- ZIRCONIUM ENOLATES AS A NEW ERYTHRO-SELECTIVE ALDOL CONDENSATION REAGENT
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Zirconium enolates, prepared from lithium enolates, ans bis(cyclopentadienyl)zirconium dichloride, undergo a facile aldol condensation with aldehydes to give predominantly the erythro product regardless of the geometry of the starting enolates.
- Yamamoto, Yoshinori,Maruyama, Kazuhiro
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- Tetrahedral boronates as basic catalysts in the aldol reaction
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β-Hydroxyketones are versatile building blocks in organic synthesis, which can be conveniently synthesized from ketones and aldehydes by aldol reactions. Unfortunately, these reactions often suffer from dehydration of the initially formed β-hydroxyketones
- Müller, Tobias,Djanashvili, Kristina,Peters, Joop A.,Arends, Isabel W.C.E.,Hanefeld, Ulf
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- Rh-catalyzed aldehyde - Aldehyde cross-aldol reaction under base-free conditions: In situ aldehyde-derived enolate formation through orthogonal activation
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The chemoselective generation of aldehyde-derived enolates to realize an aldehyde - aldehyde cross-aldol reaction is described. A combined Rh/dippf system efficiently promoted the isomerization/aldol sequence by using primary allylic, homoallylic, and bishomoallylic alcohols; secondary allylic and homoallylic alcohols; and trialkoxyboranes that were derived from primary allylic and homoallylic alcohols. The reaction proceeded at ambient temperature under base-free conditions, thus giving cross-aldol products with high chemoselectivity. Mechanistic studies, as well as its application to double-aldol processes under protecting-group-free conditions, are also described. Copyright
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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- Rhodium-catalyzed cross-aldol reaction: In situ aldehyde-enolate formation from allyloxyboranes and primary allylic alcohols
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Dip in. A Rh/dippf catalyst generates aldehyde-derived enol boranes at ambient temperature by isomerization of allyloxy- and homoallyloxyboranes. A one-pot isomerization/cross-aldol sequence provides aldehyde-aldehyde adducts in good yield with syn select
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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p. 10275 - 10279,5
(2012)
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- Synthesis of (+)-discodermolide by catalytic stereoselective borylation reactions
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The marine natural product (+)-discodermolide was first isolated in 1990 and, to this day, remains a compelling synthesis target. Not only does the compound possess fascinating biological activity, but it also presents an opportunity to test current methods for chemical synthesis and provides an inspiration for new reaction development. A new synthesis of discodermolide employs a previously undisclosed stereoselective catalytic diene hydroboration and also establishes a strategy for the alkylation of chiral enolates. Furthermore, this synthesis of discodermolide provides the first examples of the asymmetric 1,4-diboration of dienes and borylative diene-aldehyde couplings in complex-molecule synthesis. Borylation-based synthesis: The development of a strategy for stereocontrol in catalytic diene hydroboration enables the synthesis of a critical building block for the assembly of (+)-discodermolide. Combined with asymmetric catalytic diboration, hydroformylation, and borylative aldehyde-diene coupling reactions, (+)-discodermolide could then be prepared from simple hydrocarbon-based building blocks.
- Yu, Zhiyong,Ely, Robert J.,Morken, James P.
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- STEREOSELECTIVE ALDOL CONDENSATIONS VIA ALKENYLOXY DIALKYOXYBORANES: MECHANISTIC AND STEREOCHEMICAL DETAILS.
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A detailed investigation of the enolization of ketones with ethylenechloroboronate (ECB) in the presence of a tertiary amine and the subsequent aldol condensations of these boron enolates was conducted.The enolization with ECB-DPEA system was found to be
- Gennari, Cesare,Colombo, Lino,Scolastico, Carlo,Todeschini, Roberto
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- STEREOSELECTIVE ALDOL CONDENSATIONS VIA ENOLBORONATES
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Enolboronates, new enolates directly accessible from carbonyl compounds, exhibit extraordinary high erythro diastereoselection both with aliphatic and aromatic aldehydes.
- Gennari, Cesare,Cardani, Silvia,Colombo, Lino,Scolastico, Carlo
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- erythro-Selective Aldol Condensation via Triphenyltin Enolates. Stereoselection Independent of the Stereochemistry of the Enolates
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Triphenyltin enolates, prepared from lithium enolates and triphenyltin chloride, undergo a rapid aldol condensation with aldehydes without the need for the presence of Lewis acids to give predominantly the erythro-product regardless of the geometry of the starting enolates.
- Yamamoto, Yoshinori,Yatagai, Hidetaka,Maruyama, Kazuhiro
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- Novel Reactive Silyl Enolates. Highly Stereoselective Aldol and Michael Reactions without Catalysts
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Novel silyl enolates, prepared in situ from ketones and dimethylsilyl ditriflate (Me2Si(OTf)2) in the presence of a tertiary amine, reacted smoothly with electrophiles such as aldehydes, acetals, or α,β-unsaturated ketones without catalyst at -78 deg C to
- Kobayashi, Shu,Nishio, Koichi
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- Zn(pybox)-complex-catalyzed asymmetric aqueous Mukaiyama-Aldol reactions
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Catalytic asymmetric aldol reactions in aqueous media have been developed using chiral zinc complex. The aldol products have been obtained in high yields, high diastereocontrol, and good level of enantioselectivity. Various aromatic and α,β-unsaturated al
- Jankowska, Joanna,Mlynarski, Jacek
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- Gallium(III) triflate catalyzed diastereoselective mukaiyama aldol reaction by using low catalyst loadings
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A mild method for the diastereoselective Mukaiyama aldol reaction is reported. By using a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%), the transformation proceeds efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. To the best of our knowledge, this is the first report of a metal triflate acting as a safe, bench-stable, and slow-releasing source of triflic acid for the Mukaiyama aldol reaction. A diastereoselective Mukaiyama aldol reaction was performed under mild conditions with a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%). The transformation proceeded efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. Copyright
- Plancq, Baptiste,Justafort, Lyse Carole,Lafantaisie, Mathieu,Ollevier, Thierry
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- Unusual highly regioselective direct aldol additions with a moisture-resistant and highly efficient titanium catalyst
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The extremely robust and water-stable tetranuclear complex Ti 4(μ-BINOLato)6(μ3-OH)4 was found to catalyze the direct aldol addition with high regioselectivities at the more steric α-encumbered side of unsymmetr
- Mahrwald, Rainer,Schetter, Bernd
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- A new class of ligands for aqueous, lanthanide-catalyzed, enantioselective Mukaiyama aldol reactions
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The development of aqueous methods for generating enantiopure β-hydroxy carbonyl compounds is an important goal because these subunits compose many bioactive compounds and the ability to synthesize these groups in water has environmental and cost benefits. In this communication, we report a new class of ligands for aqueous, lanthanide-catalyzed, asymmetric Mukaiyama aldol reactions for the synthesis of chiral β-hydroxy ketones. Furthermore, we have used luminescence-decay measurements to unveil mechanistic information regarding the catalytic reaction via changes in water-coordination number. The precatalysts presented here yielded β-hydroxy carbonyls from aliphatic and aryl substrates with outstanding syn:anti ratios and enantiometric excesses of up to 49:1 and 97%, respectively.
- Mei, Yujiang,Dissanayake, Prabani,Allen, Matthew J.
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- Insight into the mechanism of direct catalytic aldol addition mediated by ambifunctional titanium complexes
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X-Ray structure analysis of a titanium(IV) isopropoxide/mandelic acid complex provides an insight into the mechanism of this novel direct enantioselective aldol addition. The catalytic cycle mediated by the titanium(IV) alkoxide/mandelic acid complex is presented.
- Mahrwald,Ziemer
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- B,B-dihaloterpenylboranes as reagents for the diastereo- and enantioselective synthesis of syn-aldols
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A series of known and new B,B-dihaloterpenylboranes, readily synthesized from the corresponding terpenes, were examined for the diastereo- and enantioselective synthesis of syn-aldols. Thus, IpcBCl2, EapBCl2, LgfBCl2, cis-MyrBCl2, 2-IcrBCl2', 4-IcrBCl2, and 2-IcrBBr2 in the presence of i-Pr2NEt, convert 3-pentanone to ≤99% Zenolates, converted by aldehydes to pure syn-aldols in 7-74% enantiomeric excess (ee). The most efficient of these reagents, B,B-dibromo-2-isocaranylborane, was tested for the enolboration of 3-pentanone, followed by aldolization with a series of aldehydes.
- Ramachandran, P. Veeraraghavan,Xu, Wei-Chu,Brown, Herbert C.
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- Iridium-catalyzed crossed aldol coupling and a new concept to form an Ir-Si species
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[Ir(COD)(PPh3)2]X (X=PF6, ClO4, and OTf) activated by H2 molecule catalyzes Mukaiyama-type aldol coupling between enoxysilanes and acetals or aldehydes. An Ir-Si species formed in the first stage of t
- Matsuda, Isamu,Hasegawa, Yuki,Makino, Tatsuya,Itoh, Kenji
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- Investigation of a novel diamine based chiral auxiliary in the asymmetric alkylation of ketones
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A novel chiral auxiliary containing a pyrrolidine ring has been utilised in the preparation of various chiral ketones with good to excellent enantioselectivities (up to 92%). It has been successfully employed in aldol and Michael reactions giving moderate to high selectivity.
- Clarke, Sarah L.,McSweeney, Christina M.,McGlacken, Gerard P.
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p. 356 - 361
(2014/04/03)
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- Iron- and bismuth-catalyzed asymmetric mukaiyama aldol reactions in aqueous media
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We have developed asymmetric Mukaiyama aldol reactions of silicon enolates with aldehydes catalyzed by chiral FeII and BiIII complexes. Although previous reactions often required relatively harsh conditions, such as strictly anhydrous conditions, very low temperatures (-78 °C), etc., the reactions reported herein proceeded in the presence of water at 0 °C. To find appropriate chiral water-compatible Lewis acids for the Mukaiyama aldol reaction, many Lewis acids were screened in combination with chiral bipyridine L1, which had previously been found to be a suitable chiral ligand in aqueous media. Three types of chiral catalysts that consisted of a FeII or BiIII metal salt, a chiral ligand (L1), and an additive have been discovered and a wide variety of substrates (silicon enolates and aldehydes) reacted to afford the desired aldol products in high yields with high diastereo- and enantioselectivities through an appropriate selection of one of the three catalytic systems. Mechanistic studies elucidated the coordination environments around the FeII and BiIII centers and the effect of additives on the chiral catalysis. Notably, both Bronsted acids and bases worked as efficient additives in the Fe II-catalyzed reactions. The assumed catalytic cycle and transition states indicated important roles of water in these efficient asymmetric Mukaiyama aldol reactions in aqueous media with the broadly applicable and versatile catalytic systems. Copyright
- Kitanosono, Taku,Ollevier, Thierry,Kobayashi, Shu
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supporting information
p. 3051 - 3062
(2014/01/06)
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- Rhodium-catalyzed cross-aldol reaction: In situ aldehyde-enolate formation from allyloxyboranes and primary allylic alcohols
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Dip in! A Rh/dippf catalyst generates aldehyde-derived enol boranes at ambient temperature by isomerization of allyloxy- and homoallyloxyboranes. A one-pot isomerization/cross-aldol sequence provides aldehyde-aldehyde adducts in good yield with syn select
- Lin, Luqing,Yamamoto, Kumiko,Matsunaga, Shigeki,Kanai, Motomu
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supporting information
p. 10275 - 10279
(2013/01/15)
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- Study of the lanthanide-catalyzed, aqueous, asymmetric Mukaiyama aldol reaction
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The development of efficient methods for the asymmetric Mukaiyama aldol reaction in aqueous solution has received great attention. We have developed a new series of chiral lanthanide-containing complexes that produce Mukaiyama aldol products with outstanding enantioselectivities. In this paper, we describe an optimized ligand synthesis, trends in stereoselectivity that result from changing lanthanide ions, and an exploration of substrate scope that includes aromatic and aliphatic aldehydes and silyl enol ethers derived from aromatic and aliphatic ketones.
- Mei, Yujiang,Averill, Derek J.,Allen, Matthew J.
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scheme or table
p. 5624 - 5632
(2012/09/05)
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- Tetranuclear BINOL-titanium complex in selective direct aldol additions
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(Chemical Equation Presented) The extremely robust and water-stable tetranuclear complex Ti4(μ-BINOLato)6(μ3- OH)4 (1) catalyzes the direct aldol addition with high degrees of regioselectivity at the sterically more encumbered α-side of unsymmetrical ketones. The formation of quaternary stereocenters is described. Oxygen-containing ene components can also be used as starting material in these reactions. When used with aliphatic aldehydes, acetals 18 or acetals of aldol adducts 20 were observed. As few as 0.2 mol % loadings with this catalyst 1 were enough to complete the reactions. Mechanistical aspects of the reactions are discussed.
- Schetter, Bernd,Ziemer, Burkhard,Schnakenburg, Gregor,Mahrwald, Rainer
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p. 813 - 819
(2008/09/18)
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- Enantioselective direct aldol-tishchenko reaction: Access to chiral stereopentads
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(Chemical Equation Presented) The aldol-Tishchenko reaction of aromatic aldehydes in the presence of titanium(IV) tertbutoxide and amino alcohols is described. When used with cinchona alkaloids, stereopentads were isolated for the first time with a high d
- Rohr, Kerstin,Herre, Robert,Mahrwald, Rainer
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p. 4499 - 4501
(2007/10/03)
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- A highly enantioselective, moderately anti-selective aldol reaction using a novel hydrazone moiety as stereo director
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The use of novel hydrazones as stereo directors with a view to develop a highly enantioselective, anti-diastereoselective aldol addition procedure has been investigated. A number of proline-derived hydrazones were produced and their effectiveness in direc
- McGlacken, Gerard P.,Breeden, Simon W.
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p. 3615 - 3618
(2007/10/03)
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- Aqueous asymmetric Mukaiyama aldol reaction catalyzed by chiral gallium Lewis acid with trost-type semi-crown ligands
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The combination of Ga(OTf)3 with chiral semi-crown ligands (1a-e) generates highly effective chiral gallium Lewis acid catalysts for aqueous asymmetric aldol reactions of aromatic silyl enol ethers with aldehydes. A ligand-acceleration effect was observed. Water is essential for obtaining high diastereoselectivity and enantioselectivity. The p-phenyl substituent in aromatic silyl enol. ether (2 h) plays an important role and increases the enantioselectivity up to 95% ee. Although aliphatic silyl enol ethers provided low enantioselectivities and silylketene acetal is easily hydrolyzed in aqueous alcohol, the aldol reactions of silylketene thioacetal (12) with aldehydes in the presence of gallium-Lewis acid catalysts give the β-hydroxy thioester with reasonable yields and high diastereo- (up to 99:1) and enantioselectivities (up to 96% ee).
- Li, Hui-Jing,Tian, Hong-Yu,Wu, Yan-Chao,Chen, Yong-Jun,Liu, Li,Wang, Dong,Li, Chao-Jun
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p. 1247 - 1256
(2007/10/03)
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- Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter
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The first example of a direct aldehyde-ketone coupling using the secondary amine piperidine as base in the presence of MgI2 to generate high selectivity of anti-aldol products from unmodified ethyl ketones in high yield is reported. The couplin
- Wei, Han-Xun,Jasoni, Richard L.,Shao, Huawu,Hu, Jiali,Paré, Paul W.
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p. 11829 - 11835
(2007/10/03)
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- Syn-anti isomerization of aldols by enolization
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A variety of aldol adducts are shown to undergo efficient syn-anti isomerization in the presence of imidazole by an enolization mechanism. Isomerizations are high yielding and occur with little or none of the usual byproducts arising from competing elimination or retroaldol reactions. Most substrates reach equilibrium within 0.3-3 days at ambient temperature in chloroform, benzene, or dichloromethane containing 0.3-1 M imidazole. The process is particularly facile for aldols derived from tetrahydro-4H-thiopyran- 4-one with rate constants for equilibration varying over ca. 1 order of magnitude for the adducts studied; structurally related aldols derived from cyclohexanone isomerized ca. 3-4 times slower. Isomerization of the acyclic aldol 5-hydroxy-4-methyl-5-phenyl-3-pentanone required heating to 60 °C but was achieved with minimal (A methoxymethyl ether derivative isomerized 30-40 times slower than the parent aldol. Isomerization of α,α′-disubstituted aldols and α,α′-bisaldols indicated low regioselectivity in the enolization. The synthetic utility of the process was demonstrated with the effective preparation of aldol stereoisomers unobtainable by direct methods.
- Ward, Dale E.,Sales, Marcelo,Sasmal, Pradip K.
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p. 4808 - 4815
(2007/10/03)
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- Proline-catalyzed asymmetric aldol reactions of tetrahydro-4H-thiopyran-4- one with aldehydes
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Proline-catalyzed enantioselective direct intermolecular aldol reactions of tetrahydro-4H-thiopyran-4-one with various aldehydes give anti adducts with high diastereo- and enantioselectivities in moderate to excellent yields. With the aromatic aldehydes b
- Ward, Dale E.,Jheengut, Vishal
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p. 8347 - 8350
(2007/10/03)
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- Crossed aldol reaction using polymer-bound lithium amides
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Polymer-bound lithium amides were used in an aldol reaction. The introduction of a spacer between the polymer backbone and the reactive site was important to enhance yields of the aldol products. The polymer-bound reagent was repeatedly used in the same r
- Seki, Atsushi,Takizawa, Youichi,Ishiwata, Fusae,Asami, Masatoshi
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p. 342 - 343
(2007/10/03)
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- Stereoselective crossed aldol reaction via boron enolates generated from α-iodo ketones and 9-borabicyclo[3.3.1]nonane
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Boron enolates were in situ-generated reductively by treating various α-iodo ketones such as 2-iodo-1-phenylpropan-1-one, 2-iodo-1-(4-methoxyphenyl)propan-1-one, 2-iodopentan-3-one, 2-iodo-2-methyl-1-phenylpropan-1-one, 3,4-dihydro-2-iodo-1(2H)-naphthalenone, 2-iodo-1-phenylethan-1-one and 1-iodo-4-phenylbutan-2-one with 9-borabicyclo[3.3.1]nonane (9-BBN). Aldols were produced in good yields with good to high diastereoselectivities by subsequent reaction of boron enolates thus formed with various aldehydes. Several boron enolates derived from α-iodo ketones and pinacolatoborane were successfully isolated by distillation, though the yields were rather moderate.
- Mukaiyama, Teruaki,Takuwa, Tomofumi,Yamane, Keiko,Imachi, Shouhei
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p. 813 - 823
(2007/10/03)
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- Aldol- and Mannich-type reactions via in situ olefin migration in ionic liquid.
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An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl(2)(PPh(3))(3) was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactivity.
- Yang, Xiao-Fan,Wang, Mingwen,Varma, Rajender S,Li, Chao-Jun
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p. 657 - 660
(2007/10/03)
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- Stereoselective aldol additions of achiral ethyl ketone-derived trichlorosilyl enolates
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Methods for the preparation of geometrically defined enoxy(trichlorosilanes) derived from ethyl ketone enolates have been developed. The addition of enoxy(trichlorosilanes) (trichlorosilyl enolates) to aldehydes proceeds with good yields in the presence of catalytic amounts of chiral phosphoramides. The reaction of Z-trichlorosilyl enolates to aryl aldehydes affords aldol products with good to excellent diastereo- and enantioselectivities. Phosphoramide-catalyzed aldol additions lacked substrate generality providing modest selectivities with unsaturated and aliphatic aldehydes. In all cases, the phosphoramide-catalyzed aldol addition of E-trichlorosilyl enolates to aldehydes provided good yields with moderate to good stereoselectivities.
- Denmark, Scott E.,Pham, Son M.
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p. 5045 - 5055
(2007/10/03)
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- Stereoselective crossed aldol reaction via boron enolate generated from α-iodoketones and 9-BBN-H
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Boron enolates were in situ generated smoothly by treating α-iodo ketones with 9-BBN-H, and aldols were produced in highly diastereoselective manner by successive reaction with various aldehydes at low temperature.
- Mukaiyama, Teruaki,Imachi, Shouhei,Yamane, Keiko,Mizuta, Masahiro
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p. 698 - 699
(2007/10/03)
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- Efficient synthesis of B-iododialkyl- and B-alkyldiiodoboranes as their acetonitrile complexes: Application for the enolboration - Aldolization of ethyl ketones
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A series of B-(iododialkyl)boranes and B-(alkyldiiodo)boranes have been readily synthesized as their MeCN complexes from the corresponding chloro- and bromoboranes by treatment with NaI or KI in MeCN. In the presence of EtN(i-Pr)2, the B-(cyclo
- Veeraraghavan Ramachandran,Zou, Mu-Fa,Brown, Herbert C.
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p. 3027 - 3032
(2007/10/03)
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- Catalytic use of a boron source for boron enolate mediated stereoselective aldol reactions in water
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Use of boron enolates in water! Boron enolates can be generated and used for aldol reactions in water by using a catalytic amount of Ph2BOH (see scheme). This is the first example of a catalytic use of a boron enolates. The mechanism of the rea
- Mori, Yuichiro,Manabe, Kei,Kobayashi
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p. 2816 - 2818
(2007/10/03)
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- Syn-anti isomerization of aldols by enolization
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Figure presented A variety of aldol adducts (i.e., 3-hydroxy ketones) are shown to undergo syn-anti isomerization in the presence of imidazole by an enolization mechanism with negligible retroaldol or elimination products.
- Ward, Dale E.,Sales, Marcelo,Sasmal, Pradip K.
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p. 3671 - 3673
(2007/10/03)
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- Chiral Lewis acid catalysis in aqueous media. Catalytic asymmetric aldol reactions of silyl enol ethers with aldehydes in a protic solvent including water
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Chiral copper(II)-catalyzed asymmetric aldol reactions of silyl enol ethers with aldehydes have been successfully carried out in a water-ethanol solution. The use of the protic solvent including water is essential in these reactions, and this report has proposed and demonstrated a new concept for solvents in catalytic asymmetric aldol reactions.
- Kobayashi, Shu,Nagayama, Satoshi,Busujima, Tsuyoshi
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- Diastereoselective aldol reaction of α-bromo ketones with aliphatic aldehydes by using titanium(II) chloride and copper
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Highly diastereoselective aldol reaction of α-bromo ketones with aliphatic aldehydes was successfully carried out by using titanium(II) chloride and copper in dichloromethane at low temperature. Similarly, Reformatsky-type reaction of α-bromo thioester with aliphatic aldehydes was promoted under mild conditions to afford β-hydroxy thioesters in good to moderate yields.
- Mukaiyama, Teruaki,Kagayama, Akifumi,Igarashi, Koji,Shiina, Isamu
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p. 1157 - 1158
(2007/10/03)
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- Rhodium promoted isomerisation of allylic alkoxides: A new method for enolate anion formation
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Transition metal mediated isomerisation of allylic alkoxides is presented as a new method for enolate anion generation. The scope and limitations of enolate formation with the catalysts [Rh(dppe)(THF)2]+ClO4- and (Ph3P)3RhCl are explored and the synthetic potential of the methodology demonstrated in the stereoselective formation and reactions of certain ketone and aldehyde enolates.
- Gazzard, Lewis J.,Motherwell, William B.,Sandham, David A.
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p. 979 - 993
(2007/10/03)
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- Stereocontrol in one-pot syntheses of 1,3-diols
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Titanium mediated aldol addition reduction sequence is described for the synthesis of stereodefined 1,3-diols. Diastereochemical control is surprisingly achieved through the careful selection of starting materials used.
- Mahrwald,Ziemer
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p. 14005 - 14012
(2007/10/03)
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- Scandium trisdodecylsulfate (STDS). A new type of Lewis acid that forms stable dispersion systems with organic substrates in water and accelerates aldol reactions much faster in water than in organic solvents
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A new type of Lewis acid, scandium trisdodecylsulfate (STDS), was prepared. In the presence of a catalytic amount of STDS, aldol reactions of silyl enol ethers with aldehydes proceeded smoothly in water without using any organic solvents. It was proven th
- Kobayashi, Shu,Wakabayashi, Takeshi
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p. 5389 - 5392
(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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- Reductive intramolecular cyclization of α-bromo silyl ethers mediated by samarium diiodide
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A new SmI2-promoted intramolecular reductive cyclization of β-(α-bromo siloxy) carbonyl compounds is reported.
- Park,Lee,Kwon,Kim
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p. 2745 - 2746
(2007/10/03)
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- B,B-dihaloalkylboranes as efficient reagents for the stereoselective synthesis of Syn-aldols
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The easily synthesized B,B-dihaloalkylboranes, in the presence of either Et3N or i-Pr2NEt, converts ethyl ketones, RCOEt, to 96-≤ 99% Z-enolates, converted by aldehydes to essentially pure syn-aldols.
- Ramachandran, P. Veeraraghavan,Wei-Chu, Xu,Brown, Herbert C.
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p. 769 - 772
(2007/10/03)
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- Catalytic, Diastereoselective Aldol Reactions Using Titanium(IV) Halides
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The aldol reaction in the presence of titanium halides is described.Good yields of aldols 10-17 were obtained even with only catalytic amounts of titanium tetrafluoride.The reactions were carried out in the absence of a base. - Keywords: Aldol reaction /
- Mahrwald, Rainer
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p. 919 - 922
(2007/10/02)
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- Stereoselective Aldol Reaction Using Titanium Ate Complexes - An Efficient Method For Achieving Anti Aldol Selectivity
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Carbonyl compounds react in the presence of titanium ate complexes in the sense of an aldol reaction.The influence of ligands on controlling stereoselection of syn and anti aldol products of the titanium ate complexes used are described.High yield of anti
- Mahrwald, Rainer
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p. 9015 - 9022
(2007/10/02)
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- Ytterbium Trifluoromethanesulfonate Mediated Cross-Aldol Reaction between Ketones and Aldehydes
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The cross-aldol reaction between a ketone and an aldehyde proceeded smoothly with threo diastereoselection favorably mediated by ytterbium trifluoromethanesulfonate and tertiary amine in diethyl ether or in dichloromethane.A ytterbium enolate was trapped
- Fukuzawa, Shin-ichi,Tsuchimoto, Teruhisa,Kanai, Takeshi
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p. 2227 - 2232
(2007/10/02)
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- Enolboration. 5. An Examination of the Effects of Amine, Solvent, and Other Reaction Parameters on the Stereoselective Enolboration of Ketones with Various Chx2BX Reagents. An Optimized Procedure To Achieve the Stereoselective Synthesis of E Enol Borinate
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The effects of amine, solvent, concentration, temperature and other reaction parameters in controlling the enolate geometry have been systematically investigated in the present study.A 11B NMR study of the interaction of representative tertiary amines of
- Ganesan, Kumeraperumal,Brown, Herbert C.
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p. 7162 - 7169
(2007/10/02)
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- Enolboration. 4. An Examination of the Effect of the Leaving Group (X) on the Stereoselective Enolboration of Ketones with Various R2BX/Et3N. New Reagents for the Selective Generation of either Z or E Enol Borinates from Representative Ketones
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A smooth, rapid, quantitative and stereoselective enolboration of representative ketones to either Z or E enol borinates is achieved with many new R2BX/Et3N reagents.Representative B-X-9-BBN and Chx2BX reagents with various leaving groups, such as triflat
- Brown, Herbert C.,Ganesan, Kumaraperumal,Dhar, Raj K.
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p. 147 - 153
(2007/10/02)
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- Catalytic Asymmetric Aldol-Type Reactions Using a Chiral (Acyloxy)borane Complex
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In the presence of 20 molpercent of a chiral (acyloxy)borane (CAB) complex prepared from BH3*THF and a chiral mono-O-acylated tartaric acid, achiral silyl enol ethers or ketene silyl acetals react with achiral aldehydes to afford the corresponding aldol-t
- Ishihara, Kazuaki,Maruyama, Tohru,Mouri, Makoto,Gao, Qingzhi,Furuta,Kyoji,Yamamoto, Hisashi
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p. 3483 - 3491
(2007/10/02)
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