- Ligand-controlled cobalt-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes
-
The Co-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes were realized by a ligand-controlled strategy. The remote hydroboration with dcype provided borylethers, while xantphos favored the formation of silyl enol ethers.
- Huang, Jiaxin,Li, Jie,Yang, Wen,Zhang, Kezhuo,Zhao, Pei,Zhao, Wanxiang
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supporting information
p. 302 - 305
(2022/01/03)
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- Stereoselective Carbocyclization of Vinyloxiranes Catalyzed by Lewis Acids: Construction of the Musellarin Tricyclic Core
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Stereoselective carbocyclizations of vinyloxiranes were efficiently catalyzed by Lewis acids to provide cyclic homoallyl alcohols as single isomers. The choice of Lewis acid, B(C6F5)3 was crucial for the stereoselective tr
- Yang, Sehui,Park, Euijin,Kim, Jimin
-
supporting information
p. 667 - 670
(2021/02/05)
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- Iridium-Catalyzed Regioselective Hydroalkynylation of Internal Alkenes Directed by an Oxime
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We report here an iridium-catalyzed hydroalkynylation of allylic alcohols protected by an oxime group. Catalytic alkynylation occurs exclusively at the distal position of the alkene. This method generates γ-alkynyl alcohol oximes directly from internal alkenes and terminal alkynes. The oxime group can be readily removed to afford a free alcohol, thus providing an indirect route for the catalytic hydroalkynylation of allylic alcohols.
- Gao, Peng-Chao,Li, Bi-Jie,Wang, Zi-Xuan
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p. 9500 - 9504
(2021/12/14)
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- A Sequential Acyl Thiol-Ene and Thiolactonization Approach for the Synthesis of δ-Thiolactones
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A novel strategy for the synthesis of δ-thiolactones from inexpensive and readily available ?-unsaturated esters has been developed. This strategy incorporates a radical acyl thiol-ene reaction as the key C-S bond forming step. Cyclization is achieved via a Steglich-type thiolactonization of 5-mercaptopentanoic acids. We report the facile and scalable synthesis of δ-thiolactones in moderate to good yield under mild reaction conditions with tolerance for a range of functional groups.
- McCourt, Ruairí O.,Scanlan, Eoin M.
-
supporting information
p. 3460 - 3464
(2019/05/10)
-
- Copper-Catalyzed Perfluoroalkylation of Allyl Phosphates with Stable Perfluoroalkylzinc Reagents
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A general and practical method for copper-catalyzed cross-coupling of allyl phosphates with stable perfluoroalkylzinc reagents has been developed. The reaction proceeds under mild reaction conditions with high efficiency, good functional group tolerance, and high regio- A nd stereoselectivities and provides general, straightforward, and useful access to allyl-perfluoroalkyl compounds. Preliminary mechanistic studies reveal that the allyl copper intermediate may be involved in the catalytic cycle.
- Liu, Lihua,Bao, Xifei,Xiao, Hua,Li, Junlan,Ye, Feifan,Wang, Chaoqin,Cai, Qinhua,Fan, Shilu
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p. 423 - 434
(2019/01/08)
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- Trifluoromethylation of Unactivated Alkenes with Me3SiCF3 and N-Iodosuccinimide
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A novel approach to the trifluoromethylation of unactivated alkenes is presented. This reaction is promoted by N-iodosuccinimide (NIS) under visible light irradiation without the need for photocatalysts. The mild conditions allow the direct synthesis of u
- Yang, Xinkan,Tsui, Gavin Chit
-
supporting information
p. 1521 - 1525
(2019/03/07)
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- Cascade reaction including a formal [5?+?2] cycloaddition by use of alkyne-Co2(CO)6 complex
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A new cascade reaction including formal [5 + 2] cycloaddition was developed. Treatment of homocinnamyl alcohol and Co2(CO)6-complexed arylpropynal with BF3·OEt2 resulted in the generation of hydrobenzocyclohepta
- Sakata, Yuki,Yasui, Eiko,Mizukami, Megumi,Nagumo, Shinji
-
supporting information
p. 755 - 759
(2019/02/20)
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- Acid-catalyzed chirality-transferring intramolecular Friedel-Crafts cyclization of α-hydroxy-α-alkenylsilanes
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Acid-catalyzed intramolecular Friedel-Crafts cyclization of optically active α-hydroxy-α-alkenylsilanes possessing a benzene ring (>99% ee) with TMSOTf as a Lewis acid gave enantio-enriched tetrahydronaphthalenes (up to 98% ee). The silyl group attached to the chiral carbon played a crucial role in the chirality transfer.
- Sakaguchi, Kazuhiko,Kubota, Shunnichi,Akagi, Wataru,Ikeda, Naoko,Higashino, Masato,Ariyoshi, Shoma,Shinada, Tetsuro,Ohfune, Yasufumi,Nishimura, Takahiro
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supporting information
p. 8635 - 8638
(2019/07/25)
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- Formation of COOH-Ylides, and Their Reactivities and Selectivities in Wittig Reactions
-
Whereas two equivalents of base are typically required to prepare carboxylate (CO 2-) ylides [Ph 3 P + C - (H)-alk-CO 2- ] (alk = alkanediyl) from carboxy (CO 2 H) pho
- Suganuma, Yuta,Kobayashi, Yuichi
-
supporting information
p. 333 - 337
(2019/02/12)
-
- Stereodivergence in the Ireland-Claisen Rearrangement of α-Alkoxy Esters
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A systematic investigation into the Ireland-Claisen rearrangement of α-alkoxy esters is reported. In all cases, the use of KN(SiMe3)2 in toluene gave rearrangement products corresponding to a Z-enolate intermediate with excellent diastereoselectivity, presumably because of chelation control. On the other hand, chelation-controlled enolate formation could be overcome for most substrates through the use of lithium diisopropylamide (LDA) in tetrahydrofuran (THF).
- Podunavac, Ma?a,Lacharity, Jacob J.,Jones, Kerry E.,Zakarian, Armen
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supporting information
p. 4867 - 4870
(2018/08/24)
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- Remote sp3 C–H Amination of Alkenes with Nitroarenes
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Direct installation of a functional group at remote, unfunctionalized sites in an alkyl chain is a synthetically valuable but rarely reported process. The remote relay hydroarylamination of distal and proximal olefins, and of olefin isomeric mixtures, has been achieved through NiH-catalyzed alkene isomerization and sequential reductive hydroarylamination with nitroarenes. This provides an attractive approach to the direct installation of a distal arylamino group within alkyl chains. The single-step conversion of simple olefins and nitro(hetero)arenes to value-added arylamines is a practical strategy for amine synthesis as well as the remote activation of sp3 C–H bonds. The value of this transformation is further supported by the regioconvergent arylamination of isomeric mixtures of olefins. Modern organic synthesis requires more efficient strategies, such as C–H functionalization, with which to construct complex molecules from readily available chemicals. Undirected functionalization of remote aliphatic C–H bonds is a synthetically valuable but largely unknown process. Synergistic combination of metal-catalyzed chainwalking (migration of a double bond along the hydrocarbon chain, a process involving repeated migratory insertions and β-hydride eliminations) and cross-coupling chemistry offers a general approach to the remote functionalization of easily accessed unsaturated hydrocarbon substrates. In this paper, we demonstrate that direct installation of a distal arylamino group can be achieved from two common feedstock chemicals (olefins and nitroarenes) via nickel hydride chemistry. It is anticipated that the strategy could inspire the development of other remote functionalizations with different regioselectivity as well as asymmetric transformations. Zhu and colleagues describe the remote hydroamination of alkenes with nitro(hetero)arenes through nickel-catalyzed alkene isomerization and sequential reductive relay hydroamination process. Using two common feedstock chemicals, olefins and nitroaromatics, in an operationally simple procedure, this attractive protocol provides efficient and practical access to a wide range of arylamines under mild conditions.
- Xiao, Jichao,He, Yuli,Ye, Feng,Zhu, Shaolin
-
supporting information
p. 1645 - 1657
(2018/05/16)
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- Radical-mediated reactions of α-bromo aluminium thioacetals, α-bromothioesters, and xanthates for thiolactone synthesis
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Thiolactones have attracted considerable attention in recent years as bioactive natural products, lead compounds for drug discovery, molecular probes, and reagents for polymerisation. We have investigated radical-mediated C-C bond forming reactions as a s
- McCourt, Ruairí O.,Dénès, Fabrice,Scanlan, Eoin M.
-
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- Multicatalytic Stereoselective Synthesis of Highly Substituted Alkenes by Sequential Isomerization/Cross-Coupling Reactions
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Starting from readily available alkenyl methyl ethers, the stereoselective preparation of highly substituted alkenes by two complementary multicatalytic sequential isomerization/cross-coupling sequences is described. Both elementary steps of these sequences are challenging processes when considered independently. A cationic iridium catalyst was identified for the stereoselective isomerization of allyl methyl ethers and was found to be compatible with a nickel catalyst for the subsequent cross-coupling of the in situ generated methyl vinyl ethers with various Grignard reagents. The method is compatible with sensitive functional groups and a multitude of olefinic substitution patterns to deliver products with high control of the newly generated C=C bond. A highly enantioselective variant of this [Ir/Ni] sequence has been established using a chiral iridium precatalyst. A complementary [Pd/Ni] catalytic sequence has been optimized for alkenyl methyl ethers with a remote C=C bond. The final alkenes were isolated with a lower level of stereocontrol. Upon proper choice of the Grignard reagent, we demonstrated that C(sp2) - C(sp2) and C(sp2) - C(sp3) bonds can be constructed with both systems delivering products that would be difficult to access by conventional methods.
- Romano, Ciro,Mazet, Clément
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supporting information
p. 4743 - 4750
(2018/04/10)
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- Chemo- and Enantioselective Pd/B Hybrid Catalysis for the Construction of Acyclic Quaternary Carbons: Migratory Allylation of O-Allyl Esters to α- C-Allyl Carboxylic Acids
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We describe herein the asymmetric synthesis of α-allyl carboxylic acids containing an α-quaternary stereocenter by a chiral hybrid catalyst system comprising palladium and boron complexes. The reaction proceeded through palladium-catalyzed ionization of α,α-disubstituted O-allyl esters for the generation of chiral π-allyl palladium complex as an electrophile, boron-catalyzed enolization of the carboxylate part for the generation of chiral α,α-disubstituted carboxylic acid-derived enolates as a nucleophile, and enantioselective coupling between the thus-generated nucleophile and electrophile. Proper combinations of chiral ligands for the boron and palladium catalysts were crucial. The reaction proceeded chemoselectively at the α-position of the carboxylic acid group.
- Fujita, Taiki,Yamamoto, Tomohiro,Morita, Yuya,Chen, Hongyu,Shimizu, Yohei,Kanai, Motomu
-
supporting information
p. 5899 - 5903
(2018/05/14)
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- Photoredox/Nickel-Catalyzed Single-Electron Tsuji–Trost Reaction: Development and Mechanistic Insights
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A regioselective, nickel-catalyzed photoredox allylation of secondary, benzyl, and α-alkoxy radical precursors is disclosed. Through this manifold, a variety of linear allylic alcohols and allylated monosaccharides are accessible in high yields under mild reaction conditions. Quantum mechanical calculations [DFT and DLPNO-CCSD(T)] support the mechanistic hypothesis of a Ni0 to NiII oxidative addition pathway followed by radical addition and inner-sphere allylation.
- Matsui, Jennifer K.,Gutiérrez-Bonet, álvaro,Rotella, Madeline,Alam, Rauful,Gutierrez, Osvaldo,Molander, Gary A.
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supporting information
p. 15847 - 15851
(2018/11/23)
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- Tandem Catalysis: Transforming Alcohols to Alkenes by Oxidative Dehydroxymethylation
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We report a Rh-catalyst for accessing olefins from primary alcohols by a C-C bond cleavage that results in dehomologation. This functional group interconversion proceeds by an oxidation-dehydroformylation enabled by N,N-dimethylacrylamide as a sacrificial acceptor of hydrogen gas. Alcohols with diverse functionality and structure undergo oxidative dehydroxymethylation to access the corresponding olefins. Our catalyst protocol enables a two-step semisynthesis of (+)-yohimbenone and dehomologation of feedstock olefins.
- Wu, Xuesong,Cruz, Faben A.,Lu, Alexander,Dong, Vy M.
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p. 10126 - 10130
(2018/08/23)
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- Regioselective Ni-Catalyzed Carboxylation of Allylic and Propargylic Alcohols with Carbon Dioxide
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An efficient Ni-catalyzed reductive carboxylation of allylic alcohols with CO2 has been successfully developed, providing linear β,γ-unsaturated carboxylic acids as the sole regioisomer with generally high E/Z stereoselectivity. In addition, the carboxylic acids can be generated from propargylic alcohols via hydrogenation to give allylic alcohol intermediates, followed by carboxylation. A preliminary mechanistic investigation suggests that the hydrogenation step is made possible by a Ni hydride intermediate produced by a hydrogen atom transfer from water.
- Chen, Yue-Gang,Shuai, Bin,Ma, Cong,Zhang, Xiu-Jie,Fang, Ping,Mei, Tian-Sheng
-
supporting information
p. 2969 - 2972
(2017/06/07)
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- Enantioselective C-C Bond Formation during the Oxidation of 5-Phenylpent-2-enyl Carboxylates with Hypervalent Iodine(III)
-
The oxidation of (5-acyloxypent-3-enyl)benzene with hypervalent iodine(III) afforded 2-oxy-1-(oxymethyl)tetrahydronaphthalene under metal-free conditions. The acyloxy group may nucleophilically participate in the oxidative cyclization. A lactate-based chi
- Shimogaki, Mio,Fujita, Morifumi,Sugimura, Takashi
-
p. 11836 - 11840
(2017/11/27)
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- Photoredox Activation of SF6for Fluorination
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We report the first practical use of SF6as a fluorinating reagent in organic synthesis. Photoredox catalysis enables the in situ conversion of SF6, an inert gas, into an active fluorinating species by using visible light. Under these conditions, deoxyfluorination of allylic alcohols is effected with high chemoselectivity and is tolerant of a wide range of functional groups. Application of the methodology in a continuous-flow setup achieves comparable yields to those obtained with a batch setup, while providing drastically increased material throughput of valuable allylic fluoride products.
- McTeague, T. Andrew,Jamison, Timothy F.
-
supporting information
p. 15072 - 15075
(2016/11/25)
-
- Dual Palladium(II)/Tertiary Amine Catalysis for Asymmetric Regioselective Rearrangements of Allylic Carbamates
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The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β- and γ-aminoalcohols as well as α- and β-aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N-tosylisocyanate in a single step into highly enantioenriched N-tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation-induced [3,3]-rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl-protected allylic amines, which can be deprotected under non-reductive conditions.
- Bauer, Johannes Moritz,Frey, Wolfgang,Peters, René
-
supporting information
p. 5767 - 5777
(2016/04/20)
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- Enantioselective desymmetrization via carbonyl-directed catalytic asymmetric hydroboration and Suzuki-Miyaura cross-coupling
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The rhodium-catalyzed enantioselective desymmetrization of symmetric γ,δ-unsaturated amides via carbonyl-directed catalytic asymmetric hydroboration (directed CAHB) affords chiral secondary organoboronates with up to 98% ee. The chiral γ-borylated products undergo palladium-catalyzed Suzuki-Miyaura cross-coupling via the trifluoroborate salt with stereoretention.
- Hoang, Gia L.,Yang, Zhao-Di,Smith, Sean M.,Miska, Judy L.,Prez, Damaris E.,Zeng, Xiao Cheng,Takacs, James M.,Pal, Rhitankar,Pelter, Libbie S. W.
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supporting information
p. 940 - 943
(2015/03/30)
-
- Dialkylzinc-mediated allylic polyfluoroarylation reaction
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Abstract We present an allylic polyfluoroarylation reaction with broad substrate scope and excellent functional group tolerance, using organozinc reagents under mild conditions. A catalytic amount of triphenylphosphine oxide efficiently promotes iodine-zinc exchange reaction between polyfluoroaryl iodide and dimethylzinc, and the resulting phosphine oxide-activated polyfluoroarylzinc undergoes substitution reaction with allylic halides to afford the corresponding polyfluoroarylated products.
- Kurauchi, Daisuke,Hirano, Keiichi,Kato, Hisano,Saito, Tatsuo,Miyamoto, Kazunori,Uchiyama, Masanobu
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supporting information
p. 5849 - 5857
(2015/08/03)
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- Highly enantioselective copper(i)-catalyzed conjugate addition of 1,3-diynes to α,β-unsaturated trifluoromethyl ketones
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The conjugate diynylation of α,β-unsaturated trifluoromethyl ketones is carried out in the presence of a low catalytic load (2.5 mol%) of a copper(i)-MeOBIPHEP complex, triethylamine and a terminal 1,3-diyne. Pre-metalation of the terminal 1,3-diyne with stoichiometric or higher amounts of dialkylzinc reagent is not required. The corresponding internal diynes bearing a propargylic stereogenic center are obtained with good yields and excellent enantioselectivities. This journal is
- Sanz-Marco, Amparo,Blay, Gonzalo,Mu?oz, M. Carmen,Pedro, José R.
-
supporting information
p. 8958 - 8961
(2015/05/27)
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- Toward a Unified Mechanism for Oxoammonium Salt-Mediated Oxidation Reactions: A Theoretical and Experimental Study Using a Hydride Transfer Model
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A range of oxoammonium salt-based oxidation reactions have been explored computationally using density functional theory (DFT), and the results have been correlated with experimentally derived trends in reactivity. Mechanistically, most reactions involve a formal hydride transfer from an activated C-H bond to the oxygen atom of the oxoammonium cation. Several new potential modes of reactivity have been uncovered and validated experimentally.
- Hamlin, Trevor A.,Kelly, Christopher B.,Ovian, John M.,Wiles, Rebecca J.,Tilley, Leon J.,Leadbeater, Nicholas E.
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p. 8150 - 8167
(2015/09/02)
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- Oxidative cleavage of allyl ethers by an oxoammonium salt
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A method to oxidatively cleave allyl ethers to their corresponding aldehydes mediated by an oxoammonium salt is described. Using a biphasic solvent system and mild heating, cleavage proceeds readily, furnishing a variety of α,β-unsaturated aldehydes and ketones.
- Kelly, Christopher B.,Ovian, John M.,Cywar, Robin M.,Gosselin, Taylor R.,Wiles, Rebecca J.,Leadbeater, Nicholas E.
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supporting information
p. 4255 - 4259
(2015/04/14)
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- Titanocene(III) chloride mediated radical-induced opening of monosubstituted epoxy acetates for the synthesis of primary allylic alcohols
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A simple and efficient method for the synthesis of primary allylic alcohols from monosubstituted epoxy acetates has been developed using titanocene(III) chloride mediated epoxide ring opening via acetate elimination.
- Chakraborty,Mandal,Roy
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p. 893 - 901
(2015/08/18)
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- Ring Expansion of Epoxides under Br?nsted Base Catalysis: Formal [3+2] Cycloaddition of β,γ-Epoxy Esters with Imines Providing 2,4,5-Trisubstituted 1,3-Oxazolidines
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A novel ring-expansion reaction of epoxides under Br?nsted base catalysis was developed. The formal [3+2] cycloaddition reaction of β,γ-epoxy esters with imines proceeds in the presence of triazabicyclodecene (TBD) as a superior Br?nsted base catalyst to afford 2,4,5-trisubstituted 1,3-oxazolidines in a highly diastereoselective manner. This reaction involves the ring opening of the epoxides with the aid of the Br?nsted base catalyst to generate α,β-unsaturated esters having an alkoxide at the allylic position, which would formally serve as a synthetic equivalent of the 1,3-dipole, followed by a cycloaddition reaction with imines in a stepwise fashion. This methodology enables the facile synthesis of enantioenriched 1,3-oxazolidines from easily accessible enantioenriched epoxides.
- Kondoh, Azusa,Odaira, Kenta,Terada, Masahiro
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p. 11240 - 11244
(2016/07/06)
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- Copper-catalyzed enantioselective allylic alkylation of terminal alkyne pronucleophiles
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The copper-catalyzed enantioselective allylic alkylation of terminal alkynes with primary allylic phosphates was developed by the use of a new chiral N-heterocyclic carbene ligand bearing a phenolic hydroxy group at the ortho position of one of the two N-aryl groups. This reaction occurred with excellent γ-branch regioselectivity and high enantioselectivity, forming a controlled stereogenic center at the allylic/propargylic position. Various terminal alkynes, including silyl, aliphatic, and aromatic alkynes, could be used directly without premetalation of the C(sp)-H bond. On the basis of the results of experiments using an isomeric secondary allylic phosphate, which gave a branched product through an α-selective substitution reaction with retention of configuration, a reaction pathway involving 1,3-allylic migration of Cu in a ([σ + π]-allyl)copper(III) species is proposed.
- Harada, Ayumi,Makida, Yusuke,Sato, Tatsunori,Ohmiya, Hirohisa,Sawamura, Masaya
-
supporting information
p. 13932 - 13939
(2015/02/05)
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- An efficient partial reduction of α,β-unsaturated esters using DIBAL-H in flow
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The partial reduction of α,β-unsaturated esters and benzoate derivatives to form the corresponding aldehydes was achieved using a flow reactor system within 1 s at a high flow rate (18 mL min-1) under cryogenic conditions (-97°C). Commercially available diisobutylaluminium hydride (DIBAL-H) was used as the reductant. The desired enals and benzaldehyde derivatives, except for 4-methoxycinnamate and 4-methoxybenzoate, were formed selectively and redox economically in moderate to high yields.
- Yoshida, Masahito,Otaka, Hiroyuki,Doi, Takayuki
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p. 6010 - 6016
(2015/03/30)
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- Asymmetric cascade reaction to allylic sulfonamides from allylic alcohols by palladium(II)/base-catalyzed rearrangement of allylic carbamates
-
A regio- and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl-protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step-economy with operational simplicity (e.g. no need for inert-gas atmosphere or catalyst activation). Mechanistic studies support a Pd II-catalyzed [3,3] rearrangement of allylic carbamates - generated in situ from the allylic alcohol and an isocyanate - as the key step, which is followed by a decarboxylation.
- Bauer, Johannes Moritz,Frey, Wolfgang,Peters, Rene
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supporting information
p. 7634 - 7638
(2014/08/05)
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- Palladium catalyzed cyclizations of oxime esters with 1,2-disubstituted alkenes: Synthesis of dihydropyrroles
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Pd-catalyzed cyclizations of oxime esters with 1,2-dialkylated alkenes provide an entry to chiral dihydropyrroles. Substrate and catalyst controlled strategies for selective product formation (vs alternative pyrroles) are outlined.
- Race, Nicholas J.,Bower, John F.
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supporting information
p. 4616 - 4619
(2013/09/24)
-
- Catalytic enantioselective dibromination of allylic alcohols
-
A new dibromination reaction involving the combination of dibromomalonate as the bromonium source and a titanium bromide species as the bromide source has been developed. Enantioselective catalysis has been achieved through apparent ligand acceleration by a tartaric acid-derived diol.
- Hu, Dennis X.,Shibuya, Grant M.,Burns, Noah Z.
-
supporting information
p. 12960 - 12963
(2013/09/24)
-
- NOVEL 1,3-BENZOXAZOL-2(3H)-ONES AND THEIR USE AS MEDICAMENTS AND COSMETICS
-
The present invention relates to a novel class of 1,3-benzoxazol-2(3H) -ones of formula (1) and their use as a medicament, preferably as a dermatologic agent, and as a cosmetic. These novel compounds are particularly useful in treating and/or preventing inflammation, irritation, itching, pruritus, pain, oedema and/or pro-allergic or allergic conditions in a patient. Usually they are topically applied to the skin or mucosa in the form of a pharmaceutical or cosmetic composition comprising the compound and a pharmaceutically and/or cosmetically acceptable carrier.
- -
-
Page/Page column 33
(2014/01/07)
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- Titanium-catalyzed intermolecular hydroaminoalkylation of conjugated dienes
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Ti me kangaroo down: Conjugated dienes undergo intermolecular hydroaminoalkylation in the presence of Ti catalyst [Ind2TiMe 2] (Ind=η5-indenyl). This new reaction offers a highly atom-efficient approach to homoallylic amines from 1,3-butadienes. Copyright
- Preuss, Till,Saak, Wolfgang,Doye, Sven
-
supporting information
p. 3833 - 3837
(2013/04/24)
-
- Palladacyclic imidazoline-naphthalene complexes: Synthesis and catalytic performance in Pd(II)-catalyzed enantioselective reactions of allylic trichloroacetimidates
-
A new family of air- and moisture-stable enantiopure C,N-palladacycles (PIN-acac complexes) were prepared in good overall yield in three steps from 2-iodo-1-naphthoic acid and enantiopure β-amino alcohols. Three of these PIN complexes were characterized by single-crystal X-ray analysis. As anticipated, the naphthalene and imidazoline rings of PIN-acac complexes 18a and 18b were canted significantly from planarity and projected the imidazoline substituents R1 and R2 on opposite faces of the palladium square plane. Fifteen PIN complexes were evaluated as catalysts for the rearrangement of prochiral (E)-allylic trichloroacetimidate 19 (eq 2) and the SN2′ allylic substitution of acetic acid with prochiral (Z)-allylic trichloroacetimidate 23. Although these complexes were kinetically poor catalysts for the Overman rearrangement, they were good catalysts for the allylic substitution reaction, providing branched allylic esters in high yield. However, enantioselectivities were low to moderate and significantly less than that realized with palladacyclic complexes of the COP family. Computational studies support an anti-acetoxypalladation/syn-deoxypalladation mechanism analogous to that observed with COP catalysts. The computational study further suggests that optimizing steric influence in the vicinity of the carbon ligand of a chiral C,N-palladacycle, rather than near the nitrogen heterocycle, is the direction to pursue in future development of improved enantioselective catalysts of this motif.
- Cannon, Jeffrey S.,Frederich, James H.,Overman, Larry E.
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supporting information; body text
p. 1939 - 1951
(2012/04/23)
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- Copper-catalyzed enantioselective allylic substitution with alkylboranes
-
The first catalytic enantioselective allylic substitution reaction with alkylboron compounds has been achieved. The reaction between alkyl-9-BBN reagents and primary allylic chlorides proceeded with excellent γ-selectivities and high enantioselectivities under catalysis of a Cu(I)-DTBM-SEGPHOS system. The protocol produces terminal alkenes with an allylic stereogenic center branched with functionalized sp3-alkyl groups. The reaction with a γ-silicon-substituted allyl chloride affords an efficient strategy for the enantioselective synthesis of functionalized α-stereogenic chiral allylsilanes.
- Shido, Yoshinori,Yoshida, Mika,Tanabe, Masahito,Ohmiya, Hirohisa,Sawamura, Masaya
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p. 18573 - 18576
(2013/01/15)
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- Diastereoselective nucleophilic addition to aldehydes with polar α- And α,β-substituents
-
The stereoselectivities obtained in Lewis acid-promoted Mukaiyama aldol additions and Sakurai allylations of mono-, and syn- and anti-disubstituted aldehydes possessing various polar α- and β-substituents under non-chelating conditions are presented. The
- Borg, Tessie,Danielsson, Jakob,Mohiti, Maziar,Restorp, Per,Somfai, Peter
-
supporting information; experimental part
p. 2022 - 2036
(2011/10/31)
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- Disubstituted Z-allylic esters by Wittig-Schlosser reaction using methylenetriphenylphosphorane
-
β-Lithiooxyphosphonium ylides, generated in situ from aldehydes and methylenetriphenylphosphorane, react with halomethyl esters to form disubstituted allylic esters in good yields and with high Z-selectivity.
- Hodgson, David M.,Arif, Tanzeel
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supporting information; experimental part
p. 2685 - 2687
(2011/04/25)
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- Conjugate addition-initiated Nazarov cyclization
-
A reaction sequence involving the 1,6-conjugate addition of a nucleophile to a dienyl diketone followed by Nazarov cyclization is described. Several nucleophiles are identified as competent initiators for the sequence. A different reaction outcome is observed when catalytic amounts of nucleophile are employed, involving elimination of the nucleophile after the electrocyclization.
- Brooks, Joshua L.,Caruana, Patrick A.,Frontier, Alison J.
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supporting information; experimental part
p. 12454 - 12457
(2011/10/09)
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- Catalytic asymmetric synthesis of chiral allylic esters
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A broadly useful catalytic enantioselective synthesis of branched allylic esters from prochiral (Z)-2-alkene-1-ols has been developed. The starting allylic alcohol is converted to its trichloroacetimidate intermediate by reaction with trichloroacetonitrile, either in situ or in a separate step, and this intermediate undergoes clean enantioselective SN2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst (Rp,S)-di-μ-acetatobis[(η5- 2-(2′-(4′-methylethyl)oxazolinyl)cyclopentadienyl-1-C,3′-N) (η4-tetraphenylcyclobutadiene)cobalt]dipalladium, (R p,S)-[COP-OAc]2, or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined.
- Cannon, Jeffrey S.,Kirsch, Stefan F.,Overman, Larry E.
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supporting information; experimental part
p. 15185 - 15191
(2010/12/25)
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- Stereoselective synthesis and biological evaluation of (R)-rugulactone, (6R)-((4R)-hydroxy-6-phenyl-hex-2-enyl)-5,6-dihydro-pyran-2-one and its 4S epimer
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A simple and highly efficient synthetic route has been developed for synthesis of (R)-rugulactone (1a), (6R)-((4R)-hydroxy-6-phenyl-hex-2-enyl)-5,6- dihydro-pyran-2-one (1b) and its 4S epimer 1c by employing proline-catalyzed α-aminooxylation, Sharpless epoxidation, Mitsunobu reaction as chirality introuducing steps. The antibacterial and antifungal activity of the compounds 1a, 1b and 1c were evaluated. 1a and 1b showed better antibacterial activity against Pseudomonas aeroginosa (MIC =12.5 μg/ml for 1a, 25 μg/ml for 1b) Klebsiella pneumonia (MIC =25 μg/ml for 1a). Compounds (1a, 1b, 1c) exhibited good to moderate antifungal activity.
- Reddy, D. Kumar,Shekhar,Prabhakar,Chinna Babu,Siddhardha,Murthy,Venkateswarlu
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experimental part
p. 4657 - 4663
(2010/10/19)
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- Rearrangement of 2,3-epoxy alcohol dimethylthiocarbamate derivatives. Synthesis of 2,3-epithio alcohol derivatives under mild conditions
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(Figure presented) Transformation of representative 2,3-epoxy alcohols, including 3-trimethylsilyl- and 3-triphenylsilylglycidols, into the corresponding 2,3-epithio alcohol dimethylthiocarbamate derivatives under mild alkaline conditions is reported.
- Kalicki, Przemyslaw,Karchier, Michal,Michalak, Karol,Wicha, Jerzy
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supporting information; experimental part
p. 5388 - 5391
(2010/10/19)
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- New general method for regio- and stereoselective allylic substitution with aryl and alkenyl coppers derived from grignard reagents
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Allylic substitution with sp2-carbon reagents (aryl and alkenyl anions) was realized by using allylic picolinates and copper reagents derived from RMgBr and CuBr-Me2S to afford anti SN2 products regioand stereoselectively. Steric and electronic factors in the reagents and the size of the methylene substituents around the allylic moiety marginally affected the selectivity. The reaction system was compatible with alkyl reagents as well. Furthermore, the substitution was applied to construction of a quaternary center and synthesis of (-)-sesquichamaenol. Electron-withdrawing nature of the pyridyl group and chelation of the C(=O)-C5H4N to MgBr2 generated in situ were found to be responsible for the high efficiency of the substitution.
- Kiyotsuka, Yohei,Katayama, Yuji,Acharya, Hukuni P.,Hyodo, Tomonori,Kobayashi, Yuichi
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supporting information; experimental part
p. 1939 - 1951
(2009/08/07)
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- The asymmetric aza-claisen rearrangement: development of widely applicable pentaphenylferrocenyl palladacycle catalysts
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Systematic studies have been performed to develop highly efficient catalysts for the asymmetric aza-Claisen rearrangement of trihaloacetimidates. Herein, we describe the stepwise development of these catalyst systems involving four different catalyst generations finally resulting in the development of a planar chiral pentaphenylferrocenyl oxazoline palladacycle. This complex is more reactive and has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza-Claisen rearrange-ments. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza-Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines, but also secondary and tertiary amines; al-lylic amines with N-substituted quaternary stereocenters are conveniently accessible as well. The reaction conditions tolerate many important functional groups, thus providing stereoselective access to valuable functionalized building blocks, for example, for the synthesis of unnatural amino acids. Our results suggest that face-selective olefin coordination is the enantioselectivitydetermining step, which is almost exclusively controlled by the element of planar chirality.
- Fischer, Daniel F.,Barakat, Assem,Xin, Zhuo-Qun,Weiss, Matthias E.,Peters, Rene
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supporting information; experimental part
p. 8722 - 8741
(2010/03/31)
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- Catalytic organocopper chemistry from organosiloxane reagents
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The coupling of organosilanes with vinyl epoxides in the presence of a copper catalyst has been reported. Functional-group-tolerant synthetic methods of organosilanes can be developed through activation and transmetalation with a transition-metal catalyst
- Herron, Jessica R.,Russo, Vincenzo,Valente, Edward J.,Ball, Zachary T.
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supporting information; experimental part
p. 8713 - 8716
(2010/03/24)
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- Picolinoxy group, a new leaving group for anti SN2 selective allylic substitution with Aryl Anions Based on Grignard Reagents
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The picolinoxy group was found to be an extremely powerful leaving group for allylic substitution with aryl nucleophiles derived from ArMgBr and CuBr?Me2S. The substitution proceeds with anti SN2 pathway and with high chirality transfer. The electron-withdrawing effect of the pyridyl group and chelation to MgBr2 are likely the origin of success. Results suggesting these effects were obtained.
- Kiyotsuka, Yohei,Acharya, Hukum P.,Katayama, Yuji,Hyodo, Tomonori,Kobayashi, Yuichi
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supporting information; experimental part
p. 1719 - 1722
(2009/04/10)
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- Palladium(II)-catalyzed isomerization of olefins with tributyltin hydride
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(Chemical Equation Presented) A new efficient method for the synthesis of geometrically pure (E)-alkenes from (Z)-alkenes is described. The reaction of aryl- or alkyl-substituted (Z)-alkenes with tributyltin hydride and triethylamine in the presence of a catalytic amount of palladium acetate afforded the corresponding (E)-alkenes in good yields.
- In, Su Kim,Guang, Ri Dong,Young, Hoon Jung
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p. 5424 - 5426
(2008/02/07)
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- Iterative approach to polyketide-type structures: Stereoselective synthesis of 1,3-polyols utilizing the catalytic asymmetric Overman esterification
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An iterative systematic approach to the 1,3-polyol motif has been developed to provide access to all possible stereoisomers by utilizing the catalytic asymmetric Overman esterification for the construction of all stereogenic centres. The Royal Society of
- Binder, Joerg T.,Kirsch, Stefan F.
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p. 4164 - 4166
(2008/03/27)
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- Enantioselective total synthesis of both the stereoisomers of dihydrokawain-5-ol
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The enantioselective synthesis of both the stereoisomers of dihydrokawain-5-ol is described. The key features of the synthetic strategy include (a) Sharpless asymmetric dihydroxylation, (b) Wittig olefination, and (c) formation of β-keto ester to access t
- Kamal, Ahmed,Krishnaji, Tadiparthi,Reddy, P. Venkat
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p. 1775 - 1779
(2008/02/11)
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- Superbase-promoted rearrangement of oxiranes to cyclopropanes
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Aryl- and alkenyl substituted oxiranes, when submitted to treatment with superbasic reagents, undergo a highly regio- and stereoselective rearrangement leading to cyclopropylmethanol derivatives. The process can also be applied to mono- and dihydroxy subs
- Mordini, Alessandro,Peruzzi, Daniela,Russo, Francesco,Valacchi, Michela,Reginato, Gianna,Brandi, Alberto
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p. 3349 - 3360
(2007/10/03)
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