- Essential structural features of (2Z,4E)-5-phenylpenta-2,4-dienoic acid for inhibition of root gravitropism
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Previously, we found (2Z,4E)-5-phenylpenta-2,4-dienoic acid (ku-76) to be a selective inhibitor of root gravitropic bending of lettuce radicles at 5 μM, with no concomitant growth inhibition. Here, we describe a structure-activity relationship study of ku
- Shindo, Mitsuru,Makigawa, Saki,Matsumoto, Kenji,Iwata, Takayuki,Wasano, Naoya,Kano, Arihiro,Morita, Miyo Terao,Fujii, Yoshiharu
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- Carbocation Lewis Acid TrBF4-Catalyzed 1,2-Hydride Migration: Approaches to (Z)-α,β-Unsaturated Esters and α-Branched β-Ketocarbonyls
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Carbocation Lewis acid TrBF4-catalyzed 1,2-hydride migration of α-alkyldiazoacetates themselves or in situ-generated cross-coupling adducts of aldehydes and α-alkyldiazoacetates has been developed, affording (Z)-α,β-unsaturated esters and α-branched β-ketocarbonyls, respectively, in good yields and with high regioselectivities.
- Duan, Depeng,Liu, Yongjun,Lv, Jian,Shang, Wansong
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supporting information
(2019/10/08)
-
- Cis-cinnamic acid analogue, gravitropism modifier (by machine translation)
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[Problem] cinnamic acid or cinnamic acid analogue comprising adjusting agent gravitropism cis. [Solution] cinnamic acid and/or cinnamic acid as an active ingredient to adjust gravitropism cis edge agents, cinnamic acid edge is, for example obtained by reacting compounds of the following formula. (In the formula, R is a phenyl group. )Figure 6 [drawing] (by machine translation)
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-
Paragraph 0083-0085
(2019/11/30)
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- Facile synthesis of α, β-unsaturated esters through a one-pot copper-catalyzed aerobic oxidation-Wittig reaction
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An efficient one-pot synthesis of α, β-unsaturated esters through the aerobic oxidation – Wittig tandem reaction of alcohols and phosphorous ylide is developed. This new method operates under mild reaction conditions, and uses CuI/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) as co-catalyst and air (O2) as the oxidant. It tolerates a wide range of functionalized benzylic alcohol and aliphatic alcohols.
- Ren, Cheng,Shi, Zhenyu,Ding, Weijie,Liu, Zhiqing,Jin, Huile,Yu, Xiaochun,Wang, Shun
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supporting information
p. 14 - 17
(2017/12/06)
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- One-Pot Synthesis of α,β-Unsaturated Esters, Ketones, and Nitriles from Alcohols and Phosphonium Salts
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A general method for the synthesis of α,β-unsaturated esters, ketones, and nitriles is successfully achieved by a one-pot copper-catalyzed oxidation with O 2 in air as oxidant. The solvent mixture of acetonitrile and formamide (1:1) is optimized to ensure the oxidation of alcohols, deprotonation of phosphonium salt, and Wittig reaction occur efficiently in one pot. A broad range of substrates has been explored for this process, including three electron-withdrawing group (CO 2 Et, COPh, CN) functionalized phosphonium salts. They reacted not only with benzylic and heteroaromatic alcohols, but also with aliphatic alcohols, forming the corresponding α,β-unsaturated esters, ketones, and nitriles in moderate to excellent yields.
- Ding, Weijie,Hu, Juan,Jin, Huile,Yu, Xiaochun,Wang, Shun
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p. 107 - 118
(2017/09/28)
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- Highly syn-selective elimination of peterson anti-adducts to give Z-α,β-unsaturated esters
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Peterson adducts have been known to stereospecifically give syn-elimination products upon treatment with base except when the product olefin is in conjugation with an electron-withdrawing group. The missing piece has been put in place by using a catalytic amount of DBU, by which syn-elimination could be effected to provide the thermally less stable Z-olefin from the anti-adduct with high selectivity.
- Murai, Yutaka,Nakagawa, Akira,Kojima, Satoshi
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supporting information
p. 228 - 231
(2017/02/10)
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- Tandem Palladium and Isothiourea Relay Catalysis: Enantioselective Synthesis of α-Amino Acid Derivatives via Allylic Amination and [2,3]-Sigmatropic Rearrangement
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A tandem relay catalytic protocol using both Pd and isothiourea catalysis has been developed for the enantioselective synthesis of α-amino acid derivatives containing two stereogenic centers from readily accessible N,N-disubstituted glycine aryl esters and allylic phosphates. The optimized process uses a bench-stable succinimide-based Pd precatalyst (FurCat) to promote Pd-catalyzed allylic ammonium salt generation from the allylic phosphate and the glycine aryl ester. Subsequent in situ enantioselective [2,3]-sigmatropic rearrangement catalyzed by the isothiourea benzotetramisole forms syn-α-amino acid derivatives with high diastereo- and enantioselectivity. This methodology is most effective using 4-nitrophenylglycine esters and tolerates a variety of substituted cinnamic and styrenyl allylic ethyl phosphates. The use of challenging unsymmetrical N-allyl-N-methylglycine esters is also tolerated under the catalytic relay conditions without compromising stereoselectivity.
- Spoehrle, Stéphanie S. M.,West, Thomas H.,Taylor, James E.,Slawin, Alexandra M. Z.,Smith, Andrew D.
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supporting information
p. 11895 - 11902
(2017/09/07)
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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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- Stereoselective Synthesis of 2 Z,4 e -Configured Dienoates through Tethered Ring Closing Metathesis
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A two-step sequence leading from racemic allylic alcohols and vinylacetic acid to ethyl (2Z,4E)-dienoates is described. The sequence involves Steglich esterification of the reactants, followed by a one-pot ring closing metathesis-base induced elimination-
- Schmidt, Bernd,Aud?rsch, Stephan,Kunz, Oliver
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p. 4509 - 4518
(2016/12/16)
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- CIS CINNAMIC ACID ANALOG AND GRAVITROPISM MODIFIER
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PROBLEM TO BE SOLVED: To provide a gravitropism modifier having effects on creeping property of plants or sugar content of fruits. SOLUTION: There is provided a gravitropism modifier containing cis cinnamic acid and/or a cinnamic acid analog represented by the formula (1) as active ingredients. (1), where A is cyclic hydrocarbon which may have a substituent, X is a bound or a C1 to 5 substituted or unsubstituted hydrocarbon chain, R1 is H, a hydroxyl group, an alkali earth metal salt or the like, R2 is a bond or a C1 to 5 substituted or unsubstituted hydrocarbon chain and R3 and R4 are H or together form C5 to 8 cyclic hydrocarbon. SELECTED DRAWING: Figure 6 COPYRIGHT: (C)2016,JPOandINPIT
- -
-
Paragraph 0082; 0083; 0084
(2017/06/02)
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- Tandem oxidation–Wittig reaction using nanocrystalline barium manganate (BaMnO4); an improved one-pot protocol
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A one-pot, tandem oxidation–Wittig procedure has been developed in which the reacting components are generated in situ from alcohols, triphenyl phosphine, and ethyl bromoacetate using barium manganate as a mild oxidizing agent without the addition of an external base.
- Gholinejad, Mohammad,Firouzabadi, Habib,Bahrami, Maedeh,Nájera, Carmen
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supporting information
p. 3773 - 3775
(2016/07/26)
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- Polyethyleneimine-Supported Triphenylphosphine and Its Use as a Highly Loaded Bifunctional Polymeric Reagent in Chromatography-Free One-Pot Wittig Reactions
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A polyethyleneimine-supported triphenylphosphine reagent has been synthesized and used as a highly loaded bifunctional homogeneous reagent in a range of one-pot Wittig reactions that afforded high yields of the desired products after simple purification procedures. The approach also served efficiently in tandem reaction sequences involving a one-pot Wittig reaction followed by conjugate reduction of the newly formed alkene product in situ. In these transformations, the phosphine oxide groups generated in the Wittig reaction served as the catalyst for activating trichlorosilane in the subsequent reduction reaction.
- Xia, Xuanshu,Toy, Patrick H.
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supporting information
p. 1737 - 1743
(2015/07/20)
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- Key structural features of cis-cinnamic acid as an allelochemical
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1-O-cis-cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals isolated from Spiraea thunbergii Sieb. It is suggested that it derives its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. It was synthesized to confirm its structure and bioactivity, and also a series of cis-cinnamic acid analogues were prepared to elucidate the key features of cis-cinnamic acid for lettuce root growth inhibition. The cis-cyclopropyl analogue showed potent inhibitory activity while the saturated and alkyne analogues proved to be inactive, demonstrating the importance of the cis-double bond. Moreover, the aromatic ring could not be replaced with a saturated ring. However, the 1,3-dienylcyclohexene analogue showed strong activity. These results suggest that the geometry of the C-C double bond between the carboxyl group and the aromatic ring is essential for potent inhibitory activity. In addition, using several light sources, the photostability of the cinnamic acid derivatives and the role of the C-C double bond were also investigated.
- Abe, Masato,Nishikawa, Keisuke,Okuda, Katsuhiro,Shindo, Mitsuru,Fukuda, Hiroshi,Nakanishi, Kazunari,Tazawa, Yuta,Taniguchi, Tomoya,Park, So-Young,Hiradate, Syuntaro,Fujii, Yoshiharu
-
p. 56 - 67,12
(2012/12/12)
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- A novel oxidative transformation of alcohols to nitriles: An efficient utility of azides as a nitrogen source
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An efficient methodology to oxidize benzylic and cinnamyl alcohols to their corresponding nitriles in excellent yields has been developed. This methodology employs DDQ as an oxidant and TMSN3 as a source of nitrogen in the presence of a catalytic amount of Cu(ClO4)2·6H 2O.
- Rokade, Balaji V.,Malekar, Sanjeev K.,Prabhu, Kandikere Ramaiah
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p. 5506 - 5508
(2012/07/03)
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- Ligand effects on the stereochemical outcome of suzuki-miyaura couplings
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The ligands associated with various Pd catalysts play a crucial role in determining the stereochemistry of cross-couplings between boronic acids and Z-alkenyl halides. A ligand on palladium has been found that leads to the desired products under mild conditions and in high yields that, in most cases, retain their Z-olefin geometry.
- Lu, Guo-Ping,Voigtritter, Karl R.,Cai, Chun,Lipshutz, Bruce H.
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experimental part
p. 3700 - 3703
(2012/06/15)
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- Diastereoselective liquid assisted grinding: 'Cracking' functional resins to advance chromatography-free synthesis
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As regulations that restrict the use of organic solvents become more stringent, ball milling remains an attractive substitute for traditional organic synthesis. However, the mechanochemistry community does not have a purification pathway to complement the solvent-free, ball milling process. Functional resins have proven to be powerful synthetic tools that simplify purification, but traditional handling of these resins restricts their utility, as hazardous organic solvents are needed to swell the resin. Ball milling the functional resin exposes the functional groups as a function of surface area. This report details the use of ball milling and functional resins to perform an environmentally attractive version of the Wittig reaction.
- Shearouse, William C.,MacK, James
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p. 2771 - 2775,5
(2020/09/14)
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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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- Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation - Pd-catalyzed cross-coupling
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All four stereoisomers (7-10) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (E)- and (Z)-β-bromoacrylates. Although the stereoisomeric purity of the 2Z,4E-isomer (8) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤95%, as reported earlier, the use of CsF or nBu4NF as a promoter base has now been found to give all of 7-10 in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2E,4E and 2E,4Z isomers of ≥98% purity, but the purity of the 2Z,4E isomer was ≤95%. Mutually complementary Horner-Wadsworth-Emmons and Still-Gennari (SG) olefinations are also of considerably limited scopes. Neither 2E,4Z nor 2Z,4Z isomer is readily prepared in ≥90% selectivity. In addition to (2Z,4E)-dienoic esters, some (2Z,4E,6E)- and (2Z,4E,6Z)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation-SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (23-30) have been prepared in ≥98% overall selectivity.
- Wang, Guangwei,Mohan, Swathi,Negishi, Ei-Ichi
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scheme or table
p. 11344 - 11349
(2011/10/30)
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- Wittig reaction with ion-supported Ph3P
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Ion-supported Ph3P, 4-(diphenylphosphino)benzyltrimethylammonium bromide A and N-methyl-N-[4-(diphenylphosphino)benzyl]pyrrolidinium bromide B, were used for the Wittig reaction. Ion-supported phosphonium salts A1 and B1, which were prepared from the reactions of ion-supported Ph3P A and B with ethyl bromoacetate, respectively, reacted with aromatic and aliphatic aldehydes in the presence of K2CO3 to give the corresponding α,β-unsaturated ethyl esters in good yields with high purity by simple filtration of the reaction mixture and subsequent removal of the solvent from the filtrate. Similarly, ion-supported phosphonium salts A2 and B2, which were prepared from the reactions of ion-supported Ph3P A and B with p-methylbenzyl bromide, respectively, reacted with aromatic and aliphatic aldehydes in the presence of NaH to provide the corresponding p-methylstyrene derivatives in good yields with high purity by simple filtration of the reaction mixture and the subsequent removal of the solvent from the filtrate. In both reactions, the co-product, ion-supported Ph3PO, could be obtained quantitatively by simple filtration, and was converted into the corresponding ion-supported Ph3P A and B again in high yields using dimethyl sulfate, followed by the reduction with LiAlH4. Recovered and regenerated ion-supported Ph3P A and B could be reused for the same Wittig reaction while maintaining good yields of ethyl (E)-3-(4′-chlorophenyl)-2-propenoate and 1-(4′-chlorophenyl)-2- (4″-methylphenyl)ethene with high purity by simple filtration and removal of the solvent from the filtrate.
- Shimojuh, Naoya,Imura, Yumi,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 951 - 957
(2011/03/18)
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- Site-specific introduction of gold-carbenoids by intermolecular oxidation of ynamides or ynol ethers
-
Ynamides and ynol ethers undergo intermolecular gold-catalysed reaction with a nucleophilic oxidant to access metal-carbenoid reactivity patterns. A site-specific oxidation/1,2-insertion cascade is used for a general access to functionalised α,β-unsaturat
- Davies, Paul W.,Cremonesi, Alex,Martin, Nicolas
-
supporting information; experimental part
p. 379 - 381
(2011/02/27)
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- New polymer-supported phosphonate reagents for the synthesis of Z-α,β-unsaturated esters
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New polymer-supported phosphonate reagents have been prepared and evaluated for the synthesis of Z-α,β-unsaturated esters. High Z-selectivity was obtained using the reagent having two o-t-BuC6H4 groups.
- Ando, Kaori,Suzuki, Yusaku
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scheme or table
p. 2323 - 2325
(2010/06/13)
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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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- Rasta resin-PPh3 and its use in chromatography-free wittig reactions
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Rasta resin-PPh3, a new heterogeneous polystyrene-based phosphine, has been synthesized and used in one-pot Wittig olefination reactions of aldehydes. In these reactions an excess of rasta resin-PPh3 was used for the in situ generation of the phosphorane reactant and allowed for isolation of a high yield of very pure alkene product after only filtration and solvent removal. The excellent results obtained in this study are attributed to the flexible nature of the rasta resin structure, which makes it less dependant upon swelling than other heterogeneous polystyrene materials previously used to support phosphine reagents in Wittig reactions. Georg Thieme Verlag Stuttgart.
- Leung, Peter Shu-Wai,Teng, Yan,Toy, Patrick H.
-
supporting information; experimental part
p. 1997 - 2001
(2010/10/02)
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- Chromatography-free wittig reactions using a bifunctional polymeric reagent
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The first example of a polystyrene bearing two distinct reagent groups has been prepared. This phosphine and amine functionalized material was used in one-pot Wittig reactions with an aldehyde and either an α-halo-ester, -ketone, or -amide. Due to the heterogeneous nature of the polymer, the desired alkene product of these reactions could be isolated in excellent yield in essentially pure form after only filtration and solvent removal.
- Leung, Peter Shu-Wai,Teng, Yan,Toy, Patrick H.
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supporting information; experimental part
p. 4996 - 4999
(2010/12/25)
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- P(i-PrNCH2CH2)3N: Efficient catalyst for synthesizing β-hydroxyesters and α,β-unsaturated esters using α-trimethylsilylethylacetate (TMSEA)
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(Chemical Equation Presented) We present an efficient synthesis of β-hydroxyesters and R,β-unsaturated esters via activation of the silicon-carbon bond of α-trimethylsilylethylacetate using catalytic amounts of the commercially available P(i-PrNCH2CH2) 3N 1a. Selectivity for either of these two products can be achieved simply by altering the catalyst loading and reaction temperature to afford addition or stereoselective condensation. This method is mild and tolerates a wide array of functional groups.
- Wadhwa, Kuldeep,Verkade, John G.
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supporting information; experimental part
p. 4368 - 4371
(2009/09/06)
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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)
-
- 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)
-
- Ruthenium/halide catalytic system for C-C bond forming reaction between alkynes and unsaturated carbonyl compounds
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A ruthenium complex [triruthenium dodecacarbonyl, Ru3(CO) 12] in the presence of bis(triphenylphosphine)iminium chloride ([PPN]Cl) catalyzes the conjugate addition of terminal alkynes to alkyl acrylates to give high yields of γ,δ-alkynyl esters. On the other hand, the linear codimerization reaction of terminal alkynes with alkyl acrylates proceeds in the presence of a catalytic amount of Ru 3(CO)12 and lithium iodide to give the corresponding conjugate dienes. These two different types of catalytic carbon-carbon bond forming reactions are controlled only by the nature of halide ions, either a chloride or an iodide, with other conditions being kept almost the same.
- Nishimura, Takahiro,Washitake, Yosuke,Uemura, Sakae
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p. 2563 - 2571
(2008/09/19)
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- A one-pot synthesis of (E)-disubstituted alkenes by a bimetallic [Rh-Pd]-catalyzed hydrosilylation/hiyama cross-coupling sequence
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A bimetallic [Rh-Pd] catalyst was prepared by soaking into an iodide ionic gel an equimolar solution of [RhCl(PPh3)3] and Pd(OAc)2 in CH2Cl2. Its catalytic activity was evaluated by rhodium-catalyzed hydrosilylation (H), palladium-catalyzed Hiyama coupling (C), and in the one-pot hydrosilylation/Hiyama coupling sequence (H/C). It was found that the homogeneous combination [RhCl(PPh3) 3]/NaI was a superior system compared to the polyionic mono- and bimetallic rhodium catalysts in the hydrosilylation of terminal alkynes. Interestingly, the most effective catalyst in terms of stereo- and chemoselectivities was observed to be the bimetallic ionic gel [Rh-Pd] in the one-pot process leading to (E)-alkenes with good yields. The remarkable stereocontrol is ascribed to a beneficial Pd-catalyzed isomerization from the mixture of stereoisomeric vinylsilanes obtained in the initial hydrosilylation step into the more stable (E)-adduct. The [Rh-Pd] heterogeneous catalyst also showed a higher chemoselectivity than the homogeneous catalytic combination, and no detrimental formation of Sonogashira side product was observed due to an ionic-gel-mediated kinetic modulation. To illustrate its scope and limitations, the described one-pot bimetallic catalytic sequence was extended to functionalized terminal alkynes and various iodide substrates. Conjugated systems, such as hydroxycinnamaldehyde, dienes, and trienes, were synthesized in good overall yields. To avoid deactivation of the Rh species, N-heterocyclic iodides had to be added sequentially after completion of hydrosilylation.
- Thiot, Carine,Schmutz, Marc,Wagner, Alain,Mioskowski, Charles
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p. 8971 - 8978
(2008/09/17)
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- The first sequential reaction promoted by manganese: Complete stereoselective synthesis of (E)-α,β-unsaturated esters from 2,2-dichloroesters and aldehydes
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(Chemical Equation Presented) α,β-Unsaturated esters were obtained with complete control of stereoselectivity utilizing a sequential reaction of dichloroesters with a variety of aldehydes, promoted by active manganese. This methodology is generally applicable, and the C-C double bond can be di- or trisubstituted. A mechanism based on a successive aldol-type reaction/β-elimination is proposed to explain these results.
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Diaz, Pamela,Llavona, Ricardo
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p. 4396 - 4400
(2008/02/05)
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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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- New application of bromotrimethylsilane: Elaboration of aldehydes/ketones into homologous α,β-unsaturated esters via β-hydroxy esters
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α,β-Unsaturated esters are formed when β-hydroxy esters react with bromotrimethylsilane which is generated from chlorotrimethylsilane- lithium bromide in acetonitrile. Copyright Taylor & Francis, Inc.
- Suri, Suresh C.,Marcischak, Jacob C.
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p. 379 - 387
(2007/10/03)
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- Generation of phosphoranes derived from phosphites. A new class of phosphorus ylides leading to high E selectivity with semi-stabilizing groups in Wittig Olefinations
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Tosylhydrazones derived from aryl aldehydes react with t-BuOK, ClFeTPP, (MeO)3P, and aldehydes to furnish olefins with high E selectivity. These reactions occur through a Wittig-type pathway via the corresponding diazo compounds, metal carbenes and phosphorous ylides, with the water-soluble trimethyl phosphate as the byproduct. Similar reactions can also be performed using ethyl diazoacetate; however, high E selectivity was only observed in the presence of LiBr. In this case, the reaction is believed to occur via the phosphonate anion, formed through an Arbuzov reaction. Thus this olefination reaction occurs through a Horner-Wadsworth-Emmons (HWE) reaction but the phosphonate anion is generated under completely base-free conditions. Copyright
- Aggarwal, Varinder K.,Fulton, J. Robin,Sheldon, Chris G.,De Vicente, Javier
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p. 6034 - 6035
(2007/10/03)
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- Iron(III) and ruthenium(II) porphyrin complex-catalyzed selective olefination of aldehydes with ethyl diazoacetate
-
The commercially available Fe(III) and Ru(II) porphyrin complexes Fe(TPP)Cl and Ru(TPP)(CO) are efficient catalysts for selective olefination of a variety of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine. The reactions were carried out under mild conditions in a one-pot fashion with the use of a stoichiometrical amount of EDA, which proceeded with excellent yields and high (E)-selectivity. Air atmosphere, low catalyst loadings, and functional group tolerance were also demonstrated.
- Chen, Ying,Huang, Lingyu,Ranade, Meera A.,Zhang, X. Peter
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p. 3714 - 3717
(2007/10/03)
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- Unexpected catalyst for Wittig-type and dehalogenation reactions
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A novel catalyst 2 for Wittig-type and dehalogenation reactions was developed. In the presence of triphenyl phosphite, a wide variety of aldehydes could react with α-bromoacetates to afford α,β-unsaturated esters or ketones in high yields with excellent E-stereoselectivity when 1-2 mol % of compound 2 was used. Compound 2 was also an effective catalyst for reductive dehalogenation of α-bromocarbonyl compounds. The mechanisms for the above reactions were also proposed.
- Huang, Zheng-Zheng,Tang, Yong
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p. 5320 - 5326
(2007/10/03)
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- Reactivity of substituted and unsubstituted diphenylphosphonium diylides towards carbonic acids derivatives
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In order to further delimit the scope of application of diphenylphosphonium diylides, their reactivity towards carbonic acid derivatives was investigated. Non-stabilized diylides react with ethyl carbonate to give new monoylide intermediates which lead, by in situ Wittig reaction with carbonyl compounds, to the synthesis of α,β-unsaturated esters or acids the double bond being di- or trisubstituted. The reaction proceeds in mild conditions and with high E stereoselectivity. Stabilized diylides are inactive towards carbonates but semi-stabilized diylides react with ethyl carbonate leading to the synthesis of non-functionalized alkenes instead of the α,β-unsaturated esters or acids.
- Cristau,Taillefer
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p. 1507 - 1522
(2007/10/03)
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- 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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p. 625 - 626
(2007/10/03)
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- 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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p. 8125 - 8128
(2007/10/03)
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- HMPT/zinc mediated one-pot convenient synthesis of β-substituted acrylates
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A new one pot convenient synthesis of β-substituted acrylates involving the reaction of aldehydes with ethyl bromoacetate via concomitant Reformatsky and dehydration reactions prompted by HMPT and zinc has been described.
- Khan, R H,Rastogi, R C
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- A novel olefination of diazo-compounds with carbonyl compounds mediated by tributylstibine and catalytic amount of Cu(I)I
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A one-pot reaction of tributylstibine, diazo-compounds including dimethyl diazomalonate, ethyl diazoacetate and diazoacetylacetone, carbonyl compounds and catalytic amount of Cu(I)I resulted in olefination in high yields.
- Liao,Huang
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p. 5897 - 5900
(2007/10/02)
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