- Antimony(v) catalyzed acetalisation of aldehydes: An efficient, solvent-free, and recyclable process
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A highly selective, solvent-free process for the acetalisation of aldehydes was achieved by the use of a readily accessible antimony(v) catalyst which we previously prepared in our lab as a tetraarylstibonium triflate salt ([1][OTf]). High yields of the acetals were achieved in the presence of stoichimetric amounts of either triethoxymethane or triethoxysilane. It was found that triethoxymethane reactions required longer time to reach completion when compared to triethoxysilane reactions which were completed upon mixing of the reagents. The products can be easily separated from the catalyst by distillation which enabled further use of [1][OTf] in additional calytic reactions (up to 6 cycles). Moreover, [1]+ also catalyzed the deprotection of the acetals into their corresponding aldehydes using only water as a solvent.
- Ugarte, Renzo Arias,Hudnall, Todd W.
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p. 1990 - 1998
(2017/06/09)
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- Characterization of aroma compounds of Chinese "Wuliangye" and "Jiannanchun" liquors by aroma extract dilution analysis
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Aroma compounds in Chinese "Wuliangye" liquor were identified by gas chromatography-olfactometry (GC-O) after fractionation. A total of 132 odorants were detected by GC-O in Wuliangye liquor on DB-wax and DB-5 columns. Of these, 126 aromas were identified by GC-mass spectrometry (MS). Aroma extract dilution analysis (AEDA) was further employed to identify the most important aroma compounds in "Wuliangye" and "Jiannanchun" liquors. The results showed that esters could be the most important class, especially ethyl esters. Various alcohols, aldehydes, acetals, alkylpyrazines, furan derivatives, lactones, and sulfur-containing and phenolic compounds were also found to be important. On the basis of flavor dilution (FD) values, the most important aroma compounds in Wuliangye and Jiannanchun liquors could be ethyl butanoate, ethyl pentanoate, ethyl hexanoate, ethyl octanoate, butyl hexanoate, ethyl 3-methylbutanoate, hexanoic acid, and 1,1-diethoxy-3-methylbutane (FD ≥ 1024). These compounds contributed to fruity, floral, and apple- and pineapple-like aromas with the exception of hexanoic acid, which imparts a sweaty note. Several pyrazines, including 2,5-dimethyl-3-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2,6-dimethylpyrazine, 2,3,5-tri-methylpyrazine, and 3,5-dimethyl-2-pentylpyrazine, were identified in these two liquors. Although further quantitative analysis is required, it seems that most of these pyrazine compounds had higher FD values in Wuliangye than in Jiannanchun liquor, thus imparting stronger nutty, baked, and roasted notes in Wuliangye liquor.
- Fan, Wenlai,Qian, Michael C.
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p. 2695 - 2704
(2007/10/03)
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- A convenient and highly efficient method for the protection of aldehydes using very low loading hydrous ruthenium(III) trichloride as catalyst
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A convenient method for the chemoselective protections of both aliphatic and aromatic aldehydes has been developed. Ruthenium(III) trichloride (0.1 mol %) has found to be an highly efficient catalyst in the acetalizations of aldehydes with various simple alcohols such as methanol, ethanol, or diols such as 1,2-ethylanediol and 1,3-propanediol under mild reaction conditions.
- Qi, Jian-Ying,Ji, Jian-Xin,Yueng, Chi-Hung,Kwong, Hoi-Lun,Chan, Albert S.C.
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p. 7719 - 7721
(2007/10/03)
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- Action d'organometalliques sur les dialkylphenylorthoformiates. Preparation facile d'acetals
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The reaction of dialkylphenylorthoformiates with organometallic compounds proceeds with a good yield, at room temperature, giving the corresponding dialkylacetals ; it allows an easy preparation of acetals which are otherwise difficult to prepare.
- Barbot, Francis,Poncini, Laurence,Randrianoelina, Benjamin,Miginiac, Philippe
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p. 4016 - 4035
(2007/10/02)
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- Une voie d'acces aux alcoxy-5 trimethyl-4,4,7a hexahydro-3aα,4,5,6,7,7aα (3H)-benzofurannones-2
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Starting from 2-methoxy (or ethoxy)-3,4-dihydro-2H-pyran, a series of four reactions allows to obtain a good yield of two 4-alcoxy-3,3-dimethyl-1-hydroxymethyl cyclohexenes which are converted to methylenecyclohexylacetic acids by different or sigmatropic reactions.These acids are cyclized at room temperature with concentrated sulfuric acid into bicyclic γ-lactones having a cis-junction.The stereospecificity of this reaction and the stability of the isomers obtained are discussed.
- Gosselin, Pascal,Rouessac, Francis,Zamarlik, Henri
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p. 192 - 198
(2007/10/02)
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- High-pressure kinetics of electron donor-acceptor complex formation and cycloaddition between tetracyanoethylene and enol ethers
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The kinetics of the high-pressure cycloaddition reaction between tetracyanoethylene and enol ethers (n-butyl vinyl ether and ethyl 2-methylpropenyl ether) in chloroform have been studied, by following spectrophotometrically the disappearance of the electron donor-acceptor complex (e.d.a. complex) at 25°C and up to 1 500 bar. It is concluded that the e.d.a. complex is on the pathway to the zwitterionic intermediate and the final cycloaddition product. The reaction volume ΔV1 of e.d.a. complex formation is -11.0 ± 1.4 and -5.8 ± 1.0 cm3 mol-1 for n-butyl vinyl ether and ethyl 2-methylpropenyl ether, respectively. The volume of activation ΔV2? of cycloaddition step from e.d.a. complex to the adduct is -30.8 ± 1.5 and -41.8 ± 1.5 cm3 mol-1 for n-butyl vinyl ether and ethyl 2-methylpropenyl ether, respectively. The variation of ΔV 1 and ΔV2? is discussed from the viewpoint of the ionization potential and the electron density at the β-carbon atom of the enol ether.
- Sasaki, Muneo,Tsuzuki, Hideaki,Osugi, Jiro
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p. 1596 - 1600
(2007/10/02)
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