- Reduction of aromatic and aliphatic keto esters using sodium borohydride/MeOH at room temperature: a thorough investigation
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Reduction of keto esters is a valuable alternative to produce diols. Sodium borohydride/MeOH system at room temperature and short reaction time efficiently reduced α, β, γ, and δ-keto esters having α-keto esters as the most reactive. The ester functionality was reduced effectively due to the presence of oxo group that somehow facilitates the formation of ring intermediate. As expected, the chemoselective experiments showed that ester functionality was not reduced using this system. This study presents a simple, easy, and benign reduction process of various keto esters to its corresponding diols.
- Kim, Juryoung,De Castro, Kathlia A.,Lim, Minkyung,Rhee, Hakjune
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supporting information; experimental part
p. 3995 - 4001
(2010/07/05)
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- A simple and efficient procedure of low valent iron- or copper-mediated reformatsky reaction of aldehydes
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(Chemical Equation Presented) An operationally simple and very efficient procedure of Reformatsky reaction of aldehydes has been carried out in THF in the presence of low valent iron or copper which were prepared in situ employing a bimetal redox strategy through reduction of FeCl3 or CuCl 2-2H2O with magnesium.
- Chattopadhyay, Angshuman,Dubey, Akhil Kr.
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p. 9357 - 9359
(2008/03/13)
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- Stereoselective enzymatic synthesis of chiral alcohols with the use of a carbonyl reductase from Candida magnoliae with anti-prelog enantioselectivity
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In our effort to search for carbonyl reductases with anti-Prelog enantioselectivity, the activity and enantioselectivity of a carbonyl reductase from Candida magnoliae have been examined with various ketones of diverse structures. This carbonyl reductase catalyzed the reduction of a series of ketones, α-and β-ketoesters, to anti-Prelog configurated alcohols in excellent optical purity. The usefulness of this carbonyl reductase has been demonstrated by synthesis of several chiral alcohol intermediates of pharmaceutical importance.
- Zhu, Dunming,Yang, Yan,Hua, Ling
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p. 4202 - 4205
(2007/10/03)
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- Metal chloride-promoted aldol reaction of α-dimethylsilylesters with aldehydes, ketones, and α-enones
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In the presence of a catalytic amount of LiCl, α-dimethylsilylesters (α-DMS-esters) 1 smoothly reacted with various aldehydes at 30°C to give aldols in good to high yields. On the other hand, the aldol reaction with ketones was effectively promoted by MgCl2 rather than by LiCl. α-Enones also underwent the metal chloride-promoted addition of 1 at the carbonyl carbon or β-carbon. Georg Thieme Verlag Stuttgart.
- Miura, Katsukiyo,Nakagawa, Takahiro,Hosomi, Akira
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p. 1917 - 1921
(2007/10/03)
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- Synthesis of isotetronic acids by cyclization of 1,3-bis(trimethylsilyloxy) alk-1-enes with oxalyl chloride
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Isotetronic acids were regioselectively prepared by cyclization of 1,3-bis(trimethylsilyloxy)alk-1-enes with oxalyl chloride.
- Dede, Rüdiger,Michaelis, Lars,Langer, Peter
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p. 8129 - 8131
(2007/10/03)
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- Titanocene(III)-promoted Reformatsky additions
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(Equation presented) A novel method for the promotion of Reformatsky-like reactions is presented. The technique employs titanocene(III) chloride as a mild and homogeneous single-electron reductant. The reactions are rapid, operationally simple, and compatible with a wide range of functionalities. These additions are also anti diastereoselective.
- Parrish,Shelton, Daniel R.,Little, R. Daniel
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p. 3615 - 3617
(2007/10/03)
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- Ultrasound promoted synthesis of β-hydroxyesters by reformatsky reaction using indium metal
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Ultrasound promoted Reformatsky reaction by the reaction of aldehydes or ketone with ethyl bromoacetate in the presence of indium metal afforded β-hydroxyesters in good to excellent yields under mild conditions.
- Phil Ho Lee,Bang,Lee,Sung,Chang
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p. 3781 - 3789
(2007/10/03)
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- A practical method for the Reformatsky reaction of aldehydes
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Reformaksky reaction of aliphatic aldehydes has been performed successfully by the addition of BF3·OEt2 to a stirred suspension of aldehyde, bromo ester and Zn dust in aqueous THF. For aromatic aldehydes, addition of benzoyl peroxide is also required to effect the reaction.
- Chattopadhyay, Angshuman,Salaskar, Avinash
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p. 561 - 564
(2007/10/03)
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- A mild method for protodesilylation of α-dimethylphenylsilyl ester substrates
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Mild conditions (1.2 eq. Hg(OAc)2, 1.2 eq. TBAF in 1:1 MeOH/THF; 35 min at 0 °C) have been developed for the protodesilylation of α- dimethylphenylsilyl esters. An enolate-dependent mechanism for the reaction was supported through studies indicating the clean incorporation of deuterium. To further investigate the mechanism, the optimal conditions as well as the kinetics of the reaction were explored.
- Poliskie, G. Michelle,Mader, Mary M.,Van Well, Renate
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p. 589 - 592
(2007/10/03)
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- Uncatalyzed aldol reaction using a dimethylsilyl enolate and α- dimethylsilyl ester in N,N-dimethylformamide
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Dimethylsilyl enolates and α-dimethylsilyl esters reacted with aldehydes in N,N-dimethyl-formamide without an activator to give aldol adducts in moderate to good yields. Under the same conditions, the corresponding trimethylsilyl derivatives exhibited lower reactivities toward the aldol reaction.
- Miura, Katsukiyo,Sato, Hiroshi,Tamaki, Kentaro,Ito, Hajime,Hosomi, Akira
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p. 2585 - 2588
(2007/10/03)
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- 2,2-Di(ethoxy)vinyllithium: Reactions with carbonyl compounds
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2,2-Di(ethoxy)vinyllithium 2 generated from bromo ketene acetal 1 reacts with carbonyl compounds to give either β-hydroxy esters 5 or conjugated esters 6 or hydroxy ketene acetals 7 according to the work up.
- Hiouni, Abdelaziz,Duhamel, Lucette
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p. 5507 - 5510
(2007/10/03)
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- Efficient Rhodium-Catalyzed Hydrogenation of Aldehydes and Ketones
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A cationic rhodium(I) catalyst bearing the air-stable and crystalline diphosphine 1,1'-bis-(diisopropylphosphino)ferrocene (1, DiPFc) allows the hydrogenation of aldehydes and ketones under mild conditions.
- Burk, Mark J.,Harper, T. Gregory P.,Lee, Jeffrey R.,Kalberg Christopher
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p. 4963 - 4966
(2007/10/02)
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- One-pot Preparation of β-Hydroxy Esters Catalysed by a Bis(cyclopentadienyl)titanium(IV) Dichloride-Zinc System
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The reaction of α-haloesters with carbonyl compounds catalysed by Cp2TiCl2(cat.)-Zn gives β-hydroxy esters.
- Ding, Yu,Zhao, Gang
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p. 941 - 942
(2007/10/02)
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- Stereoselective Acetalization of 1,3-Alkanediols by l-Menthone: Application to the Resolution of Racemic 1,3-Alkanediols and to the Determination of the Absolute Configuration of Enantiomeric 1,3-Alkanediols
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A general and reliable method for the resolution of racemic 1,3-alkanediols, which involves their conversion into diastereomeric spiroacetals derived from l-menthone, is described.Thus, the reaction of the bis-O-trimethylsilyl derivatives of racemic 1,3-alkanediols with l-menthone in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate affords the diastereomeric spiroacetals 3 and 4.The two can be readily separated by silica gel column chromatography.Hydrolysis of each diastereomer under acidic conditions liberates the corresponding enantiomerically pure diol.An empirically derived correlation of configuration and 1H NMR chemical shifts for spiroacetals 3 and 4 has been developed which is rationalized based on long-range effects due to the magnetic anisotropy inherent to the menthane ring in a rigid spiroacetal conformation.The method described here should be widely applicable to the determination of the absolute configuration of various 1,3-alkanediols.
- Harada, Toshiro,Kurokawa, Hideaki,Kagamihara, Yasuhiro,Tanaka, Sachi,Inoue, Atsushi,Oku, Akira
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p. 1412 - 1421
(2007/10/02)
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- Reactivity of α-Metal(group 4) Esters. Lewis Acid Mediated Reactions of α-Triphenyltin Esters with Aldehydes and Acetals
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Ethyl triphenylstannylacetate and ethyl α-triphenylstannylpropionate reacted with aldehydes and acetals to give β-hydroxy and β-alkoxy esters at room temperature in the presence of TiCl4 in moderate yields.Under these conditions ethyl triphenylgermylacetate and ethyl trimethylsilylacetate did not work.
- Kiyooka, Syun-ichi,Nakata, Masumi
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p. 721 - 722
(2007/10/02)
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- Reduction of α-Diazo-β-Hydroxy Esters to β-Hydroxy Esters: Application in One of Two Convergent Syntheses of a (22S)-22-Hydroxy Bile Acid from Fish Bile and its (22R)-Epimer
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α-Diazo-β-hydroxy esters (3) prepared by condensation of aldehydes (1) with ethyl (lithio)diazoacetate (2) are reduced with 5percent palladium over charcoal in methanol into the corresponding β-hydroxy esters (5) in high yield.This sequence is applied to a new synthesis of haemulcholic acid (14c), a (22S)-22-hydroxy bile acid from fish bile and its (22R)-epimer (14d).A convergent synthesis of (14c) and (14d) involves, as a key step, the dirhodium(II) tetra-acetate conversion of (12) into the corresponding β-keto ester (13).
- Pellicciari, Roberto,Natalini, Benedetto,Cecchetti, Sergio,Fringuelli, Renata
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p. 493 - 498
(2007/10/02)
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- Studies in Decarboxylation. Part 13. The Incursion of a Stepwise Mechanism in the Gas-phase Decarboxylation of Cyclopropylacetic Acids
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The cyclopropylacetic acids (I)-(IV) have been decarboxylated in the temperature range 720-820 K.It is demonstrated that at 725 K, 2',2'-dimethylcyclopropylacetic acid is decarboxylated by both concerted and stepwise mechanisms.The latter is favoured by higher temperature.Cyclopropylacetic acid is decarboxylated by the concerted mechanism at 725 K, but also exhibits the stepwise mechanism at higher temperature.
- Bigley, David B.,Fetter, Clive L.,Clarke, Michael J.
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p. 553 - 556
(2007/10/02)
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