometalate framework of the catalyst results in an unusual selectivity that can lead to the oxidation of secondary rather than the weaker tertiary C-H bonds. The catalyst also avoids wasteful decomposition of the stoichiometric oxidant, which can result in the production of hydroxyl radicals and lead to non-selective oxidation and overoxidation of the desired products.
- Kamata, Keigo,Yonehara, Kazuhiro,Nakagawa, Yoshinao,Uehara, Kazuhiro,Mizuno, Noritaka
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scheme or table
p. 478 - 483
(2010/09/17)
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- Diastereoselectivity control of the radical carboazidation of substituted methylenecyclohexanes
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A systematic study of the diastereoselectivity of the radical carboazidation of methylenecyclohexane derivatives is presented. Several substitution patterns leading to a high level of stereocontrol have been identified. Axial attack is the preferred reaction pathway for cyclohexyl radicals, and excellent stereoselectivities can be obtained by introducing an axial substitutent at position 2. In this case, a second equatorial substituent at position 2 may be tolerated without a large detrimental effect on the diastereoselectivity. Finally, a high level of equatorial attack is observed with a very bulky substituent at position 2.
- Cren, Sylvaine,Schar, Pascal,Renaud, Philippe,Schenk, Kurt
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supporting information; experimental part
p. 2942 - 2946
(2009/09/06)
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- Copper-catalyzed asymmetric conjugate addition with Grignard reagents and SimplePhos ligands
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Herein we report the copper-catalyzed asymmetric conjugate addition of Grignard reagents to cyclic and acyclic enones, with SimplePhos as chiral ligands. A variety of Grignard reagents can be added to a range of cyclic and acyclic enones, with moderate to good enantioselectivities (ee's up to 86%).
- Palais, Laetitia,Alexakis, Alexandre
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experimental part
p. 2866 - 2870
(2010/04/05)
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- Stereoselective hydrogenation of tert-butylphenols over charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent
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Hydrogenation of 2-, 3-, and 4-tert-butylphenols was studied over a charcoal-supported rhodium catalyst in supercritical carbon dioxide (scCO2) solvent, and the results were compared with those in organic solvents. In the hydrogenation of 4-ter
- Hiyoshi, Norihito,Rode, Chandrashekhar V.,Sato, Osamu,Tetsuka, Hiroyuki,Shirai, Masayuki
-
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- COMPOUNDS FOR INHIBITING KSP KINESIN ACTIVITY
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The present invention provides compounds of Formula (I) (wherein R1, R3, X, W, Z and ring Y are as defined herein). The present invention also provides compositions comprising these compounds that are useful for treating cellular proliferative diseases or disorders associated with KSP kinesin activity and for inhibiting KSP kinesin activity.
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Page/Page column 93
(2010/11/23)
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- Deprotonation of β,β-disubstituted α,β-unsaturated amides -Mechanism and stereochemical consequences
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A detailed study of the lithium dialkylamide induced deprotonation of β,β-disubstituted α,β-unsaturated amides is presented. The preferential γ-Z-deprotonation and stereochemical outcome of substituents on the γ-Z carbon atom are rationalized in terms of a cyclic eight-membered transition state, which is supported by DFT calculations. Analogous deprotonations on cyclohexylidenecarboxamides reveal a delicate balance of the preference for the eight-membered cyclic transition state with the effects of existing substituents on the ring and the intervention of a twist-boat transition state.
- Green, James R.,Majewski, Marek,Snieckus, Victor
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p. 1397 - 1410
(2007/10/03)
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- Triethylaluminum- or triethylborane-induced free radical reaction of alkyl iodides and α,β-unsaturated compounds
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A series of α,β-unsaturated compounds, 1a-c, 9, 13, and 17, were used as reactants in free radical conjugate addition reactions with different radicals generated from alkyl iodides such as 3, 4, or 5 in the presence of triethylborane-oxygen in air or via the use of triethylaluminum-benzoyl peroxide as a free radical initiator. When the reactions were carried out using triethylborane-air, the products, in most cases, were clean and were easily purified. However, higher yields of the 1,4-adducts and less side reactions occurred when less reactive substrates were used as Michael acceptors in reactions with triethylaluminum-benzoyl peroxide and alkyl iodide under similar conditions. A mechanism for this is proposed in Scheme 1.
- Liu, Jing-Yuan,Jang, Yoeng-Jiunn,Lin, Wen-Wei,Liu, Ju-Tsung,Yao, Ching-Fa
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p. 4030 - 4038
(2007/10/03)
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- Effect of InCl3 on the addition of Grignard reagents to α,β-unsaturated carbonyl compounds
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Control of 1,2- versus 1,4-addition of organometallic reagents to enones remains a long-standing problem. There is still no satisfactory 1,2-directing agent comparable to the 1,4-directing effect of copper salts. We report that the presence of just 5 mol% indium(III) chloride can significantly alter the amount of 1,2-product formed in these reactions.
- Kelly, Brian G.,Gilheany, Declan G.
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p. 887 - 890
(2007/10/03)
-
- Preparation and reactivity of cyanocuprates containing alkylseleno and alkyltelluro groups as non-transferable ligands
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Alkylseleno and alkyltelluro groups are efficient non-transferable ligands of cyanocuprates in 1,4-addition reactions to enones.
- Zinn, Fabiano K.,Ramos, Eduardo C.,Comasseto, Jo?o V.
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p. 2415 - 2417
(2007/10/03)
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- Exploitation of aldoxime esters as radical precursors in preparative and EPR spectroscopic roles
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Photolyses of aldoxime esters, containing a considerable range of alkyl groups, lead to cleavage of their N-O bonds and formation of aryliminyl and alkyl radicals. The process was found to be favoured by 4-methoxyacetophenone as a photosensitiser and by methoxy substituents in the aryl rings. 4-Nitro- and pentafluoro-substitutions of the aryl rings were, on the other hand, deleterious. The intermediate iminyl radicals, together with primary, secondary and tertiary alkyl radicals were characterised by 9 GHz EPR spectroscopy. Cyclopropyl, CF3, and CCl3 radicals were probably also formed, but were too reactive for direct EPR spectroscopic detection. Photosensitised reaction of benzophenone oxime O-nonanoyl ester produced the diphenylmethaniminoxyl, as well as the expected n-octyl and iminyl radicals. This indicated that O-C bond scission accompanied O-N scission for this ketoxime ester. At higher temperatures the C-centred radicals added to the starting oxime esters to produce alkoxyaminyl radicals that were also spectroscopically detected in some cases. No evidence for abstraction of the iminyl hydrogen by tertbutoxyl radicals was obtained. Instead, the t-BuO radicals added to the C=N double bonds of the oxime esters. Similarly, chlorine abstraction from alkylbenzohydroximoyl chlorides by trimethyltin radicals did not take place. Preparative scale experiments with oxime esters containing suitably unsaturated alkyl groups showed that good yields of cyclised products could be obtained in the presence of the photosensitiser. This process constitutes a general method by which carboxylic acids or acid chlorides can be converted into alkyl radicals and hence to cyclised derivatives.
- McCarroll, Andrew J.,Walton, John C.
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p. 2399 - 2409
(2007/10/03)
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- Diethylzinc: A chain-transfer agent in intermolecular radical additions. A parallel with triethylborane
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In the presence of oxygen, diethylzinc can be used to promote radical additions to C=N bond containing radical acceptors and to enones. In these reactions, it plays at the same time the role of the initiator and the role of the chain-transfer reagent. A p
- Bertrand, Michele P.,Feray, Laurence,Nouguier, Robert,Perfetti
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p. 9189 - 9193
(2007/10/03)
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- Reductive free-radical alkylations and cyclisations mediated by 1-alkylcyclohexa-2,5-diene-1-carboxylic acids
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A range of 1-alkylcyclohexa-2,5-diene-1-carboxylic acids were prepared by Birch reduction-alkylation of benzoic acid and their efficiency as mediators of alkyl radical chain addition and cyclisation processes was investigated. Reductive alkylations were respectably successful, even with only one or two equivalents of alkene, for secondary, tertiary and benzylic radicals. Reaction of 1-[2-(cyclohex-2-enyloxy)ethyl]cyclohexa-2,5-diene-1-carboxylic acid yielded the product of exo-trig-cyclisation, i.e. 7-oxabicyclo[4.3.0]nonane, in a yield comparable to that obtained from the tributyltin hydride induced cyclisation of 3-(2′-iodoethoxy)-cyclohexene. This, together with the isolation of both exo- and endo-cyclisation products from 1-[2-(6,6-dimethylbicyclo[3.1.1]hept-2-en-2-ylmethoxy)ethyl]cyclohexa-2,5-diene- 1-carboxylic acid established that ring closures could also be satisfactorily mediated with these reagents. Preparations were completely free of metal contaminants and direct reduction of the alkyl radicals, prior to addition or cyclisation, was completely absent. However, the desired products were accompanied by alkylbenzenes, together with by-products from the initiator decompositions, and this complicated work-up. Failure to obtain 1-[2-(prop-2-yn-1-yloxy)cyclohexyl]cyclohexa-2,5-diene-1-carboxylic acid in Birch reductive alkylations with trans-1-iodo-2-(prop-2-yn-1-yloxy)cyclohexane (and the corresponding bromide) indicated a limitation on precursor synthesis. The Birch reduction-alkylation was not of universal applicability and was suppressed for alkyl halides having β-substituents.
- Baguley, Paul A.,Walton, John C.
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p. 2073 - 2082
(2007/10/03)
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- Beryllium dichloride: Efficient promoter for the addition of organolithiums and organomagnesiums to cyclohexen-2-one
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Organoberyllium compounds, generated by transmetallation from Grignard and organolithium reagents react with 2-cyclohexenone to give predominantly the adducts resulting from conjugated addition. The chemoselectivity of this reaction was found to be highly dependent upon the nature of organic moiety and of the conditions used.
- Krief, Alain,De Vos, Marie Joelle,De Lombart, Stephane,Bosret, Jean,Couty, Francois
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p. 6295 - 6298
(2007/10/03)
-
- Tandem energy transfer-electron transfer in the photosensitized alkylation of α,β-unsaturated ketones
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α,β-Unsaturated ketones are not conveniently alkylated by radicals generated from tetraalkylstannanes via photoinduced electron transfer (PET), either by direct irradiation or when a singlet sensitizer (an aromatic nitrile, a pyrilium salt) is used. However, the procedure is successful with tetramethyl pyromellitate (TMPM) as the sensitizer. TMPM is promoted to the triplet state by energy transfer from the unsaturated ketones and then sensitizes the cleavage of alkylstannanes by electron transfer. The alkyl radicals thus formed finally add to the unsaturated ketones, giving the β-alkyl derivatives.
- Fagnoni, Maurizio,Mella, Mariella,Albini, Angelo
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p. 777 - 780
(2007/10/03)
-
- Cyclic compounds
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The present invention is concerned with novel odorant compositions which are characterized by a content of cyclic compounds of the formula STR1 From this group of compounds the compounds I' with the meanings b), d), f) and g) are novel compounds.
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-
-
- Unique carbon-carbon bond homolysis in 3-alkylcyclohexa-1,4-dienyl-3-carboxylic acid radicals
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3-Substituted cyclohexadienyl radicals generated by hydrogen abstraction from 3-alkylcyclohexa-1,4-diene-3-carboxylic acids readily fragment to produce alkyl radicals and benzoic acid; suitably functionalised alkyl groups cyclize in moderate yields.
- Baguley, Paul A.,Binmore, Gavin,Milne, Aynsley,Walton, John C.
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p. 2199 - 2200
(2007/10/03)
-
- Enantioselective Allylation and t-Butylation of 2-Cyclohexenone in Aqueous Media in the Presence of β-Cyclodextrins as Chiral Auxiliaries
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β-Cyclodextrins promote enantioselective allylation and t-butylation of 2-cyclohexenone, using Zn-dust and alkyl halides in 5:1 (v/v) H2O-THF, affording optically active products with e.e. up to 50percent.
- Fornasier, Roberto,Marcuzzi, Franco,Piva, Marco,Tonellato, Umberto
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p. 633 - 634
(2007/10/03)
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- Direct formation of secondary and tertiary alkylzinc bromides and subsequent Cu(I)-mediated couplings
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Secondary and tertiary alkylzinc bromides can be generated from the direct oxidative addition of Rieke zinc to secondary and tertiary alkyl bromides in high yield. These organozinc reagents have been found to undergo copper-catalyzed conjugate addition, cross-coupling with acid chlorides, and carbocupration to activated alkynes.
- Rieke, Reuben D.,Hanson, Mark V.,Brown, Jeffrey D.,Niu, Q. Jason
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p. 2726 - 2730
(2007/10/03)
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- Reductive alkylation of electronegatively-substituted alkenes by alkylmercury halides
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Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCH2CH(EWG).] that in some cases react with RHgX to form RCH2CH(HgX)(EWG), e.g., EWG = (EtO)2PO or PhSO2. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCl/KI in Me2SO leads to the adduct mercurial via reaction of the adduct radicals with RHgI2-. The reactions of tertiary-enolyl adduct radicals are inefficient with RHgX/KI, and disproportionation of the adduct radicals is the major reaction pathway. For secondary- or tertiary-adduct radicals the reductive alkylation products are formed in excellent yield by reaction with RHgCl and silyl hydrides in Me2SO solution in a process postulated to involve RHgH as an intermediate. The relative reactivities of a number of α,β-unsaturated systems toward t-Bu. have been measured by competitive techniques. The results demonstrate a high reactivity of s-cis enones relative to the s-trans conformers.
- Russell, Glen A.,Shi, Bing Zhi,Jiang, Wan,Hu, Shuiesheng,Kim, Byeong H.,Baik, Woonphil
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p. 3952 - 3962
(2007/10/02)
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- The functionalization of saturated hydrocarbons. Part 24. The use of tert-butyl hydroperoxide: GoAggIV and GoAggV
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The use of tert-butyl hydroperoxide as an oxidant in Gif-type systems (GoAggIV and GoAgfV) catalyzed by various Fe(III) species is examined. Regioselectivity studids of these systems have revealed several characteristics similar to those observed for other prdviously reported Gif-type reactions. A common rdaction pathway for the GoAggIV and GoAggV oxidation systems and other Gif-type reactions (from alkane via alkyl hydroperoxide to ketone or alcohol) is seen.
- Barton, Derek H. R.,Chavasiri, Warinthorn
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- 3-Metallated enamines XI. Transmetallation of 3-Stannylated enamines - A new method to generate 1-aminoallyllithium compounds
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The transmetallation of 3-stannylated enamines, 1-morpholino-3-(trialkylstannyl)cycloalk-1-enes and 3-morpholino-5-(tributylstannyl)hex-3-ene, with butyllithium is a new and general way to generate s1-aminoallyllithium compounds. Stabilization by aromatic substituents is not further necessarily as in the case of preparation by deprotonation and even the thermodynamically less stable exoamino derivatives are accessible. Therefore homoenolate-equivalents of cyclic ketones are made available. Thus, the corresponding 3-alkylated or 3-silylated cycloalkanones and alken-3-ones were prepared via the 1-morpholinoallyllithium compounds.
- Ahlbrecht,Weber
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p. 1018 - 1025
(2007/10/02)
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- Mechanism of the Grignard Adddition Reaction. XVI. Homolytic and Concerted Mechanisms in the Reaction of α,β-Unsatureted Carbonyl Compounds with Grignard Reagents
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Kinetic measurements have shown that the addition of Grignard reagents to α,β-unsaturated carbonyl compounds takes place either by a concerted mechanism or by a homolytic mechanism.Phenylmagnesium bromide, which is incapable of homolysis, reacts rapidly in a 1,4-fashion if an s-cis conformation exists between the C=C and the C=O bonds, but only 1,2-addition takes place if the conformation is s-trans.tert-Butylmagnesium bromide is unsuited to the concerted reaction, but 1,4-addition takes place via homolysis.Primary and secondary Grignard reagents, like phenyl, react rapidly in a concerted manner with s-cis substrates, but unlike phenyl, these Grignard reagents may, with s-trans substrates, produce some 1,4-adduct via the homolytic mechanism.
- Holm, Torkil
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p. 925 - 929
(2007/10/02)
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- Electron Transfer Processes. Part 47. Reactions of Organometallic Reagents Involving Electron Transfer
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Radical chain processes occur in conjugate addition reactions of 2-cycloalkenones with t-BuHgl2(1-), (t-Bu)2CuLi or (t-Bu)3ZnLi as judged by the relative reactivity of 2-cyclopentenone > 2-cyclohexenone and by the effect of CH2=CPh2 as a radical trap.On t
- Russell, Glen A.,Baik, Woonphil,Ngoviwatchai, Preecha,Kim, Byeong Hyo
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p. 170 - 177
(2007/10/02)
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- γ-Silicon Stabilization of Carbonium Ions in Solvolysis. 4. Solvolysis of cis- and trans-3-(Trimethylsilyl)cyclohexyl and -3-tert-Butylcyclohexyl p-Bromobenzenesulfonates
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The solvolyses of cis- and trans-3-(trimethylsilyl)cyclohexyl and -3-tert-butylcyclohexyl p-bromobenzenesulfonates (1-4) have been examined in several ethanol- and trifluoroethanol-water solvent mixtures.The α- and β-deuterium kinetic isotope effects have
- Shiner, V.J.,Ensinger, Mark W.,Kriz, George S.,Halley, Karen A.
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p. 653 - 661
(2007/10/02)
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- Stereochemical Aspects of Oxirane Ring Opening. Heterogeneous Catalytic Deuterolysis of cis and trans-1,2-Epoxy-4-t-butylcyclohexanes
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2H NMR analysis of deuterolyzed products from cis- and trans-1,2-epoxy-4-t-butylcyclohexane indicated that the cleavage of the oxirane C-O bond proceeds with inversion of configuration over noble metal catalysts except for Ru, while with retention over Co
- Ishiyama, Jun-ichi,Yashima, Hiroaki,Matsuo, Hironobu,Senda, Yasuhisa,Imaizumi, Shin,et al.
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p. 989 - 992
(2007/10/02)
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- The Willgerodt-Kindler Reactions. 6. Isomerization of the Carbonyl Group in Alkanones and Cycloalkanones
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The most unusual feature of the Willgerodt-Kindler Reactions is the facile isomerization of the carbonyl function along a chain of unbranched methylene groups, or around a cycloaliphatic ring containing several connected methylene groups.We have demonstrated that the first step in the Kindler process is the formation of enamines by reaction of the carbonyl function with secondary aliphatic amines, followed by reaction of the enamine with certain sulfur-amine catalysts to form reactive heterocyclic sulfur intermediates that facilitate the elimination-readdition of the amines reversibly along the chain.It was shown that compounds of the type R2N-S-S-NR2 are effective catalysts but not compounds of the type R2N-S-NR2.Some cyclohexanone derivatives undergo aromatization, with anomalous results in certain cases.
- Carmack, Marvin,Behforouz, Mohammad,Berchtold, Glenn A.,Berkowitz, Samuel M.,Wiesler, Donald,Barone, Ralph
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p. 1305 - 1318
(2007/10/02)
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- ORGANOCOPPER REAGENTS IN DIMETHYL SULFIDE
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Organocopper(I) reagents, RCu, are both more stable and more reactive when prepared in dimethyl sulfide instead of ether or tetrahydrofuran.A wide range of Li reagents has been investigated with good results, as has a selection of Grignard reagents.Excellent yields of products are observed with typical substrates as α,β-unsaturated ketones and acid chlorides.
- Bertz, Steven H.,Dabbagh, Gary
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p. 425 - 434
(2007/10/02)
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- ORGANOMANGANESE (II) REAGENTS XVI: COPPER-CATALYZED 1,4-ADDITION OF ORGANOMANGANESE CHLORIDES TO CONJUGATED ENONES
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Copper-catalyzed conjugate addition of organomanganese chlorides to conjugated enones in THF, at 0 deg C, leads to the 1,4-addition products in high yields.The scope of the reaction is very large and the results are generally better than those obtained from organomagnesium compounds in the presence of a copper salts as well as from organocopper or cuprate reagents.Furthermore organomanganese chlorides are indisputably cheaper and more stable than the latter.
- Cahiez, Gerard,Alami, Mouad
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p. 3541 - 3544
(2007/10/02)
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- Mixed Organocuprates Derived from ortho-Heterosubstituted ArCu Species. Reactions with Simple α,β-Unsaturated Ketones
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We describe the reaction of new organocuprates of the form ArRTCuLi (Ar an ortho-heterosubstituted non-transferable ligand), and their reactions with simple α,β-unsaturated ketones.
- Arevalo, F.,Castedo, L.,Fernandez, B. R.,Mourino, A.,Sarandeses, L.
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p. 745 - 748
(2007/10/02)
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- 1,4-Addition of Triorganozincates and Silyldiorganozincates to α,β-Unsaturated Ketones
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Lithium and magnesium triorganozincates, prepared by combination of ZnCl2(TMEDA) with 3 molar equivalents of RLi or RMgX, or from dialkylzinc and 1 molar equivalent of RLi or RMgX, react with 2-cyclohexen-1-one (1) under mild conditions to produce moderate to good yields of the 1,4-addition products 2.The approximate reactivity order obtained from the product distribution using unsymmetrical zincates is tBuCH2 tBu, Me Me2PhSi.The latter groups are transferred with good selectivity from mixed reagents derived from Me2Zn.This sequence differs strikingly from that exhibited by unsymmetrical cuprates which transfer neopentyl very easily, and also tert-butyl more easily than the corresponding zincates.The methylation with Me3ZnLi is catalyzed by cobalt complexes.Other enones (7-13) generally give poor yields, and the cobalt-catalyzed methylation of isophorone (3) is complicated by a Kharasch-type deconjugation.Mixed silyldialkylzincates, Me2PhSiZnR2Li, produce the β-silyl ketones from a variety of unhindered or moderately hindered enones in practically useful yields; one example of an α,β-unsaturated ester (12) is also included.
- Tueckmantel, Werner,Oshima, Koichiro,Nozaki, Hitosi
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p. 1581 - 1593
(2007/10/02)
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- CONJUGATE ADDITIONS TO α,β-UNSATURATED CARBONYL COMPOUNDS IN AQUEOUS MEDIA
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Alkyl halides in the presence of zinc copper couple add smoothly to α-enones and α-enals in aqueous solvents.Sonication enhances the efficiency of the process, which leads to the conjugate adducts in high yields.The reaction follows most probably a radical pathway, and can be used for the addition of functionalized groups.
- Petrier, C.,Dupuy, C.,Luche, J. L.
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p. 3149 - 3152
(2007/10/02)
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