- Combined experimental and computational studies of heterobimetallic Bi-Rh paddlewheel carboxylates as catalysts for metal carbenoid transformations
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(Chemical Equation Presented) The catalytic activity of heterobimetallic Bi-Rh paddlewheel carboxylate complexes has been evaluated for the first time in the context of metal carbenoid chemistry. The Bi-Rh carboxylate complexes were found to effectively catalyze both cyclopropanation reactions and C-H insertions as well as reactions involving ylide intermediates with similar selectivity profiles to analogous dirhodium complexes. The heterometallic complex BiRh(O2CCF3)3(O2CCH3) was found to be approximately 1600 times less reactive than its homometallic analogue Rh2(O2CCF3)3(O 2CCH3) toward the decomposition of methyl phenyldiazoacetate. The observed difference in reactivity is in good agreement with a computational model system where axial coordination to the second rhodium active site is considered for the dirhodium catalyst.
- Hansen, Jorn,Li, Bo,Dikarev, Evgeny,Autschbach, Jochen,Davies, Huw M. L.
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- Synthesis of Fatty Acetoacetates Under Microwave Irradiation Catalysed by Sulfamic Acid in a Solvent-Free System
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The 1,3-dicarbonyl compounds are important building blocks to obtain products with various biological activities and technological applications. In this work, we used a simple transesterification method to develop fatty acetoacetates in a solvent-free medium using a green catalyst, sulfamic acid (NH2SO3H), under microwave irradiation. The experimental results demonstrate good yields in a short reaction time (13?min), which makes this method an efficient approach to synthesize fatty acetoacetates from a wide range of saturated, unsaturated, and polyunsaturated long chain fatty alcohols, and ricinoleic derivatives. Experiments of recycling of the catalyst were performed and no decrease in catalytic activity of sulfamic acid was observed.
- Weber, Andressa C. H.,Batista, Thaís C.,Gon?alves, Bruno,Hack, Carolina R. L.,Porciuncula, Larissa M.,Treptow, Tamara G. M.,D’Oca, Caroline Da R. Montes,Russowsky, Dennis,D’Oca, Marcelo G. Montes
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- Ag-Cu nanoparticles as efficient catalysts for transesterification of β-keto esters under acid/base-free conditions
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Transesterification of β-keto esters and alcohols are traditionally catalyzed by acid or basic catalysts. However, these traditional catalysts do not always meet the requirements of modern synthetic chemistry which need to be highly efficient, selective, and environmentally friendly. In this work, Ag-Cu metal sites were first introduced as transesterification catalysts. The effect of the support, Ag:Cu molar ratio, and reaction conditions were investigated. The Ag-Cu metal sites were proved to be active in the β-ketoester transesterification with various alcohols, having yields comparable to the conventional acid- or base-catalysts.
- Yue, Hongmei,Yu, Hao,Liu, Sheng,Xu, Chunli
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p. 19041 - 19051
(2016/03/01)
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- Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters
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The electronic effects of tetranuclear zinc cluster catalysts on transesterification were investigated by changing the carboxylate ligands in the clusters. High catalyst activity crucially depended on the balance between Lewis acidity and Br?nsted basicity of the catalyst; this was consistent with the dual activation of both the electrophile and nucleophile by the cooperative zinc centers. In addition, tetranuclear zinc cluster catalysts achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality, in which a newly developed pentafluoropropionate-bridged zinc cluster and 4-dimethylaminopyridine additive greatly improved the reactivity of sterically congested α- and α,α-disubstituted β-keto esters. Lewis versus Br?nsted: High catalyst activity of zinc clusters on transesterification crucially depend on a balance between Lewis acidity and Br?nsted basicity of the catalyst. Zinc clusters, including a newly developed pentafluoropropionate-bridged zinc cluster, achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality (see figure).
- Agura, Kazushi,Hayashi, Yukiko,Wada, Mari,Nakatake, Daiki,Mashima, Kazushi,Ohshima, Takashi
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supporting information
p. 1548 - 1554
(2016/06/01)
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- Nano CuFe2O4: An efficient, magnetically separable catalyst for transesterification of β-ketoesters
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The preparation of a variety of β-ketoesters was achieved in high yields from methyl acetoacetate under neutral conditions through the utilization of magnetic CuFe2O4 nanoparticles as catalyst. Recycling of the catalyst was performed up to eight times without significant loss in activity. The catalyst was characterized using XRD, XPS, SEM and TEM techniques.
- Gohain, Mukut,Kumar, Vinod,Van Tonder, Johannes H.,Swart, Hendrik C.,Ntwaeaborwa, Odireleng M.,Bezuidenhoudt, Barend C. B.
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p. 18972 - 18976
(2015/03/04)
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- Efficient transesterification of ethyl acetoacetate with higher alcohols without catalysts
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The transesterification of ethyl acetoacetate (EtOAcac) without the use of catalysts is shown for primary, secondary and tertiary alcohols. The use of molecular sieves, which are used to shift the equilibrium, allows the synthesis of products in high yields and acceptable reaction times, which are on a par with those for transesterification processes using catalysts. The kinetics of the transesterification of EtOAcac with tert-amyl alcohol is studied.
- Koval,Dzyuba,Ilnitska,Pekhnyo
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p. 1645 - 1647
(2008/09/19)
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- 3-Nitrobenzeneboronic acid as an efficient and environmentally benign catalyst for the selective transesterification of β-keto esters
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An efficient and high-yielding procedure for the selective transesterification of various β-keto esters using 3-nitrobenzeneboronic acid as a catalyst in an environmentally acceptable process is described. Georg Thieme Verlag Stuttgart.
- Tale,Sagar,Santan,Adude
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p. 415 - 418
(2007/10/03)
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- Ionic liquid-regulated sulfamic acid: Chemoselective catalyst for the transesterification of β-ketoesters
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1-Propyl-3-methylimidazolium chloride ([C3MIm]Cl) ionic liquid and sulfamic acid (NH2SO3H), as a synergetic catalytic medium, were used for the transesterification of acetoacetate with alcohols of different structures. It shows the good ability for the chemoselective transesterificatin of β-ketoesters and maintains its catalytic activity in the reuse.
- Bo, Wang,Ming, Yang Li,Shuan, Suo Ji
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p. 5037 - 5039
(2007/10/03)
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- Method for preparing chiral diphosphines
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The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.
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- Zn mediated transesterification of β-ketoesters
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Methyl/ethyl β-ketoesters when treated with various alcohols along with catalytic amount of Zn dust in refluxing toluene undergo smooth transesterification.
- Bandgar,Sadavarte,Uppalla
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- Metal salts as novel catalysts for efficient transesterification of β-ketoesters
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Ethyl/methyl β-ketoesters with alcohols in presence of catalytic amount of anhydrous metal salts (FeSO4, CuSO4) undergo smooth transesterification.
- Bandgar,Sadavarte,Uppalla
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p. 2063 - 2066
(2007/10/03)
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- Asymmetric hydrogenation method of a ketonic compound and derivative
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The present invention relates to a process for the asymmetric hydrogenation of a ketonic compound and derivative. The invention relates to the use of optically active metal complexes as catalysts for the asymmetric hydrogenation of a ketonic compound and derivative. The process for the asymmetric hydrogenation of a ketonic compound and derivative is characterized in that the asymmetric hydrogenation of said compound is carried out in the presence of an effective amount of a metal complex comprising as ligand an optically active diphosphine corresponding to one of the following formulae: STR1
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- Novel 2-amino-1,4-dihydropyridine calcium antagonists. I. Synthesis and antihypertensive effects of 2-amino-1,4-dihydropyridine derivatives having nitroxyalkoxycarbonyl groups at 3- and/or 5-position
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Novel 2-amino-1,4-dihydropyridine derivatives, which contain nitroxy-alkoxycarbonyl groups at the 3- and/or 5-position, were synthesized and their pharmaceutical effect was evaluated in spontaneously hypertensive rats. The structure-activity relationships are discussed in terms of potency, onset-rapidity, and duration of antihypertensive activity. Remarkably prolonged duration of antihypertensive action was observed when a tertiary amino group was introduced on either side of an ester chain.
- Kobayashi,Inoue,Kita,Yoshiya,Nishino,Oizumi,Kimura
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p. 788 - 796
(2007/10/02)
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- Novel 2-amino-1,4-dihydropyridine calcium antagonists. II. Synthesis and antihypertensive effects of 2-amino-1,4-dihydropyridine derivatives having N,N-dialkylaminoalkoxycarbonyl groups at 3- and/or 5-positions
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Novel 2-amino-1,4-dihydropyridine derivatives I, which contain N,N-dialkylaminoalkoxycarbonyl groups at the 3- and/or 5-position, were synthesized and their antihypertensive effects were evaluated in spontaneously hypertensive rats. Remarkably prolonged duration of antihypertensive action was observed when a tertiary amino group was introduced into either the 3- or 5-ester side-chain of the 1,4-dihydropyridine ring. In particular, the compounds containing cyclic amino moieties at the 3-position showed greater potency than those with acyclic amino moieties. Chemical modification studies indicated that the two ester side-chains of 1,4-dihydropyridine at the 3- and 5-position might function in a different manner in relation to the antihypertensive activities. 3-(1-Benzhydrylazetidin-3-yl) 5-isopropyl 2-amino-1,4-dihydro-6-methyl-4-(3-nitrophenyl)-3,5-pyridine-dicarboxyl ate, I-43 (CS-905), exhibited potent and long-lasting antihypertensive effects with gradual onset of action, and is a promising candidate as an antihypertensive drug.
- Kobayashi,Inoue,Nishino,Fujihara,Oizumi,Kimura
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p. 797 - 817
(2007/10/02)
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- Cyclicondensation of alkylacetoacetates with 1,3,5-trinitrobenzene and base
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The condensation reaction between alkylacetoacetates and 1,3,5-trinitrobenzene has been carried out in the presence of triethylamine and diethylamine as the catalysing bases.The reaction kinetics with different alkylacetoacetates is studied and linear steric energy correlation is established.The resultant condensation product has been characterized by elemental analysis, IR, UV/visible and 1H NMR spectral studies.
- Radha, N.,Kamala, V.
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p. 399 - 403
(2007/10/03)
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