- Primary Alcohols via Nickel Pentacarboxycyclopentadienyl Diamide Catalyzed Hydrosilylation of Terminal Epoxides
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The efficient and regioselective hydrosilylation of epoxides co-catalyzed by a pentacarboxycyclopentadienyl (PCCP) diamide nickel complex and Lewis acid is reported. This method allows for the reductive opening of terminal, monosubstituted epoxides to form unbranched, primary alcohols. A range of substrates including both terminal and nonterminal epoxides are shown to work, and a mechanistic rationale is provided. This work represents the first use of a PCCP derivative as a ligand for transition-metal catalysis.
- Lambert, Tristan H.,Steiniger, Keri A.
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p. 8013 - 8017
(2021/10/25)
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- Systematic Engineering of Single Substitution in Zirconium Metal-Organic Frameworks toward High-Performance Catalysis
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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
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supporting information
p. 18590 - 18597
(2017/12/15)
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- Steric effects and mechanism in the formation of hemi-acetals from aliphatic aldehydes
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Some physical properties (pKa, log POW, boiling points) of hexanoic acid 1 (X = COOH) and its seven isomers 2, 3, 4, 5, 6, 7, 8 (X = COOH) are reported. Hexanal 1 (X = CHO) and its seven isomeric aldehydes 2, 3, 4, 5, 6, 7, 8 (X = CHO) are shown to equilibrate, in methanol solution, with their hemi-acetals. Logarithms of equilibrium constants correlate with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters with ρ = 0.52, reflecting the reduced steric demand of hydrogen compared to oxygen in the quaternization of ester and aldehydic carbonyl groups. Rates of equilibration have also been measured in buffered methanol. For hexanal, with a 2:1 Et3N:AcOH buffer, the buffer-independent contribution is dominated by the methoxide catalysed pathway. Rates in this medium have been determined for isomers 1, 2, 3, 4, 5, 6, 7, 8 (X = CHO), and their logarithms do not correlate with logarithms of equilibrium constants for hemi-acetal formation or with substituent steric parameters derived from ester formation or saponification, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. It is suggested that transition states for hemi-acetal formation are relatively early so that steric interactions are effectively those between the nucleophile and ground state conformations of the aldehydes. A comparison of the entropies of hemi-acetal formation with entropies of activation has provided a basis for a suggested transition structure. Comparisons with acid chloride hydrolyses are made. Copyright 2013 John Wiley & Sons, Ltd. Logarithms of equilibrium constants for formation hemi-acetals of hexanal and its seven isomeric aldehydes correlate well with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters. Logarithms of rate constants for hemi-acetal formation do not, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. The reasons for this are discussed. Copyright
- Daw, Graham,Regan, Andrew C.,Watt, C. Ian F.,Wood, Evan
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p. 1048 - 1057
(2014/01/06)
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- From olefins to alcohols: Efficient and regioselective ruthenium-catalyzed domino hydroformylation/reduction sequence
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Exploring the alternatives: Ruthenium imidazoyl phosphine complexes catalyze the domino hydroformylation/reduction of alkenes to alcohols in good yields and with good selectivities (see scheme). Linear aliphatic alcohols are synthesized under reaction conditions typically used in industrial hydroformylations. Copyright
- Fleischer, Ivana,Dyballa, Katrin Marie,Jennerjahn, Reiko,Jackstell, Ralf,Franke, Robert,Spannenberg, Anke,Beller, Matthias
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supporting information
p. 2949 - 2953
(2013/04/10)
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- Identification of a marine NADPH-dependent aldehyde reductase for chemoselective reduction of aldehydes
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A putative aldehyde reductase gene from Oceanospirillum sp. MED92 was overexpressed in Escherichia coli. The recombinant protein (OsAR) was characterized as a monomeric NADPH-dependent aldehyde reductase. The kinetic parameters Km and kcat of OsAR were 0.89 ± 0.08 mM and 11.07 ± 0.99 s-1 for benzaldehyde, 0.04 ± 0.01 mM and 6.05 ± 1.56 s-1 for NADPH, respectively. This enzyme exhibited high activity toward a variety of aromatic and aliphatic aldehydes, but no activity toward ketones. As such, it catalyzed the chemoselective reduction of aldehydes in the presence of ketones, as demonstrated by the reduction of 4-acetylbenzaldehyde or the mixture of hexanal and 2-nonanone, showing the application potential of this marine enzyme in such selective reduction of synthetic importance.
- Li, Guangyue,Ren, Jie,Wu, Qiaqing,Feng, Jinhui,Zhu, Dunming,Ma, Yanhe
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- Serine carbonates
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Serine carbonates of formula I are precursors for organoleptic compounds, masking agents and antimicrobial agents. Further they are alternative substrates for malodor producing enzymes. The symbols in formula I are defined in claim 1.
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Beta-ketoester compounds
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The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
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- Ketone precursors for organoleptic compounds
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The invention discloses ketones of formula I: wherein, Y is an optionally substituted alkyl, cycloalkyl, or cycloalkylalkyl, wherein each alkyl group is straight or branched and each alkyl and cycloalkyl group is saturated or unsaturated; R1is hydrogen or a C1-6alkyl group that is substituted, saturated or unsaturated, straight or branched; A is a chromophoric substituted aromatic ring or ring system; n is an integer; and with the proviso that formula I is not 2-ethoxy-1-phenyl-ethanone. These compositions are useful for the delivery of organoleptic compounds, especially of flavors, fragrances, masking agents and antimicrobial compounds.
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- Complete structures of the sphingosine analog mycotoxins fumonisin B1 and AAL toxin T(A): Absolute configuration of the side chains
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Fumonisin B1 and AAL toxin T(A) are sphingosine-analog mycotoxins characterized by propane-1,2,3-tricarboxylic acid side chains esterified to alkylamine backbones. The absolute configuration of all stereogenic centers in the backbones is known. Using chiral gas chromatography methodology we have determined the absolute configuration at C-3' in the side chains to the S, thereby completing structure determination of both toxins.
- Shier,Abbas,Badria
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p. 1571 - 1574
(2007/10/02)
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- INSECT PHEROMONES AND THEIR ANALOGUES. XLII. SYNTHESIS OF 1,6-DIMETHYLOCT-1-YL FORMATE - A MIMIC OF THE AGGREGATION PHEROMONE OF FLOUR BEETLES
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2,6-Dimethyloctan-1-ol, the formate of which is a mimic of the aggregation pheromome of the flour beetles Tribolium confusum and T. castaneum, has been synthesized by the hydroboration of 2,6-dimethyloct-1-ene, obtained from β-methylvaleric acid.
- Odinokov, V. N.,Ushmuratov, G. Yu.,Yakovleva, M. P.,Tolstikov, G. A.
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p. 499 - 500
(2007/10/02)
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- Effect of the metal catalyst on the mechanism of hydrogenation of C6 acetylenic carbinols
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The most probable mechanism of the hydrogenation of tertiary and of primary C6 acetylenic carbinols on group VIII metals are discussed.By using mathematical modelling and deuterium exchange methods we have shown that in the presence of Pd, Rh, and Pt the reaction takes place by a series mechanism, whereas on Ru black the acetylenic C6 alcohols are hydrogenated by a series-parallel scheme.
- Sokolo'skii, D. V.,Zhubanova, L. K.,Omarkulov, T. O.,Sadykov, U. A.,Korolev, A. V.
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- Process for producing optically active alcohols
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A process for producing an optically active alcohol represented by formula (I): STR1 wherein R1 is an alkyl group having from 2 to 11 carbon atoms, an alkenyl group having from 3 to 11 carbon atoms, an alkadienyl group having from 6 to 11 carbon atoms, a cyclohexyl group, an cyclohexylmethyl group, or a cyclohexylethyl group, provided that the olefin in the alkenyl group or alkadienyl group is not conjugated to the olefin at the 2-position thereof; and * means an asymmetric carbon atom, is disclosed, comprising subjecting an olefinic alcohol represented by formula (II): STR2 wherein R1 is the same as defined above to asymmetric hydrogenation in the presence of, as a catalyst, a ruthenium-optically active phosphine complex. According to the process of the invention, the desired optically active alcohols which are useful not only as intermediates for the manufacture of perfumes and vitamin E but also as liquid crystal materials can be produced with high optical purities.
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- Transition-Metal-Promoted Alkylations of Unsaturated Alcohols: The Ethylation of 3-Butyn-1-ol and 3-Buten-1-ol via Titanium Tetrachloride-Organoaluminum Ziegler-Natta Catalyst Systems
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Reaction of 3-butyn-1-ol with diethylaluminum chloride followed by treatment with titanium tetrachloride under a variety of conditions gave selectively up to 70 percent yields of (E)-3-hexen-1-ol, the product expected from a syn ethylmetalation of the multiple bond.No complications arising from in situ β-hydride elimination were observed.Similarly, 4-pentyn-2-ol was ethylated to give (E)-4-hepten-1-ol; however, 3-pentyn-1-ol did not give an ethylated product.Additionally, the effect of "third components", i.e., Lewis bases, on the ethylation of 3-butyn-1-ol and 3-buten-1-ol was studied.
- Schultz, F. W.,Ferguson, G. S.,Thompson, D. W.
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p. 1736 - 1739
(2007/10/02)
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- Identification of the Aggregation Pheromone of Flour Beetles Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae)
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The aggregation pheromone produced by the male red flour beetle Tribolium castaneum, and confused flour beetles, T. confusum was identified as 4,8-dimethyldecan-1-al by GLC, GC-MS, PMR spectra, and synthesis of the compound.The synthetic pheromone was less attractive compared with the natural pheromone, because the synthetic sample was composed of four optical isomers.
- Suzuki, Takahisa
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p. 1357 - 1364
(2007/10/02)
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- Tin(IV) Ethoxide-catalysed Hydride Transfer from Alcohols to Carbonyl Compounds
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In aprotic, apolar solvents tin(IV) ethoxide has been proved to be an efficient catalyst for the selective hydride transfer from alcohols to carbonyl compounds.Primary, secondary, and benzyl alcohols have shown hydride-donating ability, and this ability decreases in the order benzylsecondaryprimary.The mechanism of hydride transfer from 1-phenylethanol to cyclohexanone has been investigated.Catalysis is inferred to proceed in the following order: (a) alcoholysis of Sn(IV)ethoxide to form a mixed metal alkoxide, (b) co-ordination of the acceptor to the metal, (c) direct hydride transfer from the alkoxide moiety to the co-ordinated carbonyl compound and loss of the active catalyst.The kinetic isotope effetc measurements and other data suggest that step (c) is the rate-determining step of the reaction.
- Casiraghi, Giovanni,Casnati, Giuseppe,Sartori, Giovanni,Zanafredi, Girolamo T.
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p. 407 - 411
(2007/10/02)
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