- Enantioselective epoxidation of β,β-disubstituted enamides with a manganese catalyst and aqueous hydrogen peroxide
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Enantioselective epoxidation of β,β-disubstituted enamides with aqueous hydrogen peroxide and a novel manganese catalyst is described. Epoxidation is stereospecific and proceeds fast under mild conditions. Amides are disclosed as key functional groups to enable high enantioselectivity.
- Clarasó, Carlota,Vicens, Laia,Polo, Alfonso,Costas, Miquel
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p. 2430 - 2435
(2019/03/29)
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- HClO4·SiO2-mediated improved isomerization of glycidic esters to α-hydroxy-β,γ -unsaturated esters: Application in the formal synthesis of (R)-Baclofen and β-phenyl GABA analogues
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An efficient isomerization of glycidic esters to corresponding allylic alcohols, viz. α-hydroxy-β,γ -unsaturated esters has been brought about using HClO4·SiO2. Five of these allylic alcohols underwent selective SN2' nucleophilic substitution to generate γ-azido-α,β-unsaturated esters which were readily converted to an antispastic drug Baclofen and four other β-phenyl GABA analogues.
- Basak, Ranjan,Dharuman, Suresh,Reddy, Y. Suman,Doddi, Venkata Ramana,Vankar, Yashwant D.
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supporting information; experimental part
p. 325 - 327
(2012/06/01)
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- A versatile synthetic platform based on strained propargyl amines
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"Chemical Equation Presented" Divergent reactivity: Various ethynylaziridines behave as strained propargyl amines and can be directly converted into unprotected α-amino allenes by a highly diastereoselective SN2′ hydride delivery (see scheme). Additional reaction routes involve chemo- and regioselective transformation into either bicyclic aziridine/ enol ethers or highly strained azirine alkynes.
- He, Zhi,Yudin, Andrei K.
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supporting information; experimental part
p. 1607 - 1610
(2010/06/16)
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- Malodour reducing composition and uses thereof
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The invention relates to a malodour reducing composition comprising: A) at least one phenylglycidate of formula (1): wherein: - R1 is a C1-C4 branched or linear alkyl group, - R2 is hydrogen or methyl, and - R3 is hydrogen, a C1-C4 branched or linear alkyl group or a methoxy group, and B) at least one 1,2 diketone of formula (2) or (3): wherein: - R4, R5 and R7 may be independently, a C1-C5 linear or branched alkyl or alkenyl group; - R6 is a (C1-C5) alkylidene; - R4 and R5 may also form a C4-C7 saturated or unsaturated alicyclic or heterocyclic ring structure, optionally substituted by (C1-C4) alkyl groups; - R6 and R7 may also form a C4-C7 unsaturated, alicyclic or heterocyclic ring structure optionally substituted by (C1-C4) alkyl groups; the weight ratio of glycidate A to 1,2 diketone B being from 1:99 to 99:1. The invention also relates to the fragrance compositions and consumer products containing this malodour reducing composition.
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- An efficient synthesis of 2-bromo-3-hydroxy esters by reaction of ketones with ethyl dibromoacetate promoted by samarium diiodide
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A simple and efficient samarium diiodide mediated synthesis of 2-bromo-3-hydroxy esters 1 by the reaction of a variety of ketones 2 with ethyl dibromoacetate (3) is described. The relative configuration of the major diastereoisomer obtained was established by NOESY experiments of the corresponding α,β-epoxy esters 4 prepared from 1. Additionally, a mechanism is proposed to explain the results obtained. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Concellon, Jose M.,Concellon, Carmen,Diaz, Pamela
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p. 2197 - 2200
(2007/10/03)
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- Organic reactions catalyzed by methylrhenium trioxide: Reactions of ethyl diazoacetate and organic azides
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Methylrhenium trioxide (CH3ReO3 or MTO) catalyzes several classes of reactions of ethyl diazoacetate, EDA. It is the first high valent oxo complex for carbene transfer. Under mild conditions and in the absence of other substrates, EDA was converted to a 9:1 mixture of diethyl maleate and diethyl fumarate. In the presence of alcohols, α-alkoxy ethyl acetates were obtained in good yield. The yields dropped for the larger and more branched alcohols, the balance of material being diethyl maleate and fumarate. An electron-donating group in the para position of phenols favors the formation of α-phenoxy ethyl acetates. The use of EDA to form α-thio ethyl acetates and N-substituted glycine ethyl esters, on the other hand, is hardly affected by the size or structure of the parent thiol or amine, with all of these reactions proceeding in high yield. MTO-catalyzed cycloaddition reactions occur between EDA and aromatic imines, olefins, and carbonyl compounds. Three-membered ring products are formed: aziridines, cyclopropanes, and epoxides, respectively. The reactions favor the formation of trans products, and provide a convenient route for the preparation of aziridines. Intermediate carbenoid and nitrenoid species have been proposed. In the presence of an oxygen source such as an epoxide, ethyl diazoacetate and azibenzil are converted to an oxalic acid monoethyl ester and tobenzil; at the same time the epoxide was converted to an olefin. These results provide further support for the proposed intermediate, a cyclic species containing Re, O, and CHCO2Et (or, occasionally, CPhC(O)Ph)in a three-membered ring.
- Zhu, Zuolin,Espenson, James H.
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p. 9901 - 9907
(2007/10/03)
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- REDUCTION OF ARYLALKYLAZOMETHINES WITH SODIUM BOROHYDRIDE
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The secondary amines R1R2C6H3CH2CH(CH3)NHCHR5CHR6(CH2)nC6H3R3R4 were synthesized by the reduction of the respective azomethines with sodium borohydride.The reaction was conducted in anhydrous methanol in the presence of hydrogen chloride with the azomethine and hydrogen chloride in a molar ratio of 1:1.The yield was 50-90percent.The erythro and threo isomers were isolated, and the data from the IR spectra of the isomers are given.
- Dumpis, M. A.,Kudryashova, N. I.,Veresova, M. A.
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p. 1332 - 1337
(2007/10/02)
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- α-Bromo-, α-chloro-, and α-trimethylsilyl-zinc ester enolates. New and universal Reformatsky-type Darzens and Peterson reactions
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Low temperature reactions of ethyl dihaloacetates with carbonyl compounds in the presence of zinc/silver-graphite give α-halo-β-hydroxyalkanoates, which are readily converted into glycidates by base.Unser the same conditions ethyl(bromo)(trimethylsilyl) acetate with aldehydes and ketones forms α,β-unsaturated esters by a Reformatsky-Peterson reaction combination.
- Fuerstner, Alois
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p. C33 - C36
(2007/10/02)
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- Chromatographic Resolution of Enantiomers with Natural Polymers
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Cheap, chiral, natural polymers have been tested as stationary phases for the chromatographic resolution of the enantiomers of several very different racemates.Silk, wool, and cellulose are not suitable.Potato starch can be used well in special cases.Hesse's and Hagel's cellulose triacetate finds widest application, as shown by several new examples.This property results from a genuine chiral tertiary structure not to be destroyed during preparation.
- Konrad, Gerd,Musso, Hans
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p. 1956 - 1967
(2007/10/02)
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- MASS SPECTROMETRIC DECOMPOSITION OF β-PHENYLOXIRANECARBOXYLIC ESTERS
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The electron-impact mass spectra of the E- and Z-isomers of the α,β-methyl substituted esters of β-phenyloxiranecarboxylic acids have been studied.
- Anisimova, O. S.,Chistyakov, V. V.,Bokanov, A. I.,Shvedov, V. I.,Sheinker, Yu. N.
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p. 1058 - 1063
(2007/10/02)
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- STEREOSPECIFITY OF THE SPIN-SPIN COUPLING CONSTANTS AND CHEMICAL SHIFTS IN THE 13C NMR SPECTRA OF OXIRANECARBOXYLIC ESTERS
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It was established that the 3JCH spin-spin coupling constants and chemical shifts in the 13C NMR spectra of the cis and trans isomers of oxiranecarboxylic esters are stereospecific.The signals for the methyl groups of the cis isomer are 4-7 ppm upfield from the signals for the trans isomer.The 3JCH constant due to spin-spin coupling of the 2-CH3 (or 3-CH3) group and the proton at the C3 (or C2) atom amounts to 2 Hz for the cis isomer and is absent for the trans isomer.
- Alekseeva, L. M.,Bokanov, A. I.,Shvedov, V. I.,Sheinker, Yu. N.
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p. 1664 - 1666
(2007/10/02)
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- AN IMPROVED PROCEDURE FOR THE SYNTHESIS OF GLYCIDIC ESTERS
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Aromatic and aliphatic aldehydes and ketones readily undergo Darzens condensation on reaction with NaH and chloroacetate in CH3CN.
- Pergola, R. Della,Battista, P. Di
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p. 121 - 126
(2007/10/02)
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- Methode generale d'obtention des α-ceto esters β-fluores
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A general method of synthesis of 3-alkyl (or aryl) 3-fluoro 2-oxo esters is described.The opening of glycidic esters with HF-pyridine (70percent w/w) followed by oxidation with Jones reagent, give the corresponding derivatives of fluoropyruvic esters in good yields.
- Ourari, Ali,Condom, Roger,Guedj, Roger
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p. 2707 - 2710
(2007/10/02)
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- Rapid Acid-catalysed and Uncatalysed Hydration of Ketenimines
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The rates of hydration of a series of ketenimines (9) have been examined in water (μ 1.0; 25 deg) over the pH range 2-13.Three mechanisms of hydration to the amides (8) were noted: (a) general acid catalysis by proton transfer from H3O(1+) in the pH range 2-7 (giving kH3O(1+)/kD3O(1+) 2.65); (b) general acid catalysis by H2O at pH > 7 (where kH2O/kD2O = 4.8); (c) rate determining HO(1-) attack.The last mechanism was only shown by N-arylketenimines, e.g. (9e); other N-alkylketenimines continue to react by rate-determining proton transfer from water even at pH 13.This result is confirmed by the incorporation of just one deuterium when (9a) reacted in acidic or basic D2O, while the deuteriated ketenimine (9f) does not loose the label on the reaction in water.Substituent effects are parallel for reactions involving H(1+) transfer from H3O(1+) or H2O; the major effects are obtained on changing substituents at carbon (the protonation site).For example, replacement of C-H by C-Me reduces the reactivity by 10-20-fold, while replacement of C-Me by C-Ph reduces the rate of hydration by >100-fold.Ammonium ions also generally react with ketenimines by rate-determining H(1+) transfer to the ketenimine followed by trapping of the nitrilium ion formed by the free amine.Only with the strongest amine base studied (piperidine) does direct nucleophilic attack on the ketenimine compete.
- McCarthy, Daniel G.,Hegarty, Anthony F.
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p. 579 - 591
(2007/10/02)
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