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Asymmetric Aldol Reactions of α,β-Unsaturated Ketoester Substrates Catalyzed by Chiral Diamines  [PDF]
Sha-Sha Kan,Jian-Zhen Li,Cheng-Yan Ni,Quan-Zhong Liu,Tai-Ran Kang
Molecules , 2011, DOI: 10.3390/molecules16053778
Abstract: Highly efficient asymmetric aldol reactions between α,β-unsaturated keto esters and acyclic ketones catalyzed by chiral diamines are reported. The corresponding products were obtained in excellent yields with excellent enantioselectivities. The absolute configuration for the product was determined by X-ray analysis. A variety of substrates were tolerable in the present catalytic system.
Facile Access to Aldol Products from Aromatic and Heteroaromatic Aldehydes Using Ruthenium Catalyst  [PDF]
Khalil Tabatabaeian,Manouchehr Mamaghani,Nosrat O. Mahmoodi,Elahe Keshavarz
International Journal of Inorganic Chemistry , 2010, DOI: 10.1155/2010/621376
Abstract: A new method for the synthesis of aldol products is described. The reaction of aromatic and heteroaromatic aldehydes with 1-(thiophen-2-yl)ethanone in the presence of ruthenium chloride hydrate combined with ligand provided the related aldol adducts, in a short time at room temperature in good yields (77–84%). 1. Introduction Lewis acid catalyzed reactions belong to one of the most powerful methods in modern synthetic chemistry. Among the many Lewis acids developed so far, ruthenium has received growing attention because of the unique combinations of their strong Lewis acidity mixed with mildness and usually high selectivity [1–3]. On the other hand, there has been great demand to develop one-pot procedures for successive reactions for the formation of several C–C bonds. The aldol reaction is generally regarded as one of the most powerful and efficient C–C bond forming reactions [4–6]. Aldol reactions can be catalyzed by bases. The reactions catalyzed by bases are not easily controlled, and the dehydration of the product is often unavoidable [7]. Organic molecules have also been used as the catalysts. However the byproduct from dehydration was still existed. Therefore, many efforts have been devoted to the development of catalytic aldol reactions [8–12]. In this research, cross-aldol reactions were carried out in a one-pot reaction by mixing the reaction components at room temperature. In the presence of catalytic quantities of RuCl3 nH2O with triphenylphosphine, the reaction of 1-(thiophen-2-yl)ethanone with aldehydes resulted aldol adducts in good yields without the formation of any side product. Although a large number of catalytic and organocatalytic reactions exist, this work adds new knowledge to the field because to the best of our knowledge R combined with ligand had never been used as a catalyst in catalytic cross aldol reactions of 1-(thiophen-2-yl)ethanone with aromatic and heteroaromatic aldehydes. 2. Results and Discussion As part of our continuing studies toward ruthenium catalyzed aldol reactions [13], it was found that R in the presence of triphenylphosphine would be a more suitable catalyst for the mild formation of aldol adducts. In this method, the aldol products produced a shorter reaction times and simple experimental procedures. On the other hand, amount of PPh3 ligand used in this work was lower than when R [14] was used. Here we report our new findings on the application of this catalytic system for the synthesis of aldol products at room temperature. At the outset of this research, in order to optimize the reaction condition,
Kinetics of Aldol Condensation of Furfural with Acetone Catalyzed by 1,8-Diazabicyclo[5.4.0]undec-7-ene  [PDF]
Chengjun Jiang, Lin Cheng, Guilin Cheng
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.62005
Abstract: The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.
A green, inexpensive and efficient organocatalyzed procedure for aqueous aldol condensations
Abaee, M. Saeed;Mojtahedi, Mohammad M.;Forghani, Soudabeh;Ghandchi, Nafiseh M.;Forouzani, Mehdi;Sharifi, Roholah;Chaharnazm, Behnam;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009001000018
Abstract: a facile and general procedure is presented for diethylamine-catalyzed double crossed aldol condensation of cyclic ketones with various aromatic aldehydes under aqueous conditions. excellent yields of 3,5-bisarylmethylidenes of homocyclic and heterocyclic ketones are achieved in a one-pot procedure. furthermore, the methodology is efficiently applied to the synthesis of chalcones from their corresponding methyl ketones. in the majority of the cases studied, products precipitate from the reaction mixtures and the medium is recycled in subsequent several reactions without significant loss of activity.
Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step
Dieter Enders,Jeanne Fronert,Tom Bisschops,Florian Boeck
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.123
Abstract: The first organocatalytic asymmetric synthesis of smyrindiol, by using an (S)-proline catalyzed enantioselective intramolecular aldol reaction as the key step, is described. Smyrindiol was synthesized from commercially available 2,4-dihydroxybenzaldehyde in 15 steps, with excellent stereoselectivity (de = 99%, ee = 99%). In the course of this total synthesis a new and mild coumarin assembly was developed.
Infrared study of spin crossover Fe-picolylamine complex  [PDF]
Hidekzu Okamura,Masato Matsubara,Takeshi Tayagaki,Koichiro Tanaka,Yuka Ikemoto,Hiroaki Kimura,Taro Moriwaki,Takao Nanba
Physics , 2003, DOI: 10.1143/JPSJ.73.1355
Abstract: Infrared (IR) absorption spectroscopy has been used to probe the evolution of microscopic vibrational states upon the temperature- and photo-induced spin crossovers in [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic). To overcome the small sizes and the strong IR absorption of the crystal samples used, an IR synchrotron radiation source and an IR microscope have been used. The obtained IR spectra of Fe-pic show large changes between high-spin and low-spin states for both the temperature- and the photo- induced spin crossovers. Although the spectra in the temperature- and photo-induced high-spin states are relatively similar to each other, they show distinct differences below 750 cm-1. This demonstrates that the photo-induced high-spin state involves microscopically different characters from those of the temperature-induced high-spin state. The results are discussed in terms of local pressure and structural deformations within the picolylamine ligands, and in terms of their possible relevance to the development of macroscopic photo-induced phase in Fe-pic.
Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis
Hunter Roger,Rees-Jones Sophie CM,Su Hong
Beilstein Journal of Organic Chemistry , 2007, DOI: 10.1186/1860-5397-3-38
Abstract: Background The diastereoselectivity of a vinylogous Mukaiyama aldol reaction of a series of N-substituted 4-oxy-2-trimethylsilyloxypyrroles with a tartrate-based aldehyde has been explored as a model reaction for castanospermine synthesis. Results The study has revealed that the reaction is sensitive to the nature of the combination of N- and 4-oxy substituents. With a N-PMB or N-Bn and 4-methoxy combination, the reaction generates an aldol adduct with the correct absolute configurations for C-8 and C-8a of the indolizidine alkaloid castanospermine. The adduct was transformed to an indolizidine, whose ketal could not be transformed appropriately for the target alkaloid. Conclusion The first successful diastereoselective Mukaiyama aldol strategy for the C-8 and C-8a stereogenic centres of castanospermine is presented using silyloxypyrrole chemistry. The results suggest that a full enantioselective synthesis can be realized provided that C-1 functionalisation is accomplished early in the synthesis, post-coupling.
Metal-catalyzed asymmetric aldol reactions
Dias, Luiz C.;Lucca Jr., Emílio C. de;Ferreira, Marco A. B.;Polo, Ellen C.;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012001200003
Abstract: the aldol reaction is one of the most powerful and versatile methods for the construction of c-c bonds. traditionally, this reaction was developed in a stoichiometric version; however, great efforts in the development of chiral catalysts for aldol reactions were performed in recent years. thus, in this review article, the development of metal-mediated chiral catalysts in mukaiyama-type aldol reaction, reductive aldol reaction and direct aldol reaction are discussed. moreover, the application of these catalysts in the total synthesis of complex molecules is discussed.
Novel chiral ionic liquid (CIL) assisted selectivity enhancement to (L)-proline catalyzed asymmetric aldol reactions
Zhang, Long;Zhang, Haibo;Luo, Huadong;Zhou, Xiaohai;Cheng, Gongzhen;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000900016
Abstract: a significant improvement of the chemical yields (up to 88%), stereoselectivity (> 99:1) and enantiomeric excesses (up to 98%) of (l)-proline catalyzed direct asymmetric aldol reaction was found when proline based chiral ionic liquids (cils) were added as additives. different ratios of dmso/h2o as solvent and chiral ionic liquids (cils) with chiral cations of different chain length were investigated
Stereoselective Aldol Reaction in Aqueous Solution Using Prolinamido-Glycosides as Water-Compatible Organocatalyst  [PDF]
Daisuke Miura, Tomoya Machinami
Modern Research in Catalysis (MRC) , 2015, DOI: 10.4236/mrc.2015.41003
Abstract: Prolinamido-glycoside catalyzed asymmetric aldol reaction in aqueous media is reported. The reactions are rapid and highly stereoselective when water is used as solvent. The stereoselectivities were under influence of configurations of a prolyl residue of the catalyst and α-chiral aldehydes. Water soluble prolinamido-glycoside catalysts are easily separable from reaction mixture and can be recycled and re-used several times.
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