- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Reusable shuttles for exchangeable functional cargos: Reversibly assembled, magnetically powered organocatalysts for asymmetric aldol reactions
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A supramolecular approach has been followed to support adamantyl substituted proline organocatalysts onto the surface of magnetite nanoparticles decorated with a β-cyclodextrin motif. The resulting magnetic nanoparticles (ca. ~10 nm diameter) were used as modular, magnetically recyclable catalysts in the asymmetric aldol reaction of aromatic aldehydes with cyclic ketones in water. The catalytic assemblies can be easily dismantled in organic media, and the recovered nanoparticles (magnetically powered chemical shuttles) re-complexed with another suitably substituted catalytic unit (replaceable functional cargo).
- Mendoza, Carolina,de la Croix, Augustin,Riente, Paola,Llorens, Lluís,de Mendoza, Javier,Pericàs, Miquel A.
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supporting information
(2019/09/17)
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- Ion-Tagged Prolinamide Organocatalysts for the Direct Aldol Reaction On-Water
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A concise synthesis of two imidazolium ion-tagged prolinamide organocatalysts 3 and 4, varying in anionic component (CF3COO- and PF6 -, respectively) is presented. The latter could be classified as an ionic liqu
- Eyckens, Daniel J.,Brozinski, Hannah L.,Delaney, Joshua P.,Servinis, Linden,Naghashian, Sahar,Henderson, Luke C.
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p. 212 - 219
(2016/02/23)
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- Synthesis of sulphur-modified bifunctional hydrotalcites and study of their surface characteristics by inverse gas chromatography
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In this study, various sulphur-modified hydrotalcite catalysts were prepared, and the influence of calcination temperature on their acid-base properties was investigated. Structural characterization of the catalysts was studied using X-ray powder diffraction, scanning electron microscopy, N2 physisorption, elemental analysis and Fourier transform infrared spectroscopy. The structural characterization indicated that the layer structure of all catalysts was retained but the specific surface areas were enlarged. Inverse gas chromatography was carried out to quantitatively determine the catalysts' acid-base properties by calculating the thermodynamic parameters, including dispersive surface free energy, adsorption free energy, adsorption enthalpy, and acid-base interaction constants. The results showed that the strength and content of acidic and alkaline sites were enhanced with increasing calcination temperature. Moreover, several typical aldol condensation reactions were selected to study the catalytic activity of the developed catalysts. The results showed that the sulphur-modified hydrotalcite catalysts possess high activity and good regenerability for typical aldol condensation reactions.
- Ren, Xiaoqian,Hu, Xi,Zhang, Feng,Wang, Junge,Liang, Jinhua,Wu, Wenliang,Jiang, Min,Wang, Jun
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p. 4813 - 4820
(2015/10/05)
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- Chiral Br?nsted Acid as a True Catalyst: Asymmetric Mukaiyama Aldol and Hosomi-Sakurai Allylation Reactions
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Highly diastereo- and enantioselective Mukaiyama aldol reaction catalyzed by a new chiral Br?nsted acid, N-(perfluorooctanesulfonyl)thiophosphoramide, is described. The perfluorooctyl substituent on the sulfonyl group of the catalyst plays an essential role in the stereoselection. The catalyst also allows the asymmetric Hosomi-Sakurai allylation, which has been considerably challenging due to the low reactivity of allylsilanes. 29Si and 31P NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Br?nsted acid even in the presence of excess silyl nucleophiles, which cannot be found in other related phosphoric acid analogues.
- Sai, Masahiro,Yamamoto, Hisashi
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supporting information
p. 7091 - 7094
(2015/06/25)
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- Highly Enantio- and Diastereoselective l -Proline Derived Acetylglucose Amide Catalyzed Aldol Reaction of Ketones to Aldehydes under Solvent-Free Conditions
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A novel organocatalyst was developed from d-glucosamine and l-proline, which was shown to catalyze the direct aldol reaction of ketones with aldehydes in a highly diastereoselective and enantioselective manner under solvent-free conditions. The presence o
- Han, Xiaoyu,Wang, Yongjiang,Gai, Xikun,Zeng, Xiaofei
-
supporting information
p. 2858 - 2862
(2015/12/18)
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- Enantiopure azetidine-2-carboxamides as organocatalysts for direct asymmetric aldol reactions in aqueous and organic media
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A family of enantiopure azetidine-2-caboxamides was asymmetrically synthesized, and was examined as organocatalyst in direct aldol reactions. A well chosen chiral azetidine-2-caboxamide was found to smoothly catalyze the direct aldol reaction of various benzaldehydes with acetone in brine, and β-hydroxy ketones were produced with enantiomeric excess up to 96%. The reaction of benzaldehydes with cyclic ketones also led to the formation of anti-products in diastereomeric ratio up to 99:1 and enantiomeric excess up to 99%.
- Song, Xixi,Liu, Ai-Xiang,Liu, Shan-Shan,Gao, Wen-Chao,Wang, Min-Can,Chang, Junbiao
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p. 1464 - 1470
(2014/02/14)
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- A magnesium-based multifunctional metal-organic framework: Synthesis, thermally induced structural variation, selective gas adsorption, photoluminescence and heterogeneous catalytic study
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Three magnesium based carboxylate framework systems were prepared through a temperature-dependent synthesis. The compounds were synthesized by a hydrothermal method and characterized by single crystal X-ray diffraction analysis. A stepwise increase in the
- Saha, Debraj,Maity, Tanmoy,Das, Soma,Koner, Subratanath
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p. 13912 - 13922
(2013/09/24)
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- Synergistic effects within a C2-symmetric organocatalyst: The potential formation of a chiral catalytic pocket
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This study describes the synthesis of five novel C2-symmetric organocatalysts that facilitate the on-water asymmetric aldol reaction at low catalyst loading (1 mol%) without the use of additives. Each catalyst is composed of two diprolinamide units joined by a symmetric alkyl bridging group allowing for systematic modulation of catalytic site proximity. Typically, catalysts in this manuscript which bear the catalytic units in close proximity gave the best reaction outcomes in terms of conversion (up to >99%), diastereomeric ratio (4/96, syn/anti) and enantiomeric excess (up to 97%). This effect has been attributed to the assembly of a chiral pocket, facilitated by hydrogen bonding at the oil-in-water interface. The Royal Society of Chemistry 2013.
- Delaney, Joshua P.,Brozinski, Hannah L.,Henderson, Luke C.
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p. 2951 - 2960
(2013/07/26)
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- Development of highly enantioselective asymmetric aldol reaction catalyzed by 1-glycyl-3-methyl imidazolium chloride-iron(III) complex
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A novel, effective asymmetric 1-glycyl-3-methyl imidazolium chloride-iron(III) [[Gmim]Cl-Fe(III)] complex was synthesized and studied as organocatalyst in asymmetric aldol addition under solvent free condition at 25 C. The hydrophobic group of amino acid
- Karthikeyan, Parasuraman,Muskawar, Prashant Narayan,Aswar, Sachin Arunrao,Sythana, Suresh Kumar,Bhagat, Pundlik Rambhau
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p. 333 - 339
(2013/10/22)
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- Water promoted enantioselective aldol Reaction by proline-cholesterol and -diosgenin based amphiphilic organocatalysts
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A series of proline-cholesterol and -diosgenin based amphiphilic organocatalysts were developed for the first time, and their catalytic activities for the enantioselective aldol reaction were investigated. The results indicated that water can significantl
- He, Ting,Li, Kun,Wu, Ming-Yu,Wu, Ming-Bo,Wang, Na,Pu, Lin,Yu, Xiao-Qi
-
supporting information
p. 5136 - 5143
(2013/06/27)
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- Copper-catalyzed 1,4-addition reaction of Grignard reagent to enones using microflow system
-
The copper-catalyzed conjugate addition of a Grignard reagent to an β-unsaturated ketone was performed in a microflow system. In the reaction using the microflow system, a chemoselective 1,4-addition reaction to an enone in the presence of a saturated ketone group proceeded successfully.
- Katayama, Haruo,Matsubara, Seijiro
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p. 471 - 472
(2013/06/05)
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- Dried chitosan-gels as organocatalysts for the production of biomass-derived platform chemicals
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Aldol condensations between sugar-derived dehydrated aldehydes (e.g. furfural) and acetone have been proposed as a route to provide useful biomass-derived chemicals. In the quest of sustainable catalytic ways for such aldol condensations, this paper assesses the use of dried chitosan-gels as naturally-immobilized, readily available and non-hazardous amino-based organocatalysts. At room temperature chitosan dried gels are not suitable catalysts for the desired reaction. However, at higher temperatures (>90 °C) reaction proceeds efficiently either in solvent-free systems (with addition of catalytic amounts of water) or in water. The set-up of closed reactor set-ups (thermoshakers or microwave reactions) proved highly beneficial for the reaction outcome. Furthermore, chitosan dried gels were successfully re-used for a number of cycles. An efficient catalyst drying method (either lyophilization or scCO2 drying) was crucial to achieve virtually full conversions in 4 h. After pertinent further process optimization, dried chitosan-gels may become very useful catalysts for their use in biomass-based reactions in biorefineries.
- Kayser, Henning,Müller, Christoph R.,García-González, Carlos A.,Smirnova, Irina,Leitner, Walter,Domínguez De María, Pablo
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p. 180 - 186
(2013/02/23)
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- Direct asymmetric aldol reactions in water catalysed by a highly active C2-symmetrical bisprolinamide organocatalyst
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A novel C2-symmetrical bisprolinamide organocatalyst was synthesised and used to facilitate asymmetric direct aldol reactions in a water emulsion. Reactions were performed at room temperature with very low catalyst loadings (1-2.5 mol%) without the required use of additives, co-catalysts or extended reaction times (24 h). This catalyst system was then used with a variety of aldehyde substrates showing good reaction generality for benzaldehydes with cyclohexanone (dr range 77/23 to 99/1, anti/syn; ee range 33% to 99%) and moderate scope with cyclopentanone (dr range 45/55 to 76/24, anti/syn; ee range 14% to 68%). Ultra-low catalysts loadings (0.1 and 0.05 mol%) were also investigated demonstrating catalyst turnover numbers in the order of 1000.
- Delaney, Joshua P.,Henderson, Luke C.
-
experimental part
p. 197 - 204
(2012/03/27)
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- Copolymer-supported heterogeneous organocatalyst for asymmetric aldol addition in aqueous medium
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In the current study, a convenient and simple way is presented to synthesize a novel type of supported heterogeneous organocatalyst in 21-81% yield by the copolymerization of 9-amino-9-deoxy-epi-cinchonine organocatalyst with acrylonitrile using AIBN as r
- Zhou, Jinqing,Wan, Jinwei,Ma, Xuebing,Wang, Wei
-
experimental part
p. 4179 - 4185
(2012/07/14)
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- Simple and inexpensive threonine-based organocatalysts as highly active and recoverable catalysts for large-scale asymmetric direct stoichiometric aldol reactions on water
-
Nine O-acylated threonines were screened as catalysts at loadings of 0.5-5 mol % for the direct asymmetric stoichiometric aldol reaction on water by using variable amounts of water. These threonine-based organocatalyst were simple, inexpensive, highly act
- Wu, Chuanlong,Long, Xiaoqin,Li, Shi,Fu, Xiangkai
-
experimental part
p. 315 - 328
(2012/07/14)
-
- New simple and recyclable O-acylation serine derivatives as highly enantioselective catalysts for the large-scale asymmetric direct aldol reactions in the presence of water
-
New classes of O-acylation serine derived organocatalysts have been synthesized one-step by rational combination of serine with acyl chlorides at room temperature in trifluoroacetic acid. No protecting groups or chromatographic techniques are involved in
- Wu, Chuanlong,Fu, Xiangkai,Li, Shi
-
supporting information; experimental part
p. 4283 - 4290
(2011/06/26)
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- Biheteroaromatic diphosphine oxides-catalyzed stereoselective direct aldol reactions
-
A highly stereoselective direct aldol condensation of ketones to aromatic aldehydes was realized; the trichlorosilyl enolether generated in situ in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomerically pure biheteroaromatic phosphine oxide to react with aldehydes, coordinated as well as activated by the chiral cationic hypervalent silicon species. This Lewis acid-mediated Lewis base-catalyzed transformation allowed, starting from two carbonyl compounds, to directly synthesize β-hydroxy ketones generally with high anti stereoselectivity and up to 93% ee for the anti isomer.
- Rossi, Sergio,Benaglia, Maurizio,Genoni, Andrea,Benincori, Tiziana,Celentano, Giuseppe
-
supporting information; experimental part
p. 158 - 166
(2011/02/27)
-
- Development of N,N-bis(perfluoroalkanesulfonyl)squaramides as new strong Br?nsted acids and their application to organic reactions
-
New strong Br?nsted acids derived from a squaric acid scaffold bearing different perfluoroalkanesulfonyl groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Br?nsted acid might be the predominant catalyst through direct protonation of carbonyl compound by the acid itself rather than the silylated Br?nsted acid. The utility of this acid 2a was further extended to Hosomi-Sakurai allylation of aldehydes and a carbonyl-ene reaction. Furthermore, other squaramides 2b and c bearing longer perfluoroalkyl chains have been developed, which are also bench-stable and displayed similar reactivities with squaramide 2a in several organic reactions.
- Cheon, Cheol Hong,Yamamoto, Hisashi
-
supporting information; experimental part
p. 4257 - 4264
(2010/07/06)
-
- Asymmetric supramolecular primary amine catalysis in aqueous buffer: Connections of selective recognition and asymmetric catalysis
-
A new approach of asymmetric supramolecular catalysis has been developed by combining the supramolecular recognition of β-cyclodextrin (β-CD) and the superior property of a chiral primary amine catalyst. The resulted β-CD enamine catalysts could effectively promote asymmetric direct aldol reactions with excellent enantioselectivity in an aqueous buffer solution (pH = 4.80). The identified optimal catalyst CD-1 shows interesting characteristics of supramolecular catalysis with selective recognition of aldol acceptors and donors. A detailed mechanistic investigation on such supramolecular catalysis was conducted with the aid of NMR, fluorescence, circular dichroism, and ESI-MS analysis. It is revealed that the reaction is initialized first by binding substrates into the cyclodextrin cavity via a synergistic action of hydrophobic interaction and noncovalent interaction with the CD-1 side chain. A rate-limiting enamine forming step is then involved which is followed by the product-generating C-C bond formation. A subsequent product release from the cavity completes the catalytic cycle. The possible connections between molecular recognition and asymmetric catalysis as well as their relevance to enamine catalysis in both natural enzymes and organocatalysts are discussed based on rational analysis.
- Hu, Shenshen,Li, Jiuyuan,Xiang, Junfeng,Pan, Jie,Luo, Sanzhong,Cheng, Jin-Pei
-
supporting information; experimental part
p. 7216 - 7228
(2010/07/08)
-
- Advances towards highly active and stereoselective simple and cheap proline-based organocatalysts
-
Ten 4-acyloxy-L-prolines were screened as catalysts at loadings of 2-0.1 mol-% for the direct asymmetric aldol reaction in water by using variable amounts of water. Among them, a new catalyst, the L-proline carrying a trans-4-(2,2-diphenylacetoxy) group, and a catalyst previously synthesized by us, the L-proline carrying a trans-4-(4-phenylbutanoyloxy) group, were found to be excellent catalysts for the aldol reaction between cyclohexanone or cyclopentanone and substituted benzaldehydes when employed in only 1 and 0.5 mol-%,respectively, at room temperature without additives. For such catalysts, high turnover numbers were obtained, which are among the highest values obtained for enamine organocatalysis. Finally, these catalysts can be synthesized by direct O-acylation from inexpensive molecules and successfully used in scaled-up reactions. Highest activity and selectivity at minor expense! Simple and cheap 4-acyloxy-L-prolines were easily prepared and successfully employed in the direct asymmetric aldol reaction in water by using a loading of2-0.1 mol-%. Interestingly, high turnover numbers, among the highest values ever reported for enamine organocatalysis, were obtained.
- Giacalone, Francesco,Gruttadauria, Michelangelo,Agrigento, Paola,Lo Meo, Paolo,Noto, Renato
-
experimental part
p. 5696 - 5704
(2010/12/25)
-
- Novel enantioselective direct aldol-type reaction promoted by a chiral phosphine oxide as an organocatalyst
-
Chiral phosphine oxide successfully catalyzed the direct aldol-type reactions of cyclohexanone derivatives and benzaldehyde derivatives in high stereoselectivities. The reaction mechanism involves the in situ formation of trichlorosilyl enol ethers. The present reaction could be extended to the cross-aldol reactions between two aldehydes.
- Kotani, Shunsuke,Shimoda, Yasushi,Sugiura, Masaharu,Nakajima, Makoto
-
supporting information; experimental part
p. 4602 - 4605
(2009/10/26)
-
- Intermolecular antiselective and enantioselective reductive coupling of enones and aromatic aldehydes with chiral rh(phebox) catalysts
-
The intermolecular reductive coupling reaction of cyclopent-2-enone and aromatic aldehydes was realized by chiral rhodium-(bisoxazolinyl)phenyl catalysts, Rh(Phebox-Ph)(OAc)2(H2O), with diphenymethylsilane as a hydride donor to give
- Shiomi, Takushi,Adachi, Takahiro,Ito, Jun-Ichi,Nishiyama, Hisao
-
supporting information; experimental part
p. 1011 - 1014
(2009/07/18)
-
- Toward an artificial aldolase
-
(Chemical Equation Presented) A new functional polymer where proline is bonded to polystyrene through a 1,2,3-triazole linker depicts characteristics targeted for an artificial aldolase. In spite of the hydrophobicity of the polymer backbone, the resin swells in water with building of an aqueous microenvironment. This property, arising from the formation of a hydrogen-bond network connecting the proline and 1,2,3-triazole fragments, is translated into a very high catalytic activity and enantioselectivity toward direct aldol reactions in water.
- Font, Daniel,Sayalero, Sonia,Bastero, Amaia,Jimeno, Ciril,Pericas, Miquel A.
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p. 337 - 340
(2008/09/19)
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- A recyclable non-immobilized siloxy serine organocatalyst for the asymmetric direct aldol reaction
-
A recyclable siloxy-l-serine organocatalyst has been developed to catalyze asymmetric direct aldol reactions in [bmim][BF4], furnishing the β-hydroxy carbonyl scaffold in high enantio- and diastereoselectivities using a selection of aromatic al
- Teo, Yong-Chua,Chua, Guan-Leong
-
p. 4235 - 4238
(2008/09/21)
-
- Methyl 12-[d-prolinoylamino]cholate as a versatile organocatalyst for the asymmetric aldol reaction of cyclic ketones
-
The use of cholic acid derivative 1, bearing a d-prolinamide moiety linked at the 12-position of cholic acid methylester, as an organocatalyst in the asymmetric aldol reaction of cyclic ketones and aromatic aldehydes, gave the corresponding aldol products in good yield and ee up to 98%. This organocatalyst has proven to be efficient both in water and in organic solvent, where it has been used with a 1% loading.
- Puleo, Gian Luigi,Iuliano, Anna
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p. 2894 - 2900
(2008/09/19)
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- Chiral phosphine oxide BINAPO as a Lewis base catalyst for asymmetric allylation and aldol reaction of trichlorosilyl compounds
-
Chiral phosphine oxide BINAPO, which was readily prepared from chiral phosphine BINAP, exhibited good catalytic activities in the reaction of trichlorosilyl compounds via hypervalent silicate intermediates. The allylation of aldehydes with allyltrichloros
- Kotani, Shunsuke,Hashimoto, Shunichi,Nakajima, Makoto
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p. 3122 - 3132
(2007/10/03)
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- Highly diastereo- and enantioselective direct aldol reactions of aldehydes and ketones catalyzed by siloxyproline in the presence of water
-
Proline-based organocatalysts have been developed for a highly enantioselective, direct aldol reaction of aldehydes and ketones in the presence of water. While several surfactant-proline combined catalysts have proved effective, proline derivatives with a hydrophobic moiety such as rraw-siloxy-L-proline and cis-siloxy-D-proline, both of which are easily prepared from the same commercially available 4-hydroxy-L-proline. have been found to be the most effective organocatalysts examined in this study, affording the aldol product with excellent diastereo- and enantioselectivities, these two catalysts generating opposite enantiomers. Water affects the selectivity, and poor results are obtained under neat reaction conditions or in dry organic solvents. More than three equivalents of water are required for the best diastereo- and enantioselectivities. while three equivalents is the recommended amount from a synthetic point of view. The reaction proceeds in the organic phase, and also proceeds in the presence of a large amount of water. The large-scale preparation of aldols with the minimal use of an organic solvent, including in the purification step. is described.
- Aratake, Seiji,Itoh, Takahiko,Okano, Tsubasa,Nagae, Norio,Sumiya, Tatsunobu,Shoji, Mitsuru,Hayashi, Yujiro
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p. 10246 - 10256
(2008/09/18)
-
- Direct asymmetric aldol reactions catalyzed by a siloxy serine organocatalyst in water
-
A siloxy-l-serine organocatalyst has been developed to catalyze direct asymmetric aldol reactions in the presence of water, furnishing the β-hydroxy carbonyl scaffold in high enantio- and diastereoselectivities. The direct aldol reaction between a selecti
- Teo, Yong-Chua
-
p. 1155 - 1158
(2008/02/05)
-
- Enantioselective aldol reactions of trichlorosilyl enol ethers catalyzed by the chiral phosphine oxide BINAPO
-
The enantioselective aldol reactions of aldehydes with trichlorosilyl enol ethers catalyzed by chiral phosphine oxide BINAPO afforded the corresponding aldol adducts with high diastereo- and enantioselectivities. Georg Thieme Verlag Stuttgart.
- Kotani, Shunsuke,Hashimoto, Shunichi,Nakajima, Makoto
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p. 1116 - 1118
(2007/10/03)
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- A heterogeneous silica-supported scandium/ionic liquid catalyst system for organic reactions in water
-
(Figure Presented) Several carbon-carbon bond-forming reactions are catalyzed by a silica-supported scandium triflate catalyst combined with an ionic liquid. The combination of these two components creates a hydrophobic reaction environment in water (see scheme; blue: water, yellow: substrate, orange: ionic liquid).
- Gu, Yanlong,Ogawa, Chikako,Kobayashi, Juta,Mori, Yuichiro,Kobayashi, Shu
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p. 7217 - 7220
(2007/10/03)
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- Chiral base-catalyzed aldol reaction of trimethoxysilyl enol ethers: Effect of water as an additive on stereoselectivities
-
An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate is described. The aldol reaction of trimethoxysilyl enol ether derived from cyclohexanone under anhydrous conditions predominantly afforded the anti-aldol adduct with moder
- Orito, Yuya,Hashimoto, Shunichi,Ishizuka, Tadao,Nakajima, Makoto
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p. 390 - 400
(2007/10/03)
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- The (S)-proline/polyelectrolyte system: An efficient, heterogeneous, reusable catalyst for direct asymmetric aldol reactions
-
A direct asymmetric aldol reaction between unmodified aldehydes and ketones was achieved using the (S)-proline/poly-(diallyldimethylammonium) hexafluorophosphate heterogeneous catalytic system with enantioselectivities and yields comparable to those obtained in the (S)-proline-catalyzed reactions performed under homogeneous conditions. Recycling of the catalyst was possible at least six times without loss of activity and enantioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Kucherenko, Alexandr S.,Struchkova, Marina I.,Zlotin, Sergei G.
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p. 2000 - 2004
(2007/10/03)
-
- Bismuth triflate catalyzed Mukaiyama aldol reaction in an ionic liquid
-
We have developed an efficient, bismuth triflate catalyzed Mukaiyama aldol reaction. The reaction proceeds rapidly and affords the corresponding β-hydroxy carbonyl compound in moderate to very good yields (up to 92%). Wiley-VCH Verlag GmbH & Co. KGaA, 200
- Ollevier, Thierry,Desyroy, Valerie,Debailleul, Blandine,Vaur, Sophie
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p. 4971 - 4973
(2007/10/03)
-
- Enantioselective direct aldol-tishchenko reaction: Access to chiral stereopentads
-
(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)
-
- Yb(OTf)3-TMSCl, a novel catalytic system in cross-aldol reactions
-
A combination of Yb(OTf)3 and TMSCl influenced the outcome of cross-aldol reactions of cycloalkanones and benzaldehyde. Interestingly, reaction of cycloheptanone and cyclooctanone with aldehydes under the Yb(OTf)3- TMSCl reagent system provides 3-(2-oxocycloalkyl)-3- phenylpropanals in conjunction with the corresponding aldol products.
- Kagawa, Natsuko,Toyota, Masahiro,Ihara, Masataka
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p. 655 - 657
(2007/10/03)
-
- Tris(pentafluorophenyl)silyl enol ethers: Synthesis and aldol reactions
-
Silyl enol ethers bearing three pentafluorophenyl groups at the silicon atom are described. These compounds undergo uncatalyzed aldol reactions with aliphatic, α,β-unsaturated, and aromatic aldehydes. The observed reactivity is analyzed in terms of the Le
- Dilman, Alexander D.,Belyakov, Pavel A.,Korlyukov, Alexander A.,Tartakovsky, Vladimir A.
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p. 3741 - 3744
(2007/10/03)
-
- Enantioselective aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate
-
(Chemical Equation Presented) An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate, in which water serves as an additive and plays a pivotal role in stereoselectivities, was developed. This is the first example of an aldol re
- Nakajima, Makoto,Orito, Yuya,Ishizuka, Tadao,Hashimoto, Shunichi
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p. 3763 - 3765
(2007/10/03)
-
- Dibutyltin dimethoxide-catalyzed aldol reaction of enol trichloroacetates
-
A catalytic aldol condensation of aldehydes with enol trichloroacetates was achieved using dibutyltin dimethoxide as a novel catalyst in a mixed solvent consisting of THF and MeOH. Various β-hydroxy ketones were diastereoselectively obtained in high yields up to 99%.
- Yanagisawa, Akira,Sekiguchi, Takayuki
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p. 7163 - 7166
(2007/10/03)
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- L-proline in an ionic liquid as an efficient and reusable catalyst for direct asymmetric aldol reactions
-
L-proline in imidazolium-based ionic liquids has been successfully used as an efficient and reusable catalyst for direct asymmetric aldol reactions.
- Loh, Teck-Peng,Feng, Li-Chun,Yang, Hai-Yan,Yang, Jian-Ying
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p. 8741 - 8743
(2007/10/03)
-
- Asymmetric aldol additions catalyzed by chiral phosphoramides: Electronic effects of the aldehyde component
-
The trichlorosilyl enolates of cyclopentanone and cycloheptanone were prepared by a mercury(II)-catalyzed metathesis from their TMS enol ethers in good yield. These enolates undergo spontaneous addition to aldehydes to provide the aldol adducts syn-4, 5a-
- Denmark, Scott E.,Stavenger, Robert A.,Wong, Ken-Tsung
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p. 10389 - 10402
(2007/10/03)
-
- Reductive intramolecular cyclization of α-bromo silyl ethers mediated by samarium diiodide
-
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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- TiCl4/Bu3N/(catalytic TMSOTf): Efficient agent for direct aldol addition and claisen condensation
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TiCl4/Bu3N conducts highly efficient cross aldol additions between different ketones and between ketones and aldehydes, in good to excellent yields with high syn-stereoselectivities. As an extension, direct Claisen condensation between methyl esters was also promoted by TiCl4/Bu3N with 0.05 equiv of TMSOTf co-catalyst.
- Yoshida, Yoshihiro,Hayashi, Ryosuke,Sumihara, Hiromasa,Tanabe, Yoo
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p. 8727 - 8730
(2007/10/03)
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- Reactions of tin(IV) enolates obtained from O-stannyl ketyls under neutral free radical conditions
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Under mild and neutral free radical conditions, an α,β-unsaturated ketone reacted with tributyltin hydride to produce an intermediate resonance-stabilized allylic O-stannyl ketyl. Upon subsequent hydrogen atom abstraction, a tin(IV) enolate was afforded which could be quenched with a variety of electrophiles and form new carbon-carbon bonds. Aldehydes react to produce aldol-type products and both intramolecular and intermolecular carbonyl addition reactions were investigated using this strategy. Using similar methodology, the tin(IV) enolate could be quenched in the presence of HMPA with various alkyl halides and α,β-unsaturated carbonyl compounds (Michael acceptors) to yield alkylated products in good yields. These reactions represent a very mild regioselective alternative to metal enolate formation which usually requires strong bases such as LDA or strongly reductive dissolving metal conditions to achieve success. New carbon skeletons for natural product synthesis can be readily constructed using this chemically neutral approach.
- Enholm, Eric J.,Whitley, Paul E.,Xie, Yongping
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p. 5384 - 5390
(2007/10/03)
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- RADICAL β-FRAGMENTATION OF BICYCLOCARBINOLAMIDES: SYNTHESIS OF FIVE- AND EIGHT-MEMBERED CYCLIC IMIDES
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The influence of 4-alkyl or 4-aryl substituents in the regioselectivity of the β-fragmentation of carbinolamidyl radicals generated from the corresponding carbinolamides (7-13) by irradiation with visible light in the presence of (diacetoxyiodo)benzene an
- Hernandez, Rosendo,Melian, Daniel,Prange, Thierry,Suarez, Ernesto
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p. 439 - 454
(2007/10/02)
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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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- INTERMOLECULAR ALDOL REACTIONS VIA ALLYLIC O-STANNYL KETYLS
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A mild and neutral free radical reaction of an α,β-unsaturated ketone and tributyltin radical produced a resonance-stabilized allylic O-stannyl ketyl intermediate.A tin(IV)enolate, produced by subsequent hydrogen atom transver, was next quenched with various aldehydes to yield an aldol product which was readily eliminated with p-toluenesulfonic acid to afford new α,β-unsaturated ketones with E/Z ratios up to > 100:1.
- Enholm, Eric J.,Whitley, Paul E.
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p. 9157 - 9160
(2007/10/02)
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