- Reactions of β-Lactones with Potassium Alkoxides and Their Complexes with 18-Crown-6 in Aprotic Solvents
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The mechanism of the reaction of β-lactones (2-oxetanones) with potassium alkoxides in aprotic solvents was investigated.Despite previous suggestions, the attack of alkoxide ion occurs on the carbonyl carbon atom of β-lactones, cleaving the acyl-oxygen bond to yield the corresponding potassium alcoholate of the respective β-hydroxycarboxylic acid ester.Next, the unsaturated ester is formed due to potassium hydroxide elimination.The nature of the alkoxide used and complexation of alkali metal cation by crown ether have no significant effect on the reaction course in aprotic solvents.
- Kurcok, Piotr,Jedlinski, Zbigniew,Kowalczuk, Marek
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Read Online
- TMSCl-mediated catalytic carbocupration of alkynoates: An unprecedented and remarkable effect of catalyst loading on highly selective stereochemical induction via a TMS-allenoate intermediate
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The TMSCl-mediated catalytic carbocupration of alkynoates has been investigated. It has been shown that catalyst loadings as low as 30 mol% readily allow for high yields and diastereoselectivities for a series of Grignard reagents. In addition, an unprecedented and remarkable effect of catalyst loading on stereochemical induction has been observed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).
- Jennings, Michael P.,Sawant, Kailas B.
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Read Online
- Olefination via Cu-Mediated Dehydroacylation of Unstrained Ketones
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The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C-C cleavage to remove the acyl moiety, followed by Cu-mediated oxidative elimination to form an alkene between the α and β carbons. The newly adopted N′-methylpicolinohydrazonamide (MPHA) reagent is key to enable efficient cleavage of ketone C-C bonds at room temperature. Diverse alkyl- and aryl-substituted olefins, dienes, and special alkenes are generated with broad functional group tolerance. Strategic applications of this method are also demonstrated.
- Dong, Guangbin,Xu, Yan,Zhou, Xukai
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supporting information
p. 20042 - 20048
(2021/12/03)
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- Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
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We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
- Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
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supporting information
p. 14806 - 14813
(2021/09/18)
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- Stereospecific Hydrogenolysis of Lactones: Application to the Total Syntheses of (R)-ar-Himachalene and (R)-Curcumene
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A straightforward strategy for the syntheses of curcumene and ar-himachalene is reported. Synthetic highlights include a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts. Notably, using Ni/Raney, the stereoselectivity outcome (inversion vs retention) of the hydrogenolysis depends on the tertiary benzylic alcohol substitution.
- Spielmann, Kim,De Figueiredo, Renata Marcia,Campagne, Jean-Marc
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p. 4737 - 4743
(2017/05/12)
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- Method for synthesizing muscone by utilizing beta-monomethyl methylglutarate
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The invention discloses a method for synthesizing muscone by utilizing beta-monomethyl methylglutarate. According to the method, beta-monomethyl methylglutarate and alpha,omega-dodecanedioic acid monomethyl ester respectively prepared through a heteropoly acid catalytic transesterification method are used as raw materials, and Kolbe electrolysis, acyloin condensation and reduction reaction are performed to prepare the muscone. The method of the present invention has advantages of high raw material utilization rate, mold condition, easy control and environmental protection, and is suitable for industrial production .
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Paragraph 0021; 0022
(2017/12/05)
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- A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
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α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
- Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
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p. 420 - 430
(2015/12/31)
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- Borane-Catalyzed Reductive α-Silylation of Conjugated Esters and Amides Leaving Carbonyl Groups Intact
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Described herein is the development of the B(C6F5)3-catalyzed hydrosilylation of α,β-unsaturated esters and amides to afford synthetically valuable α-silyl carbonyl products. The α-silylation occurs chemoselectively, thus leaving the labile carbonyl groups intact. The reaction features a broad scope of both acyclic and cyclic substrates, and the synthetic utility of the obtained α-silyl carbonyl products is also demonstrated. Mechanistic studies revealed two operative steps: fast 1,4-hydrosilylation of conjugated carbonyls and then slow silyl group migration of a silyl ether intermediate.
- Kim, Youngchan,Chang, Sukbok
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supporting information
p. 218 - 222
(2016/01/25)
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- Acrylates via Metathesis of Crotonates
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Crotonic acid has the potential to be produced from renewable resources at low cost but currently has a limited market. We are investigating catalytic routes to exploit the functionalities of crotonic acid to produce a range of established industrial chemicals. Here we report our work on converting crotonates to acrylates, where a cost-competitive bio-based alternative can provide a market advantage. Our optimized reaction conditions for the cross-metathesis between crotonates and ethylene resulted in an increase in catalyst turnover numbers by 2 orders of magnitude compared with literature values. Control experiments showed the cross-metathesis with ethylene to be an equilibrium reaction. The turnover-number-limiting factor was found to be the stability of the metathesis catalyst.
- Schweitzer, Dirk,Snell, Kristi D.
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supporting information
p. 715 - 720
(2015/07/27)
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- PROCESS FOR PRODUCING (R)-3-HYDROXYBUTYL (R)-3-HYDROXYBUTYRATE
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A process for the production of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate comprising: i) contacting poly-(R)-3-hydroxybutyrate with an alcohol to transesterify the poly-(R)-3-hydroxybutyrate under transesterification conditions to produce an ester of (R)-3-hydroxybutyrate and the alcohol; ii) separating the product of step i) into a first and second portion and reducing the first portion of the (R) 3-hydroxybutyrate ester to form (R)-1,3-butanediol; and iii) contacting under transesterification conditions the (R)-1,3-butanediol from step ii) with the second portion of the transesterified ester to produce (R)-3-hydroxybutyl-(R)-hydroxybutanoate.
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Page/Page column 6; 7
(2014/09/29)
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- Manganese phthalocyanine immobilized on silica gel: Efficient and recyclable catalyst for single-step oxidative esterification of aldehydes with alcohols
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The functionalization of silica gel was carried out using 3-aminopropyltriethoxysilane as a reactive surface modifier followed by covalent grafting of novel tetrakis-(2-methoxy-4-formylphenoxy)phthalocyaninato manganese(III) acetate complex. The resulting inorganic-organic hybrid material was found to be a highly selective and recyclable catalyst for the single-step synthesis of esters. The catalyst was characterized by elemental analysis (CHN), diffuse reflectance UV-visible, 13C CPMAS and 29Si CPMAS NMR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area analysis, energy dispersive X-ray fluorescence (ED-XRF), Fourier-transform infrared (FT-IR) and atomic absorption spectroscopy (AAS) techniques, which demonstrates the covalent grafting of the complex onto functionalized silica gel. The catalytic performance of the novel inorganic-organic hybrid catalyst was evaluated in the direct oxidative esterification of aldehydes with alcohols, at ambient temperature, using hydrogen peroxide as an environment friendly oxidant. The hybrid catalyst presented up to 100% of substrate conversion with high turn-over numbers (TONs), up to 100% of selectivity toward the ester product, and can be recovered and reused for multiple cycles without appreciable loss in its catalytic activity.
- Sharma,Gulati, Shikha
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p. 291 - 303
(2012/10/30)
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- Radical mechanism in the elimination of 2-arylsulfinyl esters
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The mechanism of the dehydrosulfenylation of 2-arylsulfinyl esters was investigated. The reaction was found to follow a homolytic cleavage mechanism as verified by electrospray ionization tandem mass spectrometry and experimental work. Rearranged sulfoxides are obtained as byproduct during the elimination reaction.
- Latorre, Antonio,Lopez, Irakusne,Ramirez, Victoria,Rodriguez, Santiago,Izquierdo, Javier,Gonzalez, Florenci V.,Vicent, Cristian
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p. 5191 - 5197
(2012/07/27)
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- Synthesis and biological evaluation of 3-substituted-indolin-2-one derivatives containing chloropyrrole moieties
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Eighteen novel 3-substituted-indolin-2-ones containing chloropyrroles were synthesized and their biological activities were evaluated. The presence of a chlorine atom on the pyrrole ring was crucial to reduce cardiotoxicity. The presence of a 2-(ethylamino) ethylcarbamoyl group as a substituent at the C-4' position of the pyrrole enhanced the antitumor activities notably. IC 50 values as low as 0.32, 0.67, 1.19 and 1.22 μM were achieved against non-small cell lung cancer (A549), oral epithelial (KB), melanoma (K111) and large cell lung cancer cell lines (NCI-H460), respectively.
- Jin, Yun-Zhou,Fu, Da-Xu,Ma, Nan,Li, Zhan-Cheng,Liu, Quan-Hai,Xiao, Lin,Zhang, Rong-Hua
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experimental part
p. 9368 - 9385
(2012/01/05)
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- Conjugate addition - SNAr domino reaction for the synthesis of benzo- or pyridyl-fused lactams and sultams
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A versatile domino reaction that can be used for the synthesis of bicyclic benzo- or pyridyl-fused lactam and sultam derivatives is presented, enabling rapid synthesis of a variety of complex structures
- Norager, Niels Gron,Juhl, Karsten
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experimental part
p. 4273 - 4281
(2011/02/22)
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- Benzylidene/2-chlorobenzylidene hydrazides: Synthesis, antimicrobial activity, QSAR studies and antiviral evaluation
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A series of benzylidene hydrazides (1-20) was synthesized and tested, in vitro, for antibacterial, antifungal and antiviral activities. The microbial screening results indicated that compounds having chloro and nitro substituents were the most active ones. The antiviral evaluation depicted that compounds 9 and 19 were active against Vesicular stomatitis virus (VSV) in HeLa cell cultures. QSAR investigations indicated that the multi-target QSAR model was effective in describing the antimicrobial (antibacterial and antifungal) activity over the one-target QSAR models. Further the mt-QSAR model indicated that the topological parameters, second order molecular connectivity index (2χ) and third order Kier's alpha shape index (κα3) are effective in describing the antimicrobial activity of synthesized hydrazides.
- Kumar, Davinder,Judge, Vikramjeet,Narang, Rakesh,Sangwan, Sonia,De Clercq, Erik,Balzarini, Jan,Narasimhan, Balasubramanian
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experimental part
p. 2806 - 2816
(2010/08/20)
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- Kinetic resolution of 1,2-diols through highly site- and enantioselective catalytic silylation
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(Chemical Equation Presented) Resolved to silylate: A chiral silylation catalyst is used for kinetic resolution of three classes of acyclic 1,2-diols. The catalyst differentiates, with excellent precision, between the two hydroxy groups of a substrate. The majority of the diols, obtained in high enantiomeric purity, cannot be accessed with similar stereochemical purity through catalytic asymmetric dihydroxylation.
- Zhao, Yu,Mitra, Aurpon W.,Hoveyda, Amir H.,Snapper, Marc L.
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p. 8471 - 8474
(2008/09/18)
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- Process for preparing optically active 3-azidocarboxylic acid derivatives and 3-aminocarboxylic acid derivatives
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A process for enantioselectively preparing 3-azidocarboxylic acid derivatives comprises reacting 3-sulfonatocarboxylic acid derivatives with an alkali metal azide in a solvent selected from the group comprising certain carboxamides; a solvent mixture which comprises such carboxamides; a solvent mixture of water and a solvent miscible homogeneously with water; water with the proviso that the addition of a phase transfer catalyst is not used in the reaction in water; and DMSO. The resulting products are optionally reduced to 3-aminocarboxylic acid derivatives.
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Page/Page column 8-10
(2008/06/13)
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- Trans-esterification in dry media using ferric perchlorate adsorbed on silica gel
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Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic grade silica gel in the presence of ethyl acetate (to be used for trans-esterification) produces a supported reagent, Fe(ClO4)3(EtOAc)6/SiO2. This reagent, has been found effective for the rapid and high yield of esters via trans- esterification on grinding in the presence of alcohols/carboxylic acids using pestle and mortar in the solid state.
- Parmar, Anupama,Goyal, Rita,Kumar, Baldev,Kumar, Harish
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p. 139 - 143
(2007/10/03)
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- An efficient use of zeolite catalysts for esterification of carboxylic acids
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A mild and practical method (batch process) for the esterification of carboxylic acids with alcohols using zeolite catalysts in good to excellent yields is described. The esterification of phenylacetic acid with ethanol has also been carried out in very high yield using continuous flow fixed bed reactor.
- Gumaste, Vikas K.,Deshmukh,Bhawal
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p. 1174 - 1179
(2007/10/03)
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- Iron (III) perchlorate: A reagent for trans-esterification
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Iron (III) perchlorate has successfully been used for the trans-esterification of ethyl acetate with alcohols and acids.
- Kumar, Baldev,Kumar, Harish,Parmar, Anupama
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p. 292 - 293
(2007/10/02)
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- REACTIONS OF N-SILYLATED LACTAMS WITH α-BROMO CARBOXYLATES
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The reactions of N-trimethylsilyl lactams with α-bromo carboxylates proceeds in two directions: the N-alkylation of the lactams, and elimination with the formation of α,β-unsaturated carboxylic esters.The proportion between the two processes depends on the structure of the initial compounds.
- Orlova, N. A.,Shipov, A. G.,Baukov, Yu. I.
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p. 1877 - 1880
(2007/10/02)
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- A facile conversion of halides, alcohols and olefins to esters using iron(III) perchlorate
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A facile method has been developed for the esterification of halides/alcohols/olefins with carboxylic acids using iron(III) perchlorate.
- Kumar,Kumar,Parmar
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p. 1087 - 1094
(2007/10/02)
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- α-SUBSTITUIERTE PHOSPHONATE 50. Electrochemisch generierte Basen als Reagenz fuer die Horner-Reaktion
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The radical anion 2 (electrochemically generated base), formed by electrochemical reduction of azobenzene (probase), is suitable for deprotonation of differently substituted phosphonates 4. α-Phosphonyl aniones 5, obtained by such approach, reacted in situ with carbonyl compounds to give α-substituted olefines 6.Similar reaction took place with stilbene as probase.---Side reactions with the solvent were observed with less acidic phosphonates, e.g. 4h.
- Costisella, Burkhard,Gross, Hans,Jeroschewski, Paul,Keitel, Iris,Schwarz, Karl-Heinz
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p. 159 - 164
(2007/10/02)
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- ESTERIFICATION AT ROOM TEMPERATURE: A MIXING AFFAIR ONLY
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Carboxylic acids in absolute alcohols, on treatment with thionyl chloride at room temperature give good yields of corresponding esters.
- Kumar, Baldev,Verma, Raman
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p. 1359 - 1364
(2007/10/02)
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- OXIDATION OF ALCOHOLS BY TRANSITION METAL COMPLEXES-IV THE RHODIUM CATALYSED SYNTHESIS OF ESTERS FROM ALDEHYDES AND ALCOHOLS
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Both RhH(CO)PPh3)3 and a catalyst made in situ from RhCl3.3H2O, PPh3 and Na2CO3 catalyse the reaction of a range of aldehydes with simple primary alcohols to give esters together with alcohols formed by reduction of the aldehydes.The proportion of ester can be increased by adding an efficient hydrogen acceptor.The reaction can also be used to produce 5- and 7-membered lactones from aromatic dialdehydes.Propan-2-ol and the in situ catalyst reduce some aromatic aldehydes to the corresponding alcohols without concomitant ester formation.
- Grigg, Ronald,Mitchell, Thomas R. B.,Sutthivaiyakit, Somyote
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p. 4313 - 4319
(2007/10/02)
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