- Synthesis and pyrolysis of two novel pyrrole ester flavor precursors
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In order to develop the high-temperature-released pyrrole aroma, two novel flavors precursors of methyl 2-methyl-5-(((2-methylbutanoyl)oxy)methyl)-1-propyl-1H-pyrrole-3-carboxylate and methyl 2-methyl-5-(((2-methylbutanoyl)oxy)methyl)-1-propyl-1H-pyrrole-3-carboxylate were synthesized using glucosamine hydrochloride and methyl acetoacetate as raw materials through cyclization, oxidation, alkylation, reduction, and esterification. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high-resolution mass spectrometry (HRMS). Thermogravimetry (TG), differential scanning calorimeter (DSC) and the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) methods were used to analyze the heating-stability of the target compounds, and the pyrolysis mechanism was inferred. Py-GC/MS results indicated that some fragrance compounds were formed during?thermal degradation such as 2-methylbutyric acid, 2-methylbutyrate, alkylpyrroles, and benzoic acid, which were important aroma components or flavor additives. This provided a theoretical reference for the application of pyrrole ester in cigarette and heat-processed food flavoring.
- Cheng, Biao,Chu, Wenjuan,Fan, Wenpeng,Feng, Yingjie,Gao, Ziting,Ji, Xiaoming,Lai, Miao,Tian, Haiying,Zhang, Zhan
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- Photocatalytic Hydromethylation and Hydroalkylation of Olefins Enabled by Titanium Dioxide Mediated Decarboxylation
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A versatile method for the hydromethylation and hydroalkylation of alkenes at room temperature is achieved by using the photooxidative redox capacity of the valence band of anatase titanium dioxide (TiO2). Mechanistic studies support a radical-based mechanism involving the photoexcitation of TiO2 with 390 nm light in the presence of acetic acid and other carboxylic acids to generate methyl and alkyl radicals, respectively, without the need for stoichiometric base. This protocol is accepting of a broad scope of alkene and carboxylic acids, including challenging ones that produce highly reactive primary alkyl radicals and those containing functional groups that are susceptible to nucleophilic substitution such as alkyl halides. This methodology highlights the utility of using heterogeneous semiconductor photocatalysts such as TiO2 for promoting challenging organic syntheses that rely on highly reactive intermediates.
- Zhu, Qilei,Nocera, Daniel G.
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supporting information
p. 17913 - 17918
(2020/12/04)
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- Method for preparing organic carboxylic ester through combined catalysis of aryl bidentate phosphine ligand
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The invention discloses a method for preparing organic carboxylic ester by combined catalysis of an aryl bidentate phosphine ligand. The method comprises the following steps: under the action of a palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, carrying out a hydrogen esterification reaction on terminal olefin, carbon monoxide and alcohol so as to generate theorganic carboxylic ester with one more carbon than olefin. According to the invention, by adoption of the palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, good catalytic activity and selectivity for the hydrogen esterification reaction of the olefin are achieved, and olefin carbonylation to synthesize organic carboxylic ester can be efficiently catalyzed. Thearyl bidentate phosphine ligand has a rigid skeleton structure of a rigid ligand and the flexibility of a flexible ligand, so the aryl bidentate phosphine ligand has proper flexibility due to the characteristic that the aryl bidentate phosphine ligand is soft and rigid, and a most favorable coordination mode and a stable active structure in space are favorably formed. In addition, the aryl bidentate phosphine ligand has the advantages of high stability, simple and convenient synthesis method and the like; and a novel industrial technology is provided for production of organic carboxylate compounds.
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Paragraph 0043
(2020/05/29)
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- Iron-catalysed 1,2-aryl migration of tertiary azides
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1,2-Aryl migration of α,α-diaryl tertiary azides was achieved by using the catalytic system of FeCl2/N-heterocyclic carbene (NHC) SIPr·HCl. The reaction generated aniline products in good yields after one-pot reduction of the migration-resultant imines.
- Wei, Kaijie,Yang, Tonghao,Chen, Qing,Liang, Siyu,Yu, Wei
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supporting information
p. 11685 - 11688
(2020/10/19)
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- mCPBA-mediated dioxygenation of unactivated alkenes for the synthesis of 5-imino-2-tetrahydrofuranyl methanol derivatives
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A mCPBA-mediated, metal-free, intramolecular dioxygenation reaction of unactivated alkenes is reported. In the presence of m-chlorobenzoic peracid, different unsaturated amide substrates could be cyclized via epoxide intermediates, producing the corresponding 5-imino-2-tetrahydrofuranyl methanol products in up to 94% yield at room temperature.
- Deng, Xiaojun,Zhang, Luwen,Liu, Huixia,Bai, Yu,He, Wei
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supporting information
(2020/11/24)
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- Acid-catalyzed oxidation of levulinate derivatives to succinates under mild conditions
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Levulinate derivatives are an attractive platform for the production of renewable chemicals. Here we report on the oxidation of methyl levulinate into dimethyl succinate with peroxides under mild conditions using Br?nsted and Lewis acid catalysts. Selectivities to succinate and acetate derivatives of approximately 60 and 40 %, respectively, were obtained with strong Br?nsted acids in methanol. Although the molecular structure (i.e., carbon-chain length and branching around the C=O group) and the oxidant type affect the product distribution, solvent choice has the strongest impact on changing the location of oxygen insertion into the carbon backbone. Specifically, switching the solvent from methanol to heptane resulted in a decrease in the succinate/acetate ratio from 1.6 to 0.3. In contrast to Br?nsted acids, we demonstrate that the nature of the metal cation is responsible for changing the reaction selectivity of water-tolerant Lewis acidic triflate salts.
- Wang, Yuran,Vogelgsang, Ferdinand,Román-Leshkov, Yuriy
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p. 916 - 920
(2015/03/18)
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- Carbogallation of alkynes using gallium tribromide and silyl ketene acetals and synthetic application to cross-coupling with aryl iodides
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Try substituted alkynes with GaBr3: The regio- and stereoselective carbogallation of alkynes has been achieved by a simple treatment of GaBr3, alkynes, and ketene silyl acetals. The produced alkenylgallium compounds can be used for the synthesis of selective trisubstituted alkenes through successive cross-coupling with aryliodides (see scheme). The usability of the carbogallation was presented by the total synthesis of meroterpenoid nodosol, which was extracted from the seagrass Cymodocea nodosa. Copyright
- Nishimoto, Yoshihiro,Ueda, Hiroki,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 11135 - 11138
(2011/10/31)
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- Oxidation of β-dicarbonyl compounds with tert-butyl hydroperoxide in the presence of vanadyl acetylacetonate
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Oxidation of β-dicarbonyl compounds with tert-butyl hydroperoxide in the presence of vanadyl acetylacetonate (benzene, 20°C) involves the activated methylene group with intermediate formation of trioxo derivatives and is accompanied by decomposition of carbon skeleton. The oxidation products are carbon dioxide, carboxylic acids, and tert-butyl and peroxy esters derived from the latter.
- Stepovik,Gulenova,Kalacheva,Potkina, A. Yu.
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scheme or table
p. 550 - 558
(2011/06/23)
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- Homogeneous asymmetric hydrogenation catalyst
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Provide that a useful catalyst for homogeneous hydrogenation, particularly a catalyst for homogeneous asymmetric hydrogenation for hydrogenation, particularly asymmetric hydrogenation, which is obtainable with comparative ease and is excellent in economically and workability, and a process for producing a hydrogenated compound of an unsaturated compound, particularly an optically active compound using said catalyst with a high yield and optical purity.
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- A cytotoxic and apoptosis-inducing sesquiterpenoid isolated from the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk)
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Repeated silica gel and octadecyl silica gel (ODS) column chromatography of the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk) led to the isolation of a new sesquiterpenoid, 3-((S)-2-methylbutyryloxy)-costu-1(10),4(5)- dien-12,6α-olide (2), along with two previously reported sesquiterpenoids: 8α-angeloyloxy-3β,4β-epoxy-6βH,7αH,8βH-guaia- 1(10),11(13)-dien-12,6α-olide (1, carlaolide B) and 3β,4β-epoxy- 8α-isobutyryloxy-6βH,7αH,8βH-guaia-1(10),11(13)-dien-12, 6α-olide (3, carlaolide A). The structure of compound 2 was elucidated by spectroscopic data analysis, including one dimensional (1D) and two dimensional (2D) nuclear magnetic resonance (NMR) experiments. Of the isolates, compound 2 exhibited potent cytotoxicity against human cervix adenocarcinoma cells and induced apoptosis.
- Bang, Myun-Ho,Han, Min-Woo,Song, Myoung-Chong,Cho, Jin-Gyeong,Chung, Hae-Gon,Jeong, Tae-Sook,Lee, Kyung-Tae,Choi, Myung-Sook,Kim, Se-Young,Baek, Nam-In
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experimental part
p. 1168 - 1172
(2009/09/06)
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- Hasubanan type alkaloids from Stephania longa
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Thirteen new hasubanan type alkaloids, stephalonines A-I (1-9), norprostephabyssine (15), isoprostephabyssine (16), isolonganone (18), and isostephaboline (21), as well as nine known ones, were isolated from the whole plants of Stephania longa, a well-known traditional Chinese medicine. Their structures were elucidated on the basis of spectroscopic data and chemical methods.
- Zhang, Hua,Yue, Jian-Min
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p. 1201 - 1207
(2008/09/17)
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- How is chemical interesterification initiated: Nucleophilic substitution or α-proton abstraction?
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Esters of carboxylic acids including 2-methylhexanoic, 2-methylbutyric, 2,2-dimethyl-4-pentenoic, palmitic, and oleic acids were tested as substrates in methoxide-catalyzed interesterification and transesterification. The aliphatic acid esters participated in the ester-ester interchange upon addition of catalytic sodium methoxide. Their isopropyl esters also produced methyl esters on heating with sodium methoxide. The esters of dimethyl-substituted acids did not participate in the ester-ester interchange. Their isopropyl esters did not react with methoxide to produce methyl esters. However, upon addition of methanol with sodium methoxide, their methyl esters were produced. These results indicate that the first step in interesterification is possibly that methoxide abstracts the α-hydrogen of an ester to form a carbanion. Interesterification is then likely completed via a Claisen condensation mechanism involving the β-keto ester anion as the active intermediate. The β-keto ester anion contains positively charged ketone and acyl carbons that are active sites for nucleophilic attack by anions such as methoxide and glycerinate, which would produce a methyl ester or rearrange acyls randomly. On the other hand, transesterification is a nucleophilic substitution by methoxide at the acyl carbon in the presence of methanol.
- Liu, Linsen
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p. 331 - 337
(2007/10/03)
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- Stereoselective Formation of cis-2,3-Dimethylcyclopropanone Hemiacetals from 2-Halo-3-pentanones. - Cycloadditions with Conjugated Diene Systems
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2-Chloro- and 2-bromo-3-pentanone (1,2) react in methanol, ethanol, and 2-propanol with the corresponding sodium alkoxides in a highly stereoselective manner to provide the hemiacetals of cis-2,3-dimethylcyclopropanone (4aα-4cα).The benzoate of 4aα was characterized by an X-ray crystal structure determination. cis-2,3-Dimethylcyclopropanone can be trapped by an aldol type addition with dimethyl malonate.It undergoes a disrotatory retro-electrocyclic ring opening to form a W-configured allylium-2-olate (oxyallyl) 10 which combines with isoprene, (E)-1,3-pentadiene,furan, and 2-methylfuran in highly stereoselective cycloadditions.With methanol and 2,2,2-trifluoroethanol, the 2-alkoxy-3-pentanones are formed.N-Methylpyrrol is oxoalkylated at the 2-position.
- Foehlisch, Baldur,Gehrlach, Eberhard,Stezowski, John J.,Kollat, Petra,Martin, Eveline,Gottstein, Wolfgang
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p. 1661 - 1682
(2007/10/02)
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- Thermochemical Studies of Carbonyl Compounds. 3. Enthalpies of Hydrolysis of Ortho Esters
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The enthalpies of hydrolysis of a series of ortho esters have been measured in aqueous dioxane.The largest effect on ΔHr was found with α-branching, in contrast to the previously reported hydrolysis of ketals which gave the larger effect with β-branching.Possible reasons for this difference in behavior are discussed.
- Wiberg, Kenneth B.,Martin, Eric J.,Squires, Robert R.
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p. 4717 - 4720
(2007/10/02)
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- Photochemical Hydroformylation with Cobalt Catalysts in Methanol
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The photochemical hydroformylation of 1-octene with cobalt/phosphane complexes in methanol leads under mild conditions (80 deg C, 80 bar CO/H2) with >= 90percent selectivity to linear aldehydes.The reaction rate increases with temperature (Ea = 5 - 6 kcal/mol) and synthesis gas pressure, and is nearly independent of the cobalt source, e.g.Co(OAc)2, Co2(CO)8, or Co2(CO)6(PBu3)2.At low pressures hydroesterification is the preferred photoreaction of 1-octene.Isoprene reacts under similar conditions to give unsaturated oxoproducts and linear isoprene dimers.With unmodified octacarbonyldicobalt the hydroformylation of internal olefins is enhanced by UV light, but not the reaction of terminal olefins or dienes.UV irradiation of cobalt acetate under hydroformylation conditions leads to rapid reduction of the Co(II) species, thus decreasing the induction period from ca. 15 h (without irradiation) to ca. 30 min.
- Mirbach, Manfred J.,Topalsavoglou, Nikolaos,Phu, Tuyet Nhu,Mirbach, Marlis F.,Saus, Alfons
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p. 1422 - 1440
(2007/10/02)
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- Free Radical Substitution. Part 38. The Effect of Solvent on the Atomic Chlorination and Bromination of 2-Substituted Butanes and the Importance of Steric Effects
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The relative selectivity of atomic halogenation of 2-substituted butanes is influenced by the phase and by solvents.There are solvents which increase the selectivity compared with the gas phase and solvents which decrease the relative selectivity.However the most striking feature of the halogenation (especially the bromination) of 2-substituted butanes is the high reactivity of the 2-position notwithstanding very unfavourable polar effects.This reactivity is attributed to the release of steric compression associated with the abstraction of the tertiary hydrogen atom.The halogenation of butan-2-ol esters is associated with some decomposition of 2-butyl radical (OCOR)CH3> and the chlorination of 2-phenylbutane with the formation of olefins 2-phenylbut -1-ene and 2-phenylbut-2-ene.
- Atto, Saeed Y.,Tedder, John M.,Walton, John C.
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p. 629 - 634
(2007/10/02)
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- Chlorination of Carboxylic Acid Derivatives. VIII. Liquid Phase Chlorination of the Aliphatic C5-Carboxylic Acids and Their Chlorides, Methyl Esters and Chloromethyl Esters with Chlorine
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The chlorination of pentanoic, 3-methylbutanoic, 2-methylbutanoic and 2,2-dimethylpropanoic acids and their derivatives with chlorine in the liquid phase have been investigated.The monochloro products formed were determined by gas-liquid chromatography (GLC) and gas-liquid chromatography-mass spectrometry (GLC-MS) as their esters through the comparison with authentic samples.The deactivation of position 2 decreases in the order COCl > CO2H > CO2CH2Cl > CO2CH3, the effect of the COCl-group in pentanoic acid derivatives being 4.3 times stronger than that of the CO2CH3-group.The deactivation is smallest in 2-methylbutanoic acid derivatives owing to the electron-donating methyl group.The EI mass spectra of the methyl and chloromethyl esters have been studied in detail.
- Kornonen, Ilpo O. O.
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p. 467 - 474
(2007/10/02)
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- Stereochemistry of the Platinum Catalyzed Hydroformylation of Olefins
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The deuterioformylation of (Z)- or (E)-2-butene catalyzed by Pt(SnCl3)Cl gives predominantly erythro- or threo-1,3-2-2-methylbutanal respectively.Hence, hydroformylation by this catalytic system must take place with cis-stereochemistry.
- Haelg, Paul,Consiglio, Giambattista,Pino, Piero
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p. 1865 - 1869
(2007/10/02)
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- 13C-NMR. Spectral Differences between Corresponding Methyl Esters, Phenyl Esters and 2-Substituted Chromones
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The 13C-NMR. spectra of 2-substituted chromones (3) are compared with the data of the analogous methyl and phenyl esters (1 and 2).The chemical shift differences found are most prominent for the C-atoms in β-position to the ester carbonyl and chromone C(2), respectively.These shift differences are discussed in terms of conformational differences between the esters 1 and 2 and the analogous chromones 3.
- Sequin, Urs
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p. 2654 - 2664
(2007/10/02)
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