- Manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives
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Herein, we report a manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives through cyclic C–C bond cleavage. The reaction happens via a radical-mediated pathway to selectively generate 1,5-ketoesters. A variety of substrates with subst
- Meyer, Tim,Yin, Zhiping,Wu, Xiao-Feng
-
supporting information
p. 864 - 867
(2019/02/20)
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- Stereoselective nucleophilic addition reactions to cyclic n-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and dft calculations
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In this study, six-membered N-acyliminium ions were generated by the “indirect cation pool” method and reacted with several nucleophiles. These reactions afforded disubstituted piperidine derivatives with high diastereoselectivities and good to excellent
- Mitsudo, Koichi,Yamamoto, Junya,Akagi, Tomoya,Yamashita, Atsuhiro,Haisa, Masahiro,Yoshioka, Kazuki,Mandai, Hiroki,Ueoka, Koji,Hempel, Christian,Yoshida, Jun-ichi,Suga, Seiji
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supporting information
p. 1192 - 1202
(2018/06/04)
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- Inorganic alkali catalytic 1, 5 - ketonic ester apperception compound synthesis method
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The invention discloses a synthesis method for a 1,5-ketonic ester compound under catalyzing of inorganic base. The synthesis method comprises the following steps: taking a compound of the general formula I as a raw material, taking inorganic base as a ca
- -
-
Paragraph 0045-0047
(2017/10/11)
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- Sequential Michael addition/retro-Claisen condensation of aromatic β-diketones with α,β-unsaturated esters: An approach to obtain 1,5-ketoesters
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A K2CO3-catalyzed one-pot protocol involving sequential C-C bond formation and cleavage of aromatic β-diketones with α,β-unsaturated esters is developed to obtain 1,5-ketoesters. The sequential reaction via Michael addition and retro-Claisen condensation proceeds smoothly under mild conditions in up to 98% isolated yield. The mechanism study disclosed that the cascade process involved C-C bond cleavage of aromatic β-diketone as a phenacyl donor under alcoholic alkalescent conditions.
- Cai, Gui-Xin,Wen, Jing,Lai, Ting-Ting,Xie, Dan,Zhou, Cheng-He
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supporting information
p. 2390 - 2394
(2016/03/01)
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- Enantioselective Photocatalytic [3 + 2] Cycloadditions of Aryl Cyclopropyl Ketones
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Control of stereochemistry in photocycloaddition reactions remains a substantial challenge; almost all successful catalytic examples to date have involved [2 + 2] photocycloadditions of enones. We report a method for the asymmetric [3 + 2] photocycloaddition of aryl cyclopropyl ketones that enables the enantiocontrolled construction of densely substituted cyclopentane structures not synthetically accessible using other catalytic methods. These results show that the dual-catalyst strategy developed in our laboratory broadens synthetic chemists' access to classes of photochemical cycloadditions that have not previously been feasible in enantioselective form.
- Amador, Adrian G.,Sherbrook, Evan M.,Yoon, Tehshik P.
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supporting information
p. 4722 - 4725
(2016/05/10)
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- Design and synthesis of lactam-thiophene carboxylic acids as potent hepatitis C virus polymerase inhibitors
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Herein we report the successful incorporation of a lactam as an amide replacement in the design of hepatitis C virus NS5B Site II thiophene carboxylic acid inhibitors. Optimizing potency in a replicon assay and minimizing potential risk for CYP3A4 induction led to the discovery of inhibitor 22a. This lead compound has a favorable pharmacokinetic profile in rats and dogs.
- Barnes-Seeman, David,Boiselle, Carri,Capacci-Daniel, Christina,Chopra, Rajiv,Hoffmaster, Keith,Jones, Christopher T.,Kato, Mitsunori,Lin, Kai,Ma, Sue,Pan, Guoyu,Shu, Lei,Wang, Jianling,Whiteman, Leah,Xu, Mei,Zheng, Rui,Fu, Jiping
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p. 3979 - 3985
(2014/11/08)
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- Stoichiometric reactions of acylnickel(II) complexes with electrophiles and the catalytic synthesis of ketones
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Acylnickel(II) complexes feature prominently in cross-electrophile coupling (XEC) reactions that form ketones, yet their reactivity has not been systematically investigated. We present here our studies on the reactivity of acylnickel(II) complexes with a series of carbon electrophiles. Bromobenzene, α-chloroethylbenzene, bromooctane, and iodooctane were reacted with (dtbbpy)NiII(C(O)C5H11)(Br) (1b) and (dtbbpy)NiII(C(O)tolyl)(Br) (1c) to form a variety of organic products. While reactions with bromobenzene formed complex mixtures of ketones, reactions with α-chloroethylbenzene were highly selective for the cross-ketone product. Reactions with iodooctane and bromooctane also produced the cross-ketone product, but in intermediate yield and selectivity. In most cases the presence or absence of a chemical reductant (zinc) had only a small effect on the selectivity of the reaction. The coupling of 1c with iodooctane (60% yield) was translated into a catalytic reaction, the carbonylative coupling of bromoarenes with primary bromoalkanes (six examples, 60% average yield).
- Wotal, Alexander C.,Ribson, Ryan D.,Weix, Daniel J.
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p. 5874 - 5881
(2015/01/09)
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- Remote ester group leads to efficient kinetic resolution of racemic aliphatic alcohols via asymmetric hydrogenation
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A highly efficient method for kinetic resolution of racemic aliphatic alcohols without conversion of the hydroxyl group has been realized; the method involves hydrogenation mediated by a remote ester group and is catalyzed by a chiral iridium complex. This powerful, environmentally friendly method provides chiral δ-alkyl-δ-hydroxy esters and δ-alkyl-1,5-diols in good yields with high enantioselectivities even at extremely low catalyst loading (0.001 mol %).
- Yang, Xiao-Hui,Wang, Ke,Zhu, Shou-Fei,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 17426 - 17429
(2015/02/02)
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- Microwave-assisted aqueous Krapcho decarboxylation
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The Krapcho decarboxylation of alkyl malonate derivatives has been adapted to aqueous microwave conditions. Various salt additives were examined, and both the cation and the anion impacted the facility of the reaction. A strong correlation was found between the pKa of the anion and the reaction rate, suggesting a straightforward base-catalyzed hydrolysis. Lithium sulfate gave the best results, obviating the need for DMSO co-solvent. Georg Thieme Verlag Stuttgart · New York.
- Mason, Jeremy D.,Murphree, S. Shaun
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supporting information
p. 1391 - 1394
(2013/07/26)
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- NEW CCR2 RECEPTOR ANTAGONISTS AND USES THEREOF
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The present invention relates to novel antagonists for CCR2 (CC chemokine receptor 2) and their use for providing medicaments for treating conditions and diseases, especially pulmonary diseases like asthma and COPD.
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Page/Page column 45
(2012/01/14)
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- Mn(III)-mediated formal [3+3]-annulation of vinyl azides and cyclopropanols: A divergent synthesis of azaheterocycles
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Mn(III)-mediated formal [3+3]-annulation has been developed using readily available vinyl azides and cyclopropanols with a wide range of substituents. Vinyl azides were successfully applied as a three-atom unit including one nitrogen to prepare pyridines and σ-lactams by the reactions with monocyclic cyclopropanols as well as to construct 2-azabicyclo[3.3.1] and 2-azabicyclo[4.3.1] frameworks with bicyclic cyclopropanols, bicyclo[3.1.0]hexan-1-ols, and bicyclo[4.1.0]heptan-1-ols. These reactions were initiated by a radical addition of β-carbonyl radicals, generated by the one-electron oxidation of cyclopropanols with Mn(III), to vinyl azides to give iminyl radicals, which cyclized with the intramolecular carbonyl groups. In addition, application of the present methodology to a synthesis of the quaternary indole alkaloid, melinonine-E, was accomplished.
- Wang, Yi-Feng,Toh, Kah Kah,Ng, Eileen Pei Jian,Chiba, Shunsuke
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scheme or table
p. 6411 - 6421
(2011/06/19)
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- Generation of β-keto radicals from cyclopropanols catalyzed by AgNO3
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Various β-keto radicals are generated from cyclopropanols by treatment with a catalytic amount of AgNO3 and (NH4) 2S2O8 as a reoxidant in the presence of pyridine. Thus, generated β-keto radicals react with alkenes to yield addition products. Copyright
- Chiba, Shunsuke,Cao, Zhengyan,El Bialy, Serry Atta Atta,Narasaka, Koichi
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- KF-alumina-mediated selective double Michael additions of aryl methyl ketones: A facile entry to the synthesis of functionalized pimelate esters and derivatives
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Here we describe simple and efficient double Michael additions of aromatic and aliphatic methyl ketones to electron deficient alkenes promoted on a surface of KF-alumina. This one-pot procedure provides an easy access to a host of functionalized pimelate
- Basu, Basudeb,Das, Pralay,Hossain, Ismail
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p. 2224 - 2226
(2007/10/03)
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- Catalytic cross-coupling reaction of esters with organoboron compounds and decarbonylative reduction of esters with HCOONH4: A new route to acyl transition metal complexes through the cleavage of acyl-oxygen bonds in esters
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The Ru3(CO)12-catalyed cross-coupling reaction of esters with organoboron compounds leading to ketones is described. A wide variety of functional groups can be tolerated under the reaction conditions. Aromatic boronates function as a coupling partner to give aryl ketones. Acyl-alkyl coupling to dialkyl ketones is also achieved by the use of 9-alkyl-9-BBN in place of boronates. The Ru3(CO)12- catalyzed decarbonylative reduction of esters with ammonium formate (HCOONH 4) leading to hydrocarbons is also described. No expected aldehydes are produced, and controlled experiments indicate that aldehydes are not intermediate for the transformation. A hydrosilane can also be used as a reducing reagent in place of HCOONH4. A wide variety of functional groups are compatible for both reactions. The key step for both catalytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.
- Tatamidani, Hiroto,Yokota, Kazuhiko,Kakiuchi, Fumitoshi,Chatani, Naoto
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p. 5615 - 5621
(2007/10/03)
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- PYRROLOPYRIDAZINE DERIVATIVES
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The invention relates to compound of the formula (I) or its salt, in which R1, R2, R3 and R4 are as defined in the description, their use of as medicament, the process for their preparation and use for the treatment of PDE-IV or TNF-α mediated diseases.
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- Michael addition of stannyl ketone enolate to α,β-unsaturated esters catalyzed by tetrabutylammonium bromide and an ab initio theoretical study of the reaction course
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Michael addition of stannyl ketone enolates to α,β-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu4NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl4 or Bu4NF) failed to give the desired products. The bromide anion from Bu4NBr coordinates to the tin center in enolate to accelerate the conjugate addition where a five-coordinated tin species was generated. The coordination of the bromide anion significantly raises the HOMO level of tin enolate and enhances its nucleophilicity. The conjugate addition provides the intermediate Michael adduct, which has an ester enolate moiety, and the adduct immediately transforms to α-stannyl γ-ketoester by keto - enol tautomerization. This step contributes to the stabilization of the product system and leads to a thermodynamically favorable reaction course. An ab initio calculation reveals that the activation energy in the reaction using the bromide anion is lower than that of the reaction without using it. The transition state in either reaction course has a linear structure, not a cyclic one. This system can be applied to a variety of tin enolates and α,β-unsaturated carbonyls involving enoates, enones, and unsaturated amides.
- Yasuda, Makoto,Chiba, Kouji,Ohigashi, Noriyuki,Katoh, Yasuhiro,Baba, Akio
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p. 7291 - 7300
(2007/10/03)
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- Synthesis of 3-arylpropenyl, 3-arylpropynyl and 3-arylpropyl 2-azetidinones as cholesterol absorption inhibitors: Application of the palladium-catalyzed arylation of alkenes and alkynes
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A series of 3-(3'-arylpropenyl)-2-azetidinones 8a-8k and 3-(3'-arylpropynyl)-2-azetidinones 16m-16p were prepared by the palladium-catalyzed arylation of 3-(3'-propenyl)-2-azetidinone 7, or by arylation of 4-pentenoic acid, or via ethyl 4-pentynoate followed by 2-azetidinone ring construction. The unsaturated 2-azetidinones were transformed to their saturated analogs 9a-9p by catalytic hydrogenation. Azetidinones 8a-8k, 9a-9p, and 16m-16p were evaluated for their biological activity as cholesterol absorption inhibitors in hamsters. (C) 2000 Elsevier Science Ltd.
- Rosenblum, Stuart B.,Huynh, Tram,Afonso, Adriano,Davis Jr., Harry R.
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p. 5735 - 5742
(2007/10/03)
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- Reactions of Grignard reagents with bis- or mono-phosphonium ions in Situ generated from Bu3P and dicarboxylic acid dichlorides or ω-ethoxycarbonyl alkanoyl chlorides as a novel method to obtain diketones and ketoesters
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Reactions of Grignard reagents with bis-phosphonium or mono-phosphonium ions in situ generated from Bu3P and ClCO(CH2)(n)COCl (5) or ClCO(CH2)(n)CO2Et (13) as a tool for preparation of symmetrical diketones or ketoesters were examined. Addition of Bu3P (2.0 eq) to a THF solution of 5 (n=2) at -40°C followed by addition of n-BuMgCl (2.0 eq) gave the corresponding diketone in good yield. When a mixture of Bu3P and the Grignard reagent (2.0 eq each) was added to the dichloride solution at the same temperature, a better result was obtained. The latter method not with PhMgBr but with n-BuMgCl or MeMgBr was shown to be useful for preparation of symmetrical alkanediones and keto alkanoates from various 5 (n=2 - 6) and 13 (n=2 or 3), respectively. For synthesis of α-diketones or α-ketoesters, only PhMgBr entered the reaction, although the yields were not satisfactory. Addition of a mixture of Bu3P (2.0 eq), MeMgBr (1.0 eq) and BuMgCl (1.0 eq) to a THF solution of 5 (n=4) at -40°C afforded a mixture of 2,7-undecanedione and the corresponding two symmetrical diketones, with the yield of the unsymmetrical diketone being 36%.
- Maeda,Hino,Yamauchi,Ohmori
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p. 1196 - 1199
(2007/10/03)
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- Intramolecular Photoaddition of Secondary α-(Aminoalkyl)styrenes
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The photophysical and photochemical behavior of a series of α-styrenes with two to four methylenes separating the styryl and amino groups and an (aminoalkyl)indene have been investigated and the results compared to those for the intermolecular reaction of α-methylstyrene with diethylamine.Both inter- and intramolecular quenching of styrene fluorescence by the amine is observed, indicative of electron-transfer quenching as the initial step in these reactions.The resulting exciplex undergoes regioselective N-H proton transfer to styrene C-βyielding a biradical, in the case of the intramolecular reaction, and a radical pair, in the case of the intermolecular reaction.Biradical or radical pair combination yields styrene-amine addition products.The conformation of the intermediate exciplex is proposed to control the regioselectivity of the intramolecular N-H proton transfer process.
- Lewis, Frederick D.,Bassani, Dario M.,Reddy, G. Dasharatha
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p. 6390 - 6393
(2007/10/02)
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- Preparation and Chemistry of the Active Copper Species Derived from CuI*PBu3, CuI*PPh3, and CuCN*nLiX Complexes
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The preparation of highly reactive copper by the reduction of CuI*PBu3, CuI*PPh3, and CuCN*nLiX copper(I) complexes with the preformed lithium naphthalenide is described.It was found, for all three Cu(I) complexes, that the reduction temperature proved crucial to reactivity of the zerovalent copper species as measured by the ability of the active copper to undergo oxidative addition to carbon-halogen bonds.The lower the reduction temperature the more reactive the zerovalent copper species becomes.The low-temperature reduction allows for the formation of highly reactive copper from CuCN*nLiX complexes.This active copper species undergoes oxidative addition to alkyl and aryl bromides in high yield to form the corresponding organocopper reagent directly without the need for other organometallic precursors.Moreover, the alkyl and aryl bromides can obtain a wide range of functional groups as they are not affected in the oxidative addition step.The functionalized organocopper reagents derived from CuCN*nLiX based active copper are the reagent of choice in the cross-coupling of acid chlorides to produce ketones as well as the 1,4-addition reaction with enones.The lack of phosphines associated with organocopper reagents stemming from CuCN-based active copper makes product isolation more facile.While the functionalized organocopper reagents derived from CuCN*nLiX complexes provide higher isolated yields in the formentioned reactions, they are not nucleophilic enough to undergo inter- or intramolecular epoxide openings.The use of both CuI*PBu3 and CuI*PPh3 Cu(I) complexes in the intramolecular epoxide openings of aryl bromoepoxides is presented.The regiochemistry, endo vs. exo, was shown to be affected by the Cu(I) complex used to generate the active copper species, the solvent, and the pattern of substitution around the epoxide moiety.The active copper species as well as the resulting organocopper reagents derived from both CuI*PBu3 and CuCN*nLiX were investigated using both 31P and 13C NMR.The data from 31P NMR investigation held some evidence for a highly reduced copper(0)-phosphine complex while the 13C studies of the CuCN*nLiX complexes indicated that these species have limited solubility in THF.
- Rieke, Reuben D.,Stack, Douglas E.,Dawson, Bryan T.,Wu, Tse-Chong
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p. 2483 - 2491
(2007/10/02)
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- Direct Formation and Reaction of Thienyl-Based Organocopper Reagents
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The preparation of a highly reactive zerovalent copper complex by the direct reduction of lithium (2-thienylcyano)cuprate with preformed lithium naphthalenide is described.This active copper species oxidatively adds to carbon-halogen bonds to form organocopper reagents.The ability to directly form the organocopper reagent from organic halides and active copper allows for the incorporation of a wide variety of functionalities to be present in the organic halides and the organocopper reagents.Significantly, this formulation of active copper was able to oxidatively add to allyl chlorides and acetates at low temperatures to allow the direct formation of allylic organocopper reagents without Wurtz-type homocoupling.These functionalized organocopper compounds are able to undergo a variety of reactions, such as cross-coupling with acid chlorides, 1,4-conjugate addition with α,β-unsaturated carbonyl compounds, and intermolecular and intramolecular epoxide-opening reactions.Subsequently, this copper species avoids the use of phosphine ligands affording the product isolation much more convenient than with phosphine-based organocopper reagents.
- Rieke, Reuben D.,Klein, Walter R.,Wu, Tse-Chong
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p. 2492 - 2500
(2007/10/02)
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- Generation of β-Carbonyl Radicals from Cyclopropanol Derivatives by the Oxidation with Manganese(III) 2-Pyridinecarboxylate and Their Reactions with Electron-Rich and -Deficient Olefins
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Various β-carbonyl radicals are generated oxidatively from cyclopropanol derivatives by the use of manganese(III) 2-pyridinecarboxylate (Mn(pic)3).These β-carbonyl radicals react with electron-rich olefins such as conjugated silyl enol ethers, a ketene th
- Iwasawa, Nobuharu,Hayakawa, Satoshi,Funahashi, Masahiro,Isobe, Koichi,Narasaka, Koichi
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p. 819 - 827
(2007/10/02)
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- The Direct Formation of Functionalized Alkyl(aryl)zinc Halides by Oxidative Addition of Highly Reactive Zinc with Organic Halides and Their Reactions with Acid Chlorides, α,β-Unsaturated Ketones, and Allylic, Aryl, and Vinyl Halides
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Highly reactive zinc, prepared by the lithium naphthalenide reduction of ZnCl2, readily undergoes oxidative addition to alkyl, aryl, and vinyl halides under mild conditions to generate the corresponding organozinc compounds in excellent yields.Significantly, the reaction will tolerate a spectrum of functional groups on the organic halides.Accordingly, this approach can now be used to prepare a wide variety of highly functionalized organozinc compounds.In the presence of Cu(I) salts, the organozinc compounds cross-couple with acid chlorides, conjugatively add to α,β-unsaturated ketones, and regioselectively undergo SN2' substitution reactions with allylic halides.They also cross-couple with aryl or vinyl halides with Pd(0) catalysts.
- Zhu, Lishan,Wehmeyer, Richard M.,Rieke, Reuben D.
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p. 1445 - 1453
(2007/10/02)
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- Generation of β-Keto Radicals from Cyclopropanol Derivatives by the Use of Manganese(III) 2-Pyridinecarboxylate as an Oxidant and Their Reactions with Olefins
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Various β-keto radicals are generated from cyclopropanol derivates such as 1- or 2-substituted cyclopropanols and a cyclopropanone hemiacetal by the use of manganese(III) 2-pyridinecarboxylate, and their reactions with electron-rich olefins give cross-addition products in good yields.
- Iwasawa, Nobuharu,Hayakawa, Satoshi,Isobe, Koichi,Narasaka, Koichi
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p. 1193 - 1196
(2007/10/02)
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- NEW ORGANOCOPPER REAGENTS PREPARED UTILIZING HIGHLY REACTIVE COPPER
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Highly reactive copper solutions have been prepared by the lithium naphthalide reduction of copper(I) iodide/trialkylphosphine complexes.These activated copper solutions will react with organic halides under very mild conditions to form stable organocopper reagents.Significantly, the organocopper reagents can contain considerable functionalities such as ester, nitrile, chloride, epoxide, and ketone groups.These functionalized organocopper species undergo many reactions typical of other organocopper species.Intermolecular 1,4-additions, epoxide-opening reactions, and ketone formation with acid chlorides have been successfully achieved.In addition, this methodology has been applied to an intramolecular epoxide-cleavage reaction.The influence of the connecting chain length, substitution pattern, reaction solvent, and CuI/phosphine complex upon the regioselectivity of the intramolecular cyclization is described.
- Rieke, Reuben D.,Wehmeyer, Richard M.,Wu, Tse-Chong,Ebert, Greg W.
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p. 443 - 454
(2007/10/02)
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- DIRECT FORMATION AND REACTION OF FUNCTIONALIZED THIENYL-BASED ORGANOCOPPER REAGENTS
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Highly reactive copper solutions have been prepared by the direct reduction of lithium 2-thienylcyanocuprate.Product isolation was much easier using the thienyl-based organocopper reagents as opposed to phosphine-based organocopper reagents
- Rieke, Reuben D.,Wu, Tse-Chong,Stinn, Dean E.,Wehmeyer, Richard M.
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p. 1833 - 1840
(2007/10/02)
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- DIRECT FORMATION OF FUNCTIONALIZED KETONES VIA THE COUPLING OF FUNCTIONALIZED ORGANOCOPPER REAGENTS WITH ACID CHLORIDES
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Highly reactive copper solutions have been prepared by the lithium naphtalide reduction of copper(I) iodide/triphenyl-phosphine complex.These copper solutions react rapidly with functionalized alkyl halides to give organocopper reagents wich have been effectively trapped with acid chlorides giving functionalized ketones in good yields.Ester, nitrile, chloride, remote epoxide, and, to some degree, ketone groups can be tolerated by this approach.
- Wehmeyer, Richard M.,Rieke, Reuben D
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p. 4513 - 4516
(2007/10/02)
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- Synthesis and Reactivity toward Acyl Chlorides and Enones of the New Highly Functionalized Copper Reagents RCu(CN)ZnI
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The new and highly functionalized copper reagents RCu(CN)ZnI obtained from readily available primary and secondary alkylzinc iodides by a transmetalation in THF with the soluble salt, CuCN*2LiX, react in good yields with acyl chlorides and enones, respectively, to afford ketones and 1,4-addition products.
- Knochel, Paul,Yeh, Ming Chang P.,Berk, Scott C.,Talbert Jason
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p. 2390 - 2392
(2007/10/02)
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- Palladium-Catalyzed Reaction of Acyliron Complexes with Aryl Halydes. A Convenient Synthesis of Aromatic Ketones
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Acyliron complexes, easily prepared from disodium tetracarbonylferrate and alkyl halides, reacted with aryl iodides in the presence of a catalytic amount of Pd(PPh3)4 and a cocatalyst, ZnCl2, to give aromatic ketones in good yields. (R)-2-Methyl-1-phenyl-octanone was prepared starting from (S)-2-bromooctane in an excellent optical yield.
- Koga, Teruyoshi,Makinouchi, Shinako,Okukado, Nobuhisa
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p. 1141 - 1144
(2007/10/02)
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- α,β-Unsaturated Orthoesters as Michael Acceptors. The Trityl Salt-Catalyzed Michael Reaction of α,β-Unsaturated Orthoesters with Silyl Enol Ethers
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In the presence of a catalytic amount of trityl salts, α,β-unsaturated orthoesters react with various silyl enol ethers to afford the corresponding Michael adducts in good yields.
- Kobayashi, Shu,Mukaiyama, Teruaki
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p. 1183 - 1186
(2007/10/02)
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- TYPE II PHOTOREACTIONS OF α-ALKYL β-OXOESTERS. NEIGHBORING GROUP EFFECT ON 1,4-BIRADICAL REACTIONS AND EFFECTIVE INTERNAL FILTER EFFECT BY THE TYPE II PHOTOPRODUCT
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The α-alkyl β-oxoesters 1 undergo type II photoreactions.The process of back hydrogen transfer in the 1,4-biradical intermediate to revert to the starting ester is suppressed because of the intramolecular hydrogen bonding between the hydroxyl and carboalkoxyl groups in the biradical intermediate.The hydrogen bonding determines the stereochemistry of 1,4-biradical cyclization.The cyclobutanols having the hydroxyl group cis to the carboalkoxyl group are formed exclusively from the α-alkyl β-oxoesters 1.The enol form of the type II elimination product, the benzoylacetate 2, acts as an effective internal filter for the photoreaction of the α-alkyl β-oxoester 1.
- Hasegawa, Tadashi,Arata, Yoshiaki,Endoh, Masaru,Yoshioka, Michikazu
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p. 1667 - 1674
(2007/10/02)
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