- Directing the Cleavage of Ester C-O Bonds by Controlling the Hydrogen Availability on the Surface of Coprecipitated Pd/Fe3O4
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The ready availability of esters from natural sources makes them promising substrates for the sustainable production of key intermediates of the chemical industry. In this context, methods to selectively cleave the alkoxy or ester C-O bond to obtain either alkane+acid or alcohol+aldehyde were investigated. Using Pd/Fe3O4(r) [(r)=reduced] as the catalyst of choice and either 2-propanol - as indirect H source - or molecular hydrogen - as ample H source - the hydrogen coverage on the surface of the catalyst was controlled. This enabled selective cleavage of either the alkoxy C-O bond or the ester C-O bond in aromatic esters as shown for the hydrogenolysis of 2-phenylethylacetate as model substrate. Noteworthy, hydrogenation of the aromatic ring was not observed. Thus, an exceptionally high chemoselectivity of Pd/Fe3O4(r) to hydrogenolysis of the ester group is combined with the option to readily direct the regioselectivity.
- Cozzula, Daniela,Vinci, Alessandro,Mauriello, Francesco,Pietropaolo, Rosario,Müller, Thomas E.
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p. 1515 - 1522
(2016/05/02)
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- Oxidative "reverse-esterification" of ethanol with benzyl/alkyl alcohols or aldehydes catalyzed by supported rhodium nanoparticles
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A very unusual role of polystyrene stabilized rhodium (Rh@PS) nanoparticles as a supported catalyst is described for "reverse-esterification" of ethanol with benzyl/alkyl alcohols or aldehydes. Faster and selective oxidation of ethanol to acetaldehyde and H2 under Rh@PS catalyzed conditions which restricted further oxidation of benzyl/alkyl alcohols and their in situ reaction gave the corresponding acetate esters following the dehydrogenative-coupling approach. A hitherto redox dehydrogenative-coupling of ethanol and aldehydes has also been explored for the same acetate ester synthesis under Rh@PS catalyzed conditions.
- Guha, Nitul Ranjan,Sharma, Saurabh,Bhattacherjee, Dhananjay,Thakur, Vandna,Bharti, Richa,Reddy, C. Bal,Das, Pralay
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supporting information
p. 1206 - 1211
(2016/03/09)
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- Polystyrene trimethyl ammonium chloride impregnated Rh(0) (Rh@PMe3NCl) as a catalyst and methylating agent for esterification of alcohols through selective oxidation of methanol
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Rhodium(0) nanoparticle (NP)-impregnated polystyrene trimethyl ammonium chloride (PMe3NCl) resin (Rh@PMe3NCl) under basic conditions acts as a cross-dehydrogenative coupling-methylating (CDCM) agent for the selective oxidation of methanol and its in situ reaction with benzyl/alkyl alcohols allowing methyl group transfer for acetate ester synthesis in a tandem approach. The redox property of methanol which restricts the oxidation of benzyl/alkyl alcohols for product formation is critically investigated.
- Guha, Nitul Ranjan,Bhattacherjee, Dhananjay,Das, Pralay
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p. 2575 - 2580
(2015/06/30)
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- In situ generated Ph3P(OAc)2as a novel reagent for the efficient acetylation of alcohols and thiols at room temperature
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Ph3P, Br2, and ammonium acetate are used for the in situ generation of Ph3P(OAc)2, which was characterized by different NMR techniques. The Ph3P(OAc)2generated was used as a novel and efficient reagent for the acetylation of alcohols and thiols in acetonitrile at room temperature under homogeneous conditions. This reaction was also performed under heterogeneous conditions using 1,3,2,4- diazadiphosphetidine as an easily prepared, stable, and heterogeneous P(III) compound.
- Iranpoor, Nasser,Firouzabadi, Habib,Elham, Etemadi Davan
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p. 1813 - 1816
(2013/04/24)
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- L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate (supported on silica gel) as a new and efficient catalyst for acylation of alcohols, phenols and amines under solvent-free conditions
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In the present work, L-pyrrolidine-2-carboxylic acid-4-hydrogen sulfate, supported on silica gel was prepared and characterized by Mass spectroscopy, 1H NMR, 13CNMR, FT IR and elemental analysis (CHN) methods. This heterogenized catalyst can be used as an efficient catalyst for the acylation of alcohols, phenols, and amines with acetic anhydride under mild and solvent-free conditions. Simple work-up, stability of the catalyst, nontoxicity and good to high yields are the advantages of this work.
- Hajjami, Maryam,Ghorbani-Choghamarani, Arash,Khani, Zahra
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p. 324 - 329
(2013/07/26)
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- Lithium trifluoromethanesulfonate (LiOTf) as a recyclable catalyst for highly efficient acetylation of alcohols and diacetylation of aldehydes under mild and neutral reaction conditions
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A variety of alcohols and aldehydes were reacted with acetic anhydride at room temperature in the presence of a catalytic amount of lithium triflate (LiOTf) to produce the corresponding esters and 1,1-diacetates, respectively, in good to excellent yields under essentially neutral reaction conditions. Sensitive functional groups such as PhCO2-, OMe, and OTBDMS ethers survived intact under the described reaction conditions.
- Karimi, Babak,Maleki, Jafar
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p. 4951 - 4954
(2007/10/03)
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- Effects of Substrate Structure on Lipase-Catalyzed Transesterification of ω-Substituted 1-Alkanols in Organic Solvents.
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Lipase-catalyzed transesterification of ω-phenyl-1-alkanols with vinyl acetate in organic solvents have been investigated.Benzyl alcohol is the most reactive substrate among those studied.It is proposed that a lipase from Pseudomonas cepacia (PCL) has a domain to attract an aromatic moiety of a substrate.
- Nakamura, Kaoru,Kawasaki, Masashi,Ohno, Atsuyoshi
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p. 3053 - 3056
(2007/10/02)
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- Insecticidal cyclopropane carboxylic acid derivatives with 3-unsaturated-side chain
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Novel isomers and mixtures thereof of cyclopropane carboxylic acid derivatives with a 3-unsaturated side chain of the formula STR1 The double bond having Z or E geometry and having insecticidal and nematocidal activity as well as plant and animal acaricidal activity.
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- Phenyl Effects in Radical Additions to Alkenes
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Reactions of cyclohexylmercuric salts 4 with NaBH4 in the presence of alkenes 8 yield products 10.The main step of the reaction sequence, the addition of a cyclohexyl radical (7) to alkene 8, can be measured using a competition technique.The data show that styrene reacts 30 - 40 times faster than expected by the ?p--value.This phenyl effect decreases in going from monosubstituted alkenes 8 to disubstituted alkenes 3, 2 and 1 because the steric hindrance of a coplanar orientation of the ?-system increases in the same order.
- Giese, Bernd,Kretzschmar, Gerhard
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p. 3267 - 3270
(2007/10/02)
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