- Direct anodic (thio)acetalization of aldehydes with alcohols (thiols) under neutral conditions, and computational insight into the electrochemical formation of the acetals
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A versatile protocol for the production of acetals/thioacetals by means of direct electrochemical oxidation is developed here under neutral conditions, providing (thio)acetals with good functional group tolerance and a wide scope for both aldehydes and (thio)alcohols. DFT calculations reveal that direct electron transfer from the anode plays a key role in carbonyl activation during this acid free acetalization process.
- Liu, Caiyan,Shen, Yongli,Xiao, Zihui,Yang, Hui,Han, Xue,Yuan, Kedong,Ding, Yi
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p. 4030 - 4034
(2019/08/07)
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- Antimony(v) catalyzed acetalisation of aldehydes: An efficient, solvent-free, and recyclable process
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A highly selective, solvent-free process for the acetalisation of aldehydes was achieved by the use of a readily accessible antimony(v) catalyst which we previously prepared in our lab as a tetraarylstibonium triflate salt ([1][OTf]). High yields of the acetals were achieved in the presence of stoichimetric amounts of either triethoxymethane or triethoxysilane. It was found that triethoxymethane reactions required longer time to reach completion when compared to triethoxysilane reactions which were completed upon mixing of the reagents. The products can be easily separated from the catalyst by distillation which enabled further use of [1][OTf] in additional calytic reactions (up to 6 cycles). Moreover, [1]+ also catalyzed the deprotection of the acetals into their corresponding aldehydes using only water as a solvent.
- Ugarte, Renzo Arias,Hudnall, Todd W.
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p. 1990 - 1998
(2017/06/09)
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- Acetaldehyde as an ethanol derived bio-building block: An alternative to Guerbet chemistry
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In this work, we describe a highly selective poly-aldol condensation of acetaldehyde, which can readily be obtained via dehydrogenation of ethanol. The process operates under mild temperatures (100°C or less) using commercially available catalysts and exhibits excellent total carbon yield of C4+ products with good selectivity for C6 products. The products derived from the reactions described herein are shown to be candidate drop-in fuel replacements for compression ignition engines and precursors to valuable chemicals.
- Moore, Cameron M.,Staples, Orion,Jenkins, Rhodri W.,Brooks, Ty J.,Semelsberger, Troy A.,Sutton, Andrew D.
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supporting information
p. 169 - 174
(2017/01/24)
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- New palladium catalyst immobilized on epoxy resin: Synthesis, characterization and catalytic activity
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A new thiol-functionalized epoxy resin as a support for palladium(II) complexes has been synthesized in good yields. A palladium catalyst was 'heterogenized' by anchoring [PdCl2(PhCN)2] complexes to these thiol-functionalized polymers via ligand exchange reaction. These new palladium catalysts were tested in Mizoroki-Heck coupling and hydrogenation reactions. The activity of the complexes in terms of yield is comparable to that of homogeneous PdCl2(PhCN)2. The stability and a good recycling efficiency of these catalysts make them useful for prolonged use. The constant and good selectivity of the supported catalysts during recycling experiments indicate that they could be useful for practical application in many organic reactions. To characterize the heterogeneous complexes before and after use, X-ray photoelectron spectroscopy, infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray microscopy, atomic absorption spectroscopy and time-of-flight secondary ion mass spectrometry were applied. Density functional theory calculations were also used to better understand the structures of the obtained palladium complexes. Polythiourethanes contain three atoms, oxygen, nitrogen and sulfur, capable of coordinating to transition metals. We examined the possibility of intra- A nd intermolecular binding for both cis and trans palladium complexes.
- Sienkiewicz, Natalia,Strzelec, Krzysztof,Pospiech, Piotr,Cypryk, Marek,Szmechtyk, Tomasz
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- Synthesis of biodiesel without formation of free glycerol
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A new approach to the synthesis of biodiesel has been developed on the basis of alcoholysis of a triglyceride in combination with acetalization of glycerol with lower carbonyl compounds or acetals derived therefrom. A model synthesis of biodiesel not involving free glycerol has been accomplished using rapeseed oil and acid catalysts, as well as without a catalyst under generation of ethanol supercritical fluid; in the latter case, monoalkyl glycerol ethers are formed in addition to the expected cyclic ketals.
- Vol'eva,Belostotskaya,Komissarova,Koverzanova,Kurkovskaya,Usmanov,Gumerov
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p. 915 - 917
(2015/08/25)
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- Hexameric resorcinarene capsule is a bronsted acid: Investigation and application to synthesis and catalysis
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Molecular capsules have attracted interest as simple enzyme mimetics and several examples of catalytic transformations in water-soluble metal-ligand based systems have been reported. This is not the case for hydrogen-bond based molecular capsules, which in contrast can be employed in organic solvents. We describe herein our investigations of such a system: The resorcin[4]arene hexamer is one of the largest hydrogen bond-based self-assembled capsules and has been studied intensively due to its ready availability. We present evidence that the capsule acts as a reasonably strong Bronsted acid (pK a approximately 5.5-6). This finding explains the capsule's high affinity toward tertiary amines that are protonated and therefore encounter cation-π interactions inside the cavity. We were able to translate this finding into a first synthetic application: A highly substrate-selective Wittig reaction. We also report that this property renders the capsule an efficient enzyme-like catalyst for substrate selective diethyl acetal hydrolysis.
- Zhang, Qi,Tiefenbacher, Konrad
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supporting information
p. 16213 - 16219
(2013/11/19)
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- Model studies on the pattern of volatiles generated in mixtures of amino acids, lipid-oxidation-derived aldehydes, and glucose
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The development of flavor and browning in thermally treated foods results mainly from the Maillard reaction and lipid degradation but also from the interactions between both reaction pathways. To study these interactions, we analyzed the volatile compounds resulting from model reactions of lysine or glycine with aldehydes originating from lipid oxidation [hexanal, (E)-2-hexenal, or (2E,4E)-decadienal] in the presence and absence of glucose. The main reaction products identified in these model mixtures were carbonyl compounds, resulting essentially from amino-acid-catalyzed aldol condensation reactions. Several 2-alkylfurans were detected as well. Only a few azaheterocyclic compounds were identified, in particular 5-butyl-2-propylpyridine from (E)-2-hexenal model systems and 2-pentylpyridine from (2E,4E)-decadienal model reactions. Although few reaction products were found resulting from the condensation of an amino acid with a lipid-derived aldehyde, the amino acid plays an important role in catalyzing the degradation and further reaction of these carbonyl compounds. These results suggest that amino-acid-induced degradations and further reactions of lipid oxidation products may be of considerable importance in thermally processed foods.
- Adams, An,Kitryte, Vaida,Venskutonis, Rimantas,De Kimpe, Norbert
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experimental part
p. 1449 - 1456
(2011/10/05)
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- A non-noble amorphous Co-Fe-B catalyst highly selective in liquid phase hydrogenation of crotonaldehyde to crotyl alcohol
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A nanosized amorphous Co-Fe-B catalyst exhibited higher selectivity and yield to crotyl alcohol than noble Pt-based catalysts in the hydrogenation of crotonaldehyde and could be prepared by a facile chemical reduction method. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.
- Pei, Yan,Wang, Jianqiang,Fu, Qiang,Guo, Pingjun,Qiao, Minghua,Yan, Shirun,Fan, Kangnian
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p. 992 - 994
(2007/10/03)
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- Bronsted acidic ionic liquids as efficient and recyclable catalysts for protection of carbonyls to acetals and ketals under mild conditions
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A series of acidic ionic liquids have been used as efficient catalysts for the protection of various carbonyl compounds at room temperature. The features of mild conditions, satisfactory isolated yield, simple workup, and the recyclability of the catalyst were present in this process. Copyright Taylor & Francis, Inc.
- Du, Yuying,Tian, Fuli
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p. 2703 - 2708
(2007/10/03)
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- Sulfamic acid as a cost-effective and recyclable catalyst for protection of carbonyls to acetals and ketals under mild conditions
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An efficient H2NSO3H-catalyzed protection of various carbonyl compounds at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple workup, and the recyclability of the catalyst were represented in this process.
- Gong, Weizhong,Wang, Bo,Gu, Yanglong,Yan, Liang,Yang, Liming,Suo, Jishuan
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p. 4243 - 4247
(2007/10/03)
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- Method for producing enol ethers
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Enol ethers of the formula I where R1is an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radical which may carry further substituents which do not react with acetylenes or allenes, and the radicals R, independently of one another, are hydrogen or aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radicals, which may be bonded to one another to form a ring, and m is 0 or 1, are prepared by reacting an acetal or ketal of the formula II with an acetylene or allene of the formula III or IV where R and R1have the abovementioned meanings, in the gas phase at elevated temperatures in the presence of a zinc- or cadmium- and silicon- and oxygen-containing heterogeneous catalyst.
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- Solvent free protection of carbonyl group under microwave irradiation
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Protection of aldehydes and ketones as acetals or dioxolanes catalysed by PTSA or KSF clay was readily achieved from orthoformates, 1,2-ethanediol or 2,2-dimethyl-1,3-dioxolane without solvent under microwave irradiation.
- Perio, Bertrand,Dozias, Marie-Joelle,Jacquault, Patrick,Hamelin, Jack
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p. 7867 - 7870
(2007/10/03)
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- A short high yielding synthesis of the potent anti-VZV carbocyclic nucleoside analogue carba-BVDU
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A short high yielding synthesis of the potent anti-varicella-zoster virus (VZV) carbocyclic nucleoside analogue carba-BVDU 1 starting from aminodiol 2 is described. Reaction of 2 with acyl carbamate 3 and subsequent ring closure under acidic conditions afforded 5-ethyl-2'-deoxy-4'a-carbauridine 5. In situ acetylation of 5 afforded 3',5'-di-O-acetyl-5-ethyl-2'-deoxy-4'a-carbauridine 6 in 78% overall yield from 2. Radical bromination of 6 with either bromine or NBS and subsequent treatment with triethylamine gave an efficient conversion to 3',5'-di-O-acetyl-5-(E)-(2-bromovinyl)-2'-deoxy-4'a- carbauridine 7. Deacetylation of 7 afforded 1 in an overall 45-53% yield from 2.
- Wyatt,Anslow,Coomber,Cousins,Evans,Gilbert,Humber,Paternoster,Sollis,Tapolczay,Weingarten
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p. 2039 - 2049
(2007/10/02)
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- Synthesis of meso-13C and 15N labelled octaethylporphyrin and optimisation of the 'symmetrical' route to octaalkylporphyrins
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A simplified synthesis of octaalkylporphyrins from aldehydes is described and was used to prepare meso-13C and 15N labelled octaethylporphyrin.
- Rohrer,Ocampo,Callot
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p. 923 - 925
(2007/10/02)
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- Synthesis and cyanation of octaalkylporphyrins using electrochemical methods
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The total synthesis of octaalkylporphyrins (ethyl, buthyl, isopropyl) and the cyanation of the meso (methine bridge) positions have been achieved using electrochemical methods.The coupled products (diketals) from anodic oxidation of aldehydes enol ethers (or enamines) in methanol, on subsequent reaction with benzyl carbamate undergo cyclisation to N-carbobenzyloxypyrroles.Deprotection and reaction with formaldehyde afforded the corresponding porphyrins.Electrolysis of zinc-octaethylporphyrin in dimethylformamide in the presence of cyanide at various concentrations and potentials (+0.45 to 0.9 V/SCE) gave mono- to tetracyano-octaethylporphyrins which were fully caracterized.
- Callot, Henry J.,Louati, Abderrazak,Gross, Maurice
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p. 317 - 320
(2007/10/02)
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