Atropisomeric amides: Achiral ligands with chiral conformations.
TL;DR: A new class of achiral ligands with atropisomeric conformations has been coordinated to titanium(IV), consisting of ortho-hydroxy benzamide derivatives which are deprotonated on reaction with titanium tetraisopropoxide to furnish Ti(L)(2)(O-iPr)(2) complexes (L=ortho-phenoxy benzamide).
About: This article is published in Chirality.The article was published on 2003-01-01. It has received 23 citations till now. The article focuses on the topics: Amide & Ligand.
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TL;DR: As the rotational barrier of the N-C(Aryl) chiral axis in the cis-2 and trans-2 photoproducts is lowered when compared with the reactant 1, the isolated optically pure trans- 2 isomer is converted to the ent-cis-2 isomer without affecting the C-5 stereogenic center, resulting in resolution of the cis -2 enantiomers.
81 citations
TL;DR: Atropisomeric maleimides were synthesized and employed for stereospecific [2 + 2] photocycloaddition and high selectivity in the photoproduct upon reaction from the triplet excited state was rationalized on the basis of conformational factors as well as the type of diradical intermediate that was preferred during the photoreaction.
Abstract: Atropisomeric maleimides were synthesized and employed for stereospecific [2 + 2] photocycloaddition. Efficient reaction was observed under direct irradiation, triplet-sensitized UV irradiation, and non-metal catalyzed visible-light irradiation, leading to two regioisomeric (exo/endo) photoproducts with complete chemoselectivity (exclusive [2 + 2] photoproduct). High enantioselectivity (ee > 98%) and diastereoselectivity (dr > 99:1%) were observed under the employed reaction conditions and were largely dependent on the substituent on the maleimide double bond but minimally affected by the substituents on the alkenyl tether. On the basis of detailed photophysical studies, the triplet energies of the maleimides were estimated. The triplet lifetimes appeared to be relatively short at room temperature as a result of fast [2 + 2] photocycloaddition. For the visible-light mediated reaction, triplet energy transfer occurred with a rate constant close to the diffusion-limited value. The mechanism was established ...
70 citations
TL;DR: Alpha-oxoamides 1 with o-tert-butyl substitution on the N-phenyl moiety were found to be stable axially chiral atropisomers and undergo enantiospecific photochemical gamma-Hydrogen abstraction in CHCl(3) to yield beta-lactams with high enantioselectivity.
Abstract: Alpha-oxoamides 1 with o-tert-butyl substitution on the N-phenyl moiety were found to be stable axially chiral atropisomers. These axially chiral alpha-oxoamides undergo enantiospecific photochemical gamma-Hydrogen abstraction in CHCl(3) to yield beta-lactams with high enantioselectivity (e.r. approximately 90:10) in solution. The extent of enantioselectivity was found to be dependent on the reaction temperature.
61 citations
TL;DR: Amidate ligands have been used as a modular ligand set for early transition-metal complexes, and have been found to exhibit high reactivity in the catalytic hydroamination of alkynes, allenes, and alkenes as mentioned in this paper.
Abstract: Amidate ligands have been used as a modular ligand set for early transition-metal complexes, and have been found to exhibit high reactivity in the catalytic hydroamination of alkynes, allenes, and alkenes. This microreview focuses on coordination metal complexes containing amidate functionality including their bonding, structure and reactivity trends. The synthesis and characterization of a number of different group-4 metal complexes is presented, and their applications in both hydroamination and organic synthesis are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
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References
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01 Jan 1999
TL;DR: Ohkuma et al. as mentioned in this paper proposed an asymmetric Dihydroxylation process for carbon-Carbon double bonds and showed that it can be used for allylation of C=O.
Abstract: 5.2. R.L. Halterman: Hydrogenation of Non-Functionalized Carbon-Carbon Double Bonds .- 6.4. T. Ohkuma, R. Noyori: Hydroboration of Carbonyl Groups .- 20.1. A. Bayer: Latest Developments in the Asymmetric Dihydroxylation Process .- 20.2. A. Bayer: Aminohydroxylation of Carbon-Carbon Double Bonds .- 24. J.-F. Paquin, M. Lautens: Allylic Substitution Reactions .- 27. A. Yanagisawa: Allylation of C=O .- 31.1. K. Tomioka: Conjugate Addition of Organometallics to Activated Olefins .- 34.2. A. Yanagisawa: Protonation of Enolates
2,497 citations
Book•
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
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.
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