cas 815-57-6, 3-METHYL-2,4-PENTANEDIONE | Articles data

Articles about 815-57-6Total 46 be found

Article title
Article abstract
Author
Journal number and time
Download

Ag-Catalyzed Insertion of Alkynyl Carbenes into C-C Bonds of β-Ketocarbonyls: A Formal C(sp2) Insertion
Here we report a silver-catalyzed alkynyl carbene insertion into β-ketocarbonyls using alkynyl N-nosylhydrazones as alkynyl carbene precursors, which provides access to trisubstituted allenyl ketones. This reaction represents the first example of an alkynyl carbene insertion into a C-C σ bond, affording products homologated with an sp2 carbon center. The products are useful substrates for further transformations. Experimental investigations and theoretical calculations suggest the reaction proceeds through a stepwise enol cyclopropanation/retro-aldol pathway.
Ning, Yongquan,Song, Qingmin,Sivaguru, Paramasivam,Wu, Lizuo,Anderson, Edward A.,Bi, Xihe
supporting information
p. 631 - 636
(2022/01/20)

Synthesis and Thermal Behavior of Heteroleptic γ-Substituted Acetylacetonate-Alkoxides of Titanium
A series of heteroleptic titanium derivatives of general formula [Ti(OiPr)2(R-acac)2] with acetylacetonate ligands modified in the internal (γ- or 3-) position by different substituents (R=OAc, NO2, Me, Et, Cl, Br) has been synthesized and completely characterized by liquid multinuclear NMR and FTIR. The influence of the nature of the group on the thermal stability of the different complexes was studied by thermogravimetric analysis (TGA) and gave the following decreasing stability ranking: H22°-acac radical, which triggers the decomposition.
Bijou, Diane,Cornier, Thibaut,Mishra, Shashank,Merzoud, Lynda,Chermette, Henry,Jeanneau, Erwann,Maudez, William,Benvenuti, Giacomo,Daniele, Stéphane
supporting information
p. 1976 - 1983
(2021/05/07)

Preparation of pyridine derivatives from the corresponding 5-acetal-1-carbonyl compounds by acid promoted cyclization
The synthesis of four alkylpyridine derivatives from 5-acetal-1-carbonyl compounds via the one-pot, acid-promoted cyclization of oxime intermediates is described. In addition, a dihydroxypyridine and pyridinium salt were also synthesized. The pyridine formation step was not affected by the stereochemistry of the precursors used.
Konno, Hiroyuki,Mihara, Hiromichi,Watanabe, Yuki
p. 1314 - 1329
(2021/07/19)

Cassis and Green Tea: Spontaneous Release of Natural Aroma Compounds from β-Alkylthioalkanones
In depth headspace analysis of the slow degradation of β-alkylthioalkanones in ambient air led to the discovery of a novel δ-cleavage pathway, by which β-mercaptoketones are released. Since β-mercaptoketones are potent natural aroma compounds occurring in many fruits, herbs and flowers, the discovery of an enzyme-independent molecular precursor for this class of high-impact molecules is of practical importance. Moreover, the formation of β-diketones and aldehydes by concomitant oxidation at the α-sulfur-position enhances the versatility of this class of aroma precursors. A mechanistic model is proposed which suggests that the oxidative degradation occurs through a novel Pummerer-type rearrangement of initially formed persulfoxides.
B?ttig, Sarah,Bochet, Christian G.,Egger, Timothy,Flachsmann, Felix,Gey, Olga
(2021/10/19)

Scalable Synthesis of Esp and Rhodium(II) Carboxylates from Acetylacetone and RhCl3· xH2O
Rhodium(II) carboxylates are privileged catalysts for the most challenging carbene-, nitrene-, and oxo-transfer reactions. In this work, we address the strategic challenges of current organic and inorganic synthesis methods to access these rhodium(II) complexes through an oxidative rearrangement strategy and a reductive ligation reaction. These studies illustrate the multiple benefits of oxidative rearrangement in the process-scale synthesis of congested carboxylates over nitrile anion alkylation reactions, and the impressive effect of inorganic additives in the reductive ligation of rhodium(III) salts.
Martínez-Castro, Elisa,Mendoza, Abraham,Suárez-Pantiga, Samuel
supporting information
p. 1207 - 1212
(2020/07/15)

Nickel-catalyzed intramolecular desymmetrization addition of aryl halides to 1,3-diketones
A nickel-catalyzed intramolecular addition of aryl halides to 1,3-diketones was first developed. This desymmetrization reaction afforded polycyclic products bearing two tetrasubstituted centers with excellent diastereoselectivities and high yields. Moderate enantioselectivities were achieved in the presence of a chiral ligand. This transformation has great potential for the synthesis of polycyclic compounds including spiro[4,4,3,0] compounds. This journal is
Xu, Tao,Zhou, Pan
supporting information
p. 8194 - 8197
(2020/08/17)

ONE-STEP, FAST, 18F-19F ISOTOPIC EXCHANGE RADIOLABELING OF DIFLUORO-DIOXABORININS AND USE OF SUCH COMPOUNDS IN TREATMENT
A compound according to Formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, wherein X1 and X2 are each independently 18F or 19F; R1 and R2 are each independently alkyl, amine, perfluoroalkyl, alkenyl, alkynyl, aryl, or aralkenyl; and R3 is H, halo, alkyl, alkyl ester, alkenyl, alkynyl, aryl, or aralkenyl; or wherein: R1 and R3 or R2 and R3 join to form a 6-membered cycloalkyl or heterocyclyl; or R1 and R3, R2 and R3, or R1, R2, and R3 join to form a substituted or unsubstituted polycyclic ring, wherein the polycyclic ring comprises fused cycloalkyl, heterocycloalkyl, aryl, or heteroaryl rings.
-
Paragraph 0019; 0202-0203

(2019/12/15)

Synthesis and spectrophotometry study of the acid-base properties of nitro-substituted 5-phenyl-β-octaalkylporphines
10,15-Dinitro-5-phenyl-2,3,7,8,12,13,17,18-octamethylporphine, 10,15,20-trinitro-5-phenyl-2,3,7,8,12,13,17,18-octamethylporphine, and 10,15,20-trinitro-5-(4-nitrophenyl)-2,3,7,8,12,13,17,18-octamethylporphine were synthesized and identified by electronic absorption, IR, and 1Н NMR spectroscopy. The acid–base properties of the synthesized compounds were studied by spectrophotometric titration in HClO4–acetonitrile and 1,8-diazabicyclo[5.4.0]undec-7-ene–acetonitrile systems at 298 K. Parameters of the electronic absorption spectra and concentration ranges of existence of the mono- and diprotonated, as well as mono- and dideprotonated forms of the corresponding ligands and the acid and base dissociation constants of the latter were determined. Comparative analysis of the effect of nitro groups on the reactivity of the synthesized compounds was performed.
Ivanova, Yu. B.,Plotnikova,Semeikin,Lyubimova,Mamardashvili, N. Zh.
p. 1742 - 1751
(2017/09/25)

Synthesis, electrochemical, structural and theoretical study of new derivatives of O[sbnd]B[sbnd]N and O[sbnd]B[sbnd]O heterocycles
Three new oxazaborine and two boron diketonate derivatives containing different structural motifs were synthesized and studied using NMR, electrochemistry (CV, RDV, and dc-polarography), UV–Vis spectra and X-ray structure analysis. The experimental data were correlated with quantum chemical calculations. The main attention was focused on determination of the first oxidation and the first reduction potentials, their relationship to the calculated HOMO and LUMO energies and to their UV–Vis spectra. The electrochemical data reflect the structure–redox properties relationship depending on location of oxidation and reduction center.
Mikysek, Tomá?,Kvapilová, Hana,Dou?ová, Hana,Josefík, Franti?ek,?im?nek, Petr,R??i?ková, Zdeňka,Ludvík, Ji?í
p. 465 - 472
(2016/12/02)

TRIFLUOROACETIC ACID MAGNESIUM SOL SOLUTION
PROBLEM TO BE SOLVED: To provide a trifluoroacetic acid magnesium sol having an ultrasmall particle size. SOLUTION: The present invention makes it possible to provide a trifluoroacetic acid magnesium sol solution having an ultrasmall particle size by making a reaction occur between magnesium diethoxide and trifluoroacetic acid, in the presence of α-substituted β-diketone as a stabilizer, in an organic solvent having a specific Hansen parameter. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
-
Paragraph 0040-0041

(2017/12/06)

Systematic Engineering of Single Substitution in Zirconium Metal-Organic Frameworks toward High-Performance Catalysis
Zirconium-based metal-organic frameworks (Zr-MOFs) exhibit great structural tunability and outstanding chemical stability, rendering them promising candidates for a wide range of practical applications. In this work, we synthesized a series of isostructural PCN-224 analogues functionalized by ethyl, bromo, chloro, and fluoro groups on the porphyrin unit, which allowed us to explicitly study the effects of electron-donating and electron-withdrawing substituents on catalytic performance in MOFs. Owing to the different electronic properties of ethyl, bromo, chloro, and fluoro substitutes, the molecular-level control over the chemical environment surrounding a catalytic center could be readily achieved in our MOFs. To investigate the effects of these substitutes on catalytic activity and selectivity, the oxidation of 3-methylpentane to corresponding alcohols and ketones was utilized as a model reaction. Within these five analogues of PCN-224, an extremely high turnover number of 7680 and turnover frequency of 10 240 h-1 was achieved by simply altering the substitutes on porphyrin rings. Moreover, a remarkable 99% selectivity of the tertiary alcohol over the five other possible by-products are realized. We demonstrate that this strategy can be used to efficiently screen a suitable peripheral environment around catalytic cores in MOFs for catalysis.
Huang, Ning,Yuan, Shuai,Drake, Hannah,Yang, Xinyu,Pang, Jiandong,Qin, Junsheng,Li, Jialuo,Zhang, Yingmu,Wang, Qi,Jiang, Donglin,Zhou, Hong-Cai
supporting information
p. 18590 - 18597
(2017/12/15)

Method for preparing 2-methyl-1,3-dicarbonyl derivative
The invention discloses a method for preparing a 2-methyl-1,3-dicarbonyl derivative. A 1,3-dicarbonyl derivative serves as an initiator, raw materials are easy to obtain, and a great variety of raw materials are available. The product obtained through the method has high type diversity and can be used directly or used for other further reactions. Besides, only organic peroxides and a catalytic amount of inorganic copper salt are used, so that cost is low. According to the method, a reaction is conducted in air, reaction conditions are mild, pollution is small, reaction time is short, the yield of the target product is high, reaction operation and aftertreatment are easy, and the method is suitable for industrial production.
-
Paragraph 0039

(2016/10/08)

The Goldilocks principle in action: Synthesis and structural characterization of a novel {Cu4(μ3-OH)4} cubane stabilized by monodentate ligands
A {Cu4(μ3-OH)4} compound, where four copper(ii) and four μ3-bridging oxygen atoms occupy alternate corners of a slightly distorted cube, has been prepared and structurally characterized. This species, formulated as [Cu4(μ3-OH) 4(Htmpz)8](ClO4)4·1.5Et 2O (Htmpz = 3,4,5-1H-trimethyl pyrazole), can be classified as belonging to type I Cu4O4 cubane complexes, and is better described as two CuII-(μ-OH)2-CuII units held together by four long Cu-O bonds. The central distorted cubane core is stabilized by neutral monodentate ligands (Htmpz) and perchlorate anions, as demonstrated by single-crystal X-ray structure analysis. The title compound was obtained by hydrolysis of a dinuclear methoxo-bridged species, [Cu(μ-OCH 3)(Htmpz)2]2(ClO4)2, which was prepared by reaction of [Cu(Htmpz)4(ClO4) 2] with methanol. All these reactions represent a nice example of the Goldilocks principle in action in coordination chemistry, since each single actor (solvent, counteranion, and ligand) has the just right electronic, steric or coordinative properties which determine the fate of the final products.
Ardizzoia, G. Attilio,Brenna, Stefano,Durini, Sara,Therrien, Bruno,Trentin, Ivan
supporting information
p. 12265 - 12273
(2013/09/02)

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies
The first photocycloadditions of aromatic and aliphatic aldehydes to methylated isoxazoles are reported. The reactions lead solely to the exo-adducts with high regio- and diastereoselectivities. Ring methylation of the isoxazole substrates is crucial for high conversions and product stability. The 6-arylated bicyclic oxetanes 9a-9c were characterized by X-ray structure analyses and showed the highest thermal stabilities. All oxetanes formed from isoxazoles were highly acid-sensitive and also thermally unstable. Cleavage to the original substrates is dominant and the isoxazole derived oxetanes show type T photochromism.
Griesbeck, Axel G.,Franke, Marco,Neudoerfl, Joerg,Kotaka, Hidehiro
experimental part
p. 127 - 134
(2011/05/16)

Convenient synthesis of 2-pyridyl thioglycosides
A reported method for preparation of a new class of pyridine thioglycosides via reaction of pyridine-2(1H)-thiones with 2,3,4-tri-O-acetyl-α-D-xylo- and -β-D-arabinopyranosyl bromides has been studied.
Elgemeie, Galal,Eltamny, Elsayed,Elgawad, Ibraheim,Mahmoud, Nashwa
scheme or table
p. 473 - 475
(2009/08/15)

Synthesis of valuable chiral intermediates by isolated ketoreductases: Application in the synthesis of α-alkyl-β-hydroxy ketones and 1,3-diols
Regio- and stereoselective reductions of α-substituted 1,3-diketones to the corresponding β-keto alcohols or 1,3-diols by using commercially available ketoreductases (KREDs) are described. A number of α-monoalkyl- or dialkyl-substituted symmetrical as well as non-symmetrical diketones were reduced in high optical purities and chemical yields, in one or two enzymatic reduction steps. In most cases, two or even three out of the four possible diastereomers of α-alkyl-β-keto alcohols were synthesized by using different enzymes, and in two examples both ketones were reduced to the 1,3-diol. By replacing the α-alkyl substituent with the OAc group, 1-keto-2,3-diols, as well as 1,2,3-triols were synthesized in high optical purities. These enzymatic reactions provide a simple, highly stereoselective and quantitative method for the synthesis of different diastereomers of valuable chiral synthons from non-chiral, easily accessible 1,3-diketones.
Kalaitzakis, Dimitris,Rozzell, J. David,Smonou, Ioulia,Kambourakis, Spiros
p. 1958 - 1969
(2007/10/03)

Synthesis of substituted 3-cyano-2-pyridones: Part IV - Influence of 3-alkyl-2,4-pentanedione and N-alkyl cyanoacetamide structure on the enzyme catalyzed synthesis of substituted 3-cyano-2-pyridones
Lipase from Candida rugosa has been used to study the influence of 3-alkyl-2,4-pentanedione and N-alkyl cyanoacetamide structure on the enzyme catalyzed reaction of pyridone ring formation in water at 40°C. Starting with 1,3-diketones and cyanoacetamides and for comparison, the expected corresponding substituted 3-cyano-2-pyridones have been synthesized by chemical methods. Bulkier substitueras lower the initial reaction rate of the enzyme catalyzed reactions and consequently the yield of the corresponding pyridones. N-alkyl cyanoacetamides are more reactive in comparison to the corresponding 3-alkyl-2,4-pentanediones with respect to the obtained yields of the corresponding substituted 3-cyano-2-pyridones.
Mijin, Du?an ?.,Mili?, Branislav D.,Mi?i?-Vukovi?, Milica M.
p. 993 - 1003
(2007/10/03)

Asymmetric aza-Wittig reactions: Enantioselective synthesis of β-quaternary azacycles
A hindrance no more: The direct asymmetric synthesis of nitrogen heterocycles containing β-quaternary stereocenters, widely found for example in alkaloids, is highly challenging. The novel approach shown exploits the desymmetrization of prochiral diketo azides to unmask the asymmetric quaternary center, and represents the first reported examples of the asymmetric aza-Wittig reaction. (Chemical Equation Presented).
Lertpibulpanya, Duanpen,Marsden, Stephen P.,Rodriguez-Garda, Ignacio,Kilner, Colin A.
p. 5000 - 5002
(2007/10/03)

Method for preparing chiral diphosphines
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.
-
(2008/06/13)

New oxidation of β-hydroxy α-methyl ketones: A convenient synthesis of 3-methylalkane-2,4-diones
The synthesis of 3-methylalkane-2,4-diones, which are intense strawlike and fruit-flavored compounds, has been performed by the aldol condensation of n-alkanal (C2-C7) and methyl ethyl ketone to give 4-hydroxy-3-methyl-2-alkanones in 31-72% yield, followed by oxidation using sodium hypochlorite in the presence of 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-Noxide in 60-86% yield.
Yuasa, Yoshifumi,Kato, Yasushi
p. 628 - 631
(2013/09/06)

Concurrent Induction of Two Chiral Centers from Symmetrical 3,4-Disubstituted and 3,3,4-Trisubstituted 4-Pentenals Using Rh-Catalyzed Asymmetric Cyclizations
Asymmetric cyclization of symmetrical 3,4-disubstituted and 3,3,4-trisubstituted 4-pentenals was studied using Rh-complexes with chiral ligands. The cyclization of symmetrical 4-pentenals 4a,b by a neutral Rh[(R)-BINAP]Cl afforded cis-3,4-disubstituted (4R)-cyclopentanones 9a,b of >95% ee in 25-31% yields; on the other hand, the cyclization of 4a-c by a cationic Rh[(R)-BINAP]ClO4 afforded trans-3,4-disubstituted (4S)-cyclopentanones 10a-c of >95% ee in 70-81% yields. All stereoisomers could be stereoselectively made by the selection of a neutral or cationic Rh-complex, and (R)- or (S)-BINAP ligand. The Rh-catalyzed cyclization could be applied to the construction of cyclopentanones 17 and 18 bearing a chiral quaternary carbon. The cyclization by the cationic Rh[(R)-BINAP]ClO4 afforded the optically active trans-3,3,4-trisubstituted cyclopentanones 18a-c of 92-95% ee in 75-83% yields. The catalytic cycle was also studied by using deuterium aldehyde, and the tentative mechanisms of the enantio- and diastereoselection were proposed.
Tanaka, Masakazu,Imai, Masanori,Fujio, Masakazu,Sakamoto, Eishi,Takahashi, Miyuki,Eto-Kato, Yasuko,Wu, Xiao Ming,Funakoshi, Kazuhisa,Sakai, Kiyoshi,Suemune, Hiroshi
p. 5806 - 5816
(2007/10/03)

Asymmetric hydrogenation method of a ketonic compound and derivative
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
-
(2008/06/13)

Use of the Nonionic Superbase P(MeNCH2CH2)3N in the Selective Monoalkylation of Active-Methylene Compounds
The symmetric active-methylene compounds CH2(CO2Et)2 and CH2[C(O)Me]2 are selectively monoalkylated in the presence of 1.1 equiv of a variety of alkyl halides and 1 equiv of the nonionic Superbase P(MeNCH2CH2)2N in 85-98% yields in 30 min at room temperature. The unsymmetrical active-methylene compound EtO2CCH2C(O)Me is selectively monoalkylated under the same conditions, except for the temperature, which is 0 °C, in 59-88% yields. The observation of selective C- rather than O-alkylation is rationalized in terms of the formation of an enolate whose negatively charged oxygen is sterically protected by a nearby HP(MeNCH2CH2)2N+ counterion in a tight ion pair.
Arumugam, Subramaniam,McLeod, Dale,Verkade, John G.
p. 3677 - 3679
(2007/10/03)

Michael reactions promoted by η1-O-enolatoruthenium(II) complexes derived from Ru(cod)(cot), diphosphine, and dimethyl malonate
The Michael reaction of 1,3-dicarbonyls with α,β-unsaturated esters and nitriles has been carried out very efficiently, under mild and neutral conditions, in the presence of a catalytic amount of trans-hydrido(η1-O- enolato) ruthenium(II) complex (2), which is prepared from the reaction of Ru(cod)(cot) (1) (cod = cycloocta-1,5-diene; cot = cycloocta-1,3,5-triene) with dimethyl malonate in the presence of 1,2-bis(diphenylphosphino)ethane (dpe).
Alvarez, Salvador G.,Hasegawa, Sachi,Hirano, Masafumi,Komiya, Sanshiro
p. 5209 - 5212
(2007/10/03)

Synthesis and spectra of meso-dialkyl-β-octamethylporphyrins
Condensation of bis(3,4-dimethyl-2-pyrrolyl)methane or bis(5-carboxy-3,4-dimethyl-2-pyrrolyl)methane with unbranched aldehydes CnH2n+1CHO (n= 1-7) results in formation of 5,15-dialkyl-2,3,7,8,12,13,17,18-octamethylporphyrins. Zinc complexes of the porphyrins are obtained.
Zdanovich,Mamardashvili,Golubchikov
p. 756 - 761
(2007/10/03)

Substituent Effects on the CC Bond Strength, 16. - Thermal Stability and Enthalpies of Formation of β-Dicarbonyl Compounds. - Stabilisation Enthalpies of α,α'-Diketoalkyl Radicals
The geminal interactions of the two carbonyl groups in seven β-diketones of the type 8-9 and 11-13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization.The radical stabilisation enthalpies RSE of the α,α'-diketoalkyl radicals 9-13 were obtained from the enthalpies of activation ΔH(excit.) of thermal CC bond cleavage of eight model compounds of the type 9-13 by their comparison with ΔH(excit.) of comparable hydrocarbons of similar strain.For non-cyclic α,α'-diacylalkyl radicals and six-membered cyclic ones RSE = 54.8 +/- 1.3 kJ mol-1 was determined, which indicates an additive stabilisation by two carbonyl groups. - Key Words: Enthalpies of formation/ Geminal substituents, energetic interaction of/ Bond cleavage, C-C, kinetics of/ Radicals, stability of/ Increments, thermochemical/ Bond strength, substituent effects on
Noelke, Margot,Verevkin, Sergej P.,Beckhaus, Hans-Dieter,Ruechardt, Christoph
p. 41 - 52
(2007/10/02)

Hydrotalcite-catalyzed alkylation of 2,4-pentanedione
A synthetic anionic clay, hydrotalcite (Mg/Al = 2.8), calcined under dry air at 450°C has proved to be an efficient catalyst for the selective C-monoalkylation of 2,4-pentanedione with reactive alylating reagents.
Cativiela,Figueras,Garcia,Mayoral,Zurbano
p. 1745 - 1750
(2007/10/02)

Surface-mediated Solid-phase Reaction. Part 2. Highly Selective Mono- and Di-C-alkylation of 1,3-Dicarbonyl Compounds on the Surface of Alumina
Highly selective mono- and di-C-alkylation of 1,3-dicarbonyl compounds with different, structurally varied alkyl halides has been achieved in high yields through a simple solvent-free reaction on the surface of alumina impregnated with sodium or potassium alkoxide.
Ranu, Brindaban C.,Bhar, Sanjay
p. 365 - 368
(2007/10/02)

ALKYLATION OF CH ACIDS IN THE PRESENCE OF POTASSIUM CARBONATE. IV. ALKYLATION OF 2,4-PENTANEDIONE AND 3-METHYL-2,4-PENTANEDIONE
The reaction of 2,4-pentanedione and 3-methyl-2,4-pentanedione with ethyl acrylate in the presence of potassium carbonate gave the Michael adducts.The acylotropic rearrangement of the products from the reaction of 3-methyl-2,4-pentanedione with ethyl α-bromoacrylate and dibromoethane under the influence of potassium carbonate was investigated.
Khachatryan, D. S.,Vardapetyan, A. A.,Panosyan, G. A.,Mirzoyan, R. G.,Morlyan, N. M.
p. 1806 - 1810
(2007/10/02)

An Improved Method for γ-Carboxylation of β-Diketones. Synthesis of 4-Alkyl-3,5-dioxohexanoic Acids and 5-Alkyl Derivatives of Triacetic Acid Lactone
γ-Carboxylation of β-diketones, 1, can be improved using samples containing 100percent of ketoenol tautomers, 3, prepared by mild hydrolysis of the corresponding copper(II) complexes 2.Cyclization of the so formed 4-alkyl-3,5-dioxohexanoic acids, 4, affords 5-alkyl-4-hydroxy-6-methyl-2-pyrones, 5.
Cervello, Jordi,Marquet, Jorge,Moreno-Manas, Marcial
p. 1931 - 1941
(2007/10/02)

Synthesis of new prim., sec. and tert. 3-amino-thieno[2,3 -b]pyridine-2-carboxamides on different ways
-
Wagner,Vieweg,Leistner,Bohm,Krasselt,Hanfe ld,Prantz,Grupe
p. 102 - 109
(2007/10/02)

Ruthenium-catalyzed Reductive Alkylation of Active Methylene Compounds with Aldehydes under Synthesis Gas
Active methylene compounds undergo reductive alkylation with aldehydes when heated at 135-230 deg C under synthesis gas of 100 atm in the presence of ruthenium carbonyl.
Abe, Fujio,Hayashi, Teruyuki,Tanaka, Masato
p. 765 - 768
(2007/10/02)

Convenient, High-Yield Method for the Methylation of 1,3-Diketones
A general method for the facile dimethylation of 1,3-diketones is presented.The method involves the use of readily available, inexpensive reagents and is carried out under mild conditions.Monomethylation may be carried out by slight modification (simplification) of the procedure.Several examples are presented which show that the method is applicable to alkylations with primary halides as well.Isolated yields for monoalkylation are approximately 95percent while those for dialkylation are ca. 90percent.Alkylation is taking place by the reaction of the enolates of 1,3-diketones with alkyl halides.
Choudhary, Anil,Baumstark, Alfons L.
p. 688 - 690
(2007/10/02)

Commercial Ion Exchange Resins as Catalysts in Solid-Solid-Liquid Reactions
Nucleophilic substitutions, base-catalyzed alkylations, and oxidation of a secondary alcohol have been carried out in a nonpolar solvent with inorganic solid reagents using polymer-bound quarternary ammonium or phosphonium catalysts.The products could be isolated simply by filtration and evaporation of the solvent.Some commercial ion exchange resins, which are known to be inactive in liquid-liquid systems, were found to have a similar or even superior activity in comparison with the usual "triphase catalysts".The resins were chemically stable under the reaction conditions, but their mechanical breakdown could be reduced only by application of unconventional means of agitation.
Arrad, Onn,Sasson, Yoel
p. 4993 - 4998
(2007/10/02)

Selective C-Alkylation of β-Diketones
-
Shono, Tatsuya,Kashimura, Shigenori,Sawamura, Masaya,Soejima, Takeshi
p. 907 - 910
(2007/10/02)

Total synthesis of symmetric bile pigments: Mesobilirubin-IVα, mesobilirubin-XIIIα and etiobilirubin-IVγ
-
Trull,Franklin,Lightner
p. 1573 - 1579
(2007/10/02)

β-DIKETONE INTERACTIONS Part 5. Solvent effects on the keto enol equilibrium
The keto enol equilibrium of pentane-2,4-dione (PD) has been measured in 21 solvents at infinite dilution and a linear free energy relationship (LFER) tested againts four solvent polarity vectors: ε, ET, ?* and A + B.The best correlation coefficient is found for A +B.Similarly 3-methyl-pentane-2,4-dione (MePD) has been studied in 14 solvents and 3-ethylpentane-2,4-dione (EtPD) in six.The results suggest that the cyclic hydrogen bonding of the enol remains intact in all the solvents studied.
Emsley, John,Freeman, Neville J.
p. 193 - 204
(2007/10/02)

Synthesis of Alternating Hydroxy- and Methyl-Substituted Hydrocarbons by Oxymercuration of Cyclopropylcarbinols
-
Collum, David B.,Still, W. Clark,Mohamadi, Fariborz
p. 2094 - 2096
(2007/10/02)

Process for the preparation of monomethyl-substituted methylene compounds
Monomethyl-substituted methylene compounds are obtained by reacting methylene compounds of the formula STR1 in which R1 and R2 independently of one another represent --CN, --CO--R3, --SO2 --R3 or --NO2 and R1 can additionally denote -aryl(R1)n, wherein R3 denotes --OH, alkyl, aralkyl, aryl, alkoxy, aralkoxy or aryloxy, or amino which is substituted by alkyl and/or aralkyl and/or aryl, and furthermore two radicals R3 together can be an alkylene group, the radical of an aliphatic diol or of an aliphatic diamine or the group --NH--CO--NH-- and n represents 1, 2 or 3, with formaldehyde and with hydrogen in the presence of a condensation catalyst and a hydrogenation catalyst at elevated temperature, the methylene compound being introduced into the liquid phase of the mixture of reactants in the course of the reaction.
-
(2008/06/13)

Selective Sequential Demasking of the Ester Functions of 1-Methyl-3,4,5-tris(methoxycarbonyl)pyrazole
The adjacent ester functions of 1-methyl-3,4,5-tris(methoxycarbonyl)pyrazole can be selectively and seqentially demasked, providing an efficient route to heterogeneous pyrazole triamides.X-ray crystallographic determination of the structure of one of these triamides shows the order of ester hydrolysis to be 5, 4, 3.
Chambers, David,Denny, William A.,Buckleton, John S.,Clark, George R.
p. 4736 - 4738
(2007/10/02)

Total synthesis of (±)-asteltoxin
A convergent synthesis of (±)-asteltoxin has been achieved in 16 steps (3.0% overall yield) from 3,4-dimethylfuran. The attachment of the triene pyrone side chain to the bis(tetrahydrofuran) skeleton proceeds by way of the addition of the Corey equivalent to anion 3 to the aldehyde 2 and a subsequent aldol condensation-dehydration reaction of pyrone 4.
Schreiber,Satake
p. 4186 - 4188
(2007/12/18)

Reactions of Mercury(II) Acetate with Nitrogen Compounds. Part 9. Oxidations of the Bis-(4-nitrophenylhydrazone)s of Some 1,3-Diketones with Mercury(II) Acetate and Lead(IV) Acetate
Oxidation of bis-(4-nitrophenylhydrazone)s of 1,3-diketones containing an α-CH between the hydrazone chains resulted in cyclization with fragmentation, giving pyrazoles.The reaction is considered to involve dehydrogenation of the conjugated tautomeric enamine form of the bis-hydrazone, giving a cis-azo-hydrazono-alkene intermediate.When the postulated azo-hydrazono-alkene intermediate had trans-stereochemistry, unfavourable for cyclization, as in the oxidation of cycylohexa-1,3-dione bis-(4-nitrophenylhydrazone), the azo-alkene was stable and was the main product.When the conjugated enamine tautomeric form of the 1,3-bis-hydrazone cold not exist, as with 3,3-dimethylpentane-2,4-dione bis-(4-nitrophenylhydrazone), pyrazoles were not formed and the hydrazone chains behaved as isolated monohydrazones.
Butler, Richard N.,James, John P.
p. 553 - 555
(2007/10/02)

Chemistry of 1,3-Glycol Derivatives. IV. Mechanism of the Solvolyses of 2,4-Pentanediol Derivatives and the Reactions of the Proposed Intermediate Acetoxonium Ions with Carbanions and Hydride
Regio- and stereochemical studies of the solvolyses of various kinds of 2,4-pentanediol derivatives, including 2-acetoxy-4-tosylates, cyclic orthoformates and orthoacetates, have been done and the previously proposed mechanism has been partially revised. The reactions of the proposed intermediate acetoxonium ions with carbanions and with a hydride ion have also been studied.
Itoh, Osamu,Iwakoshi, Naoki,Saitoh, Toshihide,Katano, Hiroaki,Fujisawa, Yoshiki,et al.
p. 177 - 181
(2007/10/02)

The Allopolarization Principle and its Applications, IV. Substituent Effects in the Methylation of Enolate Anions
The ratio of O- and C-methylated products in the reaction of the sodium salts of acetophenones 1, propiophenones 3, phenylacetones 5, β-dicarbonyl compounds 12, α-cyanocarbonyl compounds 13, acetaldehyde, propionaldehyde, and diethylketone with dimethyl sulfate, methyl iodide, and trimethyl phosphate in HMPTA has been determined with regard to the effect of substituents.In some cases the influence of solvents, concentration and temperature has also been studied.
Gompper, Rudolf,Vogt, Hans-Hubert
p. 2866 - 2883
(2007/10/02)

The Allopolarization Principle and its Applications, VI. The Alkylation of Enolate Anions: Polarity and Regioselectivity
The O/C methylation ratio in the reaction of sodium enolates with dimethylsulfate depends on the polar (electronic) effect of substituents.The relative ?-charge density Px/y = lx/ly can be used as a measure for the polarity of ambifunctional anions; in case of enolate anions PO/C = lO/lC.The change of the regioselectivity Sf = log QO/QC in the alkylation of enolates is a function of a change in the polarity PO/C; ΔSf=f(ΔPx/y).The polar effect of substituents influences the charge control during the alkylation process via a change of the polarity of the enolate system: The higher the polarity of the anion, the stronger the charge control and the higher the yield of enol ether (O-alkylation). - Keywords: Alkylation, Enolate Anions
Gompper, Rudolf,Vogt, Hans-Hubert,Wagner, Hans-Ulrich
p. 1644 - 1652
(2007/10/02)

ENHANCED CATALYTIC EFFECT OF FREEZE-DRIED POTASSIUM FLUORIDE FOR ALKYLATION OF PROTIC COMPOUNDS
Freeze-dried potassium fluoride was found to be much more effective as a hydrogen-bond forming catalytic reagent for alkylation of protic compounds than usual calcine-dried potassim fluoride.Phenol, thiophenol, aniline, and acetylacetone were easily alkylated with methyl or ethyl iodide in the presence of the reagent.Freeze-dried potassium fluoride, however, had no effect for the fluorination of activated chlorine compounds.
Ishikawa, Nobuo,Kitazume, Tomoya,Nakabayashi, Masao
p. 1089 - 1090
(2007/10/02)