- One-pot Synthesis of Acetals by Tandem Hydroformylation-acetalization of Olefins Using Heterogeneous Supported Catalysts
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Abstract: A green route for one?pot synthesis of acetals by tandem hydroformylation?acetalization of olefins using supported Rh?based?catalysts was developed. Experimental results demonstrated that suitable Rh loading (1 wt%) with appropriate reaction temperature (120?°C) and reaction time (8?h) were favorable for the formation of acetals, and a high acetals selectivity of 94.6% was achieved. More importantly, the selectivity to valuable linear products was enhanced in this tandem catalysis. Based on the catalytic mechanism study, highly dispersed RhOx nanoparticles and abundant acid sites on the supports were responsible for the hydroformylation and acetalization, respectively. Graphical abstract: One-pot synthesis of acetals directly from olefins with high selectivity was achieved over heterogeneous bifunctional catalysts via tandem hydroformylation-acetalization. [Figure not available: see fulltext.]
- Li, Xiao,Qin, Tingting,Li, Liusha,Wu, Bo,Lin, Tiejun,Zhong, Liangshu
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p. 2638 - 2646
(2021/01/05)
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- METHOD OF FORMING MONOMERS AND FURFURAL FROM LIGNOCELLULOSE
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The present disclosure relates to a method of producing monophenolicmonomers and furfural from lignocellulosic biomass beating the biomass in a solvent together with a zeolite based catalyst.
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Page/Page column 23; 24
(2020/06/05)
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- Silver-Catalyzed Olefination of Acetals and Ketals with Diazoesters to β-Alkoxyacrylates
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The first silver-catalyzed reaction of acetals or ketals with diazoesters leading to trisubstituted or tetrasubstituted β-alkoxyacrylates is now reported. A broad range of acetals and ketals bearing different substituents is compatible with this protocol and thus provides an attractive approach for the synthesis of complex β-alkoxyacrylates. The power of this method was further demonstrated by the successful synthesis of picoxystrobin, which is one of the most popular agricultural fungicides commercialized by Dupont.
- Li, Jiawen,Qian, Bo,Huang, Hanmin
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supporting information
p. 7090 - 7094
(2018/11/23)
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- 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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- Decomposition of a Β-O-4 lignin model compound over solid Cs-substituted polyoxometalates in anhydrous ethanol: acidity or redox property dependence?
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Production of aromatics from lignin has attracted much attention. Because of the coexistence of C–O and C–C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone (2-PAP), was investigated over several cesium-exchanged polyoxometalate (Cs-POM) catalysts. Decomposition of 2-PAP can follow two different mechanisms: an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox properties of the catalysts. The catalysts of POMs perform the following functions: promoting active hydrogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen liberation and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP (>99%) with excellent selectivities to the desired products (98.6% for phenol and 91.1% for acetophenone) can be achieved.
- Wu, Xuezhong,Jiao, Wenqian,Li, Bing-Zheng,Li, Yanming,Zhang, Yahong,Wang, Quanrui,Tang, Yi
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p. 1216 - 1228
(2017/07/10)
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- Tropylium salts as efficient organic Lewis acid catalysts for acetalization and transacetalization reactions in batch and flow
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Acetalization reactions play significant roles in the synthetically important masking chemistry of carbonyl compounds. Herein we demonstrate for the first time that tropylium salts can act as organic Lewis acid catalysts to facilitate acetalization and transacetalization reactions of a wide range of aldehyde substrates. This metal-free method works efficiently in both batch and flow conditions, prompting further future applications of tropylium organocatalysts in green synthesis.
- Lyons,Crocker,Enders,Nguyen
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supporting information
p. 3993 - 3996
(2017/09/08)
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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives
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Fe(BF4)2·6H2O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)2 can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.
- Chowdhury, Abhishek Dutta,Lahiri, Goutam Kumar
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supporting information; experimental part
p. 3448 - 3450
(2012/05/20)
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- Synthesis of chiral acetals by asymmetric selenenylations
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Asymmetric selenenylations of (E)-ethoxystyrene are described leading to chiral acetals. An efficient synthesis of such compounds including the determination of their absolute configuration is described.
- Uehlin, Lars,Wirth, Thomas
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experimental part
p. 1374 - 1385
(2010/03/03)
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- Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes
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Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl2 are added, which significantly stabilize the cationic Au(III). The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 3080 - 3082
(2008/02/10)
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- Acid-free, organocatalytic acetalization
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The acid-free, organocatalytic acetalization of various aldehydes and ketones with N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is presented. The neutral, double hydrogen bonding thiourea catalyst can be used at very low loadings of 0.01-1 mol% at room temperature to furnish the respective acetals in 65-99% yield at turnover frequencies around 600 h-1. Acid-labile TBDMS-protected as well as unsaturated aldehydes can be converted efficiently into their acetals utilizing this very mild and highly practical method.
- Kotke, Mike,Schreiner, Peter R.
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p. 434 - 439
(2007/10/03)
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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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- Sulfamic acid as a cost-effective and recyclable catalyst for protection of carbonyls to acetals and ketals under mild conditions
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An efficient H2NSO3H-catalyzed protection of various carbonyl compounds at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple workup, and the recyclability of the catalyst were represented in this process.
- Gong, Weizhong,Wang, Bo,Gu, Yanglong,Yan, Liang,Yang, Liming,Suo, Jishuan
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p. 4243 - 4247
(2007/10/03)
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- Solvolysis of styryliodonium salt: Products, rates, and mechanisms
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The solvolysis of phenyl[(E)-styryl]iodonium tetrafluoroborate in various solvents was examined at 50-70°C by means of product and kinetic studies with the normal and labeled substrates. The reactions involved are α-elimination and substitutions with configurational retention and inversion. In methanol and ethanol, the main reaction is α-elimination, along with about 5% of substitution with the ratio of inversion/retention from 4/6 to 3/7. As the basicity of the solvent decreases, the reaction rate and the fraction of α-elimination decrease, and at the same time the ratio of inversion/retention of substitution also decreases. In 2,2,2- trifluoroethanol, only the substitution with retention was observed. Labeling experiments showed that complete isotope scrambling occurred between the olefinic hydrogens of the retained product while the deuterium remained at the original position of the inverted product. The substitution mechanism is concluded to involve parallel pathways: an S(N) 1-type with a vinylenebenzenium ion intermediate leading to retention and a vinylic S(N) 2- type with a direct attack by the nucleophilic solvent leading to inversion.
- Okuyama, Tadashi,Ishida, Yoshimi,Ochiai, Masahito
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p. 163 - 170
(2007/10/03)
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- Diethoxymethyllithium: generation via transmetallation of diethoxymethyltributyltin, stability, nucleophilic reactivity in addition reactions, and use as a precursor of group 14 formylmetals
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Diethoxymethyltributyltin and bimethoxymethyltributyltin have been converted into the corresponding dialkoxymethyllithium reagents upon transmetallation by n-butyllithium in THF.Temperature appears to be the key parameter controlling the decomposition of diethoxy- (or dimethoxy-) methyllithium.Inside the reactor, -78 deg C appears to be the borderline temperature to allow trapping experiments with electrophiles before decomposition.Nucleophilic addition on carbonyl derivatives has been examined and the evaluation of stereochemical trends and regiochemical trends (1,2-/1,4-addition in the case of α,β-enones) has been used to characterize the chemical behavior of this type of reagent.Furthermore, in the case of electrophilic trapping by chlorosilanes or chlorogermanes, the expected α-silyl or α-germylacetals have been obtained and their hydrolysis into group 14 formylmetals has been observed using electronic spectrometry.Keywords: transmetallation / formylanion equivalent / d1 umpoled reagent / diethoxymethyllithium / nucleophilic reactivity / formylsilanes / formylgermanes / formylstannanes
- Parrain, Jean-Luc,Beaudet, Isabelle,Cintrat, Jean-Christophe,Duchene, Alain,Quintard, Jean-Paul
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p. 304 - 312
(2007/10/02)
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- Process for the preparation of arylacetaldehyde-dialkylacetals
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Arylacetaldehyde-dialkylacetals are prepared with high yields and selectivity from the corresponding chloromethylaromatics in the presence of hydrogen chloride acceptors and methyl carbonyl compounds as catalysts and in the presence of orthoesters as water-binding agents by hydroformylation with carbon monoxide and hydrogen.
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- Chemical model for a mechanism of inactivation of monoamine oxidase by heterocyclic compounds. Electronic effects on acetal hydrolysis
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Monoamine oxidase (MAO) was shown previously to undergo time-dependent inhibition by S-(aminomethyl)-3-(4-methoxyphenyl)-2-oxazolidinone (3, X = N, Y = O, R = Me, R' = H), cis- and trans-5-(aminomethyl)-3-(4-methoxyphenyl)dihydrofuran-2(3H)-one(5, R = Me), and 4-(aminomethyl)-l-(4-methoxyphenyl)-2-pyrrolidinone(6, R = Me). Two approaches are taken in this article to test the hypothesis that the cause for this inhibition is electron-withdrawing stabilization of an enzyme adduct by the heterocycles. First, the rates of reactivation of the inhibited enzyme were measured, and they correlated qualitatively with the strengths of the electron-withdrawing abilities of the heterocycles. The second approach was a chemical model study for the proposed enzyme adduct stabilities. The corresponding acetals were synthesized, and the rates of acid hydrolysis of these acetals were used as a model for the decomposition of the enzyme adducts; the rates of hydrolysis should be a qualitative measure of the stabilities of the enzyme adducts. An inverse relationship was observed between the strength of the electron-withdrawing effect of the heterocycle and the rate of acetal hydrolysis. These results support the hypothesis that inhibition of MAO by heterocyclic compounds results from electronic stabilization of the enzyme adducts produced. This realization should prove to be very beneficial to the design of new classes of MAO inhibitors. Furthermore, it cautions synthetic chemists as to the problems associated with acetal deprotection of aldehydes when electron-withdrawing groups are even three bonds away from the acetal carbon.
- Silverman, Richard B.,Ding, Charles Z.
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p. 4571 - 4576
(2007/10/02)
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- Substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents: a route to allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals
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The substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents has been examined in a search for new methods of preparing functional acetals.The efficiency of the substitution of the acetoxy group is highly dependent on the nature of the organometallic reagents: soft nucleophiles with strong electrophilic assistance by the counterion are the best reagents.Allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals have been made by this route, in which dialkoxymethylacetates often function as useful substitutes for dialkylphenylorthoformates.
- Beaudet, Isabelle,Duchene, Alain,Parrain, Jean-Luc,Quintard, Jean-Paul
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p. 201 - 212
(2007/10/02)
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- Catalyst and method for isomerization
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A catalyst for isomerization consisting essentially of a salt or complex salt represented by the formula: where M is a metal of Group IB, IIA, IIB or VIII of the periodic table, L is a ligand, Y is a conjugated base of a Bronsted acid, m is 0, 1, 2, 3 or 4 and n is 1, 2 or 3.
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- Substituent and Temperature Effects on the Reactions of Benzylchlorocarbene with Alcohol
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The insertion reaction of the para-substituted benzylchlorocarbenes with methanol shows a second-order dependence in methanol, but only a first-order dependence in ethylene glycol.The results are consistent with a mechanism whereby the carbene inserts into the O-H bond of the alcohol dimer or oligomer by electrophilic attack of the carbene on the oxigenone pair to produce a reversibly formed ylide intermediate.The effects of the substituents indicate that electron-releasing group favours rearrangement while electron-withdrawing group facilitates insertion.Photolysis of halogenodiazirines in methanol at low temperatures give rise to V-shaped Arrhenius behaviour and the importance of N2 in influencing the reactivity of the singlet halogenocarbene in the matrix is demonstrated.
- Liu, Michael T. H.,Subramanian, Ramasamy
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p. 1233 - 1240
(2007/10/02)
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- A Simple and Efficient Conversion of Aldehyde Acetals into Esters
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The reaction of aldehydic acetals with hypochlorous acid in acetic acid-acetone afforded the corresponding esters in excellent yields.From cyclic acetals, only the corresponding hydroxyalkyl esters were obtained.Keywords - acetal; hypochlorite; hypochlorous acid; conversion; ester; hydroxyalkyl ester; regioselectivity
- Sugai, Saburo,Kodama, Takashi,Akaboshi, Sanya,Ikegami, Shiro
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- TEMPERATURE AND MATRIX EFFECTS ON COMPETITIVE INTERMOLECULAR AND INTRAMOLECULAR REACTION OF BENZYLCHLOROCARBENES IN ETHANOL
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Benzylchlorocarbenes generated photolytically from diazirines in EtOH afford chlorostyrenes and acetals, whose distributions are sensitive to the reaction temperature.
- Tomioka, Hideo,Hayashi, Norihiro,Izawa, Yasuji,Liu, Michael T. H.
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p. 4413 - 4416
(2007/10/02)
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- NEW ORGANOTIN SYNTHONS PROVIDING α-ALKOXYORGANOLITHIUM REAGENTS
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Diethoxymethyltributyltin was obtained in high yield from the reaction of tributylstannylmagnesium chloride with diethylphenylorthoformate.It reacted readily with acetyl chloride to give chloroethoxymethyltributyltin, which was easily transformed to ethoxymethyltributyltin by reduction with tributyltin hydride.Diethoxymethyltributyltin, a masked aldehyde anionic equivalent, was metallated with butyllithium, and the resulting new organolithium reagent was trapped with benzyl bromide, benzaldehyde, and cyclohexenone.
- Quintard, Jean-Paul,Elissondo, Bernard,Pereyre, Michel
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p. C31 - C34
(2007/10/02)
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