- Synthesis and antifungal activity of new dihydrofurocoumarins and dihydrofuroquinolines
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We investigated the radical addition of 4-hydroxycoumarin (1a) and 4-hydroxyquinoline (1b) with conjugated dienes (2a-f) mediated by cerium(IV) ammonium nitrate (CAN) resulting in ethenyl substituted 2,3-dihydrofurocoumarin (3a-f) and 3,5-dihydrofuroquino
- Ustalar, Asli,Yilmaz, Mehmet,Osmani, Agim,Ke?eli, Sema A?kin
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Read Online
- Photoinduced Copper-Catalyzed Asymmetric C-O Cross-Coupling
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The construction of carbon-heteroatom bonds is one of the most active areas of research in organic chemistry because the function of organic molecules is often derived from the presence of heteroatoms. Although considerable advances have recently been achieved in radical-involved catalytic asymmetric C-N bond formation, there has been little progress in the corresponding C-O bond-forming processes. Here, we describe a photoinduced copper-catalyzed cross-coupling of readily available oxime esters and 1,3-dienes to generate diversely substituted allylic esters with high regio- and enantioselectivity (>75 examples; up to 95% ee). The reaction proceeds at room temperature under excitation by purple light-emitting diodes (LEDs) and features the use of a single, earth-abundant copper-based chiral catalyst as both the photoredox catalyst for radical generation and the source of asymmetric induction in C-O coupling. Combined experimental and density functional theory (DFT) computational studies suggest the formation of π-allylcopper complexes from redox-active oxime esters as bifunctional reagents and 1,3-dienes through a radical-polar crossover process.
- Chen, Jun,Liang, Yu-Jie,Wang, Peng-Zi,Li, Guo-Qing,Zhang, Bin,Qian, Hao,Huan, Xiao-Die,Guan, Wei,Xiao, Wen-Jing,Chen, Jia-Rong
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Read Online
- The Mechanism of Rhodium-Catalyzed Allylic C-H Amination
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Herein, the mechanism of catalytic allylic C-H amination reactions promoted by Cp*Rh complexes is reported. Reaction kinetics experiments, stoichiometric studies, and DFT calculations demonstrate that the allylic C-H activation to generate a Cp*Rh(π-allyl) complex is viable under mild reaction conditions. The role of external oxidants in the catalytic cycle is elucidated. Quantum mechanical calculations, stoichiometric reactions, and cyclic voltammetry experiments concomitantly support an oxidatively induced reductive elimination process of the allyl fragment with an acetate ligand proceeding through a Rh(IV) intermediate. Stoichiometric oxidation and bulk electrolysis of the proposed π-allyl intermediate are also reported to support these analyses. Lastly, evidence supporting the amination of an allylic acetate intermediate is presented. We show that Cp*Rh(III)2+ behaves as a Lewis acid catalyst to complete the allylic amination reaction.
- Harris, Robert J.,Park, Jiyong,Nelson, Taylor A. F.,Iqbal, Nafees,Salgueiro, Daniel C.,Bacsa, John,Macbeth, Cora E.,Baik, Mu-Hyun,Blakey, Simon B.
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Read Online
- Organometal-bridged PMOs as efficiency and reusable bifunctional catalysts in one-pot cascade reactions
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Two bifunctional catalysts with two kinds of organometals incorporated into the periodic mesoporous organosilica (PMO) supports, denoted as Rh/Pd@PMO(Ph) catalyst and Fe/Cp*Rh@PMO(Et) chiral catalyst, were synthesized by surfactant directed co-condensatio
- Huang, Jianlin,Zhang, Fang,Li, Hexing
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Read Online
- Flash vacuum pyrolysis of pyrazoles as an alternative way to study vinylcarbenes
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Flash vacuum pyrolysis (FVP) reactions of 3,5-diphenylpyrazole (1) and 3(5)-methyl-5(3)-phenylpyrazole (2) were carried out. The reaction products expected for nitrogen extrusion were formed through different rearrangements in the vinylcarbene intermediate. Kinetic parameters for nitrogen extrusion from 1 are reported. To show that FVP reactions of pyrazoles are useful to obtain vinylcarbenes, the reactions of other pyrazoles previously studied are also discussed.
- Moyano, Elizabeth L.,Yranzo, Gloria I.,Elguero, Jose
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Read Online
- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Palladium-Catalyzed Asymmetric Hydrosulfonylation of 1,3-Dienes with Sulfonyl Hydrazides
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A highly enantio- and regioselective hydrosulfonylation of 1,3-dienes with sulfonyl hydrazides has been realized by using a palladium catalyst containing a monodentate chiral spiro phosphoramidite ligand. The reaction provided an efficient approach to synthetically useful chiral allylic sulfones. Mechanistic studies suggest that the reaction proceeds through the formation of an allyl hydrazine intermediate and subsequent rearrangement to the chiral allylic sulfone product. The transformation of the allyl hydrazine intermediate to the product is the enantioselectivity-determining step.
- Li, Ming-Ming,Cheng, Lei,Xiao, Li-Jun,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 2948 - 2951
(2020/12/15)
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- Direct 1,2-Dicarbonylation of Alkenes towards 1,4-Diketones via Photocatalysis
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1,4-Dicarbonyl compounds are intriguing motifs and versatile precursors in numerous pharmaceutical molecules and bioactive natural compounds. Direct incorporation of two carbonyl groups into a double bond at both ends is straightforward, but also challenging. Represented herein is the first example of 1,2-dicarbonylation of alkenes by photocatalysis. Key to success is that N(n-Bu)4+ not only associates with the alkyl anion to avoid protonation, but also activates the α-keto acid to undergo electrophilic addition. The α-keto acid is employed both for acyl generation and electrophilic addition. By tuning the reductive and electrophilic ability of the acyl precursor, unsymmetric 1,4-dicarbonylation is achieved for the first time. This metal-free, redox-neutral and regioselective 1,2-dicarbonylation of alkenes is executed by a photocatalyst for versatile substrates under extremely mild conditions and shows great potential in biomolecular and drug molecular derivatization.
- Chen, Bin,Cheng, Yuan-Yuan,Hou, Hong-Yu,Lei, Tao,Tung, Chen-Ho,Wu, Li-Zhu,Yu, Ji-Xin
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supporting information
p. 26822 - 26828
(2021/11/17)
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- Regiodivergent DH or HD Addition to Alkenes: Deuterohydrogenation versus Hydrodeuterogenation
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The regioselective and regiodivergent addition of H-D to a variety of 1,1-diarylalkenes was realized utilizing selectively deuterated dihydroaromatic compounds, which were generated by cobalt catalysis. The reaction was initiated by catalytic amounts of B
- Hilt, Gerhard,Li, Luomo
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supporting information
(2020/03/03)
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- An Electroreductive Approach to Radical Silylation via the Activation of Strong Si-Cl Bond
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The construction of C(sp3)-Si bonds is important in synthetic, medicinal, and materials chemistry. In this context, reactions mediated by silyl radicals have become increasingly attractive but methods for accessing these intermediates remain limited. We present a new strategy for silyl radical generation via electroreduction of readily available chlorosilanes. At highly biased potentials, electrochemistry grants access to silyl radicals through energetically uphill reductive cleavage of strong Si-Cl bonds. This strategy proved to be general in various alkene silylation reactions including disilylation, hydrosilylation, and allylic silylation under simple and transition-metal-free conditions.
- Lu, Lingxiang,Siu, Juno C.,Lai, Yihuan,Lin, Song
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supporting information
p. 21272 - 21278
(2020/12/21)
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- Methylenation for Aldehydes and Ketones Using 1-Methylbenzimidazol-2-yl Methyl Sulfone
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The methylenation reagent 1-methylbenzimidazol-2-yl methyl sulfone 2 reacts with various aldehydes and ketones in the presence of t-BuOK (room temperature, 1 h) in dimethylformamide to give the corresponding terminal alkenes generally in high yields. For sensitive substrates, the reaction is better carried out at low temperature using sodium hexamethyldisilazide in 1,2-dimethoxyethane. The byproduct is easily removed from the products, and the reaction conditions are mild and practical. Reagent 2 can be easily prepared from commercially available 2-mercaptobenzimidazole 5 in 95% yield without any expensive reagents.
- Ando, Kaori,Oguchi, Mai,Kobayashi, Takahisa,Asano, Haruka,Uchida, Nariaki
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p. 9936 - 9943
(2020/09/04)
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- Migratory Hydrogenation of Terminal Alkynes by Base/Cobalt Relay Catalysis
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Migratory functionalization of alkenes has emerged as a powerful strategy to achieve functionalization at a distal position to the original reactive site on a hydrocarbon chain. However, an analogous protocol for alkyne substrates is yet to be developed. Herein, a base and cobalt relay catalytic process for the selective synthesis of (Z)-2-alkenes and conjugated E alkenes by migratory hydrogenation of terminal alkynes is disclosed. Mechanistic studies support a relay catalytic process involving a sequential base-catalyzed isomerization of terminal alkynes and cobalt-catalyzed hydrogenation of either 2-alkynes or conjugated diene intermediates. Notably, this practical non-noble metal catalytic system enables efficient control of the chemo-, regio-, and stereoselectivity of this transformation.
- Liu, Bingxue,Liu, Qiang,Liu, Xufang
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supporting information
p. 6750 - 6755
(2020/03/13)
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- Palladium-Catalyzed Synthesis of Indolines from Aroyloxycarbamates through a Tandem Decarboxylative Amination/Heck/Annulation Reaction
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A novel synthesis of functionalized indolines via a Pd-catalyzed tandem decarboxylative amination/Heck/annulation reaction has been developed. This process features operational simplicity, mild conditions, and the use of a readily available and environmentally friendly starting material, namely carboxylic acid. Furthermore, the reaction shows good functional group tolerance and chemical selectivity. (Figure presented.).
- Wang, Zheng,Li, Peihe,Fu, Hui,Dai, Qipu,Hu, Changwen
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p. 192 - 200
(2018/11/23)
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- Radical-Mediated Heck-Type Alkylation: Stereoconvergent Synthesis of Functionalized Polyenes
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The stereospecific synthesis of polyenes is of great synthetic value. Disclosed herein is a new, efficient, stereoconvergent approach for the synthesis of functionalized polyenes via a radical-mediated Heck-type alkylation. The easily accessed Z- and E-mixed alkenes are harnessed as starting material, leading to a unique stereoisomer of polyenes. In addition, the transformation features mild reaction conditions and broad functional group compatibility. A variety of valuable 1,3-dienes and 1,3,5-trienes are afforded in useful yields.
- Zhang, Hong,Wu, Xinxin,Wei, Yunlong,Zhu, Chen
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supporting information
p. 7568 - 7572
(2019/10/02)
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- Visible-Light-Mediated Regioselective Chlorosulfonylation of Alkenes and Alkynes: Introducing the Cu(II) Complex [Cu(dap)Cl2] to Photochemical ATRA Reactions
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A visible-light-mediated photocatalyzed protocol utilizing copper-phenanthroline-based catalysts has been developed that can convert a large number of olefins into their chlorosulfonylated products. Besides the Cu(I) complex [Cu(dap)2]Cl, now well-established in photo-ATRA processes, the corresponding Cu(II) complex [Cu(dap)Cl2] proved to be often even more efficient in the title reaction, being advantageous from an economic point of view but also opening up new avenues for photoredox catalysis. Moreover, the copper complexes outperformed commonly used ruthenium, iridium, or organic dye based photocatalysts, owing to their ability to stabilize or interact with transient radicals by inner sphere mechanisms. The use of stoichiometric Na2CO3 in combination with the copper photocatalysts was found to be essential to convert unactivated olefins to the desired products, in contrast to activated olefins for which no additive was required. As suggested by appropriate control experiments, the role of Na2CO3 is attributed to prevention of poisoning of the catalyst.
- Hossain, Asik,Engl, Sebastian,Lutsker, Eugen,Reiser, Oliver
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p. 1103 - 1109
(2019/02/10)
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- Catalytic (3+2) Palladium-Aminoallyl Cycloaddition with Conjugated Dienes
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We describe the design and application of tailored aminoallyl precursors for catalytic (3+2) cycloaddition with conjugated dienes via a Pd-aminoallyl intermediate. The new cycloaddition reactions override the conventional (4+3) selectivity of aminoallyl cation cycloaddition through a sequence of Pd-allyl transfer and ring closure. A variety of highly substituted or fused pyrrolidine rings were synthesized using the cycloaddition, and can further undergo [1,3] N-to-C rearrangement to five-membered carbocycles with a different palladium catalyst. The utility of the (3+2) cycloaddition is also demonstrated by the preparation of various derivatives from the bicyclic pyrrolidine products.
- Trost, Barry M.,Huang, Zhongxing
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supporting information
p. 6396 - 6399
(2019/04/13)
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- A regioselectivity switch in Pd-catalyzed hydroallylation of alkynes
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By exploiting the reactivity of a vinyl-Pd species, we control the regioselectivity in hydroallylation of alkynes under Pd-hydride catalysis. A monophosphine ligand and carboxylic acid combination promotes 1,5-dienes through a pathway involving isomerization of alkynes to allenes. In contrast, a bisphosphine ligand and copper cocatalyst favor 1,4-dienes via a mechanism that involves transmetalation. Our study highlights how to access different isomers by diverting a common organometallic intermediate.
- Ji, Ding-Wei,Hu, Yan-Cheng,Zheng, Hao,Zhao, Chao-Yang,Chen, Qing-An,Dong, Vy M.
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p. 6311 - 6315
(2019/07/04)
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- Copper-catalyzed pyrrole synthesis from 3,6-dihydro-1,2-oxazines
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Highly-functionalized pyrroles could be effectively synthesized from 3,6-dihydro-1,2-oxazines using a heterogeneous copper on carbon (Cu/C) under neat heating conditions. Furthermore, the in situ formation of 3,6-dihydro-1,2-oxazines via the hetero Diels-Alder reaction between nitroso dienophiles and 1,3-dienes and the following Cu/C-catalyzed pyrrole synthesis also provided the corresponding pyrrole derivatives in a one-pot manner.
- Yasukawa, Naoki,Kuwata, Marina,Imai, Takuya,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 4409 - 4413
(2018/10/17)
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- Copper-Catalyzed Dehydrogenative Diels-Alder Reaction
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A practical and effective copper-catalyzed dehydrogenative Diels-Alder reaction of gem-diesters and ketone with dienes has been established. The active dienophiles were generated in situ via a radical-based dehydrogenation process, which reacted with a wide variety of dienes to afford various polysubstituted cyclohexene derivatives in good to excellent yields.
- Jiang, Bing,Liang, Qiu-Ju,Han, Yu,Zhao, Meng,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 3215 - 3219
(2018/06/11)
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- METHOD OF CONVERTING ALCOHOL TO HALIDE
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The present invention relates to a method of converting an alcohol into a corresponding halide. This method comprises reacting the alcohol with an optionally substituted aromatic carboxylic acid halide in presence of an N-substituted formamide to replace a hydroxyl group of the alcohol by a halogen atom. The present invention also relates to a method of converting an alcohol into a corresponding substitution product. The second method comprises: (a) performing the method of the invention of converting an alcohol into the corresponding halide; and (b) reacting the corresponding halide with a nucleophile to convert the halide into the nucleophilic substitution product.
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Page/Page column 51; 114; 122; 123
(2017/01/02)
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- Silylated organometals: A family of recyclable homogeneous catalysts
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A general strategy has been developed to synthesize a family of silylated organometals (M-PPh2-TS and DPEN-Ru-PPh2-Ts, M = Pd2+, Rh+, Pt2+, Ir+, or Ru2+, PPh2-Ts = PPh2CH2CH2Si(OEt)3), DPEN = (1R,2R)-1,2-diphenylethylenediamine). They can act as homogeneous catalysts with high efficiencies in various organic reactions using THF, CH2Cl2 or toluene as the reaction medium. After reaction, they could be thoroughly settled down by adding pentane and then used repeatedly owing to the complete catalyst recovery and good preservation of the catalyst structure. This is particularly important due to the increasing concerns regarding the cost, toxicity and limited availability of these nonrenewable transition metals.
- Huang, Jian-Lin,Wang, Jun-Zhong,Li, He-Xing,Guo, Haibing,O'Doherty, George A.
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p. 1473 - 1478
(2015/03/18)
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- Catalytic stereospecific allyl-allyl cross-coupling of internal allyl electrophiles with allylB(pin)
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Application of internal electrophiles in catalytic stereospecific allyl-allyl cross-coupling enable the rapid construction of multisubstituted 1,5-dienes, including those with all carbon quaternary centers. Compounds with minimal steric differentiation ca
- Le, Hai,Batten, Amanda,Morken, James P.
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supporting information
p. 2096 - 2099
(2014/05/06)
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- A ruthenium-based catalytic system with switchable selectivity between cyclotrimerization and enyne metathesis/Diels-Alder reactions of terminal alkynes
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In this study, we report a practical catalytic system, [RuCl 2(p-cymene)]2/IPr (IPr: 1,3-bis(2,6 diisopropylphenyl) imidazol-2-ylidene), that can switch between cyclotrimerization and cross enyne metathesis. The cyclotrimerization reaction of phenylacetylene catalyzed by [RuCl2(p-cymene)]2 can be switched to enyne metathesis by the introduction of a sterically hindered N-heterocyclic carbene. The 1,3-diene formed during this reaction reacts with dienophiles to form the Diels-Alder adduct. A practical one-pot synthesis method, utilizing enyne metathesis/Diels-Alder reactions, was used to construct cyclic compounds in an efficient manner.
- Karabulut, Solmaz,Sariaslan, Begüm,?ztürk, Bengi ?zgün
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- Pd(II)-catalyzed sequential C-C/C-O bond formations: A new strategy to construct trisubstituted furans
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Palladium-catalyzed oxidative difunctionalization of enol ethers with 1,3-dicarbonyl compounds to construct trisubstituted furans in one step under mild conditions is described. The reaction is thought to proceed through a C-C bond formation along with a C-O bond closing the ring structure. Oxygen is the sole oxidant regenerating the Pd(II) catalyst.
- Zheng, Meifang,Huang, Liangbin,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 1838 - 1841
(2013/06/04)
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- Palladium-catalyzed allylic fluorination of cinnamyl phosphorothioate esters
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A highly regioselective, Pd-catalyzed allylic fluorination of phosphorothioate esters is reported. This chemistry addresses several limitations of previously reported methods in which elimination and lack of reactivity were problematic. Preliminary mechanistic investigations reveal that these reactions are stereospecific and provide fluorinated products with net retention of stereochemical configuration. In analogy to other Pd-catalyzed allylic substitution reactions, this process likely proceeds through a palladium π-allyl intermediate.
- Lauer, Andrew M.,Wu, Jimmy
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p. 5138 - 5141,4
(2012/12/12)
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- Palladium-catalyzed allylic fluorination of cinnamyl phosphorothioate esters
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A highly regioselective, Pd-catalyzed allylic fluorination of phosphorothioate esters is reported. This chemistry addresses several limitations of previously reported methods in which elimination and lack of reactivity were problematic. Preliminary mechanistic investigations reveal that these reactions are stereospecific and provide fluorinated products with net retention of stereochemical configuration. In analogy to other Pd-catalyzed allylic substitution reactions, this process likely proceeds through a palladium π-allyl intermediate.
- Lauer, Andrew M.,Wu, Jimmy
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p. 5138 - 5141
(2013/01/15)
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- A direct synthesis of functionalized styrenes and terminal 1,3-dienes via aqueous Wittig chemistry with formalin
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A direct synthesis of functionalized styrenes including synthetically valuable styryl halides and terminal 1,3-dienes is reported directly from benzylic and allylic alcohols and aqueous formalin involving microwave assisted phosphonium salt formation and Wittig olefination under mildly basic conditions.
- Das, Priyabrata,McLeod, David,McNulty, James
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experimental part
p. 199 - 201
(2011/02/26)
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- Mesoporous aluminosilicate-catalyzed Sakurai allylation and Mukaiyama aldol reaction of acetals
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In the presence of a catalytic amount of mesoporous aluminosilicate (Al-MCM-41), both allyltrimethylsilane and silyl enol ether reacted with various acetals under mild reaction conditions to afford the corresponding homoallyl ethers and β-alkoxy ketones,
- Ito, Suguru,Hayashi, Akira,Komai, Hirotomo,Kubota, Yoshihiro,Asami, Masatoshi
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scheme or table
p. 4243 - 4245
(2010/09/07)
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- Gas-phase pyrolytic reaction of 4-Aryl-3-buten-2-ols and allyl benzyl ethers: Kinetic and mechanistic study
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Flash vacuum pyrolysis (FVP) of 4-aryl-3-buten-2-ols [ArCH=CHCH(CHs)OH, where Ar is phenyl, p-MeO, p-Me, p-Cl, p-NO2] gave the corresponding buta-1,3-dien-1-ylbenzene (ArCH=CH-CH=CH2, where Ar is Ph, p-MeO, p-Me, p-Cl, pNO2) and 7-×-1,2-dihydronaphthalene derivatives (where X is H, MeO); FVP of 1-aryl-3benzyloxyl-1-butenes and benzyl cinnamyl ethers [ArCH=CHCH(X)OCH2Ph, where Ar is phenyl, p-MeO, p-Me, p-Cl, X is H, Me, Ph] gave the corresponding but-2-en-l-ylbenzene derivatives (ArCH 2CH=CH-X, where X is H, Me, Ph) together with benzaldehyde. The proposed mechanism of these pyrolytic transformations was supported by kinetic and product analysis.
- Al-Etaibi, Alya M.,Al-Awadi, Nouria A.,Ibrahim, Maher R.,Ibrahim, Yehia A.
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experimental part
p. 407 - 419
(2010/05/02)
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- Low pressure vinylation of aryl and vinyl halides via Heck-Mizoroki reactions using ethylene
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Aryl bromides and iodides in the presence of catalytic amounts of a palladacycle derived from acetophenone oxime and 2 equiv of potassium acetate react with ethylene under ambient pressure (15-30 psi) to give the corresponding vinylarenes. The reactions work with both electron-deficient and electron-rich aryl compounds and tolerate wide variety of common functional groups. Vinyl bromides lead to 1,3-dienes in moderate yields.
- Smith, Craig R.,RajanBabu
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supporting information; experimental part
p. 1102 - 1110
(2010/03/25)
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- Regioselective carboindation of simple alkenes with indium tribromide and ketene silyl acetals
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(Equation Presented). The regioselective carboindation of simple alkenes with indium tribromide and ketene silyl acetals was accomplished. Various alkenes such as ethylene, 1-alkenes, and cyclic alkenes were applicable for this reaction system. The alkyli
- Nishimoto, Yoshihiro,Ueda, Hiroki,Inamoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 3390 - 3393
(2010/11/04)
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- Stereoselective synthesis of γ-substituted (Z)-allylic boranes via kinetically controlled hydroboration of allenes with 10-TMS-9-borabicyclo[3.3.2] decane
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(Chemical Equation Presented) Kinetically controlled hydroboration of allenes 8 and 14a-d with the readily accessible Soderquist borane 7, which is generated in situ from borohydride 6, constitutes a convenient and preparatively useful method for synthesi
- Kister, Jeremy,DeBaillie, Amy C.,Lira, Ricardo,Roush, William R.
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supporting information; experimental part
p. 14174 - 14175
(2010/02/16)
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- Trapping reactive metal-carbene complexes by a bis-pocket porphyrin: X-ray crystal structures of Ru=CHCO2et and trans-[Ru(CHR)(CO)] species and highly selective carbenoid transfer reaction
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What's in my pockets? By employing Suslick's bis-pocket porphyrin (ttppp), a reactive M=CHCO2Et complex and a trans-[M(CHR)(CO)] (M = Ru) complex have been structurally characterized by X-ray crystal analysis. The sterically encumbered ttppp ligand has a significant impact on both the diastereoselectivity and chemoselectivity in metalloporphyrin-catalyzed reactions of ethyl diazoacetate with conjugated aryl dienes.
- Deng, Qing-Hai,Chen, Jian,Huang, Jie-Sheng,Chui, Stephen Sin-Yin,Zhu, Nianyong,Li, Guang-Yu,Che, Chi-Ming
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experimental part
p. 10707 - 10712
(2010/04/30)
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- Regioselective cobalt-catalyzed Diels-Alder reaction towards 1,3-disubstituted and 1,2,3-trisubstituted benzene derivatives
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A straightforward reaction sequence consisting of the Wittig olefmation of aldehydes utilizing allyltriphenylphosphonium bromide for the generation of 1-substituted 1,3-dienes, cobalt-catalyzed neutral Diels-Alder reaction with terminal and internal alkyn
- Hilt, Gerhard,Danz, Michael
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experimental part
p. 2257 - 2263
(2009/04/06)
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- A mechanistic study of the chromium(II)-mediated transformations of trichloromethyl alkyls and carbinols: evidence for carbene, carbyne, and carbenoid intermediates
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Using CrCl2 in THF at room temperature, trichloromethyl carbinols and trichloromethylalkanes are readily transformed to the highly reactive α-chlorocarbenes, carbynes and α-chloro-α-chromium(III) vinylidene carbenoids. A mechanistic study is carried out to determine the nature of the intermediates.
- Bejot, Romain,Tisserand, Steve,Li, De Run,Falck,Mioskowski, Charles
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p. 3855 - 3858
(2008/02/02)
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- Preparation of thiocyanates and isothiocyanates from alcohols, thiols, trimethylsilyl-, and tetrahydropyranyl ethers using triphenylphosphine/2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)/n-Bu4NSCN system
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A combination of triphenylphosphine (PPh3) and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) provides a safe and easily available mixed reagent system for the conversion of 1° and 2° alcohols, thiols, trimethylsilyl-, and tetrahydropyranyl ethers to their corresponding thiocyanates and the 3° ones to isothiocyanates in good to high yields.
- Iranpoor, Nasser,Firouzabadi, Habib,Nowrouzi, Najmeh
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p. 5498 - 5501
(2007/10/03)
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- Formation of P-Ylide under Neutral and Metal-Free Conditions: Transformation of Aziridines and Epoxides to Conjugated Dienes in the Presence of Phosphine
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A general approach to formation of the P-ylide from the reaction of aziridines or epoxides with organophosphine under neutral and metal-free conditions is realized. Conjugated diene derivatives based on this kind of P-ylide were prepared in a facile and c
- Fan, Ren-Hua,Hou, Xue-Long,Dai, Li-Xin
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p. 689 - 694
(2007/10/03)
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- Barbier-type addition of alkyl halides to aldehydes promoted by pentacarbonyliron
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The yield and structure of products of the Barbier-type addition of alkyl halides (perfluorobutyl iodide, allyl bromide, allyl iodide, and hexyl iodide) to para-substituted benzaldehydes in the presence of pentacarbonyliron are essentially determined, on the one hand, by the ability of alkyl halide to be reduced to carbanion and, on the other, by the electrophilicity of the aldehyde reaction center which in turn depends on the nature of para-substituent in the aromatic ring.
- Vasil'Eva,Mysova,Chakhovskaya,Terent'Ev
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p. 1014 - 1017
(2007/10/03)
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- New mechanistic aspects on the catalytic transformation of vinylthiiranes to mono and disubstituted 3,6-dihydro-1,2-dithiins by tungsten pentacarbonyl monoacetonitrile
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Various alkyl and aryl mono- and disubstituted 3,6-dihydro-1,2-dithiins have been synthesised from their corresponding vinylthiiranes exploiting Adams' tungsten pentacarbonyl monoacetonitrile catalytic transformation. New conclusions pertaining to the rate determining step, the sensitivity of the process to precursor sterics and electronics, and the nature of various reaction intermediates are highlighted.
- Lupton, David W,Taylor, Dennis K
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p. 4517 - 4527
(2007/10/03)
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- Pinacolboratamethyl-enetriphenylphosphonium iodide, a new methylene transfer reagent
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The title compound is easily prepared and reacts with various aldehydes and ketone. The reagent is compatible with free hydroxy groups. Yields with various aldehydes and ketones are in 50- > 99% range. Both aliphatic, aromatic and unsaturated carbonyls react.
- Al-Aziz Quntar, Abed,Srebnik, Morris
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p. 2575 - 2579
(2007/10/03)
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- Selective Deprotection of Acetals with Me3SiCH2MgCl. Peterson-Type Olefination of Acetals
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By employing the chelation strategy, treatment of an acetal of a contiguous diol with Me3SiCH2-MgCl liberates the corresponding diol regioselectively. In addition, acetals of different structural variety are transformed upon treatment with Me3SiCH2MgCl and ZnI2 into the corresponding olefination products in good yield.
- Chiang, Chao-Cheng,Chen, Yu-Huei,Hsieh, Yu-Tsai,Luh, Tien-Yau
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p. 4694 - 4697
(2007/10/03)
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- Preparation of γ-heterosubstituted allylindium and diindium reagents and their reactions with carbonyl compounds
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Various γ-heteroatom-substituted allylindium reagents were prepared, and their reactions with carbonyl compounds were examined. The reaction of 1,3-dibromopropene with metallic indium gave two types of organoindium species, γ-bromoallylindium and allylic
- Hirashita, Tsunehisa,Kamei, Toshiya,Horie, Tomoaki,Yamamura, Hatsuo,Kawai, Masao,Araki, Shuki
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p. 172 - 177
(2007/10/03)
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- Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
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The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
- Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
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p. 856 - 878
(2007/10/02)
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- A simplified Wittig synthesis using a solid/liquid transfer process. IX. Selectivity of the condensation reaction of moderated ylides with aldehydes
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Conjugated dienes are obtained selectively and with high yields using aldehydes of various structures. The synthesis is made in a two-phase medium, i.e. solid/liquid medium.
- Ben Attra,Le Bigot,El Gharbi,Delmas,Gaset
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p. 1421 - 1425
(2007/10/02)
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- Halogenative Allylation and Reduction of Aromatic Acetals by Double Substitution of Alkoxyl Groups in Acetal
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In the presence of excessive amount of acetyl halide along with a catalytic amount of tin(II) halide, aromatic acetals react with allyltrimethylsilane or triethylsilane to give α-allylbenzyl halides or benzyl halides, respectively, in good to excellent yields.
- Oriyama, Takeshi,Iwanami, Katsuyuki,Tsukamoto, Kazuhisa,Ichimura, Yuichi,Koga, Gen
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p. 1410 - 1412
(2007/10/02)
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- A Novel Methylenation Method of Aldehydes Mediated by Dibutyl Telluride
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In the presence of dibutyl telluride, (iodomethyl)triphenylphosphonium iodide (1) reacted with aldehydes 2 in THF at 80deg C yielding the methylenation products 3 under neutral conditions in good yields.
- Li, Sao-Wei,Huang, Yao-Zeng,Shi, Li-Lan
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p. 1441 - 1442
(2007/10/02)
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- A High-Yield Regiospecific Synthesis of Keto Oximes from Aryl-Conjugated Ethylenes and Ethyl Nitrite in the Presence of Cobalt Complex and BH4- Ion
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The title reaction of substituted styrenes, 1-phenyl-1,3-butadiene, and some cyclic aryl-conjugated ethylenes proceeds smoothly at room temperature, affording the corresponding oximes in moderate to nearly quantitative yields.The reaction mechanism is discussed on the basis of the formation of an alkylcobalt intermediate and its subsequent reaction with ethyl nitrite.
- Okamoto, Tadashi,Kobayashi, Kenji,Oka, Shinzaburo,Tanimoto, Shigeo
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p. 4897 - 4901
(2007/10/02)
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- Preparation of (Triphenylsilyl)allyl Anion and (Triphenylgermyl)allyl Anion from 1-Propenyltriphenylsilane and 1-Propenyltriphenylgermane and Their Reactions with Electrophiles
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Treatment of 1-propenyltriphenylsilane with n-BuLi in THF-HMPA provides (triphenylsilyl)allyl anion which is identical with an anion derived from 2-propenyltriphenylsilane and base.Generation of (triphenylgermyl)allyl anion is also described.Addition of alkyl halides or carbonyl compounds to these anions gives the corresponding adducts regioselectively.
- Wakamatsu, Kuni,Oshima, Koichiro,Utimoto, Kiitiro
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p. 2029 - 2032
(2007/10/02)
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- Nucleophilic Attack on a Carbonyl Group Conjugated to a Chiral Centre: A Search For a Vinylogous Cram's Rule
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In a search for a vinylogous version of Cram's rule, 1,4-diphenylbut-2-ene-1,4-dione (5), 4-methoxy-1,4-diphenylbut-2-en-1-one (9), and hex-3-ene-2,5-dione (13) are found to be reduced with low or negligible diastereoselectivity.Similarly, the phenyl Grignard reagent showed no diastereoselectivity in its reaction with 4-methoxy-4-phenylbut-2-enal (12)
- Fleming, Ian,Kuehne, Hardy,Takai, Ken
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p. 725 - 728
(2007/10/02)
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