- SmI2-H2O-mediated 5-exo/6-exo lactone radical cyclisation cascades
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The SmI2-H2O reagent system mediates challenging 5-exo/6-exo lactone radical cascade cyclisations that deliver carbo[5.4.0]bicyclic motifs in a diastereoselective, one-pot process that establish two new carbocyclic rings and four ste
- Yalavac, Irem,Lyons, Sarah E.,Webb, Michael R.,Procter, David J.
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- Peroxidase-catalyzed oxidation of 2,4,6-trichlorophenol
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2,4,6-Trichlorophenol (TCP) is an environmental contaminant that is toxic, mutagenic, and carcinogenic. We have investigated peroxidase-catalyzed oxidation of TCP as an alternative pathway of TCP bioactivation using horseradish peroxidase (HRP) as a model peroxidase. TCP was shown to function as a reducing substrate for HRP as evidenced by TCP-dependent, HRP-catalyzed reduction of 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) to its corresponding alcohol. In addition, TCP was shown to undergo hydroperoxide (H2O2, ethyl hydroperoxide, or PPHP)-dependent metabolism as evidenced by electronic absorption spectroscopic analysis of reaction mixtures. A single major product was detected by reverse phase HPLC and was identified as 2,6- dichloro-1,4-benzoquinone (2,6-dichloro-2,5-cyclohexadiene-1,4-dione, CAS no. 697-91-6) on the basis of electronic absorption spectroscopy, mass spectrometry, and cochromatography with synthetic standard. In addition, HRP- catalyzed oxidation of TCP yielded EPR-detectable phenoxyl radical intermediates whose EPR spectrum consisted of a 1:2:1 triplet characterized by proton hyperfine coupling constants a(H(3,5)) = 2.35 gauss. Mechanisms for the hydroperoxide-dependent, HRP-catalyzed oxidation of TCP are proposed that are consistent with these results.
- Wiese,Chang,Lloyd,Freeman,Samokyszyn
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- Organocatalytic, Organic Oxidant Promoted, Enamine C?H Oxidation/Cyclopropanation Reaction
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Herein, we demonstrate that organic, single-electron oxidant in the presence of diarylprolinol silylether type catalyst serves as a tool for the transformation of electron-rich enamines to iminium ions. These iminium ions take part in a subsequent Michael-initiated ring-closure (MIRC) reaction with in situ present nucleophile giving rise to overall cyclopropanation reaction of saturated aldehydes. Stereodefined cyclopropanes are obtained in high yields and selectivities. This one-pot transformation represents the additional example of saturated aldehydes being used in the coupled one-pot processes. (Figure presented.).
- Bond?i?, Aleksandra M.,Bond?i?, Bojan P.,D?ambaski, Zdravko,Kokotos, Christoforos G.,Triandafillidi, Ierasia
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- Intramolecular N-Me and N-H aminoetherification for the synthesis ofN-unprotected 3-amino-O-heterocycles
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A mild Rh-catalyzed method for synthesis of cyclic unprotected N-Me and N-H 2,3-aminoethers using an olefin aziridination-aziridine ring-opening domino reaction has been developed. The method is readily applicable to the stereocontrolled synthesis of a va
- Paudyal, Mahesh P.,Wang, Mingliang,Siitonen, Juha H.,Hu, Yimin,Yousufuddin, Muhammed,Shen, Hong C.,Falck, John R.,Kürti, László
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supporting information
p. 557 - 560
(2021/02/06)
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- Rhodium-Catalyzed Remote C(sp3)?H Borylation of Silyl Enol Ethers
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A rhodium-catalyzed remote C(sp3)?H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional-group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n-borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n-diols and aminoalcohols.
- Li, Jie,Qu, Shuanglin,Zhao, Wanxiang
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p. 2360 - 2364
(2020/01/02)
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- Copper-Catalyzed Enantioselective Hydroalkoxylation of Alkenols for the Synthesis of Cyclic Ethers
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The copper-catalyzed enantioselective intramolecular hydroalkoxylation of unactivated alkenes for the synthesis of tetrahydrofurans, phthalans, isochromans, and morpholines from 4- and 5-alkenols is reported. The substrate scope is complementary to existing enantioselective alkene hydroalkoxylations and is broad with respect to substrate backbone and alkene substitution. The asymmetric induction and isotopic labeling studies support a polar/radical mechanism involving enantioselective oxycupration followed by C-[Cu] homolysis and hydrogen atom transfer. Synthesis of the antifungal insecticide furametpyr was accomplished.
- Chen, Dake,Berhane, Ilyas A.,Chemler, Sherry R.
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p. 7409 - 7414
(2020/06/29)
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- Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer
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We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII-based photoredox catalyst, a Br?nsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
- Knowles, Robert R.,Metrano, Anthony J.,Tsuchiya, Yuto,Tsui, Elaine
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p. 11845 - 11849
(2020/05/22)
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- Enantioselective Organocatalytic Enamine C?H Oxidation/Diels- Alder Reaction
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α,β-unsaturated aldehydes have been traditionally used in LUMO lowering asymmetric aminocatalysis (iminium catalysis), while the use of saturated aldehydes as substrates in this type of catalysis has been elusive, until recently. Herein, we demonstrate that organic, single-electron oxidants in the presence of diarylprolinol silylether type catalysts serve as effective tools for the transformation of electron rich enamines to iminium ions which partake in a subsequent Diels-Alder reaction. This enantioselective one-pot transformation represents the first example of saturated aldehydes being used in domino Diels-Alder reaction processes and demonstrates the power of this protocol for construction of stereo-defined chiral compounds and building blocks. (Figure presented.).
- D?ambaski, Zdravko,Tzaras, Dimitrios-Ioannis,Lee, Sunggi,Kokotos, Christoforos G.,Bondzic, Bojan P.
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supporting information
p. 1792 - 1797
(2019/02/25)
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- Enantioselective Radical Construction of 5-Membered Cyclic Sulfonamides by Metalloradical C-H Amination
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Both arylsulfonyl and alkylsulfonyl azides can be effectively activated by the cobalt(II) complexes of D2-symmetric chiral amidoporphyrins for enantioselective radical 1,5-C-H amination to stereoselectively construct 5-membered cyclic sulfonami
- Hu, Yang,Lang, Kai,Li, Chaoqun,Gill, Joseph B.,Kim, Isaac,Lu, Hongjian,Fields, Kimberly B.,Marshall, McKenzie,Cheng, Qigan,Cui, Xin,Wojtas, Lukasz,Zhang, X. Peter
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supporting information
p. 18160 - 18169
(2019/11/19)
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- Arene Trifunctionalization with Highly Fused Ring Systems through a Domino Aryne Nucleophilic and Diels–Alder Cascade
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A convenient and efficient domino aryne process was developed under transition-metal-free conditions to generate a range of tetra- and pentacyclic ring systems. This transformation was realized via a 1,2-benzdiyne through a nucleophilic and Diels–Alder reaction cascade using styrene as the diene moiety. Three new chemical bonds, namely one C?N and two C?C bonds, and two benzofused rings could be constructed concomitantly, which was made possible by distinct chemoselective control at both the 1,2-aryne and 2,3-aryne stages. Moreover, in-depth studies were carried out on the domino aryne precursors and controlling the diastereoselectivity.
- He, Jia,Jia, Zizi,Tan, Hongcheng,Luo, Xiaohua,Qiu, Dachuan,Shi, Jiarong,Xu, Hai,Li, Yang
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supporting information
p. 18513 - 18518
(2019/11/19)
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- Rh(I)-catalyzed ring-opening of cyclobutanols via C–C bond activation: Synthesis of cis-olefin with a remote aldehyde
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A Rh(I)-catalyzed ring-opening of cyclobutanols has been developed with ring opening products bearing cis-olefin and a remote aldehyde. Various substrates bearing different substituted aryl groups, heterocyclic groups and alkyl groups were compatible with
- Nie, Yu,Chen, Jianzhong,Zhang, Wanbin
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- Stereospecific Alkene Aziridination Using a Bifunctional Amino-Reagent: An Aza-Prilezhaev Reaction
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In situ deprotection (TFA) of O-Ts activated N-Boc hydroxylamines triggers intramolecular aziridination of N-tethered alkenes to provide complex N-heterocyclic ring systems. Synthetic and computational studies corroborate a diastereospecific aza-Prilezhaev-type mechanism. The feasibility of related intermolecular alkene aziridinations is also demonstrated.
- Farndon, Joshua J.,Young, Tom A.,Bower, John F.
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supporting information
p. 17846 - 17850
(2019/01/04)
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- Aminolithiation–arylation consecutive cyclization of N-(2-fluorophenyl)methylaminoalkylstyryls giving aryl-substituted pyrido[1,2-b]isoquinolines
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Aminolithiation–arylation tandem cyclization of N-(2-fluorophenyl)methylaminoalkylstyryls proceeded smoothly to give hexahydro-2H-pyrido[1,2-b]isoquinoline using a stoichiometric amount of n-BuLi with high trans selectivity. The arylation reaction was highly accelerated by the addition of HMPA. Both pyrido- and pyrrolo-[1,2-b]isoquinoline were successfully constructed by this tandem reaction.
- Yamamoto, Yasutomo,Nakanishi, Yasue,Yamada, Ken-ichi,Tomioka, Kiyoshi
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supporting information
p. 5309 - 5318
(2018/06/11)
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- C(alkenyl)-H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis
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A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO2 as the stoichiometric oxidant or co-catalytic Co(OAc)2 and O2 (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.
- Liu, Mingyu,Yang, Pusu,Karunananda, Malkanthi K.,Wang, Yanyan,Liu, Peng,Engle, Keary M.
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supporting information
p. 5805 - 5813
(2018/05/14)
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- Aerobic Photooxidative Synthesis of β-Alkoxy Monohydroperoxides Using an Organo Photoredox Catalyst Controlled by a Base
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Transition-metal-free synthesis of β-alkoxy monohydroperoxides via aerobic photooxidation using an acridinium photocatalyst was developed. This method enables the synthesis of some novel hydroperoxides. The peroxide source is molecular oxygen, which is cost-effective and atomically efficient. Magnesium oxide plays an important role as a base in the catalytic system.
- Asano, Yuya,Nagasawa, Yoshitomo,Yamaguchi, Eiji,Itoh, Akichika
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p. 409 - 412
(2018/02/21)
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- Enantio- A nd regioselective: Ene-reductions using F420H2-dependent enzymes
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In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- A nd chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated ketones and aldehydes with good conversions (>99%) and excellent regioselectivities and enantiomeric excesses (>99% ee). Noteworthily, FDRs typically display an opposite enantioselectivity when compared to the well established FMN-dependent Old Yellow Enzymes (OYEs).
- Mathew, Sam,Trajkovic, Milos,Kumar, Hemant,Nguyen, Quoc-Thai,Fraaije, Marco W.
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p. 11208 - 11211
(2018/10/15)
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- Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides
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γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.
- Hoang,Zhang,Takacs
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supporting information
p. 4838 - 4841
(2018/05/23)
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- Indium Catalyzed Hydrofunctionalization of Styrene Derivatives Bearing a Hydroxy Group with Organosilicon Nucleophiles
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Hydrofunctionalization is one of the most important transformation reactions of alkenes. Herein, we describe the development of an indium-triiodide-catalyzed hydrofunctionalization of alkenes bearing a hydroxy group using various types of organosilicon nucleophiles. Indium triiodide was the most effective catalyst, whereas typical Lewis acids such as TiCl4, AlCl3, and BF3·OEt2 were ineffective. Many functional groups were successfully introduced, and these resulted in yields of 31-86%. Various styrene derivatives were also applicable to this reaction. Mechanistic investigation revealed that the present hydrofunctionalization proceeded through Br?nsted acid-catalyzed intramolecular hydroalkoxylation of alkenes followed by InI3-catalyzed substitution reaction of cyclic ether intermediates.
- Kita, Yuji,Yata, Tetsuji,Nishimoto, Yoshihiro,Yasuda, Makoto
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p. 740 - 753
(2018/01/28)
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- Pd(II)-Catalyzed [4 + 2] Heterocyclization Sequence for Polyheterocycle Generation
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A new Pd(II)-catalyzed cascade sequence for the formation of polyheterocycles, from simple starting materials, is reported. The sequence is applicable to both indole and pyrrole substrates, and a range of substituents are tolerated. The reaction is thought to proceed by a Pd(II)-catalyzed C-H activated Heck reaction followed by a second Pd(II)-catalyzed aza-Wacker reaction with two Cu(II)-mediated Pd(0) turnovers per sequence. The sequence can be considered a formal [4 + 2] heterocyclization.
- Glaisyer, Elizabeth L.,Watt, Michael S.,Booker-Milburn, Kevin I.
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supporting information
p. 5877 - 5880
(2018/09/25)
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- Total syntheses of surinone B, alatanones A–B, and trineurone A
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The total syntheses of four polyketides, surinone B (1), alatanones A–B (2–3), and trineurone A (4) were accomplished through an efficient and unified strategy via one-pot C-acylation reaction coupling 1,3-cyclohexadiones with EDC-activated acids under mild conditions. Alatanone A (2) was found to be a potent anti-microbial agent against Gram-positive and Gram-negative bacteria with MIC 31.25?μg/ml while alatanone B (3) was found to be a potent anti-fungal agent against Cladosporium cladosporioides with MIC 62.5?μg/ml compared to cycloheximide MIC 125?μg/ml. Our methodology allows performing kilogram scale of these scarce polyketides for the development of new antimicrobials.
- Gundoju, Narayana Rao,Bokam, Ramesh,Yalavarthi, Nageswara Rao,Buddana, Sudheer Kumar,Prakasham,Ponnapalli, Mangala Gowri
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- Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether
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Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined tri- and tetra-substituted olefins. An interesting selectivity switch was observed with internal alkynes.
- Hari Babu, Madala,Ranjith Kumar, Gadi,Kant, Ruchir,Sridhar Reddy, Maddi
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supporting information
p. 3894 - 3897
(2017/04/04)
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- Niobium-Catalyzed Intramolecular Addition of O-H and N-H Bonds to Alkenes: A Tool for Hydrofunctionalization
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A convenient, versatile, and easy to handle intramolecular hydrofunctionalization of alkenes (C-O and C-N bonds formation) is reported using a novel niobium-based catalytic system. This atom economic and eco-friendly methodology provides an additional synthetic tool for the straightforward formation of valuable building blocks enabling molecular complexity. Various pyran, furan, pyrrolidine, piperidine, lactone, and lactam derivatives as well as spirocyclic compounds are produced in high yields and selectivities.
- Ferrand, Laura,Tang, Yue,Aubert, Corinne,Fensterbank, Louis,Mouriès-Mansuy, Virginie,Petit, Marc,Amatore, Muriel
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p. 2062 - 2065
(2017/04/28)
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- Regioselective Epoxidations by Cytochrome P450 3A4 Using a Theobromine Chemical Auxiliary to Predictably Produce N-Protected β- or γ-Amino Epoxides
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N-Protected β- and γ-amino epoxides are useful chiral synthons. We report here that the enzyme cytochrome P450 3A4 can catalyze the formation of such compounds in a regio- and stereoselective manner, even in the presence of multiple double bonds or aromatic substituents. To this end, the theobromine chemical auxiliary is used not only to control the selectivity of the enzyme, but also as a masked amine, and to facilitate product recovery. Theobromine predictably directed epoxidation at the double bond of the fourth carbon from the theobromine group. Unlike with most catalysts, the selectivity did not depend on electronic or steric factors but rather on the position of the olefin relative to the theobromine group. (Figure presented.).
- Polic, Vanja,Cheong, Kin Jack,Hammerer, Fabien,Auclair, Karine
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p. 3983 - 3989
(2017/11/30)
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- Synthesis of ent-[3]-Ladderanol: Development and Application of Intramolecular Chirality Transfer [2+2] Cycloadditions of Allenic Ketones and Alkenes
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An enantioselective synthesis of ent-[3]-ladderanol is presented. The ladderanes are an interesting class of molecules for their unique structure of fused cyclobutane rings as well as their perceived biological function of organism protection. The route h
- Line, Nathan J.,Witherspoon, Brittany P.,Hancock, Erin N.,Brown, M. Kevin
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supporting information
p. 14392 - 14395
(2017/10/24)
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- Palladium-Catalyzed Aerobic Oxidative Cyclization of Aliphatic Alkenyl Amides for the Construction of Pyrrolizidine and Indolizidine Derivatives
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An efficient palladium-catalyzed aerobic oxidative cyclization has been developed to synthesize a variety of pyrrolizidine and indolizidine derivatives from simple aliphatic alkenyl amides in moderate to good yields. The reaction features the capability of accessing various N-heterocycles and the use of molecular oxygen (1 atm) as the green oxidant.
- Lo, Kai-Yip,Ye, Liu,Yang, Dan
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supporting information
p. 1570 - 1575
(2017/08/11)
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- A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
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A versatile iridium(III) metallacycle catalysed rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. The reactions proceeded in high yields at room temperature by hydrosilylation followed by desilylation. Although the reactions of various aldehydes and ketones resulted exclusively in alcohols, the hydrosilylation of esters led to alcohols or ethers, depending on the type of substrate. Regarding the carboxylic acids, again the nature of the reagent controlled the outcome of the hydrosilylation reaction, either alcohols or aldehydes being formed.
- Corre, Yann,Rysak, Vincent,Trivelli, Xavier,Agbossou-Niedercorn, Francine,Michon, Christophe
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supporting information
p. 4820 - 4826
(2017/09/07)
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- Copper-Catalyzed Diastereoselective Synthesis of Trifluoromethylated Tetrahydrofurans
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The copper-catalyzed intramolecular diastereoselective trifluoromethylcycloetherification of homoallylic alcohols with Togni's reagent as trifluoromethylating reagent was realized under mild conditions. Various trifluoromethylated tetrahydrofurans were synthesized in moderate to good yields. Moreover, a wide range of common functional groups was tolerated.
- Wang, Yanan,Jiang, Min,Liu, Jin-Tao
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supporting information
p. 1322 - 1327
(2016/04/26)
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- Radical Isomerization and Cycloisomerization Initiated by H? Transfer
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Under H2 pressure, CoII(dmgBF2)2L2 (L = H2O, THF) generates a low concentration of an H? donor. Transfer of the H? onto an olefin gives a radical that can either (1) transfer an H? back to the metal, generating an isomerized olefin, or (2) add intramolecularly to a double bond, generating a cyclized radical. Transfer of an H? back to the metal from the cyclized radical results in a cycloisomerization. Both outcomes are favored by the low concentration of the cobalt H? donor, whereas hydrogenation and cyclohydrogenation are more likely with other catalysts (when the concentration of the H? donor is high).
- Li, Gang,Kuo, Jonathan L.,Han, Arthur,Abuyuan, Janine M.,Young, Lily C.,Norton, Jack R.,Palmer, Joshua H.
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p. 7698 - 7704
(2016/07/06)
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- Stereoselective organocatalytic oxidation of alcohols to enals: A homologation method to prepare polyenes
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A novel method for organocatalytic oxidation through oxidative enamine catalysis was developed with excellent compatibility for the direct syntheses of enals from simple saturated alcohols. By using this amine-catalyzed IBX-oxidation, a wide range of aromatic and aliphatic substituted enals were successfully generated in high yields and exclusively stereoselective E-geometry. Moreover, varying the solvents and/or the loading amounts of IBX allowed for the selective oxidation of alcohols and aldehydes. Importantly, the homologous application of this method provided a selective and efficient way of preparing various highly sensitive conjugated polyene frameworks, which are enriched in natural products.
- Chen, Xiaobei,Zhang, Yinan,Wan, Huixin,Wang, Wei,Zhang, Shilei
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supporting information
p. 3532 - 3535
(2016/03/04)
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- Triphenylphosphine-N-bromosuccinimide mediated chemoselective cyclodehydration of diols
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A triphenylphosphine-N-bromosuccinimide mediated chemoselective cyclodehydration of diols is presented for the synthesis of polysubstituted tetrahydrofurans. 1,4-Diols and their derivatives can be rapidly cyclized to furnish tetrahydrofurans in high yields with one equivalent of Ph3P/NBS. Higher amount of Ph3P/NBS leads to the formation of dibromobutanes.
- Zhao, Shuo,Wu, You,Sun, Qi,Cheng, Tie-Ming,Li, Run-Tao
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p. 1154 - 1162
(2015/04/14)
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- Enantioselective synthesis of 2-substituted and 3-substituted piperidines through a bromoaminocyclization process
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A catalytic enantioselective bromocyclization of olefinic amides using amino-thiocarbamates as the catalysts has been developed. The resulting enantioenriched 2-substituted 3-bromopiperidines can readily be transformed to 3-substituted piperidines through
- Zhou, Ling,Tay, Daniel Weiliang,Chen, Jie,Leung, Gulice Yiu Chung,Yeung, Ying-Yeung
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supporting information
p. 4412 - 4414
(2013/05/22)
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- ZrCl2(η-C5Me5)2-AlHCl 2·(THF)2: Efficient hydroalumination of terminal alkynes and cross-coupling of the derived alanes
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Stabilized AlHCl2·(THF)2 hydroaluminates RCCH with exceptional chemo-, regio- and stereoselectivity under efficient ZrCl 2(η-C5Me5)2 catalysis (2-5 mol%). The resulting vinyl alanes undergo palladium cross-coupling with a wide range of sp2 electrophiles (aryl, heteroaryl and vinyl halides/pseudohalides) in good to excellent yields. The Royal Society of Chemistry 2013.
- Andrews, Philip,Latham, Christopher M.,Magre, Marc,Willcox, Darren,Woodward, Simon
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supporting information
p. 1488 - 1490
(2013/03/14)
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- Ni-catalyzed stereoselective arylation of inert C-O bonds at low temperatures
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A Ni-catalyzed arylation of inert C-O bonds that operates at temperatures as low as -40 C is described. Unlike other methods for C-O bond cleavage utilizing organometallic species, this protocol operates at low temperatures, thus allowing the presence of sensitive functional groups with exquisite site-selectivity and stereoselectivity.
- Cornella, Josep,Martin, Ruben
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supporting information
p. 6298 - 6301
(2014/01/17)
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- Selective synthesis of unsymmetrical ethers from different alcohols catalyzed by sodium bisulfite
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An efficient method for the preparation of unsymmetrical ethers from alcohols catalyzed by sodium bisulfite is reported. The procedure enables the direct dehydration of primary, secondary, and tertiary benzylic alcohols with aliphatic alcohols in the abse
- Yu, Jun-Lai,Wang, Hui,Zou, Kai-Feng,Zhang, Jia-Rui,Gao, Xiang,Zhang, Dan-Wei,Li, Zhan-Ting
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p. 310 - 315
(2013/01/15)
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- Enantioselective bromocycloetherification by Lewis base/chiral Bronsted acid cooperative catalysis
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A binary catalyst system for the enantioselective bromocycloetherification of 5-arylpentenols is described. The combination of an achiral Lewis base and a chiral Bronsted acid affords good enantioselectivities for the cyclization of Z configured 5-arylpen
- Denmark, Scott E.,Burk, Matthew T.
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supporting information; experimental part
p. 256 - 259
(2012/03/10)
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- A highly enantioselective approach towards 2-substituted 3-bromopyrrolidines
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A facile and highly enantioselective approach towards 2-substituted 3-bromopyrrolidines has been developed. The process involves an amino-thiocarbamate catalyzed bromoaminocyclization of 1,2-disubstituted olefinic amides. The pyrrolidine products could re
- Chen, Jie,Zhou, Ling,Yeung, Ying-Yeung
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supporting information; experimental part
p. 3808 - 3811
(2012/06/04)
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- Introducing a mixed-valent dirhodium(ii,iii) catalyst with increased stability in C-H amination
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A new mixed-valent Rh2II,III dimer, [Rh 2(espn)2Cl] (espn2- = α,α, α′,α′-tetramethyl-1,3-benzenedipropanamidate), is reported. This compound readily dissociates Cl- at low concentrations in solution to form the active [Rh2(espn)2]+ catalyst, which performs intramolecular C-H amination with TONs > 1400. This work expands the scope of Rh2II,III dimers to nitrenoid chemistry.
- Kornecki, Katherine P.,Berry, John F.
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supporting information
p. 12097 - 12099
(2013/01/16)
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- Synthesis of allylic and homoallylic alcohols from unsaturated cyclic ethers using a mild and selective C-O reduction approach
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Unsaturated cyclic ethers can be mildly and selectively reduced with catalytic amounts of B(C6F5)3 in the presence of an alkylsilane. The allylic position is preferentially reduced with minimal or no scrambling of olefin geometry. For electronically equivalent substrates, steric factors guide the reducing agent to the least substituted site.
- MacK, Daniel J.,Guo, Boying,Njardarson, Jon T.
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supporting information; experimental part
p. 7844 - 7846
(2012/09/05)
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- Manganese(III) acetate mediated oxidative radical cyclizations. Toward vicinal all-carbon quaternary stereocenters
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Manganese(III) acetate mediated oxidative radical cyclizations have been used to synthesize a range of densely functionalized and sterically congested cyclopentane-lactones. A number of the resulting lactones contain vicinal all-carbon quaternary stereocenters adjacent to a tertiary benzylic stereocenter and are formed with high levels of stereocontrol.
- Logan, Angus W.J.,Parker, Jeremy S.,Hallside, Michal S.,Burton, Jonathan W.
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supporting information; experimental part
p. 2940 - 2943
(2012/08/28)
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- Copper-catalyzed highly selective semihydrogenation of non-polar carbon-carbon multiple bonds using a silane and an alcohol
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A copper catalyst bearing a suitable Xantphos derivative or NHC ligand was found to be highly efficient for the selective semihydrogenation of non-polar unsaturated compounds using a mixture of a silane and an alcohol as reducing agent. The catalytic system was useful for the selective semihydrogenation of internal alkynes to (Z)-alkenes with suppression of overreduction to the corresponding alkanes. Furthermore, semihydrogenations of terminal alkyne, 1,2-diene, 1,3-diene, 1,3-enyne and 1,3-diyne systems were also achieved selectively. Copyright
- Semba, Kazuhiko,Fujihara, Tetsuaki,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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p. 1542 - 1550
(2012/08/08)
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- O-alkyl-N-acyl-N-phenylhydroxylamines as photochemical alkoxy radical precursors
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A simple and efficient technique for the photolysis of alkoxy radical precursors is developed. Irradiation of O-alkyl-N-acyl-N-phenylhydroxylamines, as representative alkoxy radical precursors, with ultraviolet light (254 nm) results in homolytic N-O bond cleavage to generate singlet alkoxy and acylaminyl caged radical pairs. These radicals, depending on the solvent employed, either escape from the cage to form fragmentation products, or undergo in-cage reactions to produce photorearrangement products. The homolytic cleavage of the N-O bond is analyzed using time-dependent density functional theory calculations. The nature of the N-acyl substituent on the O-alkyl-N-acyl-N- phenylhydroxylamines is shown to influence their ability to generate radicals. Furthermore, identification and trapping of the alkoxy radicals is demonstrated. Georg Thieme Verlag Stuttgart · New York.
- Chowdhury, Nilanjana,Anoop, Anakuthil,Singh, N.D. Pradeep
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experimental part
p. 1745 - 1754
(2012/07/27)
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- Nickel-catalyzed allylic substitution of simple alkenes
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This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. The key to success is the use of an appropriate nickel-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented.
- Matsubara, Ryosuke,Jamison, Timothy F.
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supporting information; scheme or table
p. 1860 - 1875
(2012/02/02)
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- Aminothiocarbamate-catalyzed asymmetric bromolactonization of 1,2-disubstituted olefinic acids
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An efficient and enantioselective bromolactonization of 1,2-disubstituted olefinic acids using an amino-thiocarbamate catalyst has been developed, resulting in the formation of δ-lactones containing two chiral centers with up to 99% yield, 95% ee.
- Tan, Chong Kiat,Zhou, Ling,Yeung, Ying-Yeung
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supporting information; experimental part
p. 2738 - 2741
(2011/06/26)
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- Oxidative and enantioselective cross-coupling of aldehydes and nitromethane catalyzed by diphenylprolinol silyl ether
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Synthetically important β-substituted γ-nitro aldehydes have been synthesized with excellent enantioselectivity by the cross-coupling reaction of β-aryl substituted aldehydes or Y γ-unsaturated aldehydes and nitromethane using 2,3-dichloro-5,6-dicyanoquinone (DDQ) and diphenylprolinol silyl ether as an oxidant and catalyst, respectively (see scheme; TMS=trimethylsilyl).
- Hayashi, Yujiro,Itoh, Takahiko,Ishikawa, Hayato
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p. 3920 - 3924
(2011/05/15)
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- Intramolecular hydroalkoxylation in Bronsted acidic ionic liquids and its application to the synthesis of (±)-centrolobine
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The SO3H-tethered imidazolium and triazolium salts, nonvolatile and recyclable Bronsted acidic ionic liquids, efficiently mediate intramolecular hydroalkoxylations of alkenyl alcohols. They have been successfully employed in the synthesis of (±)-centrolobine.
- Jeong, Yunkyung,Kim, Do-Young,Choi, Yunsil,Ryu, Jae-Sang
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supporting information; experimental part
p. 374 - 378
(2011/02/28)
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- Metal-free oxyaminations of alkenes using hydroxamic acids
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A radical-mediated approach to metal-free alkene oxyamination is described. This method capitalizes on the unique reactivity of the amidoxyl radical in alkene additions to furnish a general difunctionalization using simple diisopropyl azodicarboxylate (DIAD) as a radical trap. This protocol capitalizes on the intramolecular nature of the process, providing single regioisomers in all cases. Difunctionalizations of cyclic alkenes provide trans oxyamination products inaccessible using current methods with high levels of stereoselectivity, complementing cis-selective oxyamination processes.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; scheme or table
p. 11402 - 11405
(2011/09/16)
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- Metal-free, aerobic dioxygenation of alkenes using hydroxamic acids
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(Chemical equation presented) One dioxygenation please, hold the metal: In the presence of either oxygen or air as the sole oxidant and external oxygen atom source, a variety of unsaturated hydroxamic acids afford cyclic hydroxamates that are readily converted into 1,2-diols, with the potential for high levels of reaction stereocontrol.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; scheme or table
p. 4491 - 4494
(2010/08/21)
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- Palladium-catalyzed carbonylative heck-type reactions of alkyl iodides
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A palladium-catalyzed carbonylative Heck-type cyclization of alkyl halides is described. Treatment of a range of primary and secondary alkyl iodides with catalytic palladium(0) under CO pressure forms a variety of synthetically versatile enone products. The reactivity described represents a rare example of a palladium-catalyzed Heck-type cyclization involving unactivated alkyl halides with β-hydrogens. Alkene substitution is well tolerated, and mono-and bicyclic carbocycles may be easily accessed.
- Bloome, Kayla S.,Alexanian, Erik J.
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supporting information; experimental part
p. 12823 - 12825
(2010/11/03)
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- Intramolecular anodic olefin coupling reactions and the synthesis of cyclic amines
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Anodic olefin coupling reactions using a tosylamine trapping group have been studied. The cyclizations are favored by the use of a less-polar radical cation and more basic reaction conditions. The most significant factor for obtaining good yields of cyclic product is the use of the more basic reaction conditions. However, a number of factors including the nature of both the solvent and the electrolyte used can influence the yield of the cyclizations. The cyclizations allow for the rapid synthesis of both substituted proline and pipecolic acid type derivatives.
- Xu, Hai-Chao,Moeller, Kevin D.
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supporting information; experimental part
p. 2839 - 2844
(2010/06/11)
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- SmI2-promoted intra- and intermolecular C-C bond formation with chiral N-acyl oxazolidinones
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The suitability of chiral oxazolidinones in the SmI2-mediated C-C bond generation between the imide functionality of an N-acyl oxazolidinone unit and an olefinic radical acceptor, in both inter- and intramolecular reactions, was investigated. It was shown that the products from an Evans asymmetric alkylation can undergo direct carbon-carbon bond formation with an acrylamide providing chiral acyclic ketones in reasonable yields. These examples represent the first transformation of such N-acyl oxazolidinones where this chiral auxiliary is removed under the conditions for ketone formation. 5-exo-trig Cyclization studies were also undertaken with the same type of substrates, providing trans-2,5-disubstituted cyclopentanones in yields of approx. 50%. However, attempts to cyclize heteroatom-containing equivalents were less rewarding.
- Taaning, Rolf H.,Thim, Laura,Karaffa, Jacob,Campa?a, Araceli G.,Hansen, Anna-Mette,Skrydstrup, Troels
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experimental part
p. 11884 - 11895
(2009/04/07)
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- Intramolecular anodic olefin coupling reactions: The use of a nitrogen trapping group
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Anodic olefin coupling reactions using a tosylamine trapping group have been studied. The cyclizations are favored by the use of a less-polar radical cation and more basic reaction conditions. The most significant factor for obtaining good yields of cyclic product is the use of the more basic reaction conditions. The cyclizations allow for the rapid synthesis of substituted proline derivatives. Copyright
- Xu, Hai-Chao,Moeller, Kevin D.
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supporting information; experimental part
p. 13542 - 13543
(2009/02/06)
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