- Stereoselective synthesis of cis-2-aryl- and 2-alkyl-1-chlorocyclopropanecarboxaldehydes
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The title compounds were stereoselectively synthesized via a semi-benzilic Favorskii rearrangement of 3-aryl- and 3-alkyl-2,2-dichlorocyclobutanols, obtained by stereoselective reduction of the corresponding cyclobutanones. This synthetic pathway, starting from the synthesis of 3-substituted-2,2-dichlorocyclobutanones can be performed in one day with total yields up to 60% after purification. Reduction of the cyclobutanones yielded only cis-3-substituted cyclobutanols. Taking into account the stereoselectivity of the rearrangement, 1-halocyclopropanecarboxaldehydes, of which very few articles have been published, can be seen as highly interesting building blocks for further elaboration.
- Verniest, Guido,Bombeke, Filip,Kulinkovich,De Kimpe, Norbert
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Read Online
- Radical C-C Bond Cleavage/Addition Cascade of Benzyl Cycloketone Oxime Ethers Enabled by Photogenerated Cyclic Iminyl Radicals
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A light-driven, metal-free, and iminyl radical-mediated ring-opening C-C bond cleavage/addition cascade of O-4-methoxybenzyl oxime ethers and alkenes is described for the first time. The reaction shows a broad substrate scope and high functional group compatibility with both components, giving the corresponding valuable oxo nitriles in generally good yields. Key to the success of this protocol is the generation of cyclic iminyl radicals from the O-4-methoxybenzyl oxime ethers via a photocatalytic hydrogen atom transfer (HAT) process. The proposed main pathway is also supported by the preliminary mechanistic studies.
- Wang, Peng-Zi,He, Bin-Qing,Cheng, Ying,Chen, Jia-Rong,Xiao, Wen-Jing
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Read Online
- Copper-Catalyzed Sulfonylation of Cyclobutanone Oxime Esters with Sulfonyl Hydrazides
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A copper-catalyzed radical cross-coupling of cyclobutanone oxime esters with sulfonyl hydrazides has been developed. The copper-based catalytic system proved crucial for cleavage of the C-C bond of cyclobutanone oximes and for selective C-S bond-formation involving persistent sulfonyl-metal radical intermediates. This protocol is distinguished by the low-cost catalytic system, which does not require ligand, base, or toxic cyanide salt, and by the use of readily accessible starting materials, as well as broad substrate scope, providing an efficient approach to various diversely substituted cyano-containing sulfones.
- Dong, Bingbing,Lu, Jiansha,Bao, Honghao,Zhang, Yuanyuan,Liu, Yingguo,Leng, Yuting
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supporting information
p. 3769 - 3776
(2021/07/14)
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- Manganese=Catalyzed Achmatowicz Rearrangement Using Green Oxidant H2O2
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Oxidation reactions have been extensively studied in the context of the transformations of biomass=derived furans. However, in contrast to the vast literature on utilizing the stoichiometric oxidants, such as m=CPBA and NBS, catalytic methods for the oxidative furan=recyclizations remain scarcely investigated. Given this, we report a means of manganese=catalyzed oxidations of furan with low loading, achieving the Achmatowicz rearrangement in the presence of hydrogen peroxide as an environmentally benign oxidant under mild conditions with wide functional group compatibility.
- Gao, Ziwei,Gou, Jing,Hao, Zhe,Hou, Jing,Li, Chaoqun,Li, Gaoqiang,Xing, Qingzhao,Yu, Binxun
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p. 9563 - 9586
(2021/07/20)
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- Visible-Light-Promoted Selenocyanation of Cyclobutanone Oxime Esters Using Potassium Selenocyanate
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We report the visible-light-promoted selenocyanation of cyclobutanone oxime esters using potassium selenocyanate in the presence of a fac-Ir(ppy)3 catalyst for the first time. Because of the mild conditions employed and use of readily accessible potassium selenocyanate, this method is an effective and green strategy for the synthesis of cyano and selenocyano bifunctional substituted alkanes.
- Zhao, Xia,Ji, Liangshuo,Gao, Yu,Sun, Tengteng,Qiao, Jiamin,Li, Ankun,Lu, Kui
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p. 11399 - 11406
(2021/09/02)
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- Nickel-Catalyzed Favorskii-Type Rearrangement of Cyclobutanone Oxime Esters to Cyclopropanecarbonitriles
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A nickel-catalyzed base-promoted rearrangement of cyclobutanone oxime esters to cyclopropanecarbonitriles was developed. The ring opening of cyclobutanone oxime esters occurs at the sterically less hindered side. A base-promoted nickelacyclobutane intermediate, formed in situ, is assumed to be involved in the formation of the product.
- Fang, Ping,Mei, Tian-Sheng,Shuai, Bin
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supporting information
p. 1637 - 1641
(2021/10/02)
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- Visible-Light Photoredox-Catalyzed Dicarbofunctionalization of Styrenes with Oxime Esters and CO2: Multicomponent Reactions toward Cyanocarboxylic Acids and γ-Keto Acids
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A photoredox-catalyzed dicarbofunctionalization of styrenes with oxime esters and CO2 has been achieved. Notably, a series of four-, five-, or six-membered cyclic ketone oximes worked well to furnish a wide range of ε-, ζ-, and η-cyanocarboxylic acids in good yields. Furthermore, a series of γ-keto acids also could be obtained by employing acyclic ketone oxime esters as the carbonyl radical precursor. It provides convergent access to diverse biologically important cyanocarboxylic and γ-keto acids.
- Bai, Junxue,Li, Miao,Zhou, Cong,Sha, Yu,Cheng, Jiang,Sun, Jianwei,Sun, Song
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supporting information
p. 9654 - 9658
(2021/12/14)
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- Synthesis of Silylated Cyclobutanone and Cyclobutene Derivatives Involving 1,4-Addition of Zinc-Based Silicon Nucleophiles
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A copper-catalyzed conjugate silylation of various cyclobutenone derivatives with Me2PhSiZnCl ? 2LiCl or (Me2PhSi)2Zn ? xLiCl (x≤4) to generate β-silylated cyclobutanones is reported. Trapping the intermediate enolate with ClP(O)(OPh)2 affords silylated enol phosphates that can be further engaged in Kumada cross-coupling reactions to yield silylated cyclobutene derivatives.
- Cui, Ming,Oestreich, Martin
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supporting information
p. 16103 - 16106
(2021/10/12)
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- Metal-free chalcogenation of cycloketone oxime esters with dichalcogenides
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We report the metal-free chalcogenation of cycloketone oxime esters with dichalcogenides via a radical process. Because of the metal-free condition and use of readily accessible dichalcogenides, this method is an effective and green strategy for the synthesis of chalcogen-substituted butyronitrile.
- Ji, Liangshuo,Qiao, Jiamin,Liu, Junjie,Tian, Miaomiao,Lu, Kui,Zhao, Xia
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supporting information
(2021/06/15)
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- Metal-Free sp3 C-SCF3 Coupling Reactions between Cycloketone Oxime Esters and S-trifluoromethyl 4-Methylbenzenesulfonothioate
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A novel sp3 C-SCF3 coupling reaction between cycloketone oxime esters and S-trifluoromethyl 4-methylbenzenesulfonothioate was achieved. Ethanol was found to facilitate this transformation by trapping the sulfonyl cation. The metal-free and photocatalyst-free reaction conditions, as well as the broad substrate scope, make this a green protocol for the synthesis of SCF3-substituted nitriles.
- Zhao, Xia,Tian, Miaomiao,Ji, Liangshuo,Liu, Junjie,Lu, Kui
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supporting information
p. 863 - 866
(2020/02/04)
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- Photoinduced, Copper-Catalyzed Three-Component Annulation of gem-Dialkylthio Enynes
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Photoinduced, copper-catalyzed three-component radical annulation of gem-dialkylthio enynes, cyclobutanone oxime esters, and boronic acids was achieved, forming highly functionalized aryl thienyl sulfides with both good chemo- and diastereoselectivities. The reaction proceeds through a domino sequence involving cyanoalkyl radical-mediated intramolecular annulation of gem-dialkylthio enyne, alkenyl radical-promoted C(sp3)-S bond cleavage, and sulfur-centered radical-trapped Cu(II)-facilitated C-S cross-coupling. The protocol features simultaneous establishment of cyanoalkyl, cyclopentanone, and thiophene moieties and a thioether C-S bond in one pot with broad substrate scopes and versatile functional group tolerance under mild conditions.
- Lou, Jiang,Ma, Juan,Xu, Bao-Hua,Zhou, Yong-Gui,Yu, Zhengkun
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supporting information
p. 5202 - 5206
(2020/07/15)
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- Synthesis of trisubstituted alkenes by Ni-catalyzed hydroalkylation of internal alkynes with cycloketone oxime esters
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A method for Ni-catalyzed hydroalkylation of internal alkynes with cycloketone oxime esters was developed. The reaction has a broad substrate scope. This hydroalkylation shows excellent regio-and stereo-selectivity. This method enables readily available starting materials to be used to access a range of cyano-substituted single-configuration trisubstituted alkenes. These are valuable feedstock chemicals and are widely used in synthetic and medicinal chemistry.
- Lu, Xiao-Yu,Liu, Chuang-Chuang,Jiang, Run-Chuang,Yan, Lu-Yu,Liu, Qi-Le,Wang, Qing-Qing,Li, Jia-Mei
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supporting information
p. 14191 - 14194
(2020/11/24)
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- The Silicon-Hydrogen Exchange Reaction: A Catalytic σ-Bond Metathesis Approach to the Enantioselective Synthesis of Enol Silanes
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The use of chiral enol silanes in fundamental transformations such as Mukaiyama aldol, Michael, and Mannich reactions as well as Saegusa-Ito dehydrogenations has enabled the chemical synthesis of enantiopure natural products and valuable pharmaceuticals. However, accessing these intermediates in high enantiopurity has generally required the use of either stoichiometric chiral precursors or stoichiometric chiral reagents. We now describe a catalytic approach in which strongly acidic and confined imidodiphosphorimidates (IDPi) catalyze highly enantioselective interconversions of ketones and enol silanes. These "silicon-hydrogen exchange reactions"enable access to enantiopure enol silanes via tautomerizing σ-bond metatheses, either in a deprotosilylative desymmetrization of ketones with allyl silanes as the silicon source or in a protodesilylative kinetic resolution of racemic enol silanes with a carboxylic acid as the silyl acceptor.
- Zhou, Hui,Bae, Han Yong,Leutzsch, Markus,Kennemur, Jennifer L.,Bécart, Diane,List, Benjamin
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supporting information
p. 13695 - 13700
(2020/08/24)
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- Photoredox-Catalyzed Sulfonylation of O-Acyl Oximes via Iminyl Radicals with the Insertion of Sulfur Dioxide
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A multicomponent sulfonylation of O-acyl oximes via iminyl radicals with the insertion of sulfur dioxide under photoredox catalysis is achieved. This multicomponent reaction of O-acyl oximes, potassium metabisulfite, alkenes, and nucleophiles under visible-light irradiation is efficient, giving rise to a range of sulfones in moderate to good yields. A broad reaction scope is presented with good functional group compatibility.
- Zhang, Jun,Li, Xiaofang,Xie, Wenlin,Ye, Shengqing,Wu, Jie
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supporting information
p. 4950 - 4954
(2019/06/24)
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- Transition-Metal-Promoted Direct C?H Cyanoalkylation and Cyanoalkoxylation of Internal Alkenes via Radical C?C Bond Cleavage of Cycloketone Oxime Esters
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Transition-metal-catalyzed alkyl-Heck-type cross-coupling of olefinic C?H bonds has been a challenge in the C?H activation area. Herein, we report FeCl3-promoted efficient direct C?H cyanoalkylation of internal alkenes, that is, ketene dithioacetals, with cycloketone oxime esters via radical C?C bond cleavage under the redox-neutral conditions. With CuCl2 as the catalyst under a dioxygen atmosphere direct C?H cyanoalkoxylation of the same internal alkenes was achieved. The cyanoalkylated tetrasubstituted alkene products could be diversely transformed to cyanoalkyl-funtionalized N- and S-heterocyclic compounds. The mechanistic studies have revealed that these C?H cyanoalkylation and cyanoalkoxylation reactions proceed through a radical pathway. (Figure presented.).
- Lou, Jiang,He, Yuan,Li, Yunlong,Yu, Zhengkun
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supporting information
p. 3787 - 3799
(2019/07/10)
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- Manganese-Catalyzed Electrochemical Deconstructive Chlorination of Cycloalkanols via Alkoxy Radicals
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A manganese-catalyzed electrochemical deconstructive chlorination of cycloalkanols has been developed. This electrochemical method provides access to alkoxy radicals from alcohols and exhibits a broad substrate scope, with various cyclopropanols and cyclobutanols converted into synthetically useful β- and γ-chlorinated ketones (40 examples). Furthermore, the combination of recirculating flow electrochemistry and continuous inline purification was employed to access products on a gram scale.
- Allen, Benjamin D. W.,Hareram, Mishra Deepak,Seastram, Alex C.,McBride, Tom,Wirth, Thomas,Browne, Duncan L.,Morrill, Louis C.
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supporting information
p. 9241 - 9246
(2019/11/19)
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- A Visible-Light-Driven Iminyl Radical-Mediated C?C Single Bond Cleavage/Radical Addition Cascade of Oxime Esters
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A room-temperature, visible-light-driven N-centered iminyl radical-mediated and redox-neutral C?C single bond cleavage/radical addition cascade reaction of oxime esters and unsaturated systems has been accomplished. The strategy tolerates a wide range of O-acyl oximes and unsaturated systems, such as alkenes, silyl enol ethers, alkynes, and isonitrile, enabling highly selective formation of various chemical bonds. This method thus provides an efficient approach to various diversely substituted cyano-containing alkenes, ketones, carbocycles, and heterocycles.
- Yu, Xiao-Ye,Chen, Jia-Rong,Wang, Peng-Zi,Yang, Meng-Nan,Liang, Dong,Xiao, Wen-Jing
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supporting information
p. 738 - 743
(2017/12/26)
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- Copper-catalyzed tandem aerobic oxidative cyclization for the synthesis of 4-cyanoalkylpyrrolo[1,2-a]quinoxalines from 1-(2-aminophenyl)pyrroles and cyclobutanone oxime esters
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A copper-catalyzed tandem ring-opening/cyclization reaction for the synthesis of 4-cyanoalkylpyrrolo[1,2-a]quinoxalines from 1-(2-aminophenyl)pyrroles and cyclobutanone oxime esters has been developed. This reaction involves C-C bond cleavage and C-C and C-N bond constructions with good functional group tolerance. A wide range of products are obtained in moderate to good yields under mild conditions.
- An, Zhenyu,Jiang, Yong,Guan, Xin,Yan, Rulong
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supporting information
p. 10738 - 10741
(2018/09/29)
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- Photocatalytic Neophyl Rearrangement and Reduction of Distal Carbon Radicals by Iminyl Radical-Mediated C?C Bond Cleavage
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The control of selectivity in the reactions of the highly reactive open-shell carbon radicals is an attractive but often challenging task. Building on the strategy of photoinduced iminyl radical-mediated C?C bond cleavage, we have developed photocatalytic neophyl rearrangement and reduction of distal carbon radicals under visible light irradiation of O-acyl oximes. This mild protocol tolerates a wide range of readily available O-acyl oximes, enabling facile synthesis of diversely substituted α,β-unsaturated nitriles and β-functionalized saturated nitriles in a highly selective manner. (Figure presented.).
- Yu, Xiao-Ye,Wang, Peng-Zi,Yan, Dong-Mei,Lu, Bin,Chen, Jia-Rong,Xiao, Wen-Jing
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supporting information
p. 3601 - 3606
(2018/09/18)
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- A photoredox catalyzed iminyl radical-triggered C-C bond cleavage/addition/Kornblum oxidation cascade of oxime esters and styrenes: synthesis of ketonitriles
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A photoredox-catalyzed iminyl radical-triggered C-C bond cleavage/addition/Kornblum oxidation cascade of cycloketone oxime esters and styrenes in DMSO is described. This three-component, one-pot procedure features mild conditions, a broad substrate scope, and high functional group tolerance, providing an efficient approach to access diversely functionalized ketonitriles.
- He, Bin-Qing,Yu, Xiao-Ye,Wang, Peng-Zi,Chen, Jia-Rong,Xiao, Wen-Jing
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supporting information
p. 12262 - 12265
(2018/11/21)
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- Copper-Catalyzed Coupling Reactions of Cyclobutanone Oxime Esters with Sulfur Nucleophiles at Room Temperature
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A copper-catalyzed iminyl radical-mediated C-C bond cleavage/cross-coupling tandem reaction of cyclobutanone oxime esters with aryl thiols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at room temperature was developed, and aryl cyanopropyl sulfides were smoothly synthesized in 20-88% yields. By altering the copper reagent and the molar ratio of cyclobutanone oxime ester/aryl thiol/DBU, substitutional product N-arylthio cyclobutanone imines were selectively generated in 50-91% yields. Using this protocol, C-S bond and N-S bond formations using aryl thiols as sulfur sources were realized under very mild conditions without the use of photocatalysis and electrocatalysis techniques.
- He, Mingchuang,Yan, Zhaohua,Zhu, Fuyuan,Lin, Sen
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p. 15438 - 15448
(2019/01/04)
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- MACROCYCLIC BROAD SPECTRUM ANTIBIOTICS
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Provided herein are antibacterial compounds, wherein the compounds in some embodiments have broad spectrum bioactivity. In various embodiments, the compounds act by inhibition of bacterial type 1 signal peptidase (SpsB), an essential protein in bacteria. Pharmaceutical compositions and methods for treatment using the compounds described herein are also provided.
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Paragraph 00973
(2017/08/01)
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- Copper-Catalyzed Intermolecular Heck-Like Coupling of Cyclobutanone Oximes Initiated by Selective C?C Bond Cleavage
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The first example of intermolecular olefination of cyclobutanone oximes with alkenes via selective C?C bond cleavage leading to the synthesis of nitriles in the presence of a cheap copper catalyst is reported. The procedure is distinguished by mild and safe reaction conditions that avoid ligand, oxidant, base, or toxic cyanide salt. A wide scope of cyclobutanones and olefin coupling components can be used without compromising efficiency and scalability. The alternative visible-light-driven photoredox process for this coupling reaction was also uncovered.
- Zhao, Binlin,Shi, Zhuangzhi
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supporting information
p. 12727 - 12731
(2017/09/08)
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- Baeyer–Villiger monooxygenase-catalyzed desymmetrizations of cyclobutanones. Application to the synthesis of valuable spirolactones
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A series of γ-butyrolactone derivatives, including some spiranic ones, was obtained through desymmetrization of the corresponding prochiral 3-substituted cyclobutanones via Baeyer–Villiger monooxygenase (BVMO)-catalyzed oxidation. After reaction optimization using several commercial enzymes, both antipodes of various lactones were synthesized in most cases with >90% conversion and >80% enantiomeric excess under mild reaction conditions. In some cases alcohol formation was also observed (up to 40% conversion) as an undesired side reaction due to the presence of alcohol dehydrogenases in these preparations. Selected transformations were achieved on a 100 mg scale showing the possibilities of these oxidative biocatalysts as a new source of highly interesting compounds.
- Rodríguez-Mata, María,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,García-Cerrada, Susana,Mendiola, Javier,de Frutos, óscar,Collado, Iván
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supporting information
p. 7268 - 7275
(2016/10/26)
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- A rhodium(I)-catalysed formal intramolecular C-C/C-H bond metathesis
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Phenylcyclobutanes underwent skeletal reorganisation in the presence of Wilkinson's catalyst to afford indanes through a cascade process involving chelation-assisted C-C bond cleavage and intramolecular C-H bond cleavage.
- Matsuda, Takanori,Yuihara, Itaru
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supporting information
p. 7393 - 7396
(2015/04/27)
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- Lactonization reactions through hydrolase-catalyzed peracid formation. Use of lipases for chemoenzymatic Baeyer-Villiger oxidations of cyclobutanones
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A one-pot chemoenzymatic method has been described for the synthesis of γ-butyrolactones starting from the corresponding ketones through a Baeyer-Villiger reaction. The approach is based on a lipase-catalyzed perhydrolysis for the formation of peracetic acid, which is the responsible for the ketone oxidation. Optimization studies have been performed in the oxidation of cyclobutanone, finding Candida antarctica lipase type B, ethyl acetate and urea-hydrogen peroxide complex as the best system. The relative ratio of these reagents has also been analyzed in depth. This synthetic approach has been successfully extended to a family of 3-substituted cyclobutanones in high substrate concentration, yielding the corresponding lactones with excellent isolated yields and purities, under mild reaction conditions and after a simple extraction protocol.
- González-Martínez, Daniel,Rodríguez-Mata, María,Méndez-Sánchez, Daniel,Gotor, Vicente,Gotor-Fernández, Vicente
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- Direct syntheses of spiro- and fused-hydrofurans by a tunable tandem semipinacol rearrangement/oxa-michael addition protocol
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A highly chemoselective one-pot reaction has been developed involving a tandem semipinacol rearrangement/oxa-Michael addition sequence in which the in situ generated ketol diene intermediate can be transformed specifically to either the spiro- or fused-dihydrofuran products (see scheme). This one-pot tandem reaction represents a general synthetic methodology for the syntheses of the two different kinds of furan derivatives. Copyright
- Li, Bao-Sheng,Liu, Wen-Xing,Zhang, Qing-Wei,Wang, Shao-Hua,Zhang, Fu-Min,Zhang, Shu-Yu,Tu, Yong-Qiang,Cao, Xiao-Ping
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supporting information
p. 5246 - 5249
(2013/05/22)
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- Au-catalyzed formation of functionalized quinolines from 2-alkynyl arylazide derivatives
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A new method for converting 2-alkynyl arylazide derivatives into functionalized polysubstituted quinolines following a gold-catalyzed 1,3-acetoxy shift/cyclization/1,2-group shift sequence has been developed. This transformation proceeds under mild reaction conditions, is efficient, and tolerates a large variety of functional groups.
- Gronnier, Colombe,Boissonnat, Guillaume,Gagosz, Fabien
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supporting information
p. 4234 - 4237
(2013/09/12)
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- Baeyer-Villiger Oxidation of Cyclobutanones with 10-Methylacridinium as an Efficient Organocatalyst
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Baeyer-Villiger oxidation of cyclobutanones is achieved in current developed protocol with 10-methylacridinium perchlorate (AcrH +ClO4-) as a novel organocatalyst both with irradiation at room temperature and without irradiation at elevated temperature. Excellent yields of the corresponding lactones are obtained and the possible mechanism has been proposed.
- Xu, Hua-Jian,Zhu, Feng-Fei,Shen, Yong-Ya,Wan, Xin,Feng, Yi-Si
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experimental part
p. 4145 - 4151
(2012/07/27)
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- Enantioselective baeyer-villiger oxidation: Desymmetrization of meso cyclic ketones and kinetic resolution of racemic 2-arylcyclohexanones
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Catalytic enantioselective Baeyer-Villiger (BV) oxidations of racemic and meso cyclic ketones were achieved in the presence of chiral N,N'-dioxide-Sc III complex catalysts. The BV oxidations of prochiral cyclohexanones and cyclobutanones afforded series of optically active μ- and γ-lactones, respectively, in up to 99% yield and 95% ee. Meanwhile, the kinetic resolution of racemic 2-arylcyclohexanones was also realized via an abnormal BV oxidation. Enantioenriched 3-aryloxepan-2-ones, whose formation is counter to the migratory aptitude, were obtained preferentially. Both the lactones and the unreacted ketones were obtained with high ee values.
- Zhou, Lin,Liu, Xiaohua,Ji, Jie,Zhang, Yuheng,Hu, Xiaolei,Lin, Lili,Feng, Xiaoming
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supporting information
p. 17023 - 17026,4
(2012/12/12)
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- Enantioselective baeyer-villiger oxidation: Desymmetrization of meso cyclic ketones and kinetic resolution of racemic 2-arylcyclohexanones
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Catalytic enantioselective Baeyer-Villiger (BV) oxidations of racemic and meso cyclic ketones were achieved in the presence of chiral N,N'-dioxide-Sc III complex catalysts. The BV oxidations of prochiral cyclohexanones and cyclobutanones afforded series of optically active μ- and γ-lactones, respectively, in up to 99% yield and 95% ee. Meanwhile, the kinetic resolution of racemic 2-arylcyclohexanones was also realized via an abnormal BV oxidation. Enantioenriched 3-aryloxepan-2-ones, whose formation is counter to the migratory aptitude, were obtained preferentially. Both the lactones and the unreacted ketones were obtained with high ee values.
- Zhou, Lin,Liu, Xiaohua,Ji, Jie,Zhang, Yuheng,Hu, Xiaolei,Lin, Lili,Feng, Xiaoming
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supporting information
p. 17023 - 17026
(2013/01/15)
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- Palladium-catalyzed, asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones with PHOX ligands
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Described in this report is a general method for the conversion of prochiral 3-substituted cyclobutanones to enantioenriched γ-lactones through a palladium-catalyzed Baeyer-Villiger oxidation using phosphinooxazoline ligands in up to 99% yield and 81% ee. Lactones of enantiopurity ≥93% could be obtained through a single recrystallization step. Importantly, 3,3-disubtituted cyclobutanones produced enantioenriched lactones containing a β-quaternary center.
- Petersen, Kimberly S.,Stoltz, Brian M.
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experimental part
p. 4352 - 4357
(2011/07/29)
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- Enantioselective baeyer-villiger oxidation catalyzed by palladium(II) complexes with chiral P,N-ligands
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(Chemical Equation Presented) Asymmetric Baeyer-Villiger reaction of symmetrical cyclobutanones 1a-j with urea-hydrogen peroxide (UHP) can be catalyzed by a complex of Pd(II) and the new terpene-derived P,N-ligand 7. The resulting lactones 2a-j were obtained in high yields and with good enantioselectivity (≤81% ee).
- Malkov, Andrei V.,Friscourt, Frederic,Bell, Mark,Swarbrick, Martin E.,Kocovsky, Pavel
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p. 3996 - 4003
(2008/09/20)
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- Palladium-catalyzed diastereo- and enantioselective Wagner-Meerwein shift: Control of absolute stereochemistry in the C-C bond migration event
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Inducing absolute stereochemistry in Wagner-Meerwein shifts was examined in a ring expansion protocol. Initiated by generation of a π-allylpalladium intermediate by hydropalladation of allenes, the ring expansion of allenylcyclobutanol substrates proceeded with excellent diastereo- and enantioselectivities. The results demonstrate that, during the C-C bond migration process, our chiral catalysts can control the stereochemistry of both the π-allylpalladium intermediate and the corresponding migration bond. Moreover, the stereochemical outcome of the reaction can be rationalized very well with the working model of the chiral catalyst. The method provides an efficient way to synthesize highly substituted cyclopentanones with an α-chiral O-tertiary center which has various synthetic applications.
- Trost, Barry M.,Xie, Jia
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p. 6231 - 6242
(2008/12/20)
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- Comparing the stereoselective biooxidation of cyclobutanones by recombinant strains expressing bacterial baeyer - Villiger monooxygenases
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Microbial Baeyer - Villiger oxidation of representative prochiral ketones with a cyclobutanone structural motif was investigated using a collection of eight monooxygenases of different bacterial origin. This platform of enzymes is able to perform stereoselective biotransformations on an array of structurally diverse substrates. With several ketone precursors, biooxidations yielded enantiocomplementary butyrolactones as key intermediates for the synthesis of natural products and bioactive compounds. The microbial Baeyer - Villiger oxidation allows a facile and rapid entry to several compound classes in a desymmetrization reaction upon de novo generation of chirality.
- Rudroff, Florian,Rydz, Joanna,Ogink, Freek H.,Fink, Michael,Mihovilovic, Marko D.
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p. 1436 - 1444
(2008/09/17)
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- Two-carbon ring expansion of cyclobutanone skeletons by nickel-catalyzed intermolecular alkyne insertion
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The reaction of cyclobutanone with an alkyne in the presence of a nickel(0) catalyst formally achieves intermolecular alkyne insertion between the carbonyl carbon and the α-carbon of a cyclobutanone, providing a six-membered carbocyclic skeleton.
- Murakami, Masahiro,Ashida, Shinji,Matsuda, Takanori
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p. 7540 - 7546
(2007/10/03)
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- New ring expansion of cyclobutanones: Synthesis of pyrrolinones, pyrrolidines and pyrroles
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2,2-Dichlorocyclobutanones reacted with various amines to give ring opening leading to 4,4-dichlorobutanamides. These compounds proved to be suitable substrates for the synthesis of 3-pyrrolin-2-ones, 2-pyrrolidinones, pyrrolidines and pyrroles.
- Verniest, Guido,Boterberg, Stefaan,Bombeke, Filip,Stevens, Christian V.,De Kimpe, Norbert
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p. 1059 - 1063
(2007/10/03)
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- Reactivity in acid-catalyzed carbon-carbon heterolysis
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Equilibrium and rate constants have been determined for the acid-catalyzed heterolysis of two alcohols, 9-xanthydrol and p-anisyldiphenylmethanol, and two sulfides, (9-xanthyl) methyl sulfide and (7-tropyl) methyl sulfide. These data together with literature information are compared with rate constants for acid-catalyzed C-C heterolysis of several (9-xanthyl) compounds, (7-tropyl) compounds, a set of 3-arylcyclobutanones, and two 2-arylnitrocyclopropanes, all of which fragment to carbocations plus a carbon-centered nucleofuge. The fragmentation mechanisms are shown to be A1 or A1(ion pair) except for the 2-arylnitrocyclopropanes which cleave in trifluoroacetic acid by a concerted mechanism. Rate comparisons among several unstrained substrate sets indicate that O-centered nucleofuges undergo acid-catalyzed heterolysis ca. 103-104 faster than S-centered nucleofuges and ca. 109-1014 faster than the C-centered nucleofuges used here. Factors assisting C-C heterolysis (and their effectiveness) include the acidity of the medium (strong); the basicity and nucleofugality of the nucleofuge (moderate); the stability of the electrofugic carbocation (strong); and relief of ring strain (enormous). Compared with acyclic cleavages, rate accelerations worth ca. 15 kcal/mol (for cyclobutanones) and ca. 27 kcal/mol (for nitrocyclopropanes) are found. These effects are discussed in terms of transition-state structure, aided by computational evidence.
- Cao, Weiguo,Erden, Ihsan,Grow, Richard H.,Keeffe, James R.,Song, Jiangao,Trudell, Mary B.,Wadsworth, Teri L.,Xu, Fu-Pei,Zheng, Ji-Bin
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p. 1009 - 1034
(2007/10/03)
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- Preparation and Photosensitized Oxidation of Isopropylidenecyclobutanes and -cyclobutenes
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Isopropylidenecyclobutanes 2-5 underwent facile ene reaction with singlet dioxygen, yielding (upon Ph3P reduction) the corresponding pairs of epimeric allylic alcohols 9 and 10, 11 and 12, 13 and 14, and 15 and 16, respectively.A combination of spectral evidence and molecular modeling studies were utilized in the structural assignment of the epimers.The data clearly indicate that steric considerations play an important role in determining the face of the ring which 1O2 approaches.Isopropylidenecyclobutenes 6 and 7 reacted with singlet oxygen more slowly than their monoolefinic analogs, yielding upon reduction allylic alcohols 21b and 22, respectively.Benzo analog 7 also generated a small and solvent-dependent amount of isomeric aldehydes 23 and 24, presumably via a free-radical mechanism. n-Butyl diene 8 underwent rapid photosensitized oxygenation producing allylic alcohol 35 (as the 1O2 ene product) and dione 37 (the Hock-cleavage product of allylic hydroperoxide 39, formed in turn via a free-radical route) in a 1:9 ratio.Ab initio (STO-3G) calculations confirm that, in their lowest energy conformations, compounds 2-8 are planar with the methylene ring hydrogens displaced ca. 36 deg from the perpendicular.As a result, only exocyclic ene product is formed, since 1O2 strongly prefers axial or pseudoaxial allylic hydrogens.These calculations combined with the relative rate data suggest that the initial interaction between the electrophilic 1O2 and alkylidenecyclobutenes involves both ends of the singlet dioxygen molecule, in which the "front" end attacks the reactive exocyclic double bond while the "back" end obtains stabilization by interacting with the more electron rich but unreactive endocyclic olefin linkage.Because of this added, and presumably substantial, stabilization, the relative rates within this system are determined in part by the orbital coefficients at the latter olefinic center.
- Frimer, Aryeh A.,Weiss, Joseph,Gottlieb, Hugo E.,Wolk, Joel L.
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p. 780 - 792
(2007/10/02)
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- A NEW TWO-CARBON OLEFIN HOMOLOGATION PROCEDURE THAT LEADS TO α-CHLOROENONES. AN EFFICIENT SYNTHESIS OF d,l-MUSCONE
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Dichloroketene-olefin cycloadducts, α,α-dichlorocyclobutanones, are easily converted to α-chloroenones through a 3-step (2-pot) sequence of reactions.The overall result is the insertion of a functionalized 2-carbon unit between the original olefinic carbons.The efficiency of the method is demonstrated by a high-yield synthesis of d,l-muscone.
- Depres, Jean-Pierre,Navarro, Brigitte,Greene, Andrew E.
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p. 2989 - 2998
(2007/10/02)
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