- Horeau amplification in the sequential acylative kinetic resolution of (±)-1,2-diols and (±)-1,3-diols in flow
-
The sequential acylative kinetic resolution (KR) of C2-symmetric (±)-1,2-syn and (±)-1,3-anti-diols using a packed bed microreactor loaded with the polystyrene-supported isothiourea, HyperBTM, is demonstrated in flow. The sequential KRs of C2-symmetric (±)-1,2-syn and (±)-1,3-anti-diols exploits Horeau amplification, with each composed of two successive KR processes, with each substrate class significantly differing in the relative rate constants for each KR process. Optimisation of the continuous flow set-up for both C2-symmetric (±)-1,2-syn and (±)-1,3-anti-diol substrate classes allowed isolation of reaction products in both high enantiopurity and yield. In addition to the successful KR of C2-symmetric (±)-1,2-syn and (±)-1,3-anti-diols, the application of this process to the more conceptually-complex scenario involving the sequential KR of C1-symmetric (±)-1,3-anti-diols was demonstrated, which involves eight independent rate constants. This journal is
- Brandolese, Arianna,Greenhalgh, Mark D.,Desrues, Titouan,Liu, Xueyang,Qu, Shen,Bressy, Cyril,Smith, Andrew D.
-
supporting information
p. 3620 - 3627
(2021/05/04)
-
- Reductive Ring-Opening 1,3-Difunctionalizations of Arylcyclopropanes with Sodium Metal
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Sodium dispersion promotes reductive ring opening of arylcyclopropanes. The presence of a reduction-resistant electrophile, such as methoxypinacolatoborane, epoxide, oxetane, paraformaldehyde, or chlorotrimethylsilane, during the reductive ring opening event leads to the formation of 1,3-difunctionalized 1-arylalkanes by immediate trappings of the resulting two reactive carbanions. In particular, the ring-opening 1,3-diborylations of arylcyclopropanes afford 1,3-diborylalkanes with high syn selectivity.
- Wang, Shuo,Kaga, Atsushi,Yorimitsu, Hideki
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p. 219 - 223
(2020/11/04)
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- NOVEL PHOSPHOROUS (V)-BASED REAGENTS, PROCESSES FOR THE PREPARATION THEREOF, AND THEIR USE IN MAKING STEREO-DEFINED ORGANOPHOSHOROUS (V) COMPOUNDS
-
The present invention relates to novel phosphorous (V) (P(V)) reagents, methods for preparing thereof, and methods for preparing organophosphorous (V) compounds by using the novel reagents.
- -
-
Paragraph 0361; 0365; 0368
(2019/11/04)
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- Cascade Reaction by Chemo- and Biocatalytic Approaches to Obtain Chiral Hydroxy Ketones and anti 1,3-Diols
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A chemo- and biocatalytic cascade approach was applied for the stereoselective synthesis of hydroxy ketones and the corresponding 1,3-diols. A new class of tridentate N,N,O ligands was used with copper(II) complexes for the asymmetric β-borylation of α,β-unsaturated compounds. The complex containing ligand L5 emerged as the best performer, and it gave the organoborane derivatives with good ee values. The corresponding keto–alcohol compounds were then bioreduced by yeasts. The biotransformation set up with Rhodotorula rubra allowed (R)-keto–alcohols and (S,S)-diols to be obtained with up to 99 % ee and up to 99 % de in favor of the anti enantiomers.
- Gandolfi, Raffaella,Facchetti, Giorgio,Christodoulou, Michael S.,Fusè, Marco,Meneghetti, Fiorella,Rimoldi, Isabella
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p. 393 - 400
(2018/06/04)
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- Double Catalytic Kinetic Resolution (DoCKR) of Acyclic anti-1,3-Diols: The Additive Horeau Amplification
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The concept of a synergistic double catalytic kinetic resolution (DoCKR) as described in this article was successfully applied to racemic acyclic anti-1,3-diols, a common motif in natural products. This process takes advantage of an additive Horeau amplif
- Merad, Jérémy,Borkar, Prashant,Caijo, Frédéric,Pons, Jean-Marc,Parrain, Jean-Luc,Chuzel, Olivier,Bressy, Cyril
-
supporting information
p. 16052 - 16056
(2017/11/21)
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- Asymmetric chemoenzymatic synthesis of 1,3-diols and 2,4-disubstituted aryloxetanes by using whole cell biocatalysts
-
Regio- and stereo-selective reduction of substituted 1,3-aryldiketones, investigated in the presence of different whole cell microorganisms, was found to afford β-hydroxyketones or 1,3-diols in very good yields (up to 95%) and enantiomeric excesses (up to 96%). The enantiomerically enriched aldols, obtained with the opposite stereo-preference by baker's yeast and Lactobacillus reuteri DSM 20016 bioreduction, could then be diastereoselectively transformed into optically active syn- or anti-1,3-diols by a careful choice of the chemical reducing agent (diastereomeric ratio up to 98 : 2). The latter, in turn, were stereospecifically cyclized into the corresponding oxetanes in 43-98% yields and in up to 94% ee, thereby giving a diverse selection of stereo-defined 2,4-disubstituted aryloxetanes.
- Vitale, Paola,Perna, Filippo Maria,Agrimi, Gennaro,Scilimati, Antonio,Salomone, Antonio,Cardellicchio, Cosimo,Capriati, Vito
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supporting information
p. 11438 - 11445
(2016/12/16)
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- Ansa-Ruthenium(II) Complexes of R2NSO2DPEN-(CH2)n(η6-Aryl) Conjugate Ligands for Asymmetric Transfer Hydrogenation of Aryl Ketones
-
New 3rd generation designer ansa-ruthenium(II) complexes featuring N,C-alkylene-tethered N,N-dialkylsulfamoyl-DPEN/η6-arene ligands, exhibited good catalytic performance in the asymmetric transfer hydrogenation (ATH) of various classes of (het)aryl ketones in formic acid/triethylamine mixture. In particular, benzo-fused cyclic ketones furnished 98 to >99.9% ee using a low catalyst loading.
- Ki?ic, Andrea,Stephan, Michel,Mohar, Barbara
-
supporting information
p. 2540 - 2546
(2015/08/18)
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- Asymmetric synthesis of new chiral 1,2- and 1,3-diols
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Seven chiral 1,2-diols and six chiral 1,3-diols were synthesized by the asymmetric reduction of the corresponding 1,2-diketones and 1,3-diketones using oxazaborolidine-BH3 catalyst. The 13 corresponding racemic 1,2- and 1,3-diols were synthesized by reducing the diketones with NaBH4 and they were used for determining the ee values through their chiral resolution on HPLC and GC. Five starting diketones, four racemic 1,2-diols, five chiral 1,2-diols, and two chiral 1,3-diols are novel compounds. The new chiral compounds were characterized by IR, 1H and 13C NMR, MS, and elemental analysis. The asymmetric reduction method, oxazaborolidine-BH 3, was applied to these diketones for the first time in this study. The relationship between the structure of the diketone and the yield, diastereoselectivity, and enantiomeric excess was discussed.
- Yildiz, Tülay,Yusufo?lu, Ay?e
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p. 183 - 190
(2013/07/27)
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- Determination of absolute configuration of the phosphonic acid moiety of fosfazinomycins
-
Fosfazinomycins A and B produced by Streptomyces lavendofoliae share the same phosphonate moiety with one chiral centre of unknown configuration which was determined by synthesising both enantiomers of 2-hydroxy-2-phosphonoacetic acid methyl ester. A chiral cyclic phosphite was reacted with methyl glyoxylate in a Pudovik reaction to give a pair of diastereomeric α- hydroxyphosphonates, which were separated by HPLC. The configurations at C-2 were assigned on the basis of single crystal X-ray structure analysis. Deprotection of these diastereomers furnished the enantiomeric α-hydroxyphosphonic acids, of which the (S)-configured had the same sign of optical rotation as the phosphonic acid moiety of the two fosfazinomycins.
- Schiessl, Katharina,Roller, Alexander,Hammerschmidt, Friedrich
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p. 7420 - 7426
(2013/10/22)
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- Selective hydroformylation of various olefins using diphosphinite ligands
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Novel diphosphinite ligands are synthesized by the reaction of various derivatives of 1,3-diols with chlorodiphenylphosphine. The synthesized ligands exhibited considerable impact on hydroformylation of various olefins with excellent regioselectivity toward branched aldehyde. The effect of solvent, temperature, pressure and catalyst loading on the hydroformylation reaction is also described. The synthesized diphosphinite ligands with rhodium precursor works under milder reaction conditions as compared to traditional phosphine and phosphite-based ligands. Copyright 2013 John Wiley & Sons, Ltd. A novel diphosphinite ligands are synthesized by the reaction of various derivatives of 1,3-diol with chlorodiphenylphosphine. The synthesized ligands exhibited a considerable impact on hydroformylation of various olefins with excellent regioselectivity toward branched aldehyde. The effect of solvent, temperature, pressure and catalyst loading on the hydroformylation reaction is also described. The synthesized diphosphinite ligands with Rhodium precursor works at milder reaction conditions as compared to traditional phosphine and phosphite based ligands. Copyright
- Khan, Shoeb R.,Bhanage, Bhalchandra M.
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p. 313 - 317
(2013/07/04)
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- Rearrangement of cyclopropylborane into boretane
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Previously unknown boron-containing four-membered unsaturated heterocycle boretane was obtained via novel thermal rearrangement of cyclopropylborane and investigated by NMR and IR spectroscopy. Formation of boretane was also confirmed through its chemical
- Rubina, M.,Rubin, M.
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p. 807 - 821,15
(2020/09/09)
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- Albumin-directed stereoselective reduction of 1,3-diketones and β-hydroxyketones to anti diols
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The reduction of 1,3-diketones and β-hydroxyketones with NaBH 4 in aqueous acetonitrile is highly stereoselective in the presence of stoichiometric amounts of bovine or human albumin, giving anti 1,3-diols with d.e. up to 96%. The same reaction, without albumin, gives syn and anti 1,3-diols in approximately 1:1 ratio. The presence of an aromatic carbonyl group is essential for diastereoselectivity in the NaBH4/albumin reduction of both 1,3-diketones and β-hydroxyketones. Thus, 3-hydroxy-1-(p-tolyl)-1- butanone is stereoselectively reduced in the presence of albumin, while reduction of its isomer 4-(p-tolyl)-4-hydroxy-2-butanone is not stereoselective. The albumin-controlled reduction is not stereospecific as both enantiomers of 1-aryl-3-hydroxy-1-butanones are reduced to diols with identical stereoselectivities. Circular dichroism of the bound substrates confirms that aromatic ketones are recognized by the protein's IIA binding site. Binding studies also suggest that 1,3-diketones are recognized in their enol form. From the effect of pH on binding of a diketone it is concluded that, in the complex with the substrate, ionizable residues His242 and Lys199 are in the neutral and protonated forms, respectively. A homology model of BSA was obtained and docking of model substrates confirms the preference of the protein for aromatic ketones. Modelling of the complexes with the substrates also allows us to propose a mechanism for the reduction of 1,3-diketones in which the chemoselective reduction of the first (aliphatic) carbonyl is followed by the diastereoselective reduction of the second (aromatic) carbonyl. The role of albumin is thus a combination of chemo- and stereocontrol.
- Berti, Federico,Bincoletto, Simone,Donati, Ivan,Fontanive, Giampaolo,Fregonese, Massimo,Benedetti, Fabio
-
experimental part
p. 1987 - 1999
(2011/04/25)
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- A radical-anion chain mechanism following dissociative electron transfer reduction of the model prostaglandin endoperoxide, 1,4-diphenyl-2,3- dioxabicyclo[2.2.1]heptane
-
The model prostaglandin endoperoxide, 1,4-diphenyl-2,3-dioxabicyclo[2.2.1] heptane (3), was investigated in N,N-dimethylformamide at a glassy carbon electrode using various electrochemical techniques. Reduction of 3 occurs by a concerted dissociative electron transfer (ET) mechanism. Electrolysis at -1.6 V yields 1,3-diphenyl-cyclopentane-cis-1,3-diol in 97% by a two-electron mechanism; however, in competition with the second ET from the electrode, the resulting distonic radical-anion intermediate undergoes a β-scission fragmentation. The rate constant for the heterogeneous ET to the distonic radical-anion is estimated to occur on the order of 2 × 107 s-1. In contrast, electrolyses conducted at potentials more negative than -2.1 V yield a mixture of primary and secondary electrolysis products including 1,3-diphenyl-cyclopentane-cis-1,3-diol, 1,3-diphenyl-1,3-propanedione, trans-chalcone and 1,3-diphenyl-1,3-hydroxypropane by a mechanism involving less than one electron equivalent. These observations are rationalized by a catalytic radical-anion chain mechanism, which is dependent on the electrode potential and the concentration of weak non-nucleophilic acid. A thermochemical cycle for calculating the driving force for β-scission fragmentation from oxygen-centred biradicals and analogous distonic radical-anions is presented and the results of the calculations provide insight into the reactivity of prostaglandin endoperoxides.
- Magri, David C.,Workentin, Mark S.
-
body text
p. 3354 - 3361
(2009/02/05)
-
- 1,3-Diol synthesis via controlled, radical-mediated C-H functionalization
-
The invention of a method for the synthesis of 1,3-diols from the corresponding alcohols is described, via controlled, radical-mediated C-H functionalization. The sequence described herein entails near quantitative conversion to the corresponding trifluoroethyl carbamate, followed by a variant of the Hofmann-Loffler-Freytag reaction, cyclization, and hydrolysis to provide the 1,3-diols. In addition to the 10 examples presented herein, the syntheses of four natural products are facilitated by this directed oxyfunctionalization. This methodology is demonstrated to be orthogonal to other known C-H oxidations. Finally, this sequence is efficient, practical, inexpensive, and scalable. Copyright
- Chen, Ke,Richter, Jeremy M.,Baran, Phil S.
-
p. 7247 - 7249
(2008/12/21)
-
- ClickFerrophos: New chiral ferrocenyl phosphine ligands synthesized by click chemistry and the use of their metal complexes as catalysts for asymmetric hydrogenation and allylic substitution
-
The new ferrocenyl P,P- and P,N-ligands 5 and 6 (collectively, "ClickFerrophos") were readily prepared in four steps using Click Chemistry methodology, starting from the commercially available aminoferrocene 1. Rhodium and ruthenium complexes of ClickFerrophos 5 were effective catalysts for the hydrogenation of alkenes and ketones, respectively, producing products with up to 99.7% ee. The analogous palladium complex with 6 worked well for asymmetric allylic alkylation.
- Fukuzawa, Shin-Ichi,Oki, Hiroshi,Hosaka, Mitsuteru,Sugasawa, Jun,Kikuchi, Satoshi
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p. 5557 - 5560
(2008/09/17)
-
- Facile deoxygenation of dicarbonyl compounds using a samarium diiodide-additive system
-
The reduction of α- and β-dicarbonyl compounds was investigated with samarium diiodide in the presence of additive. Diketones and ketocarboxylic acids were easily reduced at room temperature to give the mono-alcohols in good to excellent yield, and ketoester afforded the saturated ester as the major product in moderate yield. These reductions containing the reductive deoxygenation can be rapidly performed under the facile and mild conditions by this method.
- Kamochi, Yasuko,Kudo, Tadahiro,Masuda, Toshinobu,Takadate, Akira
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p. 1017 - 1020
(2007/10/03)
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- Reduction of β-hydroxyketones by Sml2/H2O/ Et3N
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(Chemical Equation Presented) Reduction of a series of β- hydroxyketones by Sml2/H2O/Et3N provided 1,3-diols in quantitative yields. The reactions were exceedingly clean with no byproduct formation, negating the need for f
- Davis, Todd A.,Chopade, Pramod R.,Hilmersson, Goeran,Flowers II, Robert A.
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p. 119 - 122
(2007/10/03)
-
- Efficient preparation of optically pure C2-symmetrical cyclic amines for chiral auxiliary
-
Optically pure C2-symmetrical amines were efficiently synthesized from the corresponding diols obtained from the enantioselective borohydride reduction of the diketones catalyzed by the optically active β-ketoiminato cobalt(II) complex.
- Sato, Mitsuo,Gunji, Yasuhiko,Ikeno, Taketo,Yamada, Tohru
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p. 1434 - 1438
(2007/10/03)
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- New efficient synthesis of Taniaphos ligands: Application in ruthenium- and rhodium-catalyzed enantioselective hydrogenations
-
A third generation of Taniaphos 1,5-diphosphine ferrocene ligands with the new and interesting (SFc,3S)- and (RFc,3R)-configurations has been prepared. With these ligands, the ruthenium-catalyzed hydrogenation of C=O bonds proceeded with high diastereo- and enantioselectivity (up to >99% de and 97% ee). Good results were also obtained for the rhodium-catalyzed hydrogenation of C=C (up to 96% ee) and C=N bonds (up to 65% ee).
- Tappe, Katja,Knochel, Paul
-
-
- Enantioselective borohydride reduction catalyzed by optically active cobalt complexes
-
The highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols was developed in the presence of a catalytic amount of an optically active cobalt(II) complex catalyst. This enantioselective reduction is carried out using a precisely premodified borohydride with alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol. High optical yields are obtained by choosing the appropriate alcohol as modifiers and a suitable β-ketoiminato ligand of the catalyst. The enantioselective borohydride reduction has been successfully applied to the preparation of optically active 1,3-diols, the stereoselective reduction of diacylferrocenes, and dynamic and/or kinetic resolution of 1,3-dicarbonyl compounds.
- Yamada, Tohru,Nagata, Takushi,Sugi, Kiyoaki D.,Yorozu, Kiyotaka,Ikeno, Taketo,Ohtsuka, Yuhki,Miyazaki, Daichi,Mukaiyama, Teruaki
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p. 4485 - 4509
(2007/10/03)
-
- Economic preparation of 1,3-diphenyl-1,3-bis(diphenylphosphino)propane: A versatile chiral diphosphine ligand for enantioselective hydrogenations
-
The enantioselective hydrogenation of 1,3-diarylpropane-1,3-diones with chiral Ru(II)-diphosphine catalyst has been studied. In a first approach it was found, that Tol-BINAP together with Ru(COD)methallyl2 formed the most selective catalyst. On
- Dubrovina, Natalia V.,Tararov, Vitali I.,Monsees, Axel,Kadyrov, Renat,Fischer, Christine,Boerner, Armin
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p. 2739 - 2745
(2007/10/05)
-
- New ferrocenyl ligands with broad applications in asymmetric catalysis
-
A new synthetic approach allows the synthesis of taniaphos- analogous ligands 2 with inverted α configuration (Sp, αS). This new class of ferrocenyl ligands displays excellent enantioselectivity and enhanced reactivity in several types of asymmetric hydrogenation reactions (e.g. 1→).
- Lotz, Matthias,Polborn, Kurt,Knochel, Paul
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p. 4708 - 4711
(2007/10/03)
-
- Multiple dendritic catalysts for asymmetric transfer hydrogenation
-
The first and second generation multiple dendritic ligands based on chiral diamine were synthesized in a convergent approach and were well-characterized by NMR and MS techniques. Their ruthenium complexes prepared in situ had good solubility in the reaction medium (azeotrope of formic acid and triethylamine) and demonstrated high catalytic activity and enantioselectivity comparable to monomeric catalysts in the asymmetric transfer hydrogenation of ketones and imines. Quantitative yields and for some cases a slightly higher enantioselectivity (up to 98.7% ee) were obtained in the dendritic catalysis. Considering the high local catalyst concentrations at the periphery, diones were tested for the possible synergic reactivity between catalytic units at the surface, while no apparent differences were noted.
- Chen, Ying-Chun,Wu, Tong-Fei,Deng, Jin-Gen,Liu, Hui,Cui, Xin,Zhu, Jin,Jiang, Yao-Zhong,Choi, Michael C. K.,Chan, Albert S. C.
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p. 5301 - 5306
(2007/10/03)
-
- Albumin-controlled stereoselective reduction of 1,3-diketones to anti-diols
-
An unprecedented combination of high chemo- and stereoselectivity in the NaBH4 reduction of 1:1 complexes between albumin and aromatic 1,3-diketones results in the formation of anti 1,3-diols with de up to 96%.
- Benedetti, Fabio,Berti, Federico,Donati, Ivan,Fregonese, Massimo
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p. 828 - 829
(2007/10/03)
-
- Synthesis of a new class of chiral 1,5-diphosphanylferrocene ligands and their use in enantioselective hydrogenation
-
A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position α to the ferrocene moiety. In many cases, both enantiomeric β-hydroxyesters of the reduction product can be obtained by simply replacing a dimethylamino group in the ligand with a methyl group.
- Ireland, Tania,Tappe, Katja,Grossheimann, Gabi,Knochel, Paul
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p. 843 - 852
(2007/10/03)
-
- Facile reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by an aqueous TiCl3/NH3 system: Selectivity and scope
-
A simple and rapid procedure for the almost quantitative reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by use of TiCl3/NH3 in aqueous methanol solution is reported. The reducing system distinguishes between different classes of aldehydes and/or ketones, and many functionalities that usually do not survive under reducing conditions are tolerated well. The concept of reversal of chemoselectivity has also been developed. A mechanism based on two sequential one-electron transfers from TiIII to the carbonyl carbon atom is proposed, the second SET becoming operative only in the presence of ammonium ion (either added or formed in situ). Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 3326 - 3335
(2007/10/03)
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- A highly diastereoselective TiCl4-mediated reduction of β-hydroxy ketones with BH3·py - A very efficient and general synthesis of syn-1,3-diols
-
β-Hydroxy ketones can be reduced to the corresponding 1,3-diols in high yields and with excellent diastereoselectivity by carrying out the reaction with BH3·pyridine in CH2Cl2 at -78°C in the presence of TiCl4.
- Bartoli,Bosco,Marcantoni,Massaccesi,Rinaldi,Sambri
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p. 4679 - 4684
(2007/10/03)
-
- Convenient preparation of optically pure 1,3-diaryl-1,3-propanediols
-
Optically pure 1,3-diaryl-1,3-propanediols were conveniently prepared from the corresponding 1,3-diketones by enantioselective borohydride reduction in the presence of a catalytic amount of β-ketoiminato cobalt(II) complexes.
- Ohtsuka, Yuhki,Kubota, Takeshi,Ikeno, Taketo,Nagata, Takushi,Yamada, Tohru
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p. 535 - 537
(2007/10/03)
-
- Synthesis of novel C2-symmetric ligands based on (R,R)- and (S,S)- diphenyl-1,3-propanediol
-
A range of novel C2-symmetric dioxygen and dinitrogen ligands can readily be obtained through the interconversion of the parent 1,3-diphenyl- 1,3-propanediol enantiomers which are, in turn, accessed in good yields via a Sharpless asymmetric epoxidative resolution.
- Roos, Gregory H. P.,Donovan, A. Richard
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p. 991 - 1000
(2007/10/03)
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- Functionalized organolithium compounds of DTBB-catalyzed sulfur-lithium exchange
-
The successive reaction of β- or γ-hydroxy or amino phenyl thioethers (1,4) with butyllithium and an excess of lithium powder in the presence of a catalytic amount of DTBB in THF at - 78°C leads to the formation of the corresponding β- or γ-functionalized organolithium compounds 2 or 5, respectively, which by treatment with different electrophiles [D2O, t- BuCHO, PhCHO, Me2CO, (CH2)4CO, (CH2)5CO] at temperatures ranging between - 78°C and room temperature yields, after hydrolysis with water, the expected functionalized alcohols or amines 3 or 6, respectively, in a completely regioselective manner.
- Foubelo, Francisco,Gutiérrez, Ana,Yus, Miguel
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p. 503 - 514
(2007/10/03)
-
- Reaction of α,β-unsaturated ketones with LiAlH4 under oxygen: Synthesis of 1,3-diols
-
1,3-Diols have been obtained by the reaction of α,β-unsaturated ketones with LiAlH4 in THF under a dry oxygen atmosphere.
- Csaky, Aurelio G.,Maximo, Natalia,Plumet, Joaquin,Ramila, Ainhoa
-
p. 6485 - 6487
(2007/10/03)
-
- Diastereoselective reduction of β-hydroxyketones with amineboranes in the presence of lithium perchlorate
-
The reduction of β-hydroxyketones with amineboranes in the presence of lithium perchlorate produces the corresponding anti 1,3-diols as major products.
- Narayana, Chatla,Reddy, M. Rama,Hair, Max,Kabalka, George W.
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p. 7705 - 7708
(2007/10/03)
-
- Diastereoselective reduction of acyclic hydroxyketones and diketones with an indium hydride reagent
-
Hydroxyketones and diketones have been reduced with lithium indium hydride to give meso-diols selectively. α-Hydroxyketones and α-diketones are reduced to meso-1,2-diols with high diastereoselectivities, whereas the selectivities of β-hydroxyketones and β-diketones are less satisfactory.
- Yamada, Masafumi,Horie, Tomoaki,Kawai, Masao,Yamamura, Hatsuo,Araki, Shuki
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p. 15685 - 15690
(2007/10/03)
-
- Design, reactivities, and practical application of dialkylzinc hydride ate complexes generated in Situ from dialkylzinc and metal hydride. A new methodology for activation of NaH and LiH under mild conditions
-
We designed various dialkylzinc hydride 'ate' complexes, prepared from dialkylzinc and metal hydride, and investigated the reactivities (and the transference aptitude of ligands) of these zincates toward benzophenone. The results clearly reveal that dimethylzinc hydrides are the most powerful and selective zincates for the reduction of the carbony1 group. This complex reagent turned out to be effective for the reduction of esters and amides as well as aldehydes and ketones to the corresponding alcohols and amines with good to excellent yields under mild conditions. Furthermore, the method was successfully used for the highly selective 1,2-reduction of α,β-unsaturated carbonyl compounds, the regioselective ring-opening reduction of epoxides, and the chemoselective reduction of aldehydes in the presence of ketones. We also discuss and clarify the active species and the mechanism of this reduction using the diastereoselective reductions of some carbonyl compounds with an adjacent chiral center. Also, this reducing system was found to constitute a powerful tool for the stereoselective synthesis of syn- and anti-1,2-diols. Moreover, we developed the catalytic version of this reducing system. The LiH-Me2Zn-ultrasound system proved to be effective not only for the catalytic reduction of the carbonyl compounds and epoxides but also for the partial reduction (the conversion) of carboxylic acids to aldehydes. This system is a very attractive method for several reasons (good availability, low cost, and easy operation) and would be particularly useful for large- scale reductions.
- Uchiyama, Masanobu,Furumoto, Shozo,Saito, Mariko,Kondo, Yoshinori,Sakamoto, Takao
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p. 11425 - 11433
(2007/10/03)
-
- Stereocontrolled reductive amination of 3-hydroxy ketones
-
syn-1,3-Aminoalcohols are synthesized in high diastereomeric excess by reductive amination of 3-hydroxyketones with sodium cyanoborohydride in the presence of benzylamine.
- Haddad, Mansour,Dorbais, Jerome,Larcheveque, Marc
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p. 5981 - 5984
(2007/10/03)
-
- β-Functionalised organolithium compounds through a sulfur-lithium exchange
-
The successive reaction of different β-hydroxy or β-amino tbioethers 1a-d with n-butyl-lithium and an excess of lithium powder and a catalytic amount of DTB in THF at -78°C leads to the formation of the corresponding β-functionalised organolithium compounds 2a-d, which by reaction with several electrophiles [D2O, Bu(t)CHO, PhCHO, Me2CO, (CH2)5CO] at temperatures ranging between -78 and 20°C yields, after hydrolysis with water, the expected functionalised alcohols or amines 3aa-de in a regioselective manner.
- Foubelo, Francisco,Gutierrez, Ana,Yus, Miguel
-
p. 4837 - 4840
(2007/10/03)
-
- In search of open-chain 1,3-stereocontrol
-
Methylation of methyl 4-phenylpentanoate 25 gives the diastereoisomers methyl (2RS,4SR)-2-methyl-4-phenylpentanoate 26 and methyl (2RS,4RS)- 2-methyl-4-phenylpentanoate 27 in a ratio of 44:56. The aldehydes 3-dimethyl(phenyl)silylbutanal 28, 3-dimethyl(ph
- Barbero, Asun,Blakemore, David C.,Fleming, Ian,Wesley, Robert N.
-
p. 1329 - 1352
(2007/10/03)
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- Intrazeolite photochemistry. 14. Photochemistry of α,ω-diphenyl allyl cations within zeolites
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1,3-Diphenylpropenylium (DP3+) and 1,5-diphenylpentadienylium (DP5+) ions have been generated within acid ZSM-5 and mordenite zeolites as persistent species by adsorption of α,ω-disubstituted α,ω-diphenylalkanes. It was found that be
- Garcia, Hermenegildo,Garcia, Sara,Perez-Prieto, Julia,Scaiano
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p. 18158 - 18164
(2007/10/03)
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- BCl3- and TiCl4-mediated reductions of β-hydroxy ketones
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Syn-selective reduction protocols for β-hydroxy ketones are described exploiting the intermediacy of titanium and boron chelates derived from TiCl4 and BCl3, respectively. Reductions are conducted at -78°C in CH2Cl2/
- Sarko, Christopher R.,Collibee, Scott E.,Knorr, Allison L.,DiMare, Marcello
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p. 868 - 873
(2007/10/03)
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- Enzyme catalysed resolution of 1,3-diarylpropan-1,3-diols
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Candida Rugosa Lipase (AY 30, Amano) is shown to be a very efficient catalyst for the resolution of enantiomeric 1,3-diaryl-1,3-diols by means of the transesterification reaction using vinyl acetate as an acyl donor. This enzyme also exerts a great diater
- Levayer,Rabiller,Tellier
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p. 1675 - 1682
(2007/10/02)
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- Enantioselective synthesis of γ-hydroxysilanes, 1,3-diols and cyclopropanes by reaction of a chiral epoxide with a racemic α-silyl organolithium reagent
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The racemic α-silyl organolithium reagents 2a and 2b react with (R)-styrene oxide enantioselectively to produce the chiral γ-hydroxysilanes 3a and 3b, respectively. The chiral 1,3-diol 4 and cyclopropane 7 are readily obtained in enantiomerically pure form from these γ-hydroxysilanes.
- Corey,Chen, Zhuoliang
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p. 8731 - 8734
(2007/10/02)
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- METHOXYCHLORINATION AND DIMETHOXYLATION OF ALKENES. THE REACTIONS OF SUBSTITUTED STYRENES WITH PHENYLSELENENYL CHLORIDE IN METHANOL
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The addition of PhSeCl to α- and β-substituted styrenes in methanol is regio- and stereospecific and affords the products of methoxyselenenylation.These compounds further react with PhSeCl to give the deselenenylation products.In the case of α-substituted styrenes, 1-methoxy, 2-chloroalkanes are produced, whereas with β-substituted styrenes the major reaction products are the 1,2-dimethoxyalkanes and the 2,2-dimethoxyalkanes in which phenyl migration has occured.It is shown that these reactions proceed through the intermediate formation of the alkyl phenylselenium dichlorides, PhCR(OMe)CHR1SeCl2Ph, which evolve with different mechanisms depending on the structure of the starting alkenes.
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Chianelli, Donatella,Bartoli, Donatella
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p. 2261 - 2272
(2007/10/02)
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- Fluoride Ion Catalyzed Reduction of Aldehydes and Ketones with Hydrosilanes. Synthetic and Mechanistic Aspects and an Application to the Threo-Directed Reduction of α-Substituted Alkanones
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Reduction of aldehydes and ketones with hydrosilanes proceeded in the presence of a catalytic amount of tetrabutylammonium fluoride or tris(diethylamino)sulfonium difluorotrimethylsilicate in aprotic polar solvents under mild conditions.A significant isotope effect (kH/kD = 1.50) was observed in competitive reduction of acetophenone with HSiMe2Ph and DSiMe2Ph.The reaction was of first order in the concentration of an aprotic polar solvent HMPA.Reduction of 2-methylcyclohexanone gave cis-2-methylcyclohexanol with selectivities up to 95percent.The kinetic and stereochemical results suggest that a hexavalent fluorosilicate - is involved. α-Alkoxy (acyloxy or dimethylamino) ketones were transformed to threo alcohols in high diastereoselectivities.The reduction was also applied to α-methyl-β-keto amides, RCOCH(MeCONR)2, to afford the corresponding threo alcohols in >98percent selectivity.The threo selectivity is explained in terms of the Felkin-Anh model in which interaction of carbonyl oxygen with a countercation is ideally suppressed.The threo-directed reduction was applied to (R)-1-phenyl-4-(2-tetrahydropyranyloxy)-1-penten-3-one and N-(2-benzoylpropanoyl)piperidine.The resulting threo alcohols were respectively converted into (2R,3S)-2,3-(cyclohexylidenedioxy)butanal, a key intermediate of daunosamine synthesis, and into a pharmacologically useful compound threo-N-(3-hydroxy-2-methyl-3-phenylpropyl)piperidine.
- Fujita, Makoto,Hiyama, Tamejiro
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p. 5405 - 5415
(2007/10/02)
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- DIASTEREOSELECTIVE CONJUGATE ADDITION TO CHIRAL α,β ETHYLENIC ACETALS
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The phenyl copper reagent associated with Lewis acid (BF3) reacts regio (SN2') and stereoselectively with chiral α,β ethylenic acetals.
- Mangeney, P.,Alexakis, A.,Normant, J. F.
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p. 3143 - 3146
(2007/10/02)
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- TRANSFORMATIONS OF PHENYLCYCLOPROPANES UNDER THE INFLUENCE OF VARIOUS DIACYLOXYIODO DERIVATIVES
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The reaction of phenylcyclopropanes with various (diacycloxyiodo)benzenes and iodine tristrifluoracetate was studied. (Bistrichloroacetoxyiodo)benzene and (bistrifluoracetoxyiodo)benzene react with phenylcyclopropanes exclusively in the small ring with the formation of the respective 1-phenyl-1,3-bis(acyloxy)propanes.Iodine tristrifluoroacetate in reaction with phenylcyclopropanes attacks both the small ring and the aromatic ring, which leads to the production of the esters of 1,3-diols and p-iodophenylcyclopropanes.Possible mechanisms are proposed for the oxidative cleavage of the trimethyl ring of phenylcyclopropanes.
- Saginova, L. G.,Bondarenko, O. B.,Gazzaeva, R. A.,Shabarov, Yu. S.
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p. 477 - 480
(2007/10/02)
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- STEREOSELECTIVE REDUCTION OF β-HYDROXYKETONES TO 1,3-DIOLS. HIGHLY SELECTIVE 1,3-ASYMMETRIC INDUCTION VIA BORON CHELATES
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Highly selective asymmetric induction can be achieved in the reduction of acyclic β-hydroxyketones via boron chelates.Treatment of β-hydroxyketones (1) with tributyl or triisobutylborane and successively with sodium borohydride afforded syn-1,3-diols (3)
- Koichi, Narasaka,Pai, Fong-Chang
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p. 2233 - 2238
(2007/10/02)
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- ASYMMETRIC HYDROGENATION USING CHIRAL PHOSPHINITE RHODIUM COMPLEXES
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The Cu(I) complex of (1R,3R)-bis(diphenylphosphinoxy)-1,3-diphenylpropane (BDPODP) has been prepared and used for the transfer of the ligand to Rh(I).The Rh(I) complexes of this new phosphinite obtained by this method act as efficient asymmetric homogeneous hydrogenation catalysts for (Z)-α-(acylamino)-cinnamic acids.
- Bakos, Jozsef,Toth, Imre,Heil, Balint
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p. 4965 - 4966
(2007/10/02)
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- β-Substituted Organolithium Compounds from Chlorohydrins: Application to the Direct Synthesis of Bifunctionalized Organic Cpmpounds
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The reaction of different chlorohydrins with n-butyl-lithium at -78 deg C followed by metallation wiht lithium naphthalenide at the same temperature leads to very reactive organolithium compounds bearing an alkoxide function at the β-position with respect to metal.The reaction of these intermediates with several electriphiles leads to mono- as well as bi-functionalized organic compounds.Thus, treatment of these dianions with deuterium oxide, oxygen, carbon dioxide, benzyl bromide, dimethyl disulphide, and carbonyl compounds, gave 2-deuterioalcohols, 1,2-diols, β-hydroxy-acids, 2-benzyl alcohols, 2-hydroxy-thioethers, and 1,3-diols respectively.The preparation of β-substituted organolithium derivatives can be alternatively carried out starting from α-chloroketones by the same procedure.When the lithium atom is linked to a secondary carbon atom the dianions are very unstable and decompose, even at -100 deg C, by β-elimination yielding the corresponding olefins.
- Barluenga, Jose,Florez, Josefa,Yus, Miguel
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p. 3019 - 3026
(2007/10/02)
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- Effect of Restricted Mobility of the Linking Chain on Intramolecular Excimer Formation
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Intramolecular excimer formation in a series of phenyl-substituted 1,3-propanediols, compounds in which the motions of the linking chain are restricted by intramolecular hydrogen bonding, was investigated under stationary conditions in n-hexane.The excime
- Todesco, R.,Bockstaele, D. Van,Gelan, J.,Martens, H.,Put, J.,Schryver, F. C. De
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p. 4963 - 4968
(2007/10/02)
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