- Manganese dioxide can oxidise unactivated alcohols under in situ oxidation-Wittig conditions
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The in situ alcohol oxidation-Wittig reaction using manganese dioxide as the oxidant has been applied to semi-activated and, for the first time, unactivated alcohols to furnish the corresponding α,β-unsaturated esters.
- Blackburn, Leonie,Wei, Xudong,Taylor, Richard J. K.
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Read Online
- Synthesis of unsaturated esters from aldehydes: An inexpensive, practical alternative to the Horner-Emmons reaction under neutral conditions
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A practical, efficient, and mild process is described for the synthesis of unsaturated esters from aldehydes in good yields and diastereoselectivities. All of the reagents used in the protocol are commercially available at a nominal price: N2CHCO2Et, catalytic (1 mol%) ReOCl3(PPh3)2, and (EtO)3P. Additionally, the reaction process can be carried out successfully in good yields (85%) and diastereoselectivities (>20:1) with reagent-grade solvent without prior purification of the reagents.
- Ledford, Brian E.,Carreira, Erick M.
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Read Online
- Olefination of aldehydes by ethyl diazoacetate catalyzed by a Ruthenium(II) complex
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A variety of aldehydes were stereoselectively converted to (E)-olefins by the reaction with ethyl diazoacetate and triphenylphosphine in the presence of a catalytic amount of RuCl2(PPh3)3.
- Fujimura, Osamu,Honma, Takashi
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Read Online
- Synthesis of Enantioenriched 3,4-Disubstituted Chromans through Lewis Base Catalyzed Carbosulfenylation
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A method for the catalytic, enantioselective, carbosulfenylation of alkenes to construct 3,4-disubstituted chromans is described. Alkene activation proceeds through the intermediacy of enantioenriched, configurationally stable thiiranium ions generated from catalytic, Lewis base activation of an electrophilic sulfenylating agent. The transformation affords difficult-to-generate, enantioenriched, 3,4-disubstituted chromans in moderate to high yields and excellent enantioselectivities. A variety of substituents are compatible including electronically diverse functional groups as well as several functional handles such as aryl halides, esters, anilines, and phenols. The resulting thioether moiety is amenable to a number of functional group manipulations and transformations. Notably, the pendant sulfide was successfully cleaved to furnish a free thiol which readily provides access to most sulfur-containing functional groups which are present in natural products and pharmaceuticals.
- Denmark, Scott E.,Laverny, Aragorn,Menard, Travis
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p. 14290 - 14310
(2021/11/12)
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- Active Base Hybrid Organosilica Materials based on Pyrrolidine Builder Units for Fine Chemicals Production
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The catalytic activity of “pyrrolidine type” fragments included or anchored in the mesoporous silica supports or polymeric frameworks have been fully reported for enantioselective transformation. Nevertheless, low attention was focused on their catalytic abilities to perform base-catalyzed reaction. Accordingly, hybrid materials including pyrrolidine fragments in the mesoporous silica supports were prepared following different synthesis methods, such as micellar and fluoride sol-gel routes in absence of structural directing agents. Their great catalytic performance was explored for various base-catalyzed reactions to the formation of C?C bond through Knoevenagel, Claisen-Schmidt and Henry condensations under microwave irradiation. The benefits of microwave irradiation combined with suitable catalytic properties of pyrrolidine hybrid materials with strong base sites and high accessibility to active centers, allowed carrying out successfully base-catalyzed condensation reactions for the production of fine chemicals. Moreover, the hybrid catalyst exhibited high selectivity and good stability over different catalytic cycles contributing to environmental sustainability.
- Llopis, Sebastián,Velty, Alexandra,Díaz, Urbano
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p. 5012 - 5024
(2021/10/19)
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- A One-Pot Synthesis of α,β-Unsaturated Esters From Esters
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A convenient method for reductive Horner–Wadsworth–Emmons (HWE) olefination is described. The E-selective HWE homologation of various esters to α,β-unsaturated esters was readily achieved and gave the desired products in good-to-moderate yields under mild conditions. The one-pot reaction proceeds through an in situ generated aldehyde, formed via the partial reduction of an ester with lithium diisobutyl-t-butoxyaluminum hydride. The formation of cyclized metal acetal and subsequent decompose to the aldehyde for the olefination was found to be a crucial step in this C2-carbon homologation protocol.
- Hong, Chang Whee,Lee, Yong Jin,An, Duk Keun
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p. 1121 - 1125
(2021/06/01)
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- Palladium-catalysed regio- And stereoselective arylative substitution of γ,δ-epoxy-α,β-unsaturated esters and amides by sodium tetraaryl borates
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Palladium-catalysed reactions of γ,δ-epoxy-α,β-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. A
- Artok, Levent,Bilgi, Yasemin,Ku?, Melih
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supporting information
p. 6378 - 6383
(2020/09/07)
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- Systematic Study on the Catalytic Arsa-Wittig Reaction
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Efficient catalytic arsa-Wittig reactions have been developed by using 1-phenylarsolane as a catalyst. A wide array of aldehydes was converted to the corresponding olefins in high yields with moderate to excellent E stereoselectivity in the presence of a catalytic amount of 1-phenylarsolane. Moreover, density functional theory calculations were carried out to afford insight into the E/Z selectivity.
- Inaba, Ryoto,Kawashima, Ikuo,Fujii, Toshiki,Yumura, Takashi,Imoto, Hiroaki,Naka, Kensuke
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supporting information
p. 13400 - 13407
(2020/09/21)
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- Copper-Catalyzed Azide–Ynamide Cyclization to Generate α-Imino Copper Carbenes: Divergent and Enantioselective Access to Polycyclic N-Heterocycles
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Here an efficient copper-catalyzed cascade cyclization of azide-ynamides via α-imino copper carbene intermediates is reported, representing the first generation of α-imino copper carbenes from alkynes. This protocol enables the practical and divergent synthesis of an array of polycyclic N-heterocycles in generally good to excellent yields with broad substrate scope and excellent diastereoselectivities. Moreover, an asymmetric azide–ynamide cyclization has been achieved with high enantioselectivities (up to 98:2 e.r.) by employing BOX-Cu complexes as chiral catalysts. Thus, this protocol constitutes the first example of an asymmetric azide–alkyne cyclization. The proposed mechanistic rationale for this cascade cyclization is further supported by theoretical calculations.
- Chen, Yang-Bo,Deng, Chao,Liu, Rai-Shung,Liu, Xin,Luo, Chen,Wang, Ze-Shu,Ye, Long-Wu,Zhai, Tong-Yi,Zhang, Yi-Ping
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supporting information
p. 17984 - 17990
(2020/08/21)
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- Gold-Catalyzed Asymmetric Thioallylation of Propiolates via Charge-Induced Thio-Claisen Rearrangement
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A gold(I)-catalyzed enantioselective thioallylation of propiolates with allyl sulfides is described. The key mechanistic element is a sulfonium-induced Claisen rearrangement which helps minimize the allyl dissociation and render higher enantioselectivity. This protocol features remarkable scope of the allyl moiety, allowing enantiocontrolled synthesis of all-carbon quaternary centers, and exhibits exceptional functional group compatibility with many Lewis bases and π-bonds. This intermolecular variant of Claisen rearrangement forges both C-S and C-C bonds concomitantly, providing efficient access to interesting optically active organosulfur compounds which can be transformed further through the vinyl sulfide as a functional handle. The rate of the reaction was zeroth order with respect to allyl sulfides, which suggested a reversible inhibition, providing a resting state for the catalyst. The Hammett plot displayed a correlation with σp values, suggesting a turnover-limiting sigmatropic rearrangement where decreased electron-density on sulfur accelerated the rearrangement.
- Kim, Hanbyul,Jang, Jiwon,Shin, Seunghoon
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supporting information
p. 20788 - 20795
(2020/11/27)
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- 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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- Harnessing Secondary Coordination Sphere Interactions That Enable the Selective Amidation of Benzylic C-H Bonds
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Engineering site-selectivity is highly desirable especially in C-H functionalization reactions. We report a new catalyst platform that is highly selective for the amidation of benzylic C-H bonds controlled by π-πinteractions in the secondary coordination sphere. Mechanistic understanding of the previously developed iridium catalysts that showed poor regioselectivity gave rise to the recognition that the π-cloud of an aromatic fragment on the substrate can act as a formal directing group through an attractive noncovalent interaction with the bidentate ligand of the catalyst. On the basis of this mechanism-driven strategy, we developed a cationic (ν5-C5H5)Ru(II) catalyst with a neutral polypyridyl ligand to obtain record-setting benzylic selectivity in an intramolecular C-H lactamization in the presence of tertiary C-H bonds at the same distance. Experimental and computational techniques were integrated to identify the origin of this unprecedented benzylic selectivity, and robust linear free energy relationship between solvent polarity index and the measured site-selectivity was found to clearly corroborate that the solvophobic effect drives the selectivity. Generality of the reaction scope and applicability toward versatile γ-lactam synthesis were demonstrated.
- Jung, Hoimin,Schrader, Malte,Kim, Dongwook,Baik, Mu-Hyun,Park, Yoonsu,Chang, Sukbok
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supporting information
p. 15356 - 15366
(2019/10/22)
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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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- Bu 4 N + -Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation
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Catalytic Bu 4 NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu 4 NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO - activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.
- Das, Manas,Manvar, Atul,Fox, Ian,Roberts, Dilwyn J.,O'Shea, Donal F.
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supporting information
p. 2401 - 2406
(2017/09/30)
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- N-heterocyclic carbene-catalysed Peterson olefination reaction
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N-heterocyclic carbenes (NHCs) have been utilised as highly efficient organocatalysts to catalyse Peterson olefination reaction of aldehydes with trimethylsilylketene ethyl trimethylsilyl acetal or fluoro(trimethylsilyl)ketene ethyl trimethylsilyl acetal to produce the corresponding functionalized olefines in 34-93% yields with excellent stereoselectivities.
- Wang, Ying,Du, Guang-Fen,Gu, Cheng-Zhi,Xing, Fen,Dai, Bin,He, Lin
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p. 472 - 478
(2015/12/31)
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- 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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- A graphene/hemin hybrid material as an efficient green catalyst for stereoselective olefination of aldehydes
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A hemin/graphene composite, prepared by mixing an aqueous solution of graphene oxide (GO) with hemin and sonicating the suspension for 5 h at room temperature, was investigated for olefination of aldehydes using ethyl diazoacetate in the presence of triphenylphosphine. Efficient olefination of aromatic aldehydes with high (E)-selectivity was obtained, revealing that rGO/hemin is a promising heterogeneous catalyst for the olefination reaction. The as-synthesized catalyst could easily be recovered from the reaction mixture and was subsequently used for several runs without any significantly loss in activity and selectivity.
- Joshi, Chetan,Kumar, Pawan,Behera, Babita,Barras, Alexandre,Szunerits, Sabine,Boukherroub, Rabah,Jain, Suman L.
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p. 100011 - 100017
(2015/12/04)
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- Stereoselective synthesis of either (E)- or (Z)-silyl enol ether from the same acyclic α,β-unsaturated ketone using cationic rhodium complex-catalyzed 1,4-hydrosilylation
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The stereoselective synthesis of either (E)- or (Z)-silyl enol ether from the same acyclic α,β-unsaturated ketone is reported. Highly (Z)-selective conditions were the use of [Rh(cod)2]BF 4/DPPE at room temperature with no solvent, whereas (E)-selective conditions were the use of [Rh(cod)2]BF4/P(1-Nap) 3 (1-Nap = 1-naphthyl) under refluxing dichloromethane.
- Onodera, Gen,Hachisuka, Ryosuke,Noguchi, Tomomi,Miura, Hiroki,Hashimoto, Toru,Takeuchi, Ryo
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supporting information
p. 310 - 313
(2014/01/06)
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- Catalytic enantioselective dibromination of allylic alcohols
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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.
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supporting information
p. 12960 - 12963
(2013/09/24)
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- A continuous homologation of esters: An efficient telescoped reduction-olefination sequence
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A continuous protocol for the two-carbon homologation of esters to α,β-unsaturated esters is described. This multireactor homologation telescopes an ester reduction, phosphonate deprotonation, and Horner-Wadsworth-Emmons olefination, thus converting a three-operation procedure into a single, uninterrupted system that eliminates the need for isolation or purification of the aldehyde intermediates. The homologated products are obtained in high yield and selectivity.
- Webb, Damien,Jamison, Timothy F.
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supporting information; experimental part
p. 2465 - 2467
(2012/07/01)
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- Update: An efficient synthesis of poly(ethylene glycol)-supported iron(II) porphyrin using a click reaction and its application for the catalytic olefination of aldehydes
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The facile synthesis of polyethylene glycol (PEG)-immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2] cycloaddition "click" reaction is reported. The prepared complex 5 (PEG-C 51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine, and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration, and was recycled through ten runs without significant activity loss. Copyright
- Chinnusamy, Tamilselvi,Rodionov, Valentin,Kuehn, Fritz E.,Reiser, Oliver
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supporting information; experimental part
p. 1827 - 1831
(2012/08/08)
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- A newly-designed PE-supported arsine for efficient and practical catalytic Wittig olefination
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A newly designed PE-supported arsine has been developed as an excellent catalyst for catalytic Wittig-type olefination. Simple ketones, in particular inactive ketones prove to be suitable substrates for the first time. This reaction provides an easy access to di-, tri-, and tetra-substituted olefins in high yield.
- Wang, Peng,Liu, Chun-Rong,Sun, Xiu-Li,Chen, Shuai-Shuai,Li, Jun-Fang,Xie, Zuowei,Tang, Yong
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supporting information; experimental part
p. 290 - 292
(2012/01/06)
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- A protocol for accessing the β-azidation of α,β-unsaturated carboxylic acids
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This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient β-azidation of α,β-unsaturated carboxylic acids.
- Angelini, Tommaso,Bonollo, Simona,Lanari, Daniela,Pizzo, Ferdinando,Vaccaro, Luigi
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supporting information
p. 4610 - 4613
(2012/10/30)
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- Highly E-selective solvent-free Horner-Wadsworth-Emmons reaction catalyzed by DBU
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The solvent-free Horner-Wadsworth-Emmons reaction of triethyl phosphonoacetate with a variety of aldehydes was catalyzed by DBU in the presence of K2CO3 to give E-α,β-unsaturated esters highly selectively (99:1 for most of the reactions). The reaction with ketones gave trisubstituted olefins with good to high E-selectivity by DBU-Cs2CO3.
- Ando, Kaori,Yamada, Kyohei
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supporting information; experimental part
p. 1143 - 1146
(2011/06/24)
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- A two-step ball milling method synthesizes and purifies α,β-unsaturated esters
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Over the last decade, solvent-free methods have been gaining interest as replacements for traditional organic chemistry techniques. While solvent-free methods are well known for many processes, a simple, solvent-free purification procedure that supplements them does not exist. We report the solvent-free synthesis of α,β-unsaturated esters using a solvent-free Horner-Wadsworth-Emmons (HWE) reaction using high-speed ball milling (HSBM). We were able to perform the HWE reaction on a variety of aldehydes, and isolate their respective a,b-unsaturated esters in high yields, purities, and diastereoselectivities. The Royal Society of Chemistry.
- Shearouse, William C.,Korte, Chelsea M.,Mack, James
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experimental part
p. 598 - 601
(2011/05/08)
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- Solvent-free Horner-Wadsworth-Emmons reaction using DBU
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The solvent-free Horner-Wadsworth-Emmons reaction with a variety of aldehydes using 1.5 equiv of DBU gave E-α,β-unsaturated esters and ketones in high yields. The E-selectivity was high and the used DBU was recovered.
- Ando, Kaori,Yamada, Kyohei
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experimental part
p. 3297 - 3299
(2010/07/18)
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- Expedient access to branched allylic silanes by copper-catalysed allylic substitution of linear allylic halides
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An unprecedented copper-catalysed allylic transposition enables the regioselective synthesis of branched allylic silanes from linear allylic halides through direct C-Si bond formation.
- Vyas, Devendra J.,Oestreich, Martin
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supporting information; experimental part
p. 568 - 570
(2010/05/01)
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- Enantioselective synthesis of allylboronates bearing a tertiary or quaternary B-substituted stereogenic carbon by NHC-Cu-catalyzed substitution reactions
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Allylic substitutions that afford α-substituted allylboronates bearing B-substituted tertiary or quaternary carbon stereogenic centers are presented. C-B bond-forming reactions, catalyzed by chiral bidentate Cu-NHC complexes, are performed in the presence of commercially available bis(pinacolato)diboron. Transformations proceed in high yield (up to >98%) and site selectivity (>98% SN2′), and in up to >99:1 enantiomer ratio. Trans- or cis-disubstituted alkenes can be used; alkyl- (linear as well as branched) and aryl-trisubstituted allylic carbonates serve as effective substrates. Allylboronates that bear a quaternary carbon center are air-stable and can be easily purified by silica gel chromatography; in contrast, secondary allylboronates cannot be purified in the same manner and are significantly less stable. Oxidation of the enantiomerically enriched products furnishes secondary or tertiary allylic alcohols, valuable small molecules that cannot be easily obtained in high enantiomeric purity by alternative synthesis or kinetic resolution approaches.
- Guzman-Martinez, Aikomari,Hoveyda, Amir H.
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supporting information; scheme or table
p. 10634 - 10637
(2010/11/05)
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- A chiral 6-membered n -heterocyclic carbene copper(I) complex that induces high stereoselectivity
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A chiral 6-membered annulated N-heterocyclic (6-NHC) copper complex that catalyzes β-borylations with high yield and enantioselectivity was developed. The chiral 6-NHC copper complex is easy to prepare on the gram scale and is very active, showing 10000 turnovers at 0.01 mol % of catalyst without significant decrease of enantioselectivity and with useful reaction rates.
- Park, Jin Kyoon,Lackey, Hershel H.,Rexford, Matthew D.,Kovnir, Kirill,Shatruk, Michael,McQuade, D. Tyler
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supporting information; experimental part
p. 5008 - 5011
(2010/12/25)
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- One-pot Wittig reaction for the synthesis of α,β-unsaturated esters using highly basic magnesium/lanthanum mixed oxide
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Highly basic Mg/La mixed oxide (Mg/La MO) is an effective heterogeneous base, at room temperature for the one-pot Wittig reaction involving aldehyde, α-halo esters and triphenylphosphine to afford α,β-unsaturated esters in good yields with high E-stereoselectivity. Mg/La mixed oxide was recovered quantitatively by simple filtration and reused. The basic properties of Mg/La mixed oxide have been compared to those of nanocrystalline magnesium oxide using the microcalorimetric adsorption of CO2, and the reactivity for Wittig reactions. Mg/La mixed oxide is a stronger base than magnesium oxide (MgO) but shows a much smaller number of sites. Hammett correlations have been determined for both bases and show that the reaction is base mediated, with values of ρ = 1.7 for Mg/La mixed oxide, and 1.1 for nanocrystalline magnesium oxide, and a compensation effect can then be observed.
- Kantam, M. Lakshmi,Kumar, K.B. Shiva,Balasubramanyam,Venkanna,Figueras
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experimental part
p. 10 - 14
(2010/10/04)
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- P[N(i-Bu)CH2CH2]3N: Nonionic Lewis base for promoting the room-temperature synthesis of α,β-unsaturated esters, fluorides, ketones, and nitriles using Wadsworth - Emmons phosphonates
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The bicyclic triaminophosphine P(RNCH2CH2) 3N (R = i-Bu, 1c) serves as an effective promoter for the room-temperature stereoselective synthesis of α,β-unsaturated esters, fluorides, and nitriles from a wide array of aromatic, aliphatic, heterocyclic, and cyclic aldehydes and ketones, using a range of Wadsworth-Emmons (WE) phosphonates. Among the analogues of 1c [R = Me (1a), i-Pr (1b), Bn (1d)], 1a and 1b performed well, although longer reaction times were involved, and 1d led to poorer yields than 1c. Functionalities such as cyano, chloro, bromo, methoxy, amino, ester, and nitro were well tolerated. We were able to isolate and characterize (by X-ray means; see above) the reactive WE intermediate species formed from 2b and 1c.
- Chintareddy, Venkat Reddy,Ellern, Arkady,Verkade, John G.
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supporting information; experimental part
p. 7166 - 7174
(2010/12/25)
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- Catalytic synthesis of (E)-a,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene
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A practical and high yielding synthesis of a,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene was developed.
- Manzano, Ruben,Ozores, Lidia,List, Benjamin,Job, Andreas,Rodefeld, Lars
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experimental part
(2010/04/22)
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- Stereoseleetive synthesis of polysubstituted alkenes through a phosphine-mediated three-component system of aldehydes, α-halo carbonyl compounds, and terminal alkenes
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A study was conducted to demonstrate stereoselective synthesis of polysubstituted alkenes through a phosphine-mediated three-component system of aldehydes, α-halo carbonyl compounds, and terminal alkenes. Triphenylphosphine, α-halo carbonyl compounds, and methyl acrylate were added to a solution of aldehyde in chloroform or 1-propanol under nitrogen at room temperature. The resulting mixture was stirred at the specified temperature until transformation was completely observed by thin layer chromatography (TLC) analysis. The mixture was cooled to room temperature and purified by column chromatography on silica gel, eluting with petroleum ether/ethyl acetate. The study demonstrated that the first one-pot and three-component reaction of aldehydes, α-haloacetates, and terminal alkenes was developed in the presence of phenylphosphine to produce a wide range of trisubstituted alkenes with significant stereoselectivity.
- Liu, Da-Neng,Tian, Shi-Kai
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supporting information; experimental part
p. 4538 - 4542
(2009/12/25)
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- Stereoselective olefination reactions promoted by Rieke manganese
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A study of the advantages of using manganese, an inexpensive and nontoxic metal, to perform stereoselective β-elimination reactions and to promote sequential olefination reactions of aldehydes to obtain α,β- unsaturated esters and amides is presented. Various elimination reactions, all of them characterized by occurring with complete stereoselectivity and in high yields, were performed using active manganese (Mn*) as metalating agent. This ability of manganese has been applied to develop a novel and direct synthesis of (E)-α,β-unsaturated esters or amides and (Z)-α,β-unsaturated α-halo esters and α-choroamides through a Mn*-mediated sequential olefination protocol of aldehydes with dichloro esters or amides and trihalo esters or trichloroamides, respectively. Georg Thieme Verlag Stuttgart.
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Del Amo, Vicente,Diaz, Pamela
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experimental part
p. 2634 - 2645
(2009/12/06)
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- An efficient synthesis of poly(ethylene glycol)-supported iron(II) porphyrin using a click reaction and its application for the catalytic olefination of aldehydes
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The first successful synthesis of poly(ethylene glycol) (PEG) immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2] cycloaddition is reported. In contrast to the existing methods for the synthesis of PEG-immobilized metalloporphyrins, the click method offers better catalyst loading under comparatively mild reaction conditions. The prepared complex 5 (PEG-C51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration and was recycled for up to ten runs without significant loss of activity.
- Jain, Suman L.,Joseph, Jomy K.,Kuehn, Fritz E.,Reiser, Oliver
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supporting information; experimental part
p. 230 - 234
(2009/09/06)
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- Highly (E)-selective wadsworth-emmons reactions promoted by methylmagnesium bromide
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(Chemical Equation Presented) An experimentally simple protocol for the very highly (E)-selective Wadsworth-Emmons reaction [(E):(Z) selectivities in excess of 180:1 in some cases] of a range of straight-chain and branched aliphatic, substituted aromatic, and base-sensitive aldehydes via reaction with an alkyl diethylphosphonoacetate and MeMgBr is reported.
- Claridge, Timothy D. W.,Davies, Stephen G.,Lee, James A.,Nicholson, Rebecca L.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Toms, Steven M.
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supporting information; experimental part
p. 5437 - 5440
(2009/06/18)
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- A convenient method for the lewis base-catalyzed synthesis of α,β-unsaturated carboxylic esters using trimethylsilylketene ethyl trimethylsilyl acetal and carbonyl compounds
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A highly useful method for the synthesis of α,β-unsaturated carboxylic esters from various carbonyl compounds that uses trimethylsilylbetene ethyl trimethylsilyl acetal in the presence of a Lewis base catalyst such as acetate salts was established. This procedure gives the corresponding esters in high yields with excellent E stereoselectivity under mild conditions. Copyright
- Michida, Makoto,Mukaiyama, Teruaki
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p. 704 - 705
(2008/12/21)
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- Lewis acid-catalyzed Meyer-Schuster reactions: methodology for the olefination of aldehydes and ketones
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In principle, the most efficient and atom-economical means of converting an aldehyde or ketone into the homologated α,β-unsaturated ester is through addition/rearrangement sequences involving acetylenic π-bonds (Scheme 1). Implementation of such a strategy for the synthesis of α,β-unsaturated esters is presented: addition of ethoxyacetylene followed by scandium(III) triflate-catalyzed Meyer-Schuster rearrangement reaction. Stereoselectivities range from good to excellent in the formation of disubstituted α,β-unsaturated esters from aldehydes (Table 3). The two-stage olefination of even the most hindered ketones proceeds with near perfect efficiency (Table 4).
- Engel, Douglas A.,Lopez, Susana S.,Dudley, Gregory B.
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p. 6988 - 6996
(2008/09/21)
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- Diazo reagents in copper(I)-catalyzed olefination of aldehydes
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The olefination of aldehydes to synthesize unsaturated ketones, esters, amides and phosphonates using diazo reagents and triphenylphosphine in the presence of copper(I) iodide as catalyst, is described. Good to excellent E:Z selectivities as well as yields were obtained for a large variety of aliphatic, aromatic and heteroaromatic aldehydes. The reaction showed also an excellent functional group compatibility and aldehydes were selectively reacted in the presence of ketone, nitro, amine, ether, acetal, thioether and halide groups. The use of a cost-effective copper salt as a catalyst is advantageous compared to previously reported expensive transition metal complexes. The method was used in the total synthesis of the scutifoliamide A, a biologically active compound that exhibits antifungal activity.
- Lebel, Helene,Davi, Michael
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supporting information; experimental part
p. 2352 - 2358
(2009/10/02)
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- Virtually complete E-selective α,β-unsaturated ester synthesis by Hg(OTf)2-catalyzed hydration of sec-ethoxyalkynyl acetate
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The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded α,β-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction.
- Nishizawa, Mugio,Hirakawa, Hiroko,Nakagawa, Yuki,Yamamoto, Hirofumi,Namba, Kosuke,Imagawa, Hiroshi
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p. 5577 - 5580
(2008/09/17)
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- Diastereoselective Method of Preparing Olefins by Means of the Horner-Wadsworth-Emmons Reaction Using a Particular Phosphonate Which Improves Diastereoselectivity at all Temperatures Including at Ambient Temperature
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The invention relates to a diastereoselective process for the preparation of olefins by the Horner-Wadsworth-Emmons reaction which consists in reacting a specific phosphonate improve the diastereoselectivity at all temperatures including at ambient temperature, with a carbonyl derivative in the presence of a base in an appropriate solvent.
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Page/Page column 7
(2010/11/29)
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- Ph3As-catalyzed Wittig-type olefination of aldehydes with diazoacetate in the presence of Na2S2O4
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(Chemical Equation Presented) In the presence of sodium hydrosulfite and a catalytic amount of AsPh3 and Fe(TCP)Cl, aldehydes react with ethyl diazoacetate to give the corresponding α,β-unsaturated esters in high yields with excellent stereoselectivities (E/Z > 50/1).
- Cao, Peng,Li, Chuan-Ying,Kang, Yan-Biao,Xie, Zuowei,Sun, Xiu-Li,Tang, Yong
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p. 6628 - 6630
(2008/02/10)
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- Immobilization of ruthenium(II) salen complexes on poly(4-vinylpyridine) and their application in catalytic aldehyde olefination
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Two Ru(II)(salen)(PPh3)2 complexes grafted on poly(4-vinylpyridine) have been synthesized and characterized. An elemental analysis shows that both grafted samples contain ca. 0.6 wt % Ru. FTIR spectra confirm the formation of metal-salen complexes attached to the carrier polymer by an interaction between the ruthenium(II) compounds with the pyridine nitrogen atoms of the poly(4-vinylpyridine). Immobilization of both Ru(II) salen complexes on the polymer increases their thermal stability as demonstrated by TG-MS analysis. The grafted materials were applied as catalysts for the olefination of various aldehydes at 60 °C under an inert gas atmosphere, showing comparable yields as their homogeneous congeners and high trans-selectivities. The ruthenium(II) compound with a larger salen ligand shows a better recyclability and selectivity than the derivative with the smaller ligand.
- Syukri, Syukri,Sun, Wei,Kühn, Fritz E.
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p. 1613 - 1617
(2008/01/27)
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- Modular polyketide synthases and cis double bond formation: Establishment of activated cis-3-cyclohexylpropenoic acid as the diketide intermediate in phoslactomycin biosynthesis
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The majority of modular polyketide synthase (PKS) systems which generate unsaturated products do so with trans double bonds. Phoslactomycin B (PLM B) presents a class of antitumor and antiviral natural polyketide products that have unique structural features, including a linear unsaturated backbone with one trans and three cis double bonds. There is substantial evidence that trans double bonds are established by ketoreductase-dehydratase (KR-DH) didomains within a PKS module. In cases where modules containing these didomains appear to generate product containing a cis double bond, there is no experimental evidence to determine if they do so directly or if they also form a trans double bond with a subsequent isomerization step. A critical step in addressing this issue is establishing the stereochemistry of the polyketide intermediate which passes to the subsequent module. Herein, we demonstrate through a series of experiments that an activated cis-3-cyclohexylpropenoic acid is the diketide intermediate which passes from module 1 to module 2 of the PLM PKS. The trans isomer of the diketide intermediate could not be processed directly into PLM B by module 2 but could be converted to PLM B by degradation to cyclohexanecarboxylic acid and elongation by the entire PLM PKS. These observations indicate not only that module 1 with a DH-KR didomain is responsible for establishing the C14-C15 cis double bond of PLM B but also that the subsequent modules of the PKS clearly discriminate between the cis- and trans-diketide intermediate and do not contain domains capable of catalyzing double bond isomerization. Copyright
- Alhamadsheh, Mamoun M.,Palaniappan, Nadaraj,DasChouduri, Suparna,Reynolds, Kevin A.
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p. 1910 - 1911
(2007/10/03)
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- The one-pot Wittig reaction: A facile synthesis of α,β- unsaturated esters and nitriles by using nanocrystalline magnesium oxide
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Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one-pot Wittig reaction to afford α,β-unsaturated esters and nitriles in excellent yields with high E-stereoselectivity in the presence of triphenylphosphine under mild conditions.
- Choudary, Boyapati M.,Mahendar, Koosam,Kantam, M. Lakshmi,Ranganath, Kalluri V. S.,Athar, Taimur
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p. 1977 - 1985
(2007/10/03)
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- The photomediated reaction of alkynes with cycloalkanes
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In the presence of a photomediator such as benzophenone, alkynes with electron-withdrawing groups react with cycloalkanes to give vinyl cycloalkanes. The reaction involves the regiospecific addition of a photochemically generated cycloalkyl radical to the β-carbon of the alkyne. The stereochemical outcome of the reaction depends on the nature of the photomediator and alkyne used. The Royal Society of Chemistry 2006.
- Doohan, Roisin A.,Hannan, John J.,Geraghty, Niall W.A.
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p. 942 - 952
(2007/10/03)
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- Manganese-promoted β-elimination reactions: Totally stereoselective synthesis of (E)-α,β-unsaturated esters
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Stereoselective β-elimination of 2-bromo-3-hydroxy-esters is achieved by using non-preactivated manganese and trimethylsilyl chloride, to yield (E)-α,β-unsaturated esters with total diastereoselectivity. Georg Thieme Verlag Stuttgart.
- Concellón, José M.,Rodríguez-Solla, Humberto,Del Amo, Vicente
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p. 315 - 317
(2007/10/03)
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- A practical, efficient, and atom economic alternative to the Wittig and Horner-Wadsworth-Emmons reactions for the synthesis of (E)-α,β- unsaturated esters from aldehydes
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We describe a highly efficient new methodology for the synthesis of (E)-α,β-unsaturated esters from aldehydes. In our DMAP-catalyzed reaction, both aromatic as well as aliphatic aldehydes furnish the desired products highly regio- and stereoselectively if treated with commercially available or synthetically easily accessible malonic acid half ester. A large scale application in the synthesis of p-methoxycinnamates, which are of use as sunscreen ingredients, is described.
- List, Benjamin,Doehring, Arno,Hechavarria Fonseca, Maria T.,Job, Andreas,Rios Torres, Ramon
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p. 476 - 482
(2007/10/03)
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- METHOD FOR THE PRODUCTION OF OLEFINS FROM CARBONYL COMPOUNDS
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A method for the production of a,?-unsaturated compounds of general formula (I) is disclosed, where R1 and R2 independently = H, substituted or unsubstituted alkyl or aryl, R3 = H, substituted or unsubstituted alkyl or aryl, or a functional group such as OR4, NR5R6, SR7, where R4, R5, R6 and R7 = common substituents in particular, alkyl- and/or aryl groups, or halogen, EWG = an electron withdrawing group such as for example, CO2H, CO2R8, CONR9R10, COSR11, CN, NO2, SO2R12, CHO, COR13, etc. where R8, R9, R10, R11, R12 and R13 = common substituents, in particular, alkyl- and/or aryl groups, in which a carbonyl compound of formula (II), in which R1 and R2 are as defined above, is reacted with a carboxylic acid of formula (III) in the presence of an amine or with the same acid generated in situ by the addition of an acid to the salt thereof in which R3 and EWG are as defined above. Under mild reaction conditions unsaturated esters with high (E)-stereoselectivity are obtained. The reaction typically occurs at room temperature or lower without particular requirements such as inert gas, exclusion of humidity, heat etc. CO2 and water are obtained as the only by-products.
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Page/Page column 5; 8
(2008/06/13)
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- Ethyl (benzothiazol-2-ylsulfonyl)acetate: A new reagent for the stereoselective synthesis of α,β-unsaturated esters from aldehydes
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The title reagent engaged in the modified Julia olefination with aldehydes under mild reaction conditions (DBU, CH2Cl2, rt or -78°C) to yield α,β-unsaturated esters; aryl aldehydes and aliphatic aldehydes possessing significant chain branching elements gave trans alkene products with high stereoselectivity (E : Z up to >98 : 2), while straight chain aliphatic aldehydes gave cis products preferentially (Z : E up to 92 : 8). The Royal Society of Chemistry 2095.
- Blakemore, Paul R.,Ho, Danny K.H.,Nap, W. Mieke
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p. 1365 - 1368
(2007/10/03)
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- Practical synthesis of (E)-α,β-unsaturated esters from aldehydes
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Based on a modification of the Doebner-Knoevenagel reaction, a practical and highly efficient synthesis of β,β-unsaturated esters with excellent regio- and stereoselectivity was developed. The reactions are catalyzed by 4-dimethylaminopyridine in DMF at room temperature or below. Both aliphatic and aromatic aldehydes can readily be used in the process.
- List, Benjamin,Doehring, Arno,Hechavarria Fonseca, Maria T.,Wobser, Kathrin,Van Thienen, Hendrik,Torres, Ramon Rios,Galilea, Pedro Llamas
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p. 1558 - 1560
(2007/10/03)
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- An easy, efficient, and completely stereoselective synthesis of (E)-α,β-unsaturated esters via sequential aldol-type/elimination reactions promoted by samarium diiodide or chromium dichloride
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(E)-α,β-Unsaturated esters can be obtained with complete stereoselectivity by reaction of different aldehydes and ethyl clibromoacetate promoted by SmI2 or CrCl2. The transformation takes place as two sequential reactions: an aldol-type reaction and a β-elimination reaction.
- Concellon, Jose M.,Concellon, Carmen,Mejica, Carmen
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p. 6111 - 6113
(2007/10/03)
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- Efficient and scalable protocol for the Z-selective synthesis of unsaturated esters by horner-wadsworth-emmons olefination
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The synthesis of a highly Z-selective Horner-Wadsworth-Emmons (HWE) reagent from cheap and readily available starting materials on a 200-g scale is described. The HWE reaction conditions have also been studied in order to design an efficient and scalable
- Touchard, Francois P.,Capelle, Nicolas,Mercier, Mathilde
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p. 707 - 711
(2007/10/03)
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