- New neryl esters from Helichrysum italicum (Roth) G. Don (Asteraceae) essential oil
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Helichrysum italicum (immortelle) is a dwarf aromatic shrub native to the Mediterranean region. The typical subspecies (italicum) produces an essential oil rich in neryl acetate and characteristic β-diketones, italidiones, highly valued in the perfume industry. As esters are an important group of aroma-active volatiles, herein the composition of the ester fraction of this immortelle chemotype essential oil was studied in detail. Chromatographic separation of Corsican immortelle essential oil enabled the discovery of numerous potentially olfactory-interesting esters of nerol and/or angelic acid, undetectable by direct GC-MS analyses of the unfractioned oil. Four esters of nerol and medium-chain branched fatty acids represent new natural products, while several other esters have a rather restricted occurrence in the Plant Kingdom.
- ?or?evi?, Miljana R.,?ivkovi? Sto?i?, Milena Z.,Aksi?, Jelena M.,Gen?i?, Marija S.,Mladenovi?, Marko Z.,Radulovi?, Niko S.
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supporting information
(2020/11/02)
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- Regioselectivity inversion tuned by iron(iii) salts in palladium-catalyzed carbonylations
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Impactful regioselectivity control is crucial for cost-effective chemical synthesis. By using cheap and abundant iron(iii) salts, the hydroxycarbonylations of both aromatic and aliphatic alkenes were significantly enhanced in both reactivity and selectivity (iso/n or n/iso up to >99:1). Moreover, Pd-catalyzed carbonylation selectivity can be switched from branched to linear by using different Fe(iii) salts. In addition, similar results were obtained for the carbonylation of secondary alcohols.
- Huang, Zijun,Cheng, Yazhe,Chen, Xipeng,Wang, Hui-Fang,Du, Chen-Xia,Li, Yuehui
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supporting information
p. 3967 - 3970
(2018/04/23)
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- A Comprehensive Study on Metal Triflate-Promoted Hydrogenolysis of Lactones to Carboxylic Acids: From Synthetic and Mechanistic Perspectives
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Direct hydrogenolysis of lactone to carboxylic acid (i.e., hydrogenolysis of the Calkoxy-O bond with the carbonyl group untouched) is generally difficult, as the current strategies employing Br?nsted acids as the catalyst usually require harsh conditions such as a high temperature and a high H2 pressure. Herein, we report a developed solvent-free catalytic transformation, in which W(OTf)6 is believed to promote the hydrogenolysis process. This strategy could efficiently hydrogenate lactones to carboxylic acids under extra mild conditions (e.g., a reaction temperature of 2) and showed a broad substrate scope. In addition, the catalytic protocol can be further applied to the hydrogenolysis of polyhydroxyalkanoate, as a renewable polymer, to the corresponding straight-chain carboxylic acids. An extensive mechanistic study was subsequently performed, and the density functional theory calculations revealed a reaction pattern, including the complete cleavage of the C=O bond with the assistance of the W(OTf)6 catalyst. Moreover, the key intermediate created in the mechanism, as an oxonium with an OTf moiety, was successfully detected by electrospray ionization mass spectra. Through a comparison with the Br?nsted acid-catalyzed system, the study confirmed that the existence of the OTf moiety can significantly lower the barriers associated with the rearrangement and elimination processes. Meanwhile, emphasis was placed on the critical role that the anion plays, as well as the fact that the anion effect is directly related to the chemoselectivity.
- Zhu, Rui,Jiang, Ju-Long,Li, Xing-Long,Deng, Jin,Fu, Yao
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p. 7520 - 7528
(2017/11/10)
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- Dianion of sulfinylacetone as a synthetic equivalent of β-enolate of propionic acid: A novel synthesis of carboxylic acids from alkyl halides with three-carbon elongation
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The reaction of the dianion of phenylsulfinylacetone with alkyl halides afforded β-keto sulfoxides, which were first chlorinated with hexachloroethane and then treated successively with KH and t-BuLi to give carboxylic acids in three-steps in moderate overall yields from the alkyl halides. This procedure affords a good method for a synthesis of carboxylic acids from alkyl halides with three-carbon elongation.
- Satoh, Tsuyoshi,Imai, Kentaro
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p. 602 - 604
(2007/10/03)
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- Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia
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The partial configurations of C25 isoprenoid alkenes isolated from the diatom Haslea ostrearia Gaillon (Simonsen) have been established. A combination of NMR spectroscopy studies of the alkenes with chiral shift reagents in conjunction with soluble silver β-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed between different laboratory cultures of the alga. (C) 2000 Elsevier Science Ltd.
- Johns, Lesley,Belt, Simon,Lewis, C. Anthony,Rowland, Steven,Masse, Guillaume,Robert, Jean-Michel,Koenig, Wilfried A.
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p. 607 - 611
(2007/10/03)
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- Processes for producing aromatic polycarbonate oligomer and aromatic polycarbonate
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A process for producing continuously an aromatic polycarbonate oligomer by reacting an aromatic dihydroxy compound and an alkali metal base or an alkaline earth metal base with a carbonyl halide compound comprises: (1) feeding continuously to a tank reactor an aromatic dihydroxy compound, water, a molecular weight controlling agent, a polymerization catalyst, a carbonyl halide compound, and an organic solvent, and an alkali metal base or an alkaline earth metal base in an amount of 1.15-1.6 equivalents based on the aromatic dihydroxy compound, (2) carrying out the reaction with a residence time as defined by the following formula, where X is an amount of the polymerization catalyst in terms of mole % based on the amount of mole of the aromatic dihydroxy compound fed per unit time, and Y is a residence time (min.), and (3) continuously withdrawing the reaction mixture from the tank reactor to obtain an aromatic polycarbonate oligomer having a number average molecular weight of 1,000-10,000. An aromatic polycarbonate is produced by polycondensation of the aromatic polycarbonate oligomer.
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- Metal Alkoxide Modified Organometallic Reagents. Preparation and Stability of Organolithium Reagents in Tetrahydrofuran in the Presence of Magnesium 2-Ethoxyethoxide
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The metalating ability of alkyllithium reagents and their tendency to cleave THF are greatly diminished in the presence of magnesium 2-ethoxyethoxide, 1.Advantage may be taken of this to generate organolithium reagents in THF in the presence of 1 under conditions not normally favorable to their stability.Thus, by reaction with metallic lithium in the presence of 1 in THF, the compounds RX (R = n-Bu, s-Bu, t-Bu, cyclohexyl, menthyl, p-methoxyphenyl, o-(methoxymethyl)phenyl; X = Cl, Br) have been converted to the corresponding organometallic reagents.In the absence of 1 the alkyllithium reagents formed react with the solvent, resulting in reduced yields and often alternative products.In the case of the preparation of the arylmetal reagents the presence of 1 suppresses either subsequent orthometalation (R = p-methoxyphenyl) or Wittig rearrangement (R = o-(methoxymethyl)phenyl) to give a clean replacement of halogen by the metal.The presence of THF is also tolerated in the preparation of these two arylmetal reagents by halogen-metal exchange using n-butyllithium in the presence of 1 whereas if 1 is absent little or none of the desired product is obtained.
- Screttas, Constantinos G.,Steele, Barry R.
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p. 1013 - 1017
(2007/10/02)
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- LITHIATED CYCLOPROPANONE KETALS
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The ketene acetal I reacted with dibromocarbene yielding the dibromocyclopropanone ketal II, which was reduced to the monobromide III by treatment with tri-n-butyltin hydride.Reaction of III with n-butyllithium at -78 degC yielded the lithiated cyclopropanone ketal IV, which yielded adducts with acetone, cyclohexanone, cyclohexenone, 3,3,3-trimethoxybutan-2-one, and 3-pentanone.
- Dowd, Paul,Kaufman, Christopher,Kaufman, Paul,Paik, Yi Hyon
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p. 2279 - 2282
(2007/10/02)
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- SYNTHESIS OF SOME NEW CHOLESTERYL ESTERS OF CHIRAL ALKANOIC ACIDS.
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Six new cholesteryl esters have been prepared from chiral alkanoic acids. Oxidation of 2(S)-methylbutanol and 2(S)-ethyl-3-methybutyraldehyde gave the corresponding butyric acids, while condensation of the tosylates of the corresponding alcohols with diethyl malonate led ultimately to the substituted hexanoic acids. 2(R)-Methylpentanoic and ( minus )-2-ethylhexanoic acids were commercially available.
- Gibson
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