- Dehydrative Beckmann rearrangement and the following cascade reactions
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The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam. By strategically using the in situ generated Appel's salt or Mitsunobu's zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this method have been demonstrated.
- Liu, Yinghui,Wei, Yongjiao,Xie, Lan-Gui
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supporting information
(2021/11/16)
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- Synthesis of 5-Vinyl-2-isoxazolines by Palladium-Catalyzed Intramolecular O-Allylation of Ketoximes
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An efficient method for the synthesis of 5-vinyl-2-isoxazolines by Pd-catalyzed intramolecular O-allylation of ketoximes has been developed. The reaction involves Pd(0)-catalyzed π-allyl formation via leaving group ionization or Pd(II)-catalyzed allylic C-H activation followed by intramolecular nucleophilic oxime oxygen attack. This methodology has been elaborated to various value-added products by epoxidation, Wacker oxidation, cross-metathesis, hydroboration-oxidation, dihydroxylation, and catalytic hydrogenation.
- Fernandes, Rodney A.,Gangani, Ashvin J.,Panja, Arpita
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supporting information
p. 6227 - 6231
(2021/08/18)
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- Diastereoselective and Stereodivergent Synthesis of 2-Cinnamylpyrrolines Enabled by Photoredox-Catalyzed Iminoalkenylation of Alkenes
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A photoredox-catalyzed iminoalkenylation of γ-alkenyl O-acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)- and (Z)-cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)-cinnamylpyrrolines are produced through a photoredox-mediated single-electron-transfer process. In tetrahydrofuran, (Z)-cinnamylpyrrolines are generated by photocatalytic contra-thermodynamic E-to-Z isomerization of (E)-cinnamylpyrrolines though an energy-transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated.
- Shen, Xu,Huang, Congcong,Yuan, Xiang-Ai,Yu, Shouyun
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p. 9672 - 9679
(2021/03/16)
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- Additive-free radical cascade reaction of oxime esters: Synthesis of pyrroline-functionalized phenanthridines
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A variety of dihydropyrrole-functionalized phenanthridines were efficiently synthesized by the metal-free, radical cascade cyclization reaction of 2-isocyanobiphenyls with γ,δ- unsaturated oxime esters. The C-N/C-C/C-C bonds were formed via the oil bath method in a one-pot procedure with broad substrate applicability. The radical process was supported by kinetic isotope effect studies and radical inhibition studies.
- Shao, Liming,Xue, Yijie,Xue, Dengqi,He, Qian,Ge, Qianwei,Li, Wei
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p. 12284 - 12293
(2020/11/10)
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- Iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines
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Herein, a new method of iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines has been developed. By using readily available substrates, 32 examples of functionalized pyrrolines were prepared in moderate to good yields. Notably, examples of reduction and cycloaddition reactions of the obtained product were given as well. This journal is
- Wang, Hai,Wu, Xiao-Feng,Yin, Zhiping,Zhang, Youcan
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p. 7045 - 7048
(2020/07/14)
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- Highly Enantioselective Construction of Dihydrooxazines via Pd-Catalyzed Asymmetric Carboetherification
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A straightforward synthesis of highly enantioenriched 5,6-dihydro-4H-1,2-oxazines is realized by Pd-catalyzed asymmetric carboetherification of γ,δ-alkenyl oximes with (hetero)aryl and alkenyl halides in the presence of a commercially available bisphosphine ligand. The enantioenriched products can be facilely converted to functionalized alcohols with high fidelity of chiral transfer.
- Li, Na,Sun, Baozhen,Liu, Shuang,Zhao, Jinbo,Zhang, Qian
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p. 190 - 193
(2020/01/02)
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- Copper-Catalyzed Cope-Type Hydroamination of Nonactivated Olefins toward Cyclic Nitrones: Scope, Mechanism, and Enantioselective Process Development
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The catalytic synthesis of cyclic nitrones, an important type of functional molecules for both synthetic chemistry and related fields, remains underdeveloped. Herein we report the copper-catalyzed Cope-type hydroamination of oximes with pendant nonactivated olefins, which enables facile access to a series of five- and six-membered cyclic nitrones under mild conditions. In this study, heterocycle-tethered oximes were employed in the Cope-type hydroamination reaction for the first time. High enantioselectivity was achieved for carbon-tethered γ,δ-vinyl oximes to afford enantioenriched five-membered cyclic nitrones. The results of preliminary mechanistic studies indicate a mononuclear catalytic species and a unified catalytic pathway over a large temperature range.
- Zhang, Mengru,Liu, Shuang,Li, Hexin,Guo, Yajing,Li, Na,Guan, Meihui,Mehfooz, Haroon,Zhao, Jinbo,Zhang, Qian
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p. 12620 - 12627
(2019/09/16)
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- Visible-Light-Mediated Iminyl Radical Generation from Benzyl Oxime Ether: Synthesis of Pyrroline via Hydroimination Cyclization
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The treatment of an O-(4-methoxybenzyl) oxime ether bearing an olefin substituent and 1-chloroanthraquinone (1-Cl-AQN) catalyst in 2-butanone under visible-light irradiation affords pyrroline via an iminyl radical intramolecular hydroimination. Mechanistic studies indicate that iminyl radical generation mainly proceeds by hydrogen abstraction of the photocatalyst from the benzyl position of the oxime. Moreover, the hydrogen atom was identified in circulation from the benzylic position of the substrates between AQN and 2-butanone to quench the carbon radical without requiring any additional reagents.
- Usami, Kaoru,Yamaguchi, Eiji,Tada, Norihiro,Itoh, Akichika
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p. 5714 - 5717
(2018/09/21)
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- Divergent Iron-Catalyzed Coupling of O-Acyloximes with Silyl Enol Ethers
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An iron-catalyzed coupling reaction of O-acyloximes and O-benzoyl amidoximes with silyl enol ethers is reported. The protocol provides access to functionalized pyrroles, 1,6-ketonitriles, pyrrolines and imidazolines via carbon-centered radicals generated from an initially formed iminyl radical. The intramolecular cyclization and ring-opening processes of the iminyl radical take place preferentially over reactions that proceed through a 1,3-hydrogen transfer, providing insights into iron-catalyzed reactions with oxime derivatives. The cheap and environmentally friendly iron catalyst, the broad substrate scope and the functional group compatibility make this protocol useful for synthesis of valuable nitrogen-containing products.
- Yang, Hai-Bin,Selander, Nicklas
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supporting information
p. 1779 - 1783
(2017/02/15)
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- Green organocatalytic synthesis of isoxazolines via a one-pot oxidation of allyloximes
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A green, sustainable, organocatalytic, and efficient synthesis of isoxazolines from allyloximes was developed. A 2,2,2-trifluoroacetophenone-catalyzed oxidation of allyloximes, utilizing H2O2 as the green oxidant, was taken advantage of in order to introduce a cheap and environmentally friendly protocol for the synthesis of substituted isoxazolines. A variety of substitution patterns, both aromatic and aliphatic moieties, are well tolerated, leading to isoxazolines in moderate to excellent yields.
- Triandafillidi, Ierasia,Kokotos, Christoforos G.
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p. 106 - 109
(2017/11/27)
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- Asymmetric Nitrone Synthesis via Ligand-Enabled Copper-Catalyzed Cope-Type Hydroamination of Cyclopropene with Oxime
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We report realization of the first enantioselective Cope-type hydroamination of oximes for asymmetric nitrone synthesis. The ligand promoted asymmetric cyclopropene "hydronitronylation" process employs a Cu-based catalytic system and readily available starting materials, operates under mild conditions and displays broad scope and exceptionally high enantio- and diastereocontrol. Preliminary mechanistic studies corroborate a CuI-catalytic profile featuring an olefin metalla-retro-Cope aminocupration process as the key C-N bond forming event. This conceptually novel reactivity enables the first example of highly enantioselective catalytic nitrone formation process and will likely spur further developments that may significantly expedite chiral nitrone synthesis.
- Li, Zhanyu,Zhao, Jinbo,Sun, Baozhen,Zhou, Tingting,Liu, Mingzhu,Liu, Shuang,Zhang, Mengru,Zhang, Qian
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supporting information
p. 11702 - 11705
(2017/09/07)
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- An Umpolung Approach to Alkene Carboamination: Palladium Catalyzed 1,2-Amino-Acylation, -Carboxylation, -Arylation, -Vinylation, and -Alkynylation
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Conventional approaches to Pd-catalyzed alkene 1,2-carboamination rely upon the combination of a nucleophilic nitrogen-based component and an internal C-based or external oxidant. In this study, we outline an umpolung approach, which is triggered by oxidative initiation at an electrophilic N-based component and employs "standard" organometallic nucleophiles to introduce the new carbon-based fragment. Specifically, oxidative addition of a Pd(0)-catalyst into the N-O bond of O-pentafluorobenzoyl oxime esters generates imino-Pd(II) intermediates, which undergo 5-exo cyclization with sterically diverse alkenes. The resultant alkyl-Pd(II) intermediates are intercepted by organometallic nucleophiles or alcohols, under carbonylative or noncarbonylative conditions, to provide 1,2-carboamination products. This approach provides, for the first time, a unified strategy for achieving alkene 1,2-amino-acylation, -carboxylation, -arylation, -vinylation, and -alkynylation. For carbonylative processes, orchestrated protodecarboxylation of the pentafluorobenzoate leaving group underpins reaction efficiency. This process is likely a key feature in related Narasaka-Heck cyclizations and accounts for the efficacy of O-pentafluorobenzoyl oxime esters in aza-Heck reactions of this type. (Chemical Equation Presented).
- Faulkner, Adele,Scott, James S.,Bower, John F.
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p. 7224 - 7230
(2015/06/25)
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- Copper-catalyzed cyclization and azidation of γ,δ-unsaturated ketone O-benzoyl oximes
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An intramolecular imination/azidation sequence has been realized through the tetrakis(acetonitrile)copper(I) hexafluorophophate [Cu(CH3CN)4PF6]-catalyzed reaction of γ,δ-unsaturated ketone O-benzoyl oximes with trimethylsi
- Su, Hailin,Li, Weifei,Xuan, Zhaoli,Yu, Wei
-
supporting information
p. 64 - 70
(2015/03/04)
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- Low-valent zirconocene-mediated cyclization of γ,δ-unsaturated oximes
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γ,δ-Unsaturated O-methyl oximes were cyclized to dihydropyrrole by the treatment of (1-butene)ZrCp2 3 prepared by Negishi's procedure (reaction with Cp2ZrCl2 and two equivalents of n-BuLi). In this cyclization, the geometr
- Kitamura, Mitsuru,Shintaku, Yuki,Kudo, Daisuke,Okauchi, Tatsuo
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scheme or table
p. 4890 - 4893
(2010/10/02)
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- Palladium-catalyzed amino-heck reaction of γ,δ-unsaturated ketone O-diethylphosphinyloximes: A new synthesis of substituted pyrroles and indoles
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γ,δ-Unsaturated ketone O-diethylphosphinyloximes, readily prepared from the corresponding ketones, were used as starting materials for the intramolecular amino-Heck reactions. In the presence of a catalytic amount of Pd(PPh3)4 in DBU, cyclization reactions occurred preferentially via a 5-exo fashion to afford a variety of 2-substituted 5-methyl-1H-pyrroles and several indole derivatives in moderate to high yields. Georg Thieme Verlag Stuttgart.
- Zhu, Jia-Liang,Chan, Yu-Hui
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experimental part
p. 1250 - 1254
(2009/04/06)
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- Regioselective synthesis of 6-halomethyl-5,6-dihydro-4H-1,2-oxazines based on cyclizations of arylalkenyl-oximes
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6-Iodo- and 6-bromomethyl-5,6-dihydro-4H-1,2-oxazines were prepared by condensation of dilithiated acetophenone-oximes with allylbromide and subsequent regioselective iodine- or NBS-mediated cyclization.
- Karapetyan, Vahuni,Mkrtchyan, Satenik,Dang, Tung T.,Villinger, Alexander,Reinke, Helmut,Langer, Peter
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p. 8010 - 8015
(2008/12/20)
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- Dioxime oxalates; new iminyl radical precursors for syntheses of N-heterocycles
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Symmetrical and unsymmetrical dioxime oxalates were prepared by treatment of oximes with oxalyl chloride. UV photolysis of these precursors was found to be an atom-efficient way of generating iminyl radicals. The process was most efficient for dioxime oxalates having aryl substituents attached to their C{double bond, long}N bonds. The method was useful for EPR spectroscopic study of iminyl and iminoxyl radicals. Photolyses in toluene solution, of dioxime oxalates containing alkenyl acceptor groups, yielded unsaturated iminyl radicals that ring closed to afford 3,4-dihydro-2H-pyrroles in good yields. Dioxime oxalates with biphenyl substituents also released iminyl radicals that ring closed onto the aromatic acceptor groups and, in acetonitrile solution, this approach provided a useful and atom-efficient method of making substituted phenanthridines.
- Portela-Cubillo, Fernando,Lymer, James,Scanlan, Eoin M.,Scott, Jackie S.,Walton, John C.
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supporting information; experimental part
p. 11908 - 11916
(2009/04/06)
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- Iminyl, Amidyl, and Carbamyl Radicals from O-Benzoyl Oximes and O-Benzoyl Hydroxamic Acid Derivatives.
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Oxime benzoates and O-benzoyl hydroxamic acid derivatives react with tributylstannane in the presence of AIBN to give iminyl, amidyl, and carbamyl radicals which can be captured by an internal olefin.
- Boivin, Jean,Callier-Dublanchet, Anne-Claude,Quiclet-Sire, Beatrice,Schiano, Anne-Marie,Zard, Samir Z.
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p. 6517 - 6528
(2007/10/02)
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- Ring-closure Reactions of Alkenyl Oximes Induced by Persulfate Anion Oxidation of Diphenyl Diselenide. Formation od 1,2-Oxazines and Cyclic Nitrones
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A strongly electrophilic phenylselenenylating agent is produced from the reaction of diphenyl diselenide with ammonium persulfate, in the presence of trifluoromethanesulfonic acid, in acetonitrile or nitromethane, at room temperature.This reagent induces
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Bagnoli, Luana,Marini, Francesca
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p. 1989 - 1994
(2007/10/02)
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- Lithiated 5,6-Dihydro-4H-1,2-oxazines: Synthesis, Highly Diastereoselective Reactions with Electrophiles, and Subsequent Transformations
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The 6-(trimethylsilyl)methyl-substituted 1,2-oxazine 1 can smoothly be deprotonated with n-butyllithium at C-4 to give a lithiated species which reacts with a variety of electrophiles to provide the new 1,2-oxazines 5-16 in good yields.Besides the prepara
- Reissig, Hans-Ulrich,Hippeli, Claudia
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p. 115 - 127
(2007/10/02)
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