- Selective Ring Transformations of 1-imidazoles
-
The title compounds underwent CsF- or BF3*Et2O-induced selective ring-opening reactions leading to the cyclobutanone derivatives or γ,δ-unsaturated carboxylic acids, respectively.
- Hirao, Toshikazu,Misu, Daisuke,Agawa, Toshio
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-
Read Online
- Exploring the physicochemical and antiproliferative properties of biaryl-linked [13]-macrodilactones
-
A macrocyclic motif fosters productive protein-small molecule interactions. There are numerous examples of both natural product and designed, synthetic macrocycles that modulate the immune system, slow microbial infection, or kill eukaryotic cells. Reported here are the synthesis, physicochemical characterization, and antiproliferative activity of a group of [13]-macrodilactones decorated with a pendant biaryl moiety. Biaryl analogs were prepared by Suzuki reactions conducted on a common intermediate that contained a bromophenyl unit alpha to one of the carbonyls of the [13]-macrodilactone. Principal component analysis placed the new compounds in physicochemical context relative to a variety of pharmaceuticals and natural products. Modest inhibition of proliferation was observed in ASZ cells, a murine basal cell carcinoma line. This work underscores the value of an approach toward the identification of bioactive compounds that places the evaluation of physicochemical parameters early in the search process.
- Chen, Chengsheng,Bosko, Cristin,McGeough, Catherine P.,McLean, Ryan,Zaino, Angela M.,Kyle Hadden,Peczuh, Mark W.
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- Direct and Selective Synthesis of Adipic and Other Dicarboxylic Acids by Palladium-Catalyzed Carbonylation of Allylic Alcohols
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A general and direct synthesis of dicarboxylic acids including industrially important adipic acid by palladium-catalyzed dicarbonylation of allylic alcohol is reported. Specifically, the combination of PdCl2 and a bisphosphine ligand (HeMaRaphos) promotes two different carbonylation reactions with high activity and excellent selectivity.
- Beller, Matthias,Ge, Yao,Huang, Weiheng,Jackstell, Ralf,Liu, Jiawang,Neumann, Helfried,Yang, Ji
-
supporting information
p. 20394 - 20398
(2020/09/21)
-
- Nitrogen-fixing of ultrasmall Pd-based bimetallic nanoclusters on carbon supports
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Synthesis of supported Pd-based bimetallic catalysts is of great importance in the heterogeneous catalysis field owing to their optimal geometric and electronic effects. Downsizing active metals to ultrasmall nanocluster (2-reduction at 400–500 °C. Through the nitrogen-fixing strategy, we prepare 9 sub-2 nm Pd-based bimetallic nanocluster catalysts by conventional impregnation process. The prepared supported bimetallic Pd-Pb nanocluster catalyst exhibit a high turnover frequency of 1092 h?1 for the semihydrogenation of phenylacetylene under a mild condition (30 °C, 5 bar H2), along with a high selectivity of >93% to styrene, demonstrating the alloying and small-size effects in the bimetallic nanocluster catalysts.
- Chen, Ping,Liang, Hai-Wei,Shen, Shan-Cheng,Wang, Lei,Xu, Shi-Long,Yin, Peng,Zhang, Le-Le
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p. 297 - 304
(2020/07/03)
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- Direct Carbon Isotope Exchange through Decarboxylative Carboxylation
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A two-step degradation-reconstruction approach to the carbon-14 radiolabeling of alkyl carboxylic acids is presented. Simple activation via redox-active ester formation was followed by nickel-mediated decarboxylative carboxylation to afford a range of complex compounds with ample isotopic incorporations for drug metabolism and pharmacokinetic studies. The practicality and operational simplicity of the protocol were demonstrated by its use in an industrial carbon-14 radiolabeling setting.
- Kingston, Cian,Wallace, Michael A.,Allentoff, Alban J.,Degruyter, Justine N.,Chen, Jason S.,Gong, Sharon X.,Bonacorsi, Samuel,Baran, Phil S.
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supporting information
p. 774 - 779
(2019/01/14)
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- Bidentate auxiliary-directed alkenyl C-H allylation: Via exo-palladacycles: Synthesis of branched 1,4-dienes
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An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-Alkenes and allyl carbonates. With the use of an 8-Aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-Assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
- Shen, Cong,Lu, Xiunan,Zhang, Jian,Ding, Liyuan,Sun, Yaling,Zhong, Guofu
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supporting information
p. 13582 - 13585
(2019/11/14)
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- A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids
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Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-Aliphatic, benzylic, hetero-Aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-Type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.
- Knaus, Tanja,Tseliou, Vasilis,Humphreys, Luke D.,Scrutton, Nigel S.,Mutti, Francesco G.
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supporting information
p. 3931 - 3943
(2018/09/11)
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- A CATALYST FOR THE CARBONYLATION OF ALKENES
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The present application relates to a metal complex of Formula (I) and a catalyst composition for the carbonylation of alkenes comprising the metal complex, wherein the metal is a group 10 element such as palladium, platinum or nickel, and the complex comprises a bidentate phosphine ligand. The present invention also relates to a process for the preparation of a dicarboxylic acid or ester thereof from an alkenoic acid or ester thereof, or a process for the preparation of a carboxylic acid or ester thereof from an alkene or alkenoic acid with high selectivity and activity using said metal complex or catalyst composition. The present application also relates to a method of preparing Nylon 6-6 comprising the step of copolymerising adipic acid with hexamethylenediamine.
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Page/Page column 44
(2017/09/02)
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- PROCESS FOR PREPARING MONO AND DICARBOXYLIC ACIDS
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The present application relates to a process for preparing a dicarboxylic acid or dicarboxylic ester according to general formula (IV) R1OOC-(CH2)m-CH2CH2-(CH2)y-COOR4 (IV), comprising the steps of subjecting alkenoic acid or alkenoate of formula (II) R1OOC-(CH2)m-CH=CH-(CH2)x-H (II) to a metathesis reaction in the presence of a metathesis catalyst to form a longer-chain alkenoic acid or alkenoate of formula (III) R1OOC-(CH2)m-CH=CH-(CH2)y-H (III) where xa carbonylation reaction in the presence of a carbonylation catalyst and a carbonyl source to form said compound of Formula (IV). Alternative embodiments provide: a process for preparing an alkenoic acid or alkenoate comprising the step of subjecting a lactone to a ring opening reaction; a process for preparing a monocarboxylic acid or monocarboxylic ester according to general formula (XI) R1OOC-(CH2)m-CH2-(CH2)y-CH3 (XI) by subjecting an alkenoic acid or alkenoate to alkene hydrogenation; and a process for preparing an alcohol or ether according to general formula (XII) R1O-CH2-(CH2)m-CH2-(CH2)y-CH3 (XII) by subjecting an alkenoic acid or alkenoate to hydrogenation. The use of the respective mono/dicarboxylic acid, mono/dicarboxylic ester, ethers or alcohols in a variety of applications is also disclosed.
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Page/Page column 33
(2018/02/03)
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- Chiral hypervalent iodine(III) catalyst promotes highly enantioselective sulfonyl-and phosphoryl-oxylactonizations
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An efficient enantioselective hypervalent iodine promoted oxylactonization of 4-pentenoic acids has been achieved using stoichiometric or a catalytic amount of chiral aryl-λ3-iodane. This reaction provides straightforward access to a wide range of sulfonyloxy-and phosphoryloxy-γ-butyrolactones in respectable yields with moderate to excellent enantioselectivities.
- Gelis, Coralie,Dumoulin, Audrey,Bekkaye, Mathieu,Neuville, Luc,Masson, Géraldine
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supporting information
p. 278 - 281
(2017/11/27)
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- Pd(II)-catalyzed allylic C-H amination for the preparation of 1,2- and 1,3-cyclic ureas
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A general synthesis of 1,2- and 1,3-cyclic ureas is accomplished by intramolecular allylic C-H amination employing Pd(TFA)2/bis-sulfoxide as a catalyst. By careful modification of substrates and catalyst, a variety of 1,2-cyclic ureas are accessible from not previously employed terminal olefins substituted in allylic or vinylic positions. Furthermore, MS4A is found to be an effective additive for the synthesis of 1,3-cyclic ureas in good yields and excellent diastereoselectivities.
- Nishikawa, Yasuhiro,Kimura, Seikou,Kato, Yuri,Yamazaki, Natsuka,Hara, Osamu
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supporting information
p. 888 - 891
(2015/03/18)
-
- Concise Enantioselective Synthesis of Naturally Active (S)-3-Hydroxypiperidine
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A short and efficient enantioselective synthesis of natural product (S)-3-hydroxypiperidine has been achieved starting from commercially available raw materials employing two catalytic routes: (i) cocatalyzed hydrolytic kinetic resolution (HKR) of racemic methyl-3-(oxiran-2-yl)propanoate; (ii) proline-catalyzed α-aminooxylation followed by Horner-Wardsworth-Emmons olefination in high enantiomeric purity (97% ee) and high overall yield (38%). (Chemical Equation Presented).
- Dey, Soumen,Karabal, Pratibha U.,Sudalai, Arumugam
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supporting information
p. 1559 - 1565
(2015/06/02)
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- CuX2-mediated oxybromination/aminochlorination of unsaturated amides: Synthesis of iminolactones and lactams
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We report herein a CuX2-mediated halocyclization of γ,δ-unsaturated amides for the synthesis of functionalized iminolactones and lactams respectively under mild reaction conditions. Mechanism studies indicated that N-attack cyclization was via a radical route while oxycyclization was via a nucleophilic attack on the activated CC bond.
- Zhang, Zhi-Qiang,Liu, Feng
-
supporting information
p. 6690 - 6693
(2015/06/25)
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- PROCESS FOR THE OXIDATION OF ORGANIC CARBONYL COMPOUNDS
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A process for the oxidation of an organic carbonyl compound comprising reacting the organic carbonyl compound, optionally in the presence of a solvent, with hydrogen peroxide in the presence of a catalyst comprising a tin-containing zeolitic material having an MWW-type framework structure.
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Page/Page column 37
(2014/05/24)
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- Process for the Oxidation of Organic Carbonyl Compounds
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A process for the oxidation of an organic carbonyl compound comprising reacting the organic carbonyl compound, optionally in the presence of a solvent, with hydrogen peroxide in the presence of a catalyst comprising a tin-containing zeolitic material having an MWW-type framework structure.
- -
-
Paragraph 0216-0217
(2014/05/20)
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- Gold I-catalyzed highly diastereo- and enantioselective alkyne oxidation/cyclopropanation of 1,6-enynes
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A highly enantioselective oxidative cyclo-propanation of 1,6-enynes catalyzed by cationic AuI/ chiral phophoramidite complexes is presented. The new method provides convenient access to densely functionalized bicyclo[3.1.0]hexanes bearing three contiguous quaternary and tertiary stereogenic centers with high enantioselectivity (up to e.r. 98:2). Control experiments suggest that the quinoline moiety of the b-gold vinyloxyquinolinium intermediate in the reaction plays an important role in promoting good enantiose-lectivity through a transitional auxiliary effect in the transition state.
- Qian, Deyun,Hu, Haoxiang,Liu, Feng,Tang, Bin,Ye, Weimin,Wang, Yidong,Zhang, Junliang
-
supporting information
p. 13751 - 13755
(2015/02/19)
-
- Metal-free, hydroacylation of CC and NN bonds via aerobic C-H activation of aldehydes, and reaction of the products thereof
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In this report, a thorough evaluation of the use of aerobically initiated, metal-free hydroacylation of various CC and NN acceptor molecules with a wide range of aldehydes is presented. The aerobic-activation conditions that have been developed are in sharp contrast to previous conditions for hydroacylation, which tend to use transition metals, peroxides that require thermal or photochemical degradation, or N-heterocyclic carbenes. The mildness of the conditions enables a number of reactions involving sensitive reaction partners and, perhaps most significantly, allows for α-functionalised chiral aldehydes to undergo radical-based hydroacylation with complete retention of optical purity. We also demonstrate how the resulting hydroacylation products can be transformed into other useful intermediates, such as γ-keto- sulfonamides, sultams, sultones, cyclic N-sulfonyl imines and amides.
- Chudasama, Vijay,Akhbar, Ahmed R.,Bahou, Karim A.,Fitzmaurice, Richard J.,Caddick, Stephen
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p. 7301 - 7317
(2013/10/22)
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- Method for Preparative Fragmenting Using an Inductively Heated Heating Medium
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A method for performing a chemical reaction to produce a target compound by heating a reaction medium containing a reactant in a reactor, the reaction medium being brought into contact with a solid heating medium that can be heated by electromagnetic induction and that is located inside the reactor and surrounded by the reaction medium and the heating medium being heated by electromagnetic induction with the aid of an inductor, causing the target compound to form, and the target compound being separated from the heating medium, wherein the target compound has a lower molar mass than the reactant and at least one covalent bond of the reactant is cleaved in order to produce said target compound from the reactant.
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Page/Page column 5-6
(2012/09/05)
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- PROCESS FOR PREPARING 4-PENTENOIC ACID
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The present invention relates to a process for preparing 4-pentenoic acid, at least comprising the oxidation of a mixture (G) comprising 4-pentenal, 3-methyl-2-butanone and cyclopentene oxide, and to the use of a mixture (G) comprising 4-pentenal, 3-methyl-2-butanone and cyclopentene oxide for preparing 4-pentenoic acid. In the context of the present invention, the mixture (G) is preferably obtained as a by-product of the oxidation of cyclopentene to cyclopentanone by means of dinitrogen monoxide.
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Page/Page column 15
(2011/04/14)
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- Inductive heating with magnetic materials inside flow reactors
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Superparamagnetic nanoparticles coated with silica gel or alternatively steel beads are new fixed-bed materials for flow reactors that efficiently heat reaction mixtures in an inductive field under flow conditions. The scope and limitations of these novel heating materials are investigated in comparison with conventional and microwave heating. The results suggest that inductive heating can be compared to microwave heating with respect to rate acceleration. It is also demonstrated that a very large diversity of different reactions can be performed under flow conditions by using inductively heated flow reactors. These include transfer hydrogenations, heterocyclic condensations, pericyclic reactions, organometallic reactions, multicomponent reactions, reductive cyclizations, homogeneous and heterogeneous transition-metal catalysis. Silica-coated iron oxide nanoparticles are stable under many chemical conditions and the silica shell could be utilized for further functionalization with Pd nanoparticles, rendering catalytically active heatable iron oxide particles.
- Ceylan, Sascha,Coutable, Ludovic,Wegner, Jens,Kirschning, Andreas
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supporting information; experimental part
p. 1884 - 1893
(2011/03/21)
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- Design and synthesis of readily degradable acyloxysilane dendrimers
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Two types of dendrimers with AB2 branching, one with acyloxysilanes at the branching position (V type) and the other at the non-branching position (Y type), were synthesized using hydrosilylation with chlorosilanes followed by heterofunctional condensation with olefin-functional carboxylic acids, and examined as readily degradable template materials. The V type dendrimer was much more susceptible to ligand redistribution with chlorosilanes during preparation, whereas the Y type was less. The acyloxysilane linkages in these dendrimers could be cleaved readily by alcoholysis or hydrolysis on demand, making for suitable templates.
- Downing, Christopher M.,Missaghi, Michael N.,Kung, Mayfair C.,Kung, Harold H.
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experimental part
p. 7502 - 7509
(2011/10/12)
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- Method for Carrying Out Chemical Reactions with the Aid of an Inductively Heated Heating Medium
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The invention relates to a method for carrying out a chemical reaction for producing a target compound by heating in a reactor a reaction medium containing at least one first reactant, such that a chemical bond inside the first reactant or between the first and a second reactant is formed or modified. The reaction medium is brought into contact with a solid heating medium that can be warmed by electromagnetic induction and that is inside the reactor and is surrounded by the reaction medium. Said heating medium is heated by electromagnetic induction with the aid of an inductor and the target bond is formed from the first reactant or from the first and a second reactant and said target bond is separated from the heating medium.
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Page/Page column 11
(2010/10/19)
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- Polyanhydride networks from thiol-ene polymerizations
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Thiol-ene photopolymerization was used in the synthesis of elastomeric polyanhydrides. Side reactions involving the addition of thiol to the anhydride were observed but take place at a much slower rate than photoinitiated thiol-ene polymerization. The thermomechanical properties, including the glass transition temperature (Tg) as well as tensile and compressive modulus, of the cross-linked material were studied using dynamic mechanical analysis. T g values ranged from -15 to approximately -50 °C and were dependent on the degree of cross-linking. The Young's and compressive modulus measurements confirm that these types of networks are a soft rubber-like material at room and body temperature and become softer as the cross-linking density is reduced. The hydrophobicity/hydrophilicity of these networks was analyzed by water contact angle measurements. The polyanhydrides were moderately hydrophobic, with water contact angle averages ranging from 82° to 92°. This hydrophobicity, coupled with the high reactivity of the anhydride groups, results in the material eroding via the surface erosion mechanism.
- Rutherglen, Broden G.,McBath, Ryan A.,Huang, Yu Ling,Shipp, Devon A.
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experimental part
p. 10297 - 10303
(2011/08/03)
-
- Catalytic Conversion of Cellulose to Liquid Hydrocarbon Fuels by Progressive Removal of Oxygen to Facilitate Separation Processes and Achieve High Selectivities
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Described is a method to make liquid chemicals, such as functional intermediates, solvents, and liquid fuels from biomass-derived cellulose. The method is cascading; the product stream from an upstream reaction can be used as the feedstock in the next downstream reaction. The method includes the steps of deconstructing cellulose to yield a product mixture comprising levulinic acid and formic acid, converting the levulinic acid to γ-valerolactone, and converting the γ-valerolactone to pentanoic acid. Alternatively, the γ-valerolactone can be converted to a mixture of n-butenes. The pentanoic acid so formed can be further reacted to yield a host of valuable products. For example, the pentanoic acid can be decarboxylated yield 1-butene or ketonized to yield 5-nonanone. The 5-nonanone can be hydrodeoxygenated to yield nonane, or 5-nonanone can be reduced to yield 5-nonanol. The 5-nonanol can be dehydrated to yield nonene, which can be dimerized to yield a mixture of C9 and C18 olefins, which can be hydrogenated to yield a mixture of alkanes. Alternatively, the nonene may be isomerized to yield a mixture of branched olefins, which can be hydrogenated to yield a mixture of branched alkanes. The mixture of n-butenes formed from γ-valerolactone can also be subjected to isomerization and oligomerization to yield olefins in the gasoline, jet and Diesel fuel ranges.
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Page/Page column 10-11
(2010/12/31)
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- Catalytic aerobic oxidation of allylic alcohols to carbonyl compounds under mild conditions
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A new catalytic aerobic oxidation of alcohols to aldehydes under green conditions was developed (room temperature and pressure, water solution, open vials). The water-soluble platinum(II) tetrasulfophthalocyanine (PtPcS) catalyst showed the best selectivity for carbonyl derivatives, and in particular for α,β-unsaturated alcohols; the reactions are slow.
- Tonucci, Lucia,Nicastro, Marco,D'Alessandro, Nicola,Bressan, Mario,D'Ambrosio, Primiano,Morvillo, Antonino
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experimental part
p. 816 - 820
(2010/04/23)
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- MACROCYCLIC HEPATITIS C SERINE PROTEASE INHIBITORS AND USES THEREFOR
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Macrocyclic inhibitors of Hepatitis C protease are provided, the inhibitors including a boronic acid or ester group, a macrocyclic ring of about 13 to 25 atoms including at least two amide linkages, a proline-analogous group, and a connecting segment joining moieties on either side of the proline-analogous group. Methods of making the HCV protease-inhibitory compounds, methods of using the compounds, formulations of the compounds, and pharmaceutical combinations including the compounds, are provided.
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Page/Page column 69-70
(2008/12/06)
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- Synthesis of unsaturated dibasic acid esters from five-, six-, and seven-membered cycloalkanones
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A new route to diesters of symmetrical octene-, decene-, and dodecenedioic acids was proposed. The ratio of the cis/trans-isomers was 1:4. The synthesis involved oxidative splitting of five-, six-, and seven-membered cycloalkanones with hydrogen peroxide into the corresponding ω-alkenoic acids followed by esterification and metathesis over Re2O7/B 2O3-Al2O3-SnMe4.
- Starostin,Furman,Ignatenko,Barkova,Nikishin
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p. 2016 - 2019
(2007/10/03)
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- PROCESS FOR THE CARBONYLATION OF A CONJUGATED DIENE
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A process for the carbonylation of a conjugated diene, comprising reacting the conjugated diene with carbon monoxide and a co-reactant having a mobile hydrogen atom in the presence of a catalyst system including: (a) a source of palladium; and (b) a bidentate diphosphine ligand of formula (II): R1R2 > p1R3m-R-R4n-p2 5R6 wherein p1 and p2 represent phosphorus atoms; R1, R2, R5, and R6 independently represent the same or different optionally substituted organic radical containing a tertiary carbon atom through which each radical is linked to the phosphorus atom; R3 and R4 independently represent the same or different optionally substituted methylene groups; R represents an organic group comprising the bivalent bridging group C1-C2 through which R is connected to R3 and R4; m and n independently represent a natural number in the range of from 0 to 4, wherein the rotation about the bond between the carbon atoms C1 and C2 of the bridging group is restricted a temperature in the range of from 0 °C to 250 °C, and wherein the dihedral angle between the plane occupied by the three atom sequence composed of C1, C2 and the atom directly bonded to C1 in the direction of p1, and the plane occupied by the three atom sequence C1, C2 and the atom directly bonded to C2 in the direction of p2, is in the range of from 0 to 120°; and (c) a source of an anion.
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-
- Method for preparing carboxylic acids by palladium carbonylation
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The present invention relates to a process for the preparation of β- or γ-unsaturated or saturated carboxylic acids. It relates more particularly to the hydroxycarbonylation of an organic compound comprising a conjugated unsaturation, such as butadiene, by the action of carbon monoxide and water in the presence of a palladium-based catalyst. The carboxylic acids thus obtained are preferably pentenoic acids. According to the invention, the reaction medium after the end of the hydroxycarbonylation stage is treated with hydrogen to reduce the palladium present in the 2+ oxidation state to palladium in the zero oxidation state and the precipitated palladium is recovered.
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-
-
- By using a palladium amidocarbonyl manufacturing method
-
The present invention relates to a process for the preparation of beta- or gamma-unsaturated or saturated carboxylic acids. It relates more particularly to the hydroxycarbonylation of an organic compound comprising a conjugated unsaturation, such as butadiene, by the action of carbon monoxide and water in the presence of a palladium-based catalyst. The carboxylic acids thus obtained are preferably pentenoic acids. According to the invention, the reaction medium after the end of the hydroxycarbonylation stage is treated with hydrogen to reduce the palladium present in the 2+ oxidation state to palladium in the zero oxidation state and the precipitated palladium is recovered.
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-
-
- Self-Protection: The Advantage of Radical Oligomeric Mixtures in Organic Synthesis
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Atom-transfer radical oligomers of allyl iodoacetates were converted to 4-pentenoic acids upon treatment with zinc. Reactions of the radical oligomers of various ω-alkenyl iodoacetates with Grignard reagents afforded the corresponding substituted tetrahydrofuran derivatives. These results indicated that radical oligomeric mixtures not only serve as versatile intermediates in organic synthesis, but also exhibit unique advantages in that the oligomeric mixtures are self-protected and the deoligomerization functions as the simultaneous deprotection.
- Yu, Hui,Li, Chaozhong
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p. 142 - 145
(2007/10/03)
-
- Microwave assisted hydrolysis of Meldrum's acid derivatives and decarboxylation of derived malonic acids
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Microwave induced hydrolysis of alkyl Medrum's acids and decarboxylation of derived malonic acids using poly-4-vinylpyridine as a catalyst gives high yields of carboxylic acids in a short time.
- Helavi,Solabannavar,Desai,Mane
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p. 174 - 175
(2007/10/03)
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- Simple, efficient, and selective deprotection of phenolic methoxymethyl ethers using silica-supported sodium hydrogen sulfate as a heterogeneous catalyst
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A simple and efficient method has been developed for chemoselective deprotection of phenolic methoxymethyl (MOM) ethers using silica-supported sodium hydrogen sulfate as a heterogeneous catalyst. The conversions occur at room temperature, and the yields of the deprotected phenols are excellent. The method is suitable for deprotection of phenolic MOM ethers of multifunctional bioactive natural products.
- Ramesh,Ravindranath,Das, Biswanath
-
p. 7101 - 7103
(2007/10/03)
-
- (P(C6H5)3)CpRu+-catalyzed deprotection of allyl carboxylic esters
-
A new and efficient catalytic method for deprotection of allyl carboxylic esters using a transition metal complex is reported. The reaction proceeds with a high substrate/catalyst ratio and without use of additional nucleophiles, giving the deprotected carboxylic acid in a quantitative yield. A variety of substrates, including the multifunctional amino acids and peptides, are also usable. The new method is more efficient, safe, and operationally simple in comparison to the conventional palladium-catalyzed method.
- Kitamura, Masato,Tanaka, Shinji,Yoshimura, Masahiro
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p. 4975 - 4977
(2007/10/03)
-
- Asymmetric photolysis of 2-phenylcycloalkanones with circularly polarized light: A kinetic model for magnetic field effects
-
Magnetic field effects (MFE) on asymmetric photolysis involving a biradical intermediate have been investigated on a kinetic model where an intersystem crossing (ISC) of the intermediate is taken into account. Changes in the enantiomeric excesses (ee) of chiral substances with circularly polarized light (CPL) irradiation have been simulated, and the necessary conditions for observing the MFE were obtained. The asymmetric photolysis of racemic 2-phenylcycloalkanones (2-PCAs) with CPL has been carried out in both the presence and absence of a magnetic field. Since the anisotropy g factors of 2-PCAs are considerably large, the CPL-induced ee are achieved to a few percent after 90% decomposition though the MFE are not observed. The photolysis mechanism of 2-PCAs in an air-saturated solution has been also clarified. Triplet acyl-benzyl biradicals, formed via photochemical α-cleavage of 2-PCAs, react with O2 dissolved in the solution and result in the formation of acetophenone and alkenoic acids. The bimolecular reactions are diffusion-controlled and the rates are comparable to those of ISC to the singlet biradicals for all 2-PCAs. The recombination yields of the biradicals are sufficiently large. However, the biradical ISC rate shows little magnetic field dependence, which explains the absence of the MFE in this asymmetric photolysis.
- Kohtani, Shigeru,Sugiyama, Masahide,Fujiwara, Yoshihisa,Tanimoto, Yoshifumi,Nakagaki, Ryoichi
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p. 1223 - 1233
(2007/10/03)
-
- Free radical allyl transfers utilizing soluble non-cross-linked polystyrene and carbohydrate scaffold supports
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(matrix presented) Free radical allylations were studied using (1) soluble non-cross-linked polystyrene supports, (2) carbohydrate scaffolds, and (3) a combination of both synthetic motifs. Allylations on these custom designer supports provide easily purified products, free of tin residues. A D-xylose carbohydrate scaffold bearing a bromoester was used for a diastereoselective allyl tin transfer thermally at 80 °C and with Lewis acids. This is the first example of a diastereoselective radical reaction directed by a removable polymer-supported carbohydrate auxiliary.
- Enholm, Eric J.,Gallagher, Maria E.,Jiang, Shujun,Batson, William A.
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p. 3355 - 3357
(2007/10/03)
-
- Silylation of 1-Alkynes with Chlorosilanes Promoted by Zinc: Preparation of Alkynylsilanes in a Single Step
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The direct silylation of 1-alkynes with chlorosilanes smoothly takes place in the presence of zinc powder in acetonitrile, giving good yields of alkynylsilanes.The reactions are tolerant of a wide range of functionalities such as carboxylic acid, ester, alcohol, and chlorine in the 1-alkynes.
- Sugita, Hikaru,Hatanaka, Yasuo,Hiyama, Tamejiro
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p. 2769 - 2772
(2007/10/02)
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- Scope and Mechanism of Deprotection of Carboxylic Esters by Bis(tributyltin) Oxide
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Methyl and ethyl esters of aliphatic and aromatic carboxylic acids as well as benzyl carboxylates, thiol esters and double esters such as (pivaloyloxy)methyl carboxylates have been successfully cleaved with bis(tributyltin) oxide to give the free carboxylic acids in good yields.The reaction is carried out in aprotic solvents under essentially neutral conditions and thus this method can serve as an ideal procedure for the cleavages of esters with other functional groups and/or protecting groups acid and/or base sensitive.We demonstrated that the reaction displays a high level of chemoselectivity between methyl and ethyl esters versus tert-butyl esters and γ-lactones.Bis(tributyltin) oxide is also a highly efficient reagent for the cleavage of acetates of primary and secondary alcohols and phenols.The limitations we found in the use of this reagent include the lack of cleavage of esters sterically hindered around the carboxyl carbon and the carbinol group (i.e., esters of tertiary alcohols) and in carboxylic esters that contain a fluoroalkyl substituent.A resonable mechanistic explanation is discussed to account for the reaction pathway of the acyloxygen cleavage of (-)-(1R)-menthyl acetate.
- Salomon, Claudio J.,Mata, Ernesto G.,Mascaretti, Oreste A.
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p. 7259 - 7266
(2007/10/02)
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- Preparation of 5-methylbutyrolactone
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5-Methylbutyrolactone is prepared by a process in which a pentenoic ester of the formula I where X is CH2 =CH--CH2 --CH2 --, CH3 --CH=CH--CH2 -- or CH3 --CH2 --CH=CH-- and R is alkyl, cycloalkyl, aralkyl or aryl, or a mixture of these esters is reacted with water at from 50° to 350° C. in the presence or absence of a diluent a) over a zeolite and/or phosphate catalyst or b) in the presence of from 0.01 to 0.25 mole of a sulfonic acid, a Lewis acid and/or a non-oxidizing mineral acid per mole of pentenoic ester or over from 0.1 to 40% by weight, based on the pentenoic ester, of a strongly acidic ion exchanger as a catalyst in a first stage, or the pentenoic ester of the formula I, where X and R have the stated meanings, is hydrolyzed in a first stage with the aid of a strongly acidic ion exchanger as a catalyst to give the pentenoic acid of the formula I, where R is hydrogen, and the resulting pentenoic acid is subjected to cyclization in a second stage in the presence of from 0.005 to 0.1 mole of a sulfonic acid, a Lewis acid or a non-oxidizing mineral acid per mole of pentenoic acid or over from 0.1 to 20% by weight, based on the pentenoic acid, of a strongly acidic ion exchanger at from 50° to 350° C.
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- Photochemical Reaction of 2-Acyloxy-1-methoxycarbonylcyclohexenes: an Efficient Aliphatic Photo-Fries Rearrangement and a Novel 1,5-Aroyl Migration
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Upon irradiation 2-acyloxy-1-methoxycarbonylcyclohexenes readily undergo photo-Fries rearrangement to give 2-acyl-2-methoxycarbonylcyclohexanones in good yields and among them 2-aroyloxy-1-methoxycarbonylcyclohexenes also undergo a novel 1,5-aroyl migration according to irradiation conditions to give 4-aroyl-2-methoxycarbonylcyclohexanones, which result from 1,3-aroyl migration following photo-Fries rearrangement.
- Seto, Hideharu,Kosemura, Hajime,Fujimoto, Yasuo
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p. 908 - 910
(2007/10/02)
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- Dispiro-1,2,4-trioxolanes by Ozonolysis of Cycloalkylidenecycloalkanes on Polyethylene
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Ozonolyses of symmetrical (1b-d) and of unsymmetrical cycloalkylidenecycloalkanes (8a, b) afforded the dispiro-1,2,4-trioxolanes 4b-d and 9a, b, respectively.Their thermal decompositions gave mixtures of the cyclic ketones (3) and lactones (6).Photolysis afforded in addition to 3 and 6 the cyclic anhydrides 13, which are isomeric with the corresponding disoiro-1,2,4-trioxolanes.
- Griesbaum, Karl,Krieger-Beck, Petra,Beck, Johannes
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p. 391 - 396
(2007/10/02)
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- The Thermal Decomposition of Diazirines: 3-(3-Methyldiazirin-3-yl)propan-1-ol and 3-(3-Methyldiazirin-3-yl)propanoic Acid
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The thermolyses of 3-(3-methyldiazirin-3-yl)propan-1-ol (1) and 3-(3-methyldiazirin-3-yl)propanoic acid (2) have been studied in solution over the temperature range 96-125 deg C.The reactions are unimolecular and fit linear Arrhenius plots with k(1)=1013.85+/-0.69exp-1/RT>s-1 and k(2)=1012.38+/-0.43exp-1/RT>s-1.The major products are the alkenes derived from the corresponding carbenes MeC2.CH2CH2CH2OH (3) and MeC2.CH2CH2CO2H (4).The new rate data, taken together with previous work, tend to confirm that diazirine thermolysis involves ring opening to a "complex" followed either by nitrogen loss or by isomerization to a diazo compound.Whereas (1) gives no product of closure onto oxygen, the acid (2) affords about 5percent γ-valerolactone.
- Stevens, Ian D. R.,Liu, Michael T. H.,Soundararajan, N.,Paike, N.
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p. 661 - 667
(2007/10/02)
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- Diverse reaction courses in the controlled carbometalation of heterocumulenes with zirconium-diene complexes and molecular structures of carbon dioxide, isocyanate, and ketene 1:1 and 1:2 inserted compounds
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The carbometalation of various heterocumulenes (carbon dioxide, isocyanates, ketenes) was systematically investigated by using a series of zirconium-diene complexes of the type ZrL2(s-cis-diene) and ZrL2(s-trans-diene) (L = η5-C5H5, η5-C5Me5; diene = butadiene, isoprene) to clarify the essential factor(s) in determining the regio- and stereochemistry of the products. The mode of CO2 insertion reaction changes drastically depending upon the bulkiness of the auxiliary ligand and the geometry (s-cis, s-trans) of ligated dienes. The 1:1 reactions of the ZrL2(butadiene) complex with t-C4H9NCO, C6H5NCO, or C6H5(CH3)CCO yield Zr-O bound complexes having (σ,syn-η3-allyl)metal structures, while the isoprene derivatives always give seven-membered-ring (Z)-oxametallacyclic isomers. The use of a bulky ketene, Ph2CCO, resulted in an abnormal addition that provides a unique six-membered oxametallacycle. (C5Me5)2Zr[C4H6C(=O)O] belongs to the monoclinic space group P21/n with a = 8.816 (1) A?, b = 28.916 (3) A?, c = 9.388 (1) A?, β = 108.89 (1)°, and Z = 4. (C5Me5)2Zr[C4H 6C(=N-t-Bu)O] crystallizes in space group Pbca with a = 14.458 (2) A?, b = 16.677 (3) A?, c = 22.446 (3) A?, and Z = 8. A 1:2 adduct, (C5Me5)2Zr[OC(=NC6H 5)C4H6C(=NC6H5)O], crystallizes in space group P212121 with a = 9.082 (2) A?, b = 17.275 (3) A?, c = 22.301 (4) A?, and Z = 4. The six-membered oxametallacycle (C5Me5)2Zr[CH=C(CH3)CH(CH 3)C(=C(C6H5)2)O] crystallizes in space group P21/c with a = 12.282 (3) A?, b = 16.082 (3) A?, c = 17.981 (4) A?, β = 108.56 (3)°, and Z = 4. Thus, the configuration of the β-carbon (sp2, sp3) in the product together with the steric bulk of substituents on C(2) and/or C(3) of the ligated diene is found to be crucial in determining the reaction courses and the regio- and stereochemistry of the products.
- Yasuda, Hajime,Okamoto, Takuji,Matsuoka, Yoshihiko,Nakamura, Akira,Kai, Yasushi,Kanehisa, Nobuko,Kasai, Nobutami
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p. 1139 - 1152
(2008/10/08)
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- THE BARRIER FOR 1,2 HYDROGEN SHIFT IN DIALKYL CARBENES
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The products from the thermolysis of 4-diazirinopentanoic acid (2) allow the estimate of an experimental value for the Ea = 1.1 +/- 1 kcal.mol-1 for the barrier height for 1,2 H shift in dialkyl carbenes.
- Stevens, Ian D. R.,Liu, Michael T. H.,Soundararajan, N.,Paike, N.
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p. 481 - 484
(2007/10/02)
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- A Facile Method for Synthesis of Three Carbon-Homologated Carboxylic Acid by Regioselective Ring-opening of β-Propiolactones with Organocopper Reagents
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Organocopper reagents, such as diorganocuprates, organocopper-tributylphosphine, and Grignard reagents in the presence of a copper (I) salt, reacted with β-propiolactones by regioselective β-carbon-oxygen fission to give 3-substituted propionic acids.Among these three kinds of organocopper reagents, diorganocuprate, especially halomagnesium cuprate gave the highest yields of the acids, which was remarkably observed in the ring-opening of sterically hindered β-propiolactones such as β-methyl- and α,β-dimethyl-β-propiolactones and also in the reactions using the organocopper reagents with vinyl and allyl substituents.The ring-opening of β-propiolactone was confirmed to proceed by SN2 pathway with predominant inversion of configuration of the β-carbon by using the reaction of cis-α,β-dimethyl-β-propiolactone with di-tert-butylcuprate to afford syn-2,3,4,4-tetramethylpentanoic acid.
- Kawashima, Masatoshi,Sato, Toshio,Fujisawa, Tamotsu
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p. 403 - 412
(2007/10/02)
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- Vibrational Spectra of Potassium 4-Pentenoate and Potassium 5-Hexenoate and Conformational Change on Micellization
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Potassium 4-pentenoate (P4P) and potassium 5-hexenoate (P5H) have been synthesized and their infrared and Raman spectra were measured in the crystalline state and aqueous solutions.The two bands of the crystalline P4P at 623-625 and 558-560 cm-1 were assigned to the characteristic bands of skew and cis forms about the C-C single bond nearest to the C=C double bond, respectively.The intensity of the 623-625 cm-1 band in the infrared spectra increases at -170 deg C, compared to that of the 558-560 cm-1 band.For P5H the intensity of the 640-643 cm-1 band characteristic of skew intercreases at low temperature.From these observations it was concluded that the skew form in the crystalline P4P and P5H is stabilized at low temperature.On the basis of these observations and X-ray diffraction and Raman studies of unsaturated fatty acids by other workers, the following assumptions were made; the infrared bands of the crystalline P4P increasing in the intensity at -170 deg C and the corresponding Raman bands arise from the TS form, and those of P5H are due to the TTS form.On these assumptions, normal mode analysis was made for possible rotational isomers.The calculated results succesfully explain the vibrational bands of P4P and P5H.The Raman spectra of P4P anf P5H in aqueous solutions were measured at various concentrations.At higher concentration the TS form of P4P and the TTS form of P5H were found to be stabilized.The inflection in the plots of the relative Raman peak heights in the 1000-800 cm-1 region vs. the inverse concentrations is clearly observed.These observations show that micelle formation brings about the conformational change.
- Tsukamoto, Koji,Ohshima, Kunihiro,Taga, Keijiro,Okabayashi, Hirofumi,Matsuura, Hiroatsu
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p. 789 - 800
(2007/10/02)
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