- Regio- and stereoselective synthesis of novel isoxazolidine heterocycles by 1,3-dipolar cycloaddition between C-phenyl- N -methylnitrone and substituted alkenes. Experimental and DFT investigation of selectivity and mechanism
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A series of isoxazolidine heterocycles was synthesized through the 1,3-dipolar cycloaddition (13DC) reaction of C-phenyl-N-methylnitrone with different substituted alkenes. The structures and stereochemistry of the cycloadducts were determined by spectroscopic methods. These 13DC reactions are characterized by complete regioselectivity and high stereoselectivity. The molecular mechanism, reactivity and selectivity of these 13DC reactions have been investigated by means of transition state theory and reactivity indices derived from conceptual DFT using DFT methods at the B3LYP/6-31G(d,p) level of theory. The obtained results indicate that these cycloaddition reactions take place through a one-step synchronous mechanism with a non-polar mechanism and high activation energies. The theoretical results are in agreement with the experimental findings.
- Hellel, Djamila,Chafaa, Fouad,Khorief Nacereddine, Abdelmalek,Djerourou, Abdelhafid,Vrancken, Emmanuel
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Read Online
- S -Tetrazine: Robust and Green Photoorganocatalyst for Aerobic Oxidation of N,N-Disubstituted Hydroxylamines to Nitrones
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Efficient photocatalytic aerobic oxidative dehydrogenation reactions of N,N-disubstituted hydroxylamines to nitrones were developed with an in situ generated photocatalyst based on commercially available 3,6-dichlorotetrazine. This process affords a wide range of nitrones in high yields under mild conditions. In addition, an oxidative (3+3) cycloaddition between an oxyallyl cation precursor and a hydroxylamine was also developed.
- Lyu, Jiyuan,Le, Tuan,Claraz, Aurélie,Allain, Clémence,Audebert, Pierre,Masson, Géraldine
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supporting information
p. 177 - 181
(2021/12/06)
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- Regio- and Enantioselective (3+3) Cycloaddition of Nitrones with 2-Indolylmethanols Enabled by Cooperative Organocatalysis
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The regio- and enantioselective (3+3) cycloaddition of nitrones with 2-indolylmethanols was accomplished by the cooperative catalysis of hexafluoroisopropanol (HFIP) and chiral phosphoric acid (CPA). Using this approach, a series of indole-fused six-membered heterocycles were synthesized in high yields (up to 98 %), with excellent enantioselectivities (up to 96 % ee) and exclusive regiospecificity. This approach enabled not only the first organocatalytic asymmetric (3+3) cycloaddition of nitrones but also the first C3-nucleophilic asymmetric (3+3) cycloaddition of 2-indolylmethanols. More importantly, theoretical calculations elucidated the role of the cocatalyst HFIP in helping CPA control the reactivity and enantioselectivity of the reaction, demonstrating a new mode of cooperative catalysis.
- Li, Tian-Zhen,Liu, Si-Jia,Sun, Yu-Wen,Deng, Shuang,Tan, Wei,Jiao, Yinchun,Zhang, Yu-Chen,Shi, Feng
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supporting information
p. 2355 - 2363
(2020/12/09)
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- Carbamoylation of Azomethine Imines via Visible-Light Photoredox Catalysis
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A versatile and robust photocatalytic methodology to install the amide functional group into azomethine imine ions is described. This protocol is distinguished by its broad scope and mild reaction conditions, which are well suited for the preparation of s
- Correia, José Tiago M.,Matsuo, Bianca T.,Oliveira, Pedro H. R.,Paix?o, Márcio W.
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supporting information
p. 6775 - 6779
(2021/09/13)
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- Nucleophilic Addition to Nitrones Using a Flow Microreactor
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Nucleophilic addition reactions of soft carbon nucleophiles to nitrones in a flow microreactor are reported for the first time. Under microflow conditions at 30 to 0 °C, a range of nitrones can be efficiently transformed into the corresponding oxyiminium ions by reaction with either acyl halides or trialkylsilyl triflates. These can subsequently undergo the addition of nucleophiles including allyltributylstannane, ketene methyl tert-butyldimethylsilyl acetal, and N-silyl ketene imines to afford the corresponding adducts in high yields; such reactions at a similar temperature under batch conditions resulted in lower yields because of undesired side reactions.
- Arakawa, Yukihiro,Imada, Yasushi,Minagawa, Keiji,Okamoto, Takuma,Ueta, Shun
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supporting information
p. 866 - 870
(2020/05/28)
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- Cucurbit[7]uril as a catalytic nanoreactor for one-pot synthesis of isoxazolidines in water
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The main objective of supramolecular chemistry is to mimic the macrosystems present in nature, a goal that fits perfectly with the green chemistry guidelines. The aim of our work is to use the hydrophobic cavity of cucurbit[7]uril (CB[7]) to mimic nature
- Floresta, Giuseppe,Gentile, Davide,Mineo, Placido G.,Nicosia, Angelo,Patamia, Vincenzo,Rescifina, Antonio
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supporting information
p. 1194 - 1203
(2020/02/22)
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- Synthesis of 1,2,4-oxadiazolidines via [3+2] cycloaddition of nitrones with carbodiimides
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An efficient [3+2] cycloaddition of nitrones and carbodiimides has been developed. This 1,3-dipolar cycloaddition features high regioselectivity, mild and metal-free conditions, excellent functional group compatibility, and a broad substrate scope. The X-ray structures of two regio-isomers confirmed the regioselectivity of this transformation.
- Chen, Yuan,Fuyue, Liuting,Wang, Gangqiang,Wang, Hang,Lu, Chun,Guo, Haibing,St. Amant, Chiara,Sun, Shaofa,Xing, Yalan
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supporting information
p. 4329 - 4332
(2019/03/19)
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- A green synthesis of nitrones in glycerol
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Abstract: An eco-friendly and efficient synthesis of nitrones is presented by condensation of an equimolar amount of aldehydes and N-substituted hydroxylamine hydrochlorides in glycerol as a recyclable solvent-catalyst. This novel protocol provides rapid and mild access to a series of nitrone derivatives in good to excellent yields in the absence of catalyst and base. Graphic abstract: SYNOPSIS In this study, a base-free protocol by using glycerol as the solvent-catalyst was applied for an eco-friendly synthesis of nitrones from the condensation of aldehydes and N-substituted hydroxylaminehydrochlorides.[Figure not available: see fulltext.].
- Shariatipour, Monire,Jadidinejad, Masoumeh,Heydari, Akbar
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- BPh3-Catalyzed [2+3] Cycloaddition of Ph3PCCO with Aldonitrones: Access to 5-Isoxazolidinones with Exocyclic Phosphonium Ylide Moieties
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A method for the generation of 5-isoxazolidinones with exocyclic phosphonium ylide functionalities via [2+3] cycloaddition of Ph3PCCO and aldonitrones has been developed and applied in the synthesis of 4-alkylidene-5-isoxazolidinones via Wittig olefination. The reaction proceeds by BPh3 catalysis under mild conditions and with a broad substrate scope. A reaction pathway involving the activation of the aldonitrone via interactions with the Lewis acid BPh3 is proposed.
- Brar, Amandeep,Unruh, Daniel K.,Ling, Natalie,Krempner, Clemens
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p. 6305 - 6309
(2019/08/20)
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- MICROBIOCIDAL PICOLINAMIDE DERIVATIVES
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Compounds of the formula (I) wherein the substituents are as defined in claim 1, useful as pesticides, and especially fungicides.
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Page/Page column 56-57
(2019/07/13)
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- (3 + 3) Cycloaddition of Oxyallyl Cations with Nitrones: Diastereoselective Access to 1,2-Oxazinanes
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Oxyallyl cations are prepared in situ from readily available α-tosyloxy ketones and act as transient electrophilic partners in (3 + 3) cycloaddition with nitrones. Under mild conditions, this method provides a chemoselective and diastereoselective route t
- Cordier, Marie,Archambeau, Alexis
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supporting information
p. 2265 - 2268
(2018/04/30)
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- A highly diastereoselective [3+3] annulation reaction of aza-oxyallyl cations and nitrones
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An efficient synthesis of 1,2,4-oxadiazinan-5-ones via [3+3] cycloaddition of in situ generated aza-oxyallyl cations with nitrones has been developed. The protocol features easy operation, excellent yields, excellent diastereo-control, broad substrate sco
- Chen, Rongxing,Sun, Shaofa,Wang, Gangqiang,Guo, Haibin
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supporting information
p. 1916 - 1920
(2018/04/19)
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- One-Pot Sequential [3 + 3] Dipolar Cycloaddition of Aldehyde or Ketone and Hydroxylamine with Spirocyclopropyl Oxindole
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A Sc(OTf)3-catalyzed highly diastereoselective one-pot sequential [3 + 3] dipolar cycloaddition reaction of aldehyde or ketone, N-alkyl hydroxylamine, and spirocyclopropyl oxindole is developed, allowing facile construction of spirocyclic oxind
- Xu, Peng-Wei,Chen, Chen,Liu, Jia-Kuan,Song, Yu-Ting,Zhou, Feng,Yan, Jun,Zhou, Jian
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p. 12763 - 12774
(2018/10/20)
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- Zinc mediated direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones and mechanistic insight
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A Lewis acid catalyzed direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones in the presence of aqueous Zn(II)-salts has been described. This investigation also provides a novel observation for the stoichiometric role of Zn-halides over what is known to date for catalytic processes. A thorough mechanistic study has been established based on the experiment using18O-labeled water in optimized reaction conditions; the incorporation of18O in the desired product was also substantiated by HRMS. This methodology is also a mild, inexpensive, and an efficient approach for this unusual conversion.
- Das, Prasanta,Hamme, Ashton T.
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supporting information
p. 1086 - 1089
(2017/03/02)
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- γ-Cyclodextrin as a Catalyst for the Synthesis of 2-Methyl-3,5-diarylisoxazolidines in Water
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A green and efficient 1,3-dipolar cycloaddition of nitrones with different styrenes and cinnamates using a catalytic amount of γ-cyclodextrin (γ-CD) in water has been developed to give substituted isoxazolidines. γ-CD was found to be highly efficacious in
- Floresta, Giuseppe,Talotta, Carmen,Gaeta, Carmine,De Rosa, Margherita,Chiacchio, Ugo,Neri, Placido,Rescifina, Antonio
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p. 4631 - 4639
(2017/05/12)
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- α,β-Unsaturated Amides as Dipolarophiles: Catalytic Asymmetric exo-Selective 1,3-Dipolar Cycloaddition with Nitrones
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1,3-Dipolar cycloaddition is a commonly exploited method to access 5-membered chemical entities with a variety of peripheral functionalities and their stereochemical arrangements. Nitrones are isolable 1,3-dipoles that exhibit sufficient reactivity toward electron-deficient olefins in the presence of Lewis acids to deliver highly substituted isoxazolidines. Herein we document that α,β-unsaturated amides, generally regarded as barely reactive in a 1,3-dipolar reaction manifold, were effectively activated using the designed 7-azaindoline auxiliary in an In(OTf)3/bishydroxamic acid catalytic system. The broad substrate scope and clean removal of the 7-azaindoline auxiliary from the product highlight the synthetic utility of the present catalysis.
- Zhang, Ming,Kumagai, Naoya,Shibasaki, Masakatsu
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supporting information
p. 12450 - 12455
(2017/09/18)
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- Cooperative Multifunctional Catalysts for Nitrone Synthesis: Platinum Nanoclusters in Amine-Functionalized Metal–Organic Frameworks
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Nitrones are key intermediates in organic synthesis and the pharmaceutical industry. The heterogeneous synthesis of nitrones with multifunctional catalysts is extremely attractive but rarely explored. Herein, we report ultrasmall platinum nanoclusters (PtNCs) encapsulated in amine-functionalized Zr metal–organic framework (MOF), UiO-66-NH2 (Pt@UiO-66-NH2) as a multifunctional catalyst in the one-pot tandem synthesis of nitrones. By virtue of the cooperative interplay among the selective hydrogenation activity provided by the ultrasmall PtNCs and Lewis acidity/basicity/nanoconfinement endowed by UiO-66-NH2, Pt@UiO-66-NH2 exhibits remarkable activity and selectivity, in comparison to Pt/carbon, Pt@UiO-66, and Pd@UiO-66-NH2. Pt@UiO-66-NH2 also outperforms Pt nanoparticles supported on the external surface of the same MOF (Pt/UiO-66-NH2). To our knowledge, this work demonstrates the first examples of one-pot synthesis of nitrones using recyclable multifunctional heterogeneous catalysts.
- Li, Xinle,Zhang, Biying,Tang, Linlin,Goh, Tian Wei,Qi, Shuyan,Volkov, Alexander,Pei, Yuchen,Qi, Zhiyuan,Tsung, Chia-Kuang,Stanley, Levi,Huang, Wenyu
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supporting information
p. 16371 - 16375
(2017/11/28)
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- Chiral: N, N ′-dioxide/Co(II)-promoted asymmetric 1,3-dipolar cycloaddition of nitrones with methyleneindolinones
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A chiral N,N′-dioxide/Co(BF4)2·6H2O complex catalytic system has been developed to efficiently catalyze the asymmetric 1,3-dipolar cycloaddition of nitrones with methyleneindolinones. The corresponding chiral multisubstituted spiroisoxazolidines with three contiguous quaternary-tertiary stereocenters were obtained in moderate to high yields with excellent dr and ee values (up to 97% yield, >19:1 dr and 98% ee).
- Zhang, Dong,Yin, Chengkai,Zhou, Yuhang,Xu, Yali,Lin, Lili,Liu, Xiaohua,Feng, Xiaoming
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supporting information
p. 7925 - 7928
(2017/07/22)
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- Direct and Co-catalytic Oxidation of Hydroxylamines to Nitrones Promoted by Rhodium Nanoparticles Supported on Carbon Nanotubes
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Rhodium nanoparticles were assembled on carbon nanotubes, and the resulting nanohybrid was studied in the aerobic oxidation of hydroxylamines to nitrones. Two catalytic systems were developed (i.e., direct or co-catalytic) and both operated to provide high yields of the products, under mild conditions, but with their own specificity as regards the kinetics and regioselectivity of the transformation. In addition, the in situ cycloaddition of the produced nitrones with different alkynes was investigated.
- Prakash, Praveen,Gravel, Edmond,Nguyen, Dinh-Vu,Namboothiri, Irishi N. N.,Doris, Eric
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p. 2091 - 2094
(2017/06/27)
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- Highly Stereoselective Synthesis of New Aziridines via Baldwin Rearrangement and Their Potential Biological Activities
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An atom-economical conversion of N-substituted isoxazoline derivatives to new N-substituted aziridines has been described using microwave irradiation through Baldwin rearrangement. N-substituted isoxazoline derivatives have been synthesized using a variet
- Chakraborty, Bhaskar,Chhetri, Manjit Singh,Chhetri, Esmita
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p. 110 - 120
(2017/02/03)
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- Nickel(II)-Catalyzed Enantioselective 1,3-Dipolar Cycloaddition of Nitrones with α,β-Unsaturated Acylcarboxylates
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The highly enantioselective 1,3-dipolar cycloaddition of nitrones with α,β-unsaturated acylcarboxylates was realized for the first time by using a chiral bis(indano-oxazoline)-based Ni complex. The reaction proceeded smoothly under mild conditions and provided isoxazolidines with three contiguous stereocenters in high yields with excellent diastereoselectivities (>20:1 dr) and enantioselectivities (up to 99 % ee). The reaction was scaled up to the gram scale, and the products were readily transformed into γ-amino alcohols and other potentially bioactive compounds.
- Xie, Lei,Yu, Xuan,Li, Jiaqi,Zhang, Zhenhua,Qin, Zhaohai,Fu, Bin
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supporting information
p. 657 - 661
(2017/02/05)
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- Controlling Asymmetric Remote and Cascade 1,3-Dipolar Cycloaddition Reactions by Organocatalysis
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The regio- and stereoselective control of cycloaddition reactions to polyconjugated systems has been demonstrated by applying asymmetric organocatalysis. Reaction of 2,4-dienals with nitrones allows for a highly regio- and stereoselective 1,3-dipolar cycl
- Poulsen, Pernille H.,Vergura, Stefania,Monleón, Alicia,J?rgensen, Danny Kaare Bech,J?rgensen, Karl Anker
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supporting information
p. 6412 - 6415
(2016/06/09)
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- RuO4-mediated oxidation of secondary amines. Part 1. Are hydroxylamines the main intermediates?
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The RuO4-catalyzed oxidation of secondary amines Bn-NH-CH2R (1a and b; R=H, Me) gave mainly amides, but minute amounts of nitrones PhCH=N(O)-CH2R (9a and b) and traces of Bn-N(OH)-CH2R (R=H, 4a) were also detect
- Florea, Cristina A.,Petride, Horia
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p. 475 - 486
(2016/07/20)
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- Synthesis and application of phenyl Nitrone derivatives as acidic and microbial corrosion inhibitors
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Nitrone has drawn great attention due to its wide applications as a 1,3-dipole in heterocyclic compounds synthesis and the bioactivities. With the special structure, nitrone can also be used as ligand in inorganic chemistry. Based on the current research,
- Chen, Shijun,Zhao, Kang,Chen, Gang
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- Formaldehyde as Tethering Organocatalyst: Highly Diastereoselective Hydroaminations of Allylic Amines
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Catalysts possessing sufficient activity to achieve intermolecular alkene hydroaminations under mild conditions are rare, and this likely accounts for the scarcity of asymmetric variants of this reaction. Herein, highly diastereoselective hydroaminations
- Hesp, Colin R.,MacDonald, Melissa J.,Zahedi, M. Mehdi,Bilodeau, Didier A.,Zhao, Shu-Bin,Pesant, Marc,Beauchemin, André M.
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supporting information
p. 5136 - 5139
(2015/11/03)
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- Water-Soluble Maleimide-Modified Gold Nanoparticles (AuNPs) as a Platform for Cycloaddition Reactions
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Maleimide-terminated triethylene glycol thiolate monolayer-protected gold nanoparticles (Mal-EG4-AuNPs) with a core size of 2.5±0.7 nm were prepared. Mal-EG4-AuNPs were modified in high yields via interfacial 1,3-dipolar cycloadditio
- Ghiassian, Sara,Gobbo, Pierangelo,Workentin, Mark S.
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p. 5438 - 5447
(2015/08/24)
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- Stereoselective synthesis of fluoroalkenoates and fluorinated isoxazolidinones: N-substituents governing the dual reactivity of nitrones
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α-Fluoroalkenoates and 4-fluoro-5-isoxazolidinones are of vast interest due to their potential biological applications. We now demonstrate the syntheses of (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones by the reactions between nitrones and α-fluoro-α-bromoacetate. By altering N-substituents in nitrones, (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones can be achieved, respectively, with high chemo- and stereoselectivities. Experimental and computational studies have been conducted to elucidate the reaction mechanisms. Linear free energy relationship studies further revealed that the N-substituent effects are primarily of electronic origin. Copyright
- Prakash, G.K. Surya,Zhang, Zhe,Wang, Fang,Rahm, Martin,Ni, Chuanfa,Iuliucci, Marc,Haiges, Ralf,Olah, George A.
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supporting information
p. 831 - 838
(2014/01/23)
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- One-pot oxidation and rearrangement of propargylamines and in situ pyrazole synthesis
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Reported here are procedures for a one-pot oxidation and rearrangement of propargylamines to synthesize enaminones, with supporting mechanistic studies. Also reported are the extended one-pot syntheses of pyrazoles, including celecoxib and various heterocyclic compounds.
- Chen, Jinshan,Properzi, Roberta,Uccello, Daniel P.,Young, Jennifer A.,Dushin, Russell G.,Starr, Jeremy T.
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supporting information
p. 4146 - 4149
(2014/09/29)
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- Oxidation of secondary amines to nitrones using magnetically separable tungstophosphoric acid supported on silica-encapsulated γ-Fe 2O3 nanoparticles
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Superparamagnetic tungstophosphoric acid supported on silica-encapsulated γ-Fe2O3 was used as an efficient catalyst for the direct oxidation of secondary amines to nitrones with hydrogen peroxide as the oxidant. The catalyst could be recycled up to four times without significant loss of activity.
- Nikbakht, Fatemeh,Heydari, Akbar,Saberi, Dariush,Azizi, Kobra
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p. 6520 - 6523
(2013/11/19)
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- Methyltrioxorhenium-catalysed oxidation of secondary amines to nitrones in ionic liquids
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Nitrones serve as starting materials for the synthesis of many heterocycles. Oxidation of secondary amines using hydrogen peroxide and the catalytic amount of methyltrioxorhenium in ionic liquids is a useful method for the preparation of nitrones. Ultrasonic irradiation and ionic liquids have a positive influence on the reaction. The nitrones required were isolated in good yields. Corresponding hydroxylamines, which can be easily oxidised to nitrones, often accompanied the main products. Methyltrioxorhenium in ionic liquids was re-used in several reaction cycles without any deteriorating effect on the course of the reaction.
- Meciarova, Maria,Mojzesova, Melinda,Sebesta, Radovan
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p. 51 - 58,8
(2020/08/20)
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- A magnetoclick imidazolidinone nanocatalyst for asymmetric 1,3-dipolar cycloadditions
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A 1,3-dipolar azide-alkyne cycloaddition has been used to prepare a magnetic nanoparticle immobilized MacMillan catalyst that catalyzes the enantioselective 1,3-dipolar cycloaddition between nitrones and α,β-unsaturated aldehydes. The catalyst can be recovered and recycled for five consecutive runs without any significant loss in yields and diastereo- and enantioselectivities of the isoxazolidines. Copyright
- Pagoti, Sreenivasarao,Dutta, Debasish,Dash, Jyotirmayee
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supporting information
p. 3532 - 3538
(2014/01/06)
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- [3 + 2] Cycloaddition reactions of ethyl (Z)-3-fluoropropenoate with nitrones
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Ethyl (Z)-2-fluoropropenoate reacts stereospecifically and regioselectively in [3 + 2] cycloadditions with aryl N-methylnitrones. The yields of the cycloaddition products range from 61 to 70%.
- Patrick, Timothy B.,Khan, Akbar H.
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- Cycloaddition reactions of diethyl (E)-2-fluoromaleate
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Diethyl E-2-fluoromaleate has been prepared in a pure state in 89% yield by a Horner-Wadsworth-Emmons Wittig procedure. The E configuration was determined by NMR spectroscopy. Diethyl E-2-fluoromaleate undergoes [3+2] cycloadditions with a series of aroma
- Patrick, Timothy B.,Shadmehr, Mehrdad,Khan, Akbar H.,Singh, Rajiv K.,Asmelash, Bethel
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p. 109 - 111,3
(2020/08/20)
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- Synthesis, structure, theoretical and experimental in vitro antioxidant/pharmacological properties of α-aryl, N-alkyl nitrones, as potential agents for the treatment of cerebral ischemia
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The synthesis, structure, theoretical and experimental in vitro antioxidant properties using the DPPH, ORAC, and benzoic acid, as well as preliminary in vitro pharmacological activities of (Z)-α-aryl and heteroaryl N-alkyl-nitrones 6-15, 18, 19, 21, and 23, is reported. In the in vitro antioxidant activity, for the DPPH radical test, only nitrones bearing free phenol groups gave the best RSA (%) values, nitrones 13 and 14 showing the highest values in this assay. In the ORAC analysis, the most potent radical scavenger was nitrone indole 21, followed by the N-benzyl benzene-type nitrones 10 and 15. Interestingly enough, the archetypal nitrone 7 (PBN) gave a low RSA value (1.4%) in the DPPH test, or was inactive in the ORAC assay. Concerning the ability to scavenge the hydroxyl radical, all the nitrones studied proved active in this experiment, showing high values in the 94-97% range, the most potent being nitrone 14. The theoretical calculations for the prediction of the antioxidant power, and the potential of ionization confirm that nitrones 9 and 10 are among the best compounds in electron transfer processes, a result that is also in good agreement with the experimental values in the DPPH assay. The calculated energy values for the reaction of ROS (hydroxyl, peroxyl) with the nitrones predict that the most favourable adduct-spin will take place between nitrones 9, 10, and 21, a fact that would be in agreement with their experimentally observed scavenger ability. The in vitro pharmacological analysis showed that the neuroprotective profile of the target molecules was in general low, with values ranging from 0% to 18.7%, in human neuroblastoma cells stressed with a mixture of rotenone/oligomycin-A, being nitrones 18, and 6-8 the most potent, as they show values in the range 24-18.4%.
- Samadi, Abdelouahid,Soriano, Elena,Revuelta, Julia,Valderas, Carolina,Chioua, Mourad,Garrido, Ignacio,Bartolomé, Bego?a,Tomassolli, Isabelle,Ismaili, Lhassane,González-Lafuente, Laura,Villarroya, Mercedes,García, Antonio G.,Oset-Gasque, María J.,Marco-Contelles, José
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experimental part
p. 951 - 960
(2011/03/19)
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- Fast method for synthesis of alkyl and aryl-N-methylnitrones
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A simple, fast, efficient and eco-friendly procedure was developed for the synthesis of alkyl and aryl-N-methylnitrones. The corresponding nitrones of aromatic aldehydes, aliphatic aldehydes and alicyclic carbonyl compounds were prepared from N-methylhydr
- Yavuz, Serkan,Ozkan, Hamdi,Colak, Naki,Yildirir, Yilmaz
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experimental part
p. 6677 - 6683
(2011/10/31)
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- Efficient synthesis of isoxazolidine-substituted bisphosphonates by 1,3-dipolar cycloaddition reactions
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Several bisphosphonates bearing a substituted isoxazolidine ring have been synthesized in good yield by direct 1,3-dipolar cyclization reaction, under microwaves catalysis, in the absence of solvent. The method allows the simultaneous incorporation, on the geminal position of the bisphosphonate framework, of a basic nitrogen and of an oxygen atom, as third hook. Hydrophobicity-hydrophilicity of BPs is discussed with the help of distribution coefficients.
- Bortolini,Mulani,De Nino,Maiuolo,Nardi,Russo,Avnet
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experimental part
p. 5635 - 5641
(2011/08/22)
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- Highly enantioselective nitrone cycloadditions with 2-alkenoyl pyridine N-oxides catalyzed by Cu
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Enantioselective nitrone cycloadditions with 2-alkenoyl pyridine N-oxides as dipolarophiles have been reported. The reaction is catalyzed by Cu (II)-BOX complexes to give the expected isoxazolidine products with high diastereo-and enantioselectivity.
- Barroso, Santiago,Blay, Gonzalo,Munoz, M. Carmen,Pedro, Jose R.
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supporting information; body text
p. 402 - 405
(2011/04/12)
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- Boronic acid catalysis for mild and selective [3+2] dipolar cycloadditions to unsaturated carboxylic acids
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Herein, the concept of boronic acid catalysis (BAC) for the activation of unsaturated carboxylic acids is applied in several classic dipolar [3 + 2] cycloadditions involving azides, nitrile oxides, and nitrones as partners. These cycloadditions can be used to produce pharmaceutically interesting, small heterocyclic products, such as triazoles, isoxazoles, and isoxazolidines. These cycloadducts are formed directly and include a free carboxylic acid functionality that can be employed for fur-ther transformations, thereby avoiding prior masking or functionalization. In all cases, BAC provides faster reactions, under milder conditions, with much improved product yields and regioselectivities. In some instances, such as triazole formation from the reaction of azides with 2-alkynoic acids, catalysis with ort/io- nitrophenylboronic acid circumvents the undesirable product decarboxylation observed when using thermal activation. By using NMR spectroscopic studies, the boronic acid catalyst was shown to provide activation by a LUMO-lowering effect in the unsaturated carboxylic acid, likely via a monoacylated hemiboronic ester intermediate.
- Zheng, Hongchao,McDonald, Robert,Hall, Dennis G.
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supporting information; experimental part
p. 5454 - 5460
(2010/09/15)
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- Zinc chloride promoted formal oxidative coupling of aromatic aldehydes and isocyanides to α-ketoamides
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Reaction of aromatic aldehydes and isocyanides in the presence of N-methylhydroxyamine, acetic acid, and zinc chloride affords the aryl α-ketoamides in moderate to good yields.
- Bouma, Marinus,Masson, Geraldine,Zhu, Jieping
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scheme or table
p. 2748 - 2751
(2010/07/17)
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- Nitrones as dipoles for rapid strain-promoted 1,3-dipolar cycloadditions with cyclooctynes
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Strain-promoted cycloadditions of nitrones with cyclooctynes (k2 = 1.5 M-1 s-1 at 25 °C) are up to 25 times more rapid than comparable reactions of azides. The Royal Society of Chemistry 2010.
- McKay, Craig S.,Moran, Joseph,Pezacki, John Paul
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body text
p. 931 - 933
(2010/06/12)
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- 1,3-Dipolar cycloadditions. Part XVII: Experimental and theoretical spectroscopic investigations of C-aryl-N-methyl nitrones
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Detailed experimental and theoretical spectroscopic studies of C-aryl-N-methyl nitrones have been reported. The optimized geometries have been calculated by DFT/B3LYP level of theory with 6-31+G(d,p) basis set. The theoretically computed frontier orbital
- Acharjee, Nivedita,Banerji, Avijit,Banerjee, Manas,Das, Tapas K.
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body text
p. 1627 - 1637
(2010/06/17)
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- Rapid, efficient, and room temperature synthesis of nitrones in excellent yields over MgO under solvent-free conditions
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A large variety of C-aryl and C-alkyl nitrones were synthesized within 0.5-15 min via the condensation of aldehydes with N-(methyl, phenyl, or t-butyl)hydroxylamines over MgO by hand-grinding with an agate mortar. These reactions were investigated under d
- Valizadeh, Hassan,Dinparast, Leila
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experimental part
p. 177 - 181
(2009/10/04)
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- A torquoselective extrusion of isoxazoline N-oxides. Application to the synthesis of aryl vinyl and divinyl ketones for Nazarov cyclization
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A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones.
- Canterbury, Daniel P.,Herrick, Ildiko R.,Um, Joann,Houk,Frontier, Alison J.
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experimental part
p. 3165 - 3179
(2009/09/05)
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- Indium (Zinc)-copper-mediated barbier-type alkylation reaction of nitrones in water: Synthesis of amines and hydroxylamines
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An efficient method for the Barbier-type alkylation reaction of various nitrones (including chiral version) and alkyl halides in water is described. The amines and hydroxylamines can be obtained in good yields, depending on the judicious choice of the metal complexes used.
- Yang, Yong-Sheng,Shen, Zhi-Liang,Loh, Teck-Peng
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supporting information; experimental part
p. 1209 - 1212
(2009/08/07)
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- 1,3-Dipolar cycloadditions. Part-XV: Systematic spectroscopic investigations of C-aryl-N-methylnitrones
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Several C-aryl-N-methylnitrones have been synthesised during the course of our work on 1,3-dipolar cycloadditions. Detailed systematic spectroscopic investigations of all these nitrones have been undertaken. These are reported along with some generalisati
- Banerji, Avijit,Acharjee, Nivedita,Biswas, Pizush Kanti
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scheme or table
p. 63 - 67
(2010/05/02)
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- Solvent-free synthesis of nitrones in a ball-mill
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Various C-aryl and C-alkyl-nitrones were synthesized within 0.5-2 h via condensation of an equimolar amount of aldehydes and N-substituted-hydroxylamines under solvent-free conditions in?a ball-mill apparatus. Reactions can be performed without the need of excluding air and moisture and yields the expected products with no need for further purification. The study has been complemented by Differential Scanning Calorimetry (DSC) and solid-state 13C MAS nuclear magnetic resonance experiments. We have also studied the temperature profile during the reaction. A comparative study with the corresponding solvent-free microwave activated reaction showed the superiority of the ball-milling method; 31 examples are described, including the synthesis of the anti-aging agent C-phenyl-N-tert-butyl nitrone (PBN) and one of its analogues C-2-pyridyl-N-tert-butylnitrone (2-PyBN).
- Colacino, Evelina,Nun, Pierrick,Colacino, Francesco Maria,Martinez, Jean,Lamaty, Frédéric
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p. 5569 - 5576
(2008/09/21)
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- Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
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Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of α-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
- Andrade, Marta M.,Barros, Maria Teresa,Pinto, Rui C.
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p. 10521 - 10530
(2008/12/23)
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- Enantioselective nitrone cycloadditions of α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl)pyridine-cerium(IV) triflate complexes
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Enantioselective nitrone cycloadditions with β-substituted α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl) pyridine-cerium(IV) triflate complexes 1 have been reported. The isoxazolidine products were efficiently transformed into densely functionalized β′-hydroxy-β-amino acid derivatives.
- Evans, David A.,Song, Hyun-Ji,Fandrick, Keith R.
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p. 3351 - 3354
(2007/10/03)
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- SUBSTITUTED IMIDAZO RING SYSTEMS AND METHODS
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Imidazo ring systems, which include, for example, imidazopyridine, imidazoquinoline, 6,7,8,9-tetrahydroimidazoquinoline, imidazonaphthyridine, and 6,7,8,9-tetrahydroimidazonaphthyridine compounds substituted at the 1-position and/or the 2-position, pharmaceutical compositions containing these compounds, methods of making these compounds, and methods of use of these compounds as immunomodulators, for inducing cytokine biosynthesis in animals and in the treatment of diseases including viral and neoplastic diseases are disclosed.
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Page/Page column 209
(2010/02/15)
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