- Gas-phase Unimolecular Chemistry of Ethyl Butyl Ketone Cations
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Mass spectra of the four isomeric ethyl butyl ketones, C2H5CO-n-C4H9 (1), C2H5CO-iso-C4H9 (2), C2H5CO-sec-C4H9 (3) and C2H5CO-t-C4H9 (4), are reported.The structure of the fragment ions produced from precursors of both high and low internal energy were identified by collision experiments in a six-sector mass-spectrometer.Metastable molecular ions 1(+.) and 2(+.) behave identically in expelling CH3(.), C3H6 and C2H5(.) to produce the same fragment ions: (+), (+.) and a mixture of (+) and (+), respectively.The key isomerization step between 1(+.) and 2(+.) is a 1,2-enol-olefin shift.Metastable molecular ions 3(+.) and 4(+.) give essentially ethene and ethyl losses, respectively; the fragment ions are (+.) and (+).Keto-enol isomerization also occurs to a significant extent for ions 1(+.) and 2(+.) and 3(+.).In contrast, 1,2- or 1,3-ethylhydroxycarbene migrations are only marginal processes.
- Bouchoux, Guy,Flammang, Robert,Jaudon, Pascale,Lefevre, Odile
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- Mammalian exocrine secretions XI. Constituents of the preorbital secretion of klipspringer, Oreotragus oreotragus
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The ketones 3-pentanone, 4-methyl-2-pentanone, 5-methyl-3-hexanone, 4-methyl-3-hexanone, and the esters ethyl propaneate, 2-methylpropyl acetate, ethyl 3-methylbutanoate, and 2-methylpropyl propanoate were identified as the only volatile organic constituents of the preorbital secretion of the klipspringer. Oreotragus oreotragus. These compounds are considerably more volatile than those found in the preorbital secretions of other antelopes belonging to the tribe Antelopini. More than 50% of the preorbital secretion consists of proteinaceous material, which probably acts as a controlled-release substance in retarding the evaporation of the volatile constituents of the secretion from territorial marks.
- Burger
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- Synthesis of β-Methyl Alcohols: Influence of Alkyl Chain Length on Diastereoselectivity and New Attractants of Rhynchophorus ferrugineus
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The diastereoselectivity of adducts in the addition reaction via the Felkin-Anh model is affected significantly by the steric effect of bulky groups. However, the influence of steric alkyl chain length has not been studied for the diastereoselectivity. In this work, we present a new strategy for the racemic synthesis of β-methyl alcohols to obtain various diastereomer ratios using the Felkin-Anh model. The addition of alkyl Grignard reagents to α-methyl aldehydes afforded diastereomer ratios of threo/erythro ≈ 2:1, while the reduction in structurally related ketones using LiAlH4 afforded ratios of threo/erythro ≈ 1:1. The experimental data showed no effect of alkyl chain length on either side on the stereoselectivity of adducts. All synthesized analogues were evaluated for attractiveness to Rhynchophorus ferrugineus weevils in the field. Five novel derivatives, including two alcohols and three ketones, were found to attract weevils in the field trials. Among them, 3-methyldecan-4-one (5b) and 4-methyldecan-5-ol (11a) were found to be the most attractive to the insects.
- Le, Van-Dung,Dang, Chi-Hien,Nguyen, Cong-Hao,Nguyen, Hong-Ung,Nguyen, Thanh-Danh
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p. 5882 - 5886
(2021/06/21)
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- Phosphine-free cobalt catalyst precursors for the selective hydrogenation of olefins
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Cobalt(ii) complexes bearing phosphine-free tridentate NNS ligands were prepared. Depending on the ligand, dimeric or monomeric complexes were isolated. Monomeric Co(NNMeS)Cl2 selectively catalysed the hydrogenation of olefins in the presence of reducible moieties such as ketones. Further investigation showed that this complex functions as a nanoparticle precursor under the reaction conditions.
- Puylaert, Pim,Dell'Acqua, Andrea,El Ouahabi, Fatima,Spannenberg, Anke,Roisnel, Thierry,Lefort, Laurent,Hinze, Sandra,Tin, Sergey,De Vries, Johannes Gerardus
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- Formation, Alkylation, and Hydrolysis of Chiral Nonracemic N-Amino Cyclic Carbamate Hydrazones: An Approach to the Enantioselective α-Alkylation of Ketones
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The α-alkylation of ketones is a fundamental synthetic transformation. The development of asymmetric variants of this reaction is important given that numerous natural products, drugs, and related compounds exist as α-functionalized ketones or derivatives thereof. We previously reported our preliminary studies on the development of a new enantioselective ketone α-alkylation procedure using N-amino cyclic carbamate (ACC) auxiliaries. In comparison to other auxiliary-based methods, ACC alkylation offers a number of advantages and is both highly enantioselective and high yielding. Herein, we provide a full account of our studies on the enantioselective ACC ketone α-alkylation method.
- Huynh, Uyen,McDonald, Stacey L.,Lim, Daniel,Uddin, Md. Nasir,Wengryniuk, Sarah E.,Dey, Sumit,Coltart, Don M.
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p. 12951 - 12964
(2018/11/30)
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- Investigating: Saccharomyces cerevisiae alkene reductase OYE 3 by substrate profiling, X-ray crystallography and computational methods
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Saccharomyces cerevisiae OYE 3 shares 80% sequence identity with the well-studied Saccharomyces pastorianus OYE 1; however, wild-type OYE 3 shows different stereoselectivities toward some alkene substrates. Site-saturation mutagenesis of Trp 116 in OYE 3 followed by substrate profiling showed that the mutations had relatively little effect, opposite to that observed previously for OYE 1. The X-ray crystal structures of unliganded and phenol-bound OYE 3 were solved to 1.8 and 1.9 ? resolution, respectively. Both structures were nearly identical to that of OYE 1, with only a single amino acid difference in the active site region (Ser 296 versus Phe 296, part of loop 6). Despite their essentially identical static X-ray structures, molecular dynamics (MD) simulations revealed that loop 6 conformations differed significantly in solution between OYE 3 and OYE 1. In OYE 3, loop 6 remained nearly as open as observed in the crystal structure; by contrast, loop 6 closed over the active site of OYE 1 by ca. 4 ?. Loop closure likely generates a greater number of active site protein contacts for substrate bound to OYE 1 as compared to OYE 3. These differences provide an explanation for the differing stereoselectivities of OYE 3 and OYE 1, despite their nearly identical X-ray crystal structures.
- Powell, Robert W.,Buteler, M. Pilar,Lenka, Sunidhi,Crotti, Michele,Santangelo, Sara,Burg, Matthew J.,Bruner, Steven,Brenna, Elisabetta,Roitberg, Adrian E.,Stewart, Jon D.
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p. 5003 - 5016
(2018/10/17)
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- α-alkylation of ketones by addition of zinc enamides to unactivated olefins
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A zinc enamide generated from the corresponding N-aryl imine undergoes addition to an unactivated olefin, such as ethylene, 1-octene, and isobutylene, to generate an α-alkylated γ-zincioimine intermediate in good to excellent yield. Terminal and gem-disubstituted olefins react with >99% regioselectivity, allowing the C-C bond formation to take place at the more hindered carbon of the double bond. The organozinc intermediate undergoes further C-C bond formation with a carbon electrophile to give, upon hydrolysis of the imine, an α-alkylated ketone bearing a variety of functionalized primary, secondary, and tertiary alkyl groups.
- Nakamura, Masaharu,Hatakeyama, Takuji,Nakamura, Eiichi
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p. 11820 - 11825
(2007/10/03)
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- Superacid-catalyzed selective formation-rearrangement of isoalkanes with carbon monoxide to branched ketones
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Efficient high octane oxygenate additives for gasoline, that is, branched aliphatic ketones, are the products of the title reaction of isoalkanes with carbon monoxide. Isobutane, for example, gives methyl isopropyl ketone in 91% yield and 93% selectivity (see scheme). The reaction gives no branched carboxylic acids, showing it to be independent of Koch carbonylation. The intriguing reaction is suggested to proceed through initial electrophilic C-H bond substitution by the formyl cation (or its protosolvated form), followed by rearrangement.
- Olah, George A.,Prakash, G. K. Surya,Mathew, Thomas,Marinez, Eric R.
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p. 2547 - 2548
(2007/10/03)
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- Oxidation by Polychromates
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The oligomeric chromates, potassium trichromate, K2Cr3O10, (K3C), and potassium tetrachromate K2Cr4O13, (K4C), are soluble in solvents such as acetone, acetonitrile, ethyl acetate, DMF and THF. Solutions of K3C or K4C in acetonitrile readily oxidized alcohols to the corresponding aldehydes or ketones in moderate to good yields.
- Carlsen, P. H. J.,Kjaerstad, Cathrine,Aasboe, Kari
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p. 152 - 154
(2007/10/02)
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- Inducibility of an Enone Reductase System in the Fungus Beauveria sulfurescens: Application in Enantioselective Organic Synthesis
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Microbiological reduction of α,β-unsaturated carbonyl compounds is studied.Inducibility of the enone reductase system of Beauveria sulfurescens is reported.The best inducer is shown to be cyclohex-2-en-1-one.An appropriate procedure using induced resting mycelium is developed to reduce substituted cyclohexenones that are shown to be unable to induce the reducing enzyme.Optically pure trans-(2R,6R)-(-)-2,6-dimethylcyclohexan-1-one and trans-(2R,6R)-(-)-2,6-dimethylcyclohexan-1-ol are obtained from (+/-)-2,6-dimethylcyclohex-2-en-1-one along with optically pure (6S)-(-)-2,6-dimethylcyclohex-2-en-1-one.
- Fauve, Annie,Renard, Michel F.,Veschambre, Henri
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p. 4893 - 4897
(2007/10/02)
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- COMPLETELY STEREOSPECIFIC 1,2-MIGRATION OF ALKYL GROUPS IN Et2AlCl PROMOTED PINACOL-TYPE REARRANGEMENT
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Completely stereospecific 1,2-migration of alkyl groups was achieved in Et2AlCl-promoted pinacol-type rearrangement of chiral β-mesyloxy alcohols to give optically pure α-alkyl ketones including both enantiomers of 4-methyl-3-hexanone, an alarm pheromone of ant.
- Tsuchihashi, Gen-ichi,Tomooka, Katsuhiko,Suzuki, Keisuke
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p. 4253 - 4256
(2007/10/02)
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- 1,2-Bond Shift Isomerization on Copper
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Besides yielding 3-ethyl-3-hydroxypentan-2-one (2) and 3-ethylpentan-2-one (4), 3-ethylpentane-2,3-diol (1) is transformed on copper catalysts into 4-methyl-4-hydroxyhexan-3-one (3) and 4-methylhexan-3-one (5), via 1,2-ethyl migration, this being the first experimental observation of 1,2-bond shift isomerization on copper.
- Bartok, Mihaly,Molnar, Arpad
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p. 1178 - 1180
(2007/10/02)
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