Nonlinear Effects in Asymmetric Synthesis and Stereoselective Reactions: Ten Years of Investigation.
TL;DR: Nonlinear effects of an enantiomerically impure catalyst on an asymmetric synthesis are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.
Abstract: Who would have thought before 1986 that an enantiomerically impure catalyst could give a product in an asymmetric synthesis with an enantiomeric excess higher than that of the catalyst? Until then it was assumed that the ee value of the product (eeprod ) from an asymmetric synthesis was linearly correlated to the ee value of the chiral auxiliary (eeaux )-in fact a large deviation is possible (see diagram). These nonlinear effects are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.
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TL;DR: The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center.
Abstract: Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.
1,630 citations
TL;DR: The recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities.
Abstract: In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.
1,235 citations
1,023 citations
TL;DR: Direct asymmetric catalytic aldol reactions have been successfully performed using aldehydes and unmodified ketones together with commercially available chiral cyclic secondary amines as catalysts and the observed stereochemistry of the products is in accordance with the proposed transition state.
Abstract: Direct asymmetric catalytic aldol reactions have been successfully performed using aldehydes and unmodified ketones together with commercially available chiral cyclic secondary amines as catalysts Structure-based catalyst screening identified l-proline and 5,5-dimethyl thiazolidinium-4-carboxylate (DMTC) as the most powerful amino acid catalysts for the reaction of both acyclic and cyclic ketones as aldol donors with aromatic and aliphatic aldehydes to afford the corresponding aldol products with high regio-, diastereo-, and enantioselectivities Reactions employing hydroxyacetone as an aldol donor provide anti-1,2-diols as the major product with ee values up to >99% The reactions are assumed to proceed via a metal-free Zimmerman−Traxler-type transition state and involve an enamine intermediate The observed stereochemistry of the products is in accordance with the proposed transition state Further supporting evidence is provided by the lack of nonlinear effects The reactions tolerate a small amount o
1,018 citations
TL;DR: A new class of bifunctional catalysts bearing a thiourea moiety and an amino group on a chiral scaffold bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to nitroolefins.
Abstract: We synthesized a new class of bifunctional catalysts bearing a thiourea moiety and an amino group on a chiral scaffold. Among them, thiourea 1e bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to nitroolefins. Furthermore, we have developed a new synthetic route for (R)-(-)-baclofen and a chiral quaternary carbon center with high enantioselectivity by Michael reaction. In these reactions, we assumed that a thiourea moiety and an amino group of the catalyst activates a nitroolefin and a 1,3-dicarbonyl compound, respectively, to afford the Michael adduct with high enantio- and diastereoselectivity.
884 citations
References
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01 Jan 1962
TL;DR: Stereochemistry of Alkenes Conformation of Acyclic Molecules Configuration and conformation of cyclic Molecule Stereoselective Synthesis Chiroptical Properties Chirality in Molecules Devoid of Chiral Centres as discussed by the authors.
Abstract: Structure Stereoisomers Symmetry Configuration Properties of Stereoisomers: Stereoisomer Discrimination Separation of Stereoisomers, Resolution, Racemization Heterotopic Ligands and Faces (Prostereoisomerism, Prochirality) Stereochemistry of Alkenes Conformation of Acyclic Molecules Configuration and Conformation of Cyclic Molecules Stereoselective Synthesis Chiroptical Properties Chirality in Molecules Devoid of Chiral Centres.
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01 Jan 1994
TL;DR: In this article, the authors present a textbook of practical organic chemistry with Electronic Structure Methods (ESM) for HPLC and HPLC-based problem solving in organic synthesis.
Abstract: General books Advanced organic chemistry March 5 ed Advanced practical organic chemistry Leonard, Lygo, Procter 2 ed Asymmetric catalysis in organic synthesis Noyori Chirotechnology Sheldon CRC Handbook of Chemistry and Physics Lide 86 ed Exploring Chemistry with Electronic Structure Methods Foresman, Frisch Modern allene chemistry vol 1 Krause, Hashmi Modern allene chemistry vol 2 Krause, Hashmi Modern oxidation methods Bäckvall Organic chemistry Solomons 6 ed Practical Problem Solving in HPLC Kromidas Protective groups in organic synthesis Greene 3 ed Purification of laboratory chemicals Armarego, Chai 5 ed Textbook of practical organic chemistry Vogel 4 ed
1,863 citations
Book•
01 Jan 1971
TL;DR: Books and internet are the recommended media to help you improving your quality and performance.
Abstract: Inevitably, reading is one of the requirements to be undergone. To improve the performance and quality, someone needs to have something new every day. It will suggest you to have more inspirations, then. However, the needs of inspirations will make you searching for some sources. Even from the other people experience, internet, and many books. Books and internet are the recommended media to help you improving your quality and performance.
256 citations
"Nonlinear Effects in Asymmetric Syn..." refers background in this paper
...Morrison and Mosher[3] proposed the use of the expression aenantiomerico excess (ee) defined as ee (%) Rÿ S R S 100....
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01 Jan 1977
1 citations