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Aliphatic Ketones (aliphatic + ketone)
Selected AbstractsOrganocatalytic Asymmetric syn -Aldol Reactions of Aldehydes with Long-Chain Aliphatic Ketones on Water and with Dihydroxyacetone in Organic SolventsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2008Ming-Kui Zhu Abstract An on-water, asymmetric, and direct syn -aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by a primary amino acid-based organocatalyst afforded the syn -aldol adducts in high yields with excellent diastereo- and enantioselectivities (up to > 20/1 dr, >99% ee), and a highly enantioselective syn -aldol reaction of dihydroxyacetone with a variety of aldehydes in THF proceeded with 14/1 to >20/1 dr and 92 to >99% ee. Water not only accelerated the reaction, but also enhanced the enantioselectivity. This positive water effect might arise from the hydrogen bond formed between a pendant hydroxy group of surface water molecules at the hydrophobic interface with the amide oxygen of the organocatalyst, which increases the acidity of the amide NH and thereby strengthens the related hydrogen bond formed with the aldehyde. [source] Aliphatic Ketones as Photoinitiators for PhotograftingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2004Huiliang Wang Abstract Summary: The photografting of methacrylic acid (MAA) onto high-density polyethylene (HDPE) initiated by butanone, pentan-3-one, and heptan-3-one is presented. These aliphatic ketones can act as photoinitiators for photografting when they are a component of a suitable solvent mixture with water and ethanol. It is possible that the photoinitiation effect of the aliphatic ketone is induced by the hydrogen bond formed between it and water. The grafting of 2 M MAA in different ketone/water/ethanol (30/30/40) solvents. [source] Regioselectivity in the Reaction of Aliphatic Ketones and Aromatic Nitriles.CHEMINFORM, Issue 15 2003Regiospecific Synthesis of Alkylarylpyrimidines. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Origin of the ,-Facial Stereoselectivity in the Addition of Nucleophilic Reagents to Chiral Aliphatic Ketones as Evidenced by High-Level Ab,Initio Molecular-Orbital CalculationsCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2006Osamu Takahashi Dr. Abstract Ab,initio molecular-orbital (MO) calculations were carried out, at the MP2/6-311++G(d,p)//MP2/6-31G(d) level, to investigate the conformational Gibbs energy of alkyl 1-cyclohexylethyl ketones, cyclo- C6H11CHCH3COR (R=Me, Et, iPr, and tBu). In each case, one of the equatorial conformations was shown to be the most stable. Conformers with the axial CHCH3COR group were also shown to be present in an appreciable concentration. Short CH,,,CO and CH,,,OC distances were found in each stable conformation. The result was interpreted on the grounds of CH,,,,(CO) and CH,,,O hydrogen bonds, which stabilize the geometry of the molecule. The ratio of the diastereomeric secondary alcohols produced in the nucleophilic addition to cyclo- C6H11CHCH3COR was estimated on the basis of the conformer distribution. The calculated result was consistent with the experimental data previously reported: the gradual increase in the product ratio (major/minor) along the series was followed by a drop at R=tBu. The energy of the diastereomeric transition states in the addition of LiH to cyclo- C6H11CHCH3COR was also calculated for R=Me and tBu. The product ratio did not differ significantly in going from R=Me to tBu in the case of the aliphatic ketones. This is compatible with the above result calculated on the basis of the conformer distribution. Thus, the mechanism of the ,-facial selection can be explained in terms of the simple premise that the geometry of the transition state resembles the ground-state conformation of the substrates and that the nucleophilic reagent approaches from the less-hindered side of the carbonyl , face. [source] Aliphatic Ketones as Photoinitiators for PhotograftingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2004Huiliang Wang Abstract Summary: The photografting of methacrylic acid (MAA) onto high-density polyethylene (HDPE) initiated by butanone, pentan-3-one, and heptan-3-one is presented. These aliphatic ketones can act as photoinitiators for photografting when they are a component of a suitable solvent mixture with water and ethanol. It is possible that the photoinitiation effect of the aliphatic ketone is induced by the hydrogen bond formed between it and water. The grafting of 2 M MAA in different ketone/water/ethanol (30/30/40) solvents. [source] 3,5-Bis(trifluoromethyl)phenyl Sulfones in the Julia,Kocienski Olefination , Application to the Synthesis of Tri- and Tetrasubstituted OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2006Diego A. Alonso Abstract 3,5-Bis(trifluoromethyl)phenyl (BTFP) sulfones 8a,d are successfully employed in the modified Julia olefination reaction with carbonyl compounds employing phosphazene base P4- tBu at room temp. in THF, affording tri- and tetrasubstituted olefins in good yields. The Julia,Kocienski olefination between primary alkyl BTFP sulfones 8a,b and aromatic and aliphatic ketones affords the corresponding trisubstituted alkenes in good yields and low stereoselectivities. On the other hand, higher yields and stereoselectivities are obtained in the synthesis of trisubstituted olefins through the other approach, the coupling of secondary alkyl BTFP sulfones 8c,d with aliphatic, aromatic and ,,,-unsaturated aldehydes. For the first time, tetrasubstituted olefins are synthesized by means of the Julia,Kocienski protocol when the isopropyl BTFP sulfone 8c reacts with aliphatic and aromatic ketones, employing P4- tBu as base at THF reflux. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Asymmetric Reduction of Ketones Under Mild Conditions Using NaBH4 and TarB-NO2: An Efficient and Unusual Chiral Acyloxyborohydride Reducing System,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005David B. Cordes Abstract High enantioselectivities are obtained for the reduction of a series of ketones using the inexpensive and mild reducing agent NaBH4 with TarB-NO2 (1). This easily prepared tartaric acid-based reagent combines a Lewis acid with carboxylic acids in a single bifunctional reagent. When combined with NaBH4, the resulting chiral acyloxyborohydride mediates the reduction of aromatic ketones to provide the product alcohols in enantiomeric excesses of 93,98,%. Several aliphatic ketones were also reduced with moderate to excellent enantioselectivity. A unique mechanism is provided with supporting calculations for the proposed active species and transition state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Highly Efficient Cyanosilylation of Sterically Bulky Ketones Catalyzed by Tin Ion-Exchanged MontmorilloniteADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Jiacheng Wang Abstract Tin ion-exchanged montmorillonite (Sn-Mont) was found to be a powerful catalyst for the cyanosilylation of aromatic and aliphatic ketones having a carbonyl group in sterically congested circumstances with cyanotrimethylsilane, giving the corresponding cyanohydrin trimethylsilyl ethers in excellent yields. [source] Organocatalytic Asymmetric syn -Aldol Reactions of Aldehydes with Long-Chain Aliphatic Ketones on Water and with Dihydroxyacetone in Organic SolventsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2008Ming-Kui Zhu Abstract An on-water, asymmetric, and direct syn -aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by a primary amino acid-based organocatalyst afforded the syn -aldol adducts in high yields with excellent diastereo- and enantioselectivities (up to > 20/1 dr, >99% ee), and a highly enantioselective syn -aldol reaction of dihydroxyacetone with a variety of aldehydes in THF proceeded with 14/1 to >20/1 dr and 92 to >99% ee. Water not only accelerated the reaction, but also enhanced the enantioselectivity. This positive water effect might arise from the hydrogen bond formed between a pendant hydroxy group of surface water molecules at the hydrophobic interface with the amide oxygen of the organocatalyst, which increases the acidity of the amide NH and thereby strengthens the related hydrogen bond formed with the aldehyde. [source] Molecular mechanics calculations on carbonyl compounds.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2001Abstract Open-chain aliphatic ketones were studied with the molecular mechanics (MM4) force field. A total of seven compounds were examined. Structures were well fit, including moments of inertia. Rotational barriers, vibrational spectra, and dipole moments were also well fit. The overall root mean square errors for MM3 and MM4 were 0.27 and 0.18%, respectively, for the six moments of inertia (known experimentally for two compounds) and 31 and 20 cm,1, respectively, for the vibrational frequencies (over 99 weighted modes). © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1426,1450, 2001 [source] Aliphatic Ketones as Photoinitiators for PhotograftingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2004Huiliang Wang Abstract Summary: The photografting of methacrylic acid (MAA) onto high-density polyethylene (HDPE) initiated by butanone, pentan-3-one, and heptan-3-one is presented. These aliphatic ketones can act as photoinitiators for photografting when they are a component of a suitable solvent mixture with water and ethanol. It is possible that the photoinitiation effect of the aliphatic ketone is induced by the hydrogen bond formed between it and water. The grafting of 2 M MAA in different ketone/water/ethanol (30/30/40) solvents. [source] Origin of the ,-Facial Stereoselectivity in the Addition of Nucleophilic Reagents to Chiral Aliphatic Ketones as Evidenced by High-Level Ab,Initio Molecular-Orbital CalculationsCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2006Osamu Takahashi Dr. Abstract Ab,initio molecular-orbital (MO) calculations were carried out, at the MP2/6-311++G(d,p)//MP2/6-31G(d) level, to investigate the conformational Gibbs energy of alkyl 1-cyclohexylethyl ketones, cyclo- C6H11CHCH3COR (R=Me, Et, iPr, and tBu). In each case, one of the equatorial conformations was shown to be the most stable. Conformers with the axial CHCH3COR group were also shown to be present in an appreciable concentration. Short CH,,,CO and CH,,,OC distances were found in each stable conformation. The result was interpreted on the grounds of CH,,,,(CO) and CH,,,O hydrogen bonds, which stabilize the geometry of the molecule. The ratio of the diastereomeric secondary alcohols produced in the nucleophilic addition to cyclo- C6H11CHCH3COR was estimated on the basis of the conformer distribution. The calculated result was consistent with the experimental data previously reported: the gradual increase in the product ratio (major/minor) along the series was followed by a drop at R=tBu. The energy of the diastereomeric transition states in the addition of LiH to cyclo- C6H11CHCH3COR was also calculated for R=Me and tBu. The product ratio did not differ significantly in going from R=Me to tBu in the case of the aliphatic ketones. This is compatible with the above result calculated on the basis of the conformer distribution. Thus, the mechanism of the ,-facial selection can be explained in terms of the simple premise that the geometry of the transition state resembles the ground-state conformation of the substrates and that the nucleophilic reagent approaches from the less-hindered side of the carbonyl , face. [source] Volatile Organic Compounds from Arctic Bacteria of the Cytophaga-Flavobacterium-Bacteroides Group: A Retrobiosynthetic Approach in Chemotaxonomic InvestigationsCHEMISTRY & BIODIVERSITY, Issue 3 2005Jeroen Volatile organic compounds emitted by different marine arctic strains of the Cytophaga-Flavobacterium-Bacteroides group were investigated by using a modified closed-loop stripping apparatus (CLSA). Seven of nine strains emitted volatiles, dominated by methyl ketones, in specific patterns. The methyl ketones were aliphatic saturated, or unsaturated, and comprised 12 to 18 C-atoms, sometimes with terminal Me branches. They were identified by GC/MS, retention-index calculations, derivatization with dimethyl disulfide for CC bond location, and GC/FTIR to elucidate their uniform (Z)-configuration. The proposed structures of all methyl ketones were subsequently confirmed by synthesis, while the absolute configuration of chiral volatiles was elucidated by stereoselective synthesis. From retrobiosynthetic considerations, it was found that strain ARK10267 uses mainly valine, and strain ARK10063 mainly isoleucine for formation of starters for the ketone biosynthesis, which is correlated to fatty acid biosynthesis. Four strains (ARK10223, ARK10044, ARK10141, and ARK10146) use leucine. These separations are supported by phylogenetic affiliations based on 16S rRNA. Strain ARK10255b, in the course of this study found to be not a member of the Cytophaga-Flavobacterium-Bacteroides phylum, did not emit aliphatic ketones of medium chain length, but methionine-derived 4-(methylsulfanyl)butan-2-one and corresponding 4-(methylsulfanyl)butan-2-ol. Most of the compounds described have not been reported previously from nature. [source] Low-valent titanium induced reductive cyclization of nitro compounds and aliphatic ketones: facile synthesis of 3, 4-dihydro(2H) - 1, 2, 4-benzothiadiazine-1, 1-dioxidesCHINESE JOURNAL OF CHEMISTRY, Issue 5 2000Wei-Hui Zhong Abstract The intermolecular reductive cyclization of o -nitrobenzene-sulfonamides with aliphatic ketones induced by TiCl4/Sm system was studied and a series of 3, 3-disubstituted-3,4-dihydro(2H)-1,2, 4-benzothiadiazine-1,1-dioxides were synthesized in moderate to high yields under mild and neutral conditions. [source] | ||||||||||||||||||||||