- Visible-light-promoted carboimination of unactivated alkenes for the synthesis of densely functionalized pyrroline derivatives
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An efficient strategy which integrates visible-light-induced iminyl-radical formation with carboimination of unactivated alkenes has been developed for the easy access of densely functionalized pyrroline derivatives. With fac-[Ir(ppy)3] as photoredox catalyst, the acyl oximes were converted into iminyl radical intermediates by one electron reduction, and evolve through a cascade of intramolecular cyclization and intermolecular carbon radical trapping to give the functionalized pyrrolines. The utilization of silyl enol ethers as coupling partners not only allows the introduction of synthetically useful ketone functionalities but also renders catalyst regeneration without any external reductants. This protocol is characterized by its mild reaction conditions and the tolerance of a broad range of functionalities.
- Cai, Sai-Hu,Xie, Jia-Hao,Song, Shengjin,Ye, Lu,Feng, Chao,Loh, Teck-Peng
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Read Online
- Method for synthesizing 2-methyl-5-phenyl-3,4-dihydro-2H-pyrrole compound
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The invention discloses a method for synthesizing a 2-methyl-5-phenyl-3,4-dihydro-2H-pyrrole compound. the method comprises the following steps: adding gamma,delta-unsaturated oxime ether, samarium metal and iodine by one-pot method into a reaction contai
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Paragraph 0016-0018; 0058-0059
(2019/07/29)
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- Iminyl Radicals by Reductive Cleavage of N-O Bond in Oxime Ether Promoted by SmI2: A Straightforward Synthesis of Five-Membered Cyclic Imines
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A new generation method of N-centered radicals from the reductive cleavage of the N-O bond in oxime ether promoted by SmI2 is reported for the first time. The in-situ-generated N-centered radicals underwent intramolecular cyclization to afford five-membered cyclic imines in two manners: N-centered radical addition and N-centered anion nucleophilic substitution. From a synthetic point of view, an efficient synthetic method of five-membered cyclic imines was developed. A mechanism of the transformation was proposed.
- Huang, Fei,Zhang, Songlin
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p. 7430 - 7434
(2019/10/11)
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- Pyrroline Synthesis via Visible-Light-Promoted Hydroimination of Unactivated Alkenes with N,N′-Dimethylpropylene Urea as H-Donor
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Synthesis of 3,4-pyrroline derivatives via visible-light-induced hydro/oxyimination of unactivated olefins is reported. In the presence of the photoredox catalyst fac-Ir(ppy)3, the key iminyl radical intermediate can be readily generated from O-acyl oximes, and undergoes intramolecular cyclization and H-abstraction from solvent or is trapped by TEMPO to give the corresponding hydro/oxyimination product, respectively. Mechanistic investigations indicate that N,N′-dimethylpropylene urea (DMPU) works as both reducing agent for catalyst regeneration and H-donor for product formation in this process. (Figure presented.).
- Cai, Sai-Hu,Wang, Ding-Xing,Ye, Lu,Liu, Ze-Yao,Feng, Chao,Loh, Teck-Peng
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supporting information
p. 1262 - 1266
(2018/02/06)
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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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- Acceptorless Dehydrogenative Coupling Using Ammonia: Direct Synthesis of N-Heteroaromatics from Diols Catalyzed by Ruthenium
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The synthesis of N-heteroaromatic compounds via an acceptorless dehydrogenative coupling process involving direct use of ammonia as the nitrogen source was explored. We report the synthesis of pyrazine derivatives from 1,2-diols and the synthesis of N-substituted pyrroles by a multicomponent dehydrogenative coupling of 1,4-diols and primary alcohols with ammonia. The acridine-based Ru-pincer complex 1 is an effective catalyst for these transformations, in which the acridine backbone is converted to an anionic dearomatized PNP-pincer ligand framework.
- Daw, Prosenjit,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 11931 - 11934
(2018/09/27)
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- Nickel-Catalyzed 1,2-Aminoarylation of Oxime Ester-Tethered Alkenes with Boronic Acids
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A nickel-catalyzed 1,2-aminoarylation of oxime-ester-tethered alkenes with boronic acids was developed. A variety of pyrroline derivatives were synthesized in good yields via the successive formation of C(sp3)-N and C(sp3)-C(sp2) bonds. For cyclobutanone-derived oxime esters, the reaction provided aliphatic nitriles incorporating an aromatic group in the γ-position. A mechanism involving iminyl radical and carbon-centered radical intermediates was proposed.
- Yang, Hai-Bin,Pathipati, Stalin R.,Selander, Nicklas
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p. 8441 - 8445
(2017/12/08)
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- Photoredox Imino Functionalizations of Olefins
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Shown herein is that polyfunctionalized nitrogen heterocycles can be easily prepared by a visible-light-mediated radical cascade process. This divergent strategy features the oxidative generation of iminyl radicals and subsequent cyclization/radical trapping, which allows the effective construction of highly functionalized heterocycles. The reactions proceed efficiently at room temperature, utilize an organic photocatalyst, use simple and readily available materials, and generate, in a single step, valuable building blocks that would be difficult to prepare by other methods.
- Davies, Jacob,Sheikh, Nadeem S.,Leonori, Daniele
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p. 13361 - 13365
(2017/10/17)
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- Visible-Light-Mediated Generation of Nitrogen-Centered Radicals: Metal-Free Hydroimination and Iminohydroxylation Cyclization Reactions
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The formation and use of iminyl radicals in novel and divergent hydroimination and iminohydroxylation cyclization reactions has been accomplished through the design of a new class of reactive O-aryl oximes. Owing to their low reduction potentials, the inexpensive organic dye eosin Y could be used as the photocatalyst of the organocatalytic hydroimination reaction. Furthermore, reaction conditions for a unique iminohydroxylation were identified; visible-light-mediated electron transfer from novel electron donor-acceptor complexes of the oximes and Et3N was proposed as a key step of this process.
- Davies, Jacob,Booth, Samuel G.,Essafi, Stephanie,Dryfe, Robert A. W.,Leonori, Daniele
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p. 14017 - 14021
(2016/01/25)
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- Highly enantioselective partial hydrogenation of simple pyrroles: A facile access to chiral 1-pyrrolines
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A highly enantioselective Pd-catalyzed partial hydrogenation of simple 2,5-disubstituted pyrroles with a Bronsted acid as an activator has been successfully developed, providing chiral 2,5-disubstituted 1-pyrrolines with up to 92% ee.
- Wang, Duo-Sheng,Ye, Zhi-Shi,Chen, Qing-An,Zhou, Yong-Gui,Yu, Chang-Bin,Fan, Hong-Jun,Duan, Ying
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supporting information; experimental part
p. 8866 - 8869
(2011/07/30)
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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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- Microwave-assisted preparations of dihydropyrroles from alkenone O-phenyl oximes
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Microwave irradiation of alkenone O-phenyl oximes produces iminyl radicals that ring close to yield dihydropyrrole derivatives; pyrroles and pyridines can be obtained from related precursors. The Royal Society of Chemistry.
- Portela-Cubillo, Fernando,Scott, Jackie S.,Walton, John C.
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p. 4041 - 4043
(2008/03/14)
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- Photochemical radical cyclization of γ,δ-unsaturated ketone oximes to 3,4-dihydro-2H-pyrroles
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3,4-Dihydro-2H-pyrroles are synthesized from γ, δ-unsaturated oximes by photochemical radical cyclization with 1,5-dimethoxynaphthalene (DMN) as the sensitizer. The cyclization of alkyl ketone O-acetyloximes proceeds via photosensitized electron transfer
- Kitamura, Mitsuru,Mori, Yutaka,Narasaka, Koichi
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p. 2373 - 2376
(2007/10/03)
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- Synthesis of Dihydropyrrole and Pyrrole Derivatives by Radical Cyclization of γ,δUnsaturated Ketone O-Acetyloximes
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Treatment of γδ-unsaturated ketone O-acetyloximes with a catalytic amount of 1,5-naphthalenediol or hydroquinone, acetic acid, and 1,4-cyclohexadiene affords various dihydropyrrole and pyrrole derivatives via radical cyclization induced by one-electron reduction of the oximes.
- Yoshida, Masayuki,Kitamura, Mitsuru,Narasaka, Koichi
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p. 2003 - 2008
(2007/10/03)
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- Synthesis of 3,4-dihydro-2H-pyrroles from γ,δ-unsaturated ketone ?-acetyloximes
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3,4-Dihydro-2H-pyrroles were synthesized from γ,δunsaturated ketone ?-acetyloximes by treatment with acetic acid and 1,4-cyclohexadiene in the presence of a catalytic amount of 1,5-naphthalenediol. During the cyclization, syn-anti isomerization of the ?-acetyloximes easily occured and so, both stereoisomers of oximes could be employed.
- Yoshida, Masayuki,Kitamura, Mitsuru,Narasaka, Koichi
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p. 144 - 145
(2007/10/03)
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- A new method for the generation and capture of iminyl radicals
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Iminyl radicals can be generated from ketoxime esters and captured by an internal olefin; the sequence may be terminated in a variety of ways depending on the nature of the ensuing carbon radical and the added external trap.
- Boivin, Jean,Schiano, Anne-Marie,Zard, Samir Z.,Zhang, Haiwen
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p. 4531 - 4534
(2007/10/03)
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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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- A new source of nitrogen centered radicals
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Exposure of thiocarbazone derivatives 6b-10b, 11c-13c, and 14a-15a to tributylstannane in the presence of AIBN leads to various nitrogen centered radicals which are easily captured by an internal olefin.
- Callier-Dublanchet, Anne-Claude,Quiclet-Sire, Beatrice,Zard, Samir Z.
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p. 8791 - 8794
(2007/10/02)
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- Iminyl radicals by stannane mediated cleavage of oxime esters
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Despite the explosive growth in the use of radical reactions which has swept organic synthesis in the past few years, nitrogen centred radicals and iminyls in particular have not yet attracted the attention they deserve This can be traced to a large extent to a lack of convenient and mild methods for generating such species. As part of a general study of the reactivity and synthetic potential of iminyls, we recently showed that the reaction of sulfenimines with tributystannane or the Barton decarboxylation of O-carboxymethyl oximes represented useful routes to these intermediates. Another promising approach, still in its preliminary stages however, involved the reduction of oxime esters with nickel powder in acetic acid. in this Letter, we describe yet another method based on the cleavage of oxime benzoates with tin centered radicals.
- Boivin, Jean,Schiano, Anne-Marie,Zard, Samir Z.
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p. 249 - 252
(2007/10/02)
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