Access to racemic and enantioenriched 3-methyl-4-chromanones: catalysed asymmetric protonation of corresponding enolic species as the key step
TL;DR: Bronsted acids induced the intramolecular cyclisation of 3-aryloxypropanoic esters affording 3-methyl-4-chromanones, which have been transformed into the corresponding racemic benzyl β-oxoesters.
About: This article is published in Tetrahedron.The article was published on 2003-11-24. It has received 35 citations till now. The article focuses on the topics: Cascade reaction & Enantioselective synthesis.
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TL;DR: This critical review of the concept of combining transition metal catalysis and organocatalysis with several recent outstanding examples is illustrated, with the aim of shedding light on the synthetic utilities and potentials of this concept as a novel tool in organic synthesis.
Abstract: In recent years, the concept of combining transition metal catalysis and organocatalysis has emerged as a promising strategy for developing new and valuable reactions, and has attracted considerable attention as it could potentially enable unprecedented transformations not currently possible by use of the transition metal complex or the organocatalyst alone. In this critical review, this strategy is illustrated with several recent outstanding examples, with the aim of shedding light on the synthetic utilities and potentials of this concept as a novel tool in organic synthesis (118 references).
652 citations
524 citations
TL;DR: In the past several years, applications of transition metal complexes in tuning the reactivity of organocatalyst-promoted transformations have attracted increasing attention in the synthetic community as discussed by the authors.
499 citations
TL;DR: This compilation clearly demonstrates the power and economical interest of asymmetric catalysed domino reactions in the field of synthetic organic chemistry including the asymmetric biocatalysed Domino reactions.
349 citations
TL;DR: This review addresses the most significant synthetic methods reported on 4-chromanone-derived compounds and consequently emphasizes on the biological relevance of such compounds.
144 citations
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TL;DR: The Hammett equation has been widely used for the study and interpretation of organic reactions and their mechanisms as mentioned in this paper, and it is astonishing that u constants, obtained simply from the ionization of organic acids in solution, can frequently predict successfully equilibrium and rate constants for a variety of families of reactions in solution.
Abstract: The Hammett equation (and its extended forms) has been one of the most widely used means for the study and interpretation of organic reactions and their mechanisms. Although the Hammett methodology has been criticized by theoreticians because of its empirical foundation, it is astonishing that u constants, obtained simply from the ionization of organic acids in solution, can frequently predict successfully equilibrium and rate constants for a variety of families of reactions in solution. Almost every kind of organic reaction has been treated via the Hammett equation, or its extended form. The literature is so voluminous and extensive that there is no complete review of all that has been accomplished. Hammett's success in treating the electronic effect of substituents on the rates and equilibria of organic reactions1P2 led Taft to apply the same principles to steric and inductive and resonance effects? Then, more recently, octanol/ water partition coefficients (P) have been used for rationalizing the hydrophobic effects of organic compounds interacting with biological systems? The use of log P (for whole molecules) or n (for substituents), when combined with electronic and steric parameters, has opened up whole new regions of biochemical and pharmacological reactions to study by the techniques of physical organic chemistry.sf3 The combination of electronic, steric, hydrophobic, hydrophilic, and hydrogen-bonding7 parameters has been used to derive quantitative structure-activity relationships (QSAR) for a host of interactions of organic compounds with living systems or parts thereof. The binding of organic compounds to proteins,8 their interaction with enzymess and with cellsloJ1 and tiasues,12 their inhibition of organelles,l' and as antimalarial^'^
6,870 citations
TL;DR: Proline-catalyzed direct asymmetric three-component Mannich reactions of ketones, aldehydes, and amines are developed and application to the highly enantioselective synthesis of 1,2-amino alcohols is presented.
Abstract: We have developed proline-catalyzed direct asymmetric three-component Mannich reactions of ketones, aldehydes, and amines. Several of the studied reactions provide β-amino carbonyl compounds (Mannich products) in excellent enantio-, diastereo-, regio-, and chemoselectivities. The scope of each of the three components and the influence of the catalyst structure on the reaction are described. Reaction conditions have been optimized, and the mechanism and source of asymmetric induction are discussed. We further present application of our reaction to the highly enantioselective synthesis of 1,2-amino alcohols.
555 citations
TL;DR: A family of chiral triazolium salts has been developed for inducing the asymmetric intramolecular Stetter reaction, with optimal results, with the product keto esters formed in 82-97% ee and very good chemical yield.
Abstract: A family of chiral triazolium salts has been developed for inducing the asymmetric intramolecular Stetter reaction. The use of an aminoindanol-derived catalyst affords optimal results, with the product keto esters formed in 82-97% ee and very good chemical yield. Aromatic and aliphatic aldehydes are equally competent substrates for this reaction. The reaction conditions are reasonably mild and allow the isolation of the newly formed stereocenter without epimerization, although the presumed carbenic intermediates are strong bases.
391 citations
Book•
19 Oct 1995
TL;DR: In this article, the active site surface frontier molecular orbitals reaction variables catalytic reactors reaction kinetics are discussed. And the catalyst: the catalyst catalyst supports oxide catalysts metal catalysts unsupported metals supported metals.
Abstract: Part 1 Basic concepts: catalysis the active site surface frontier molecular orbitals reaction variables catalytic reactors reaction kinetics. Part 2 The catalyst: the catalyst catalyst supports oxide catalysts metal catalysts unsupported metals supported metals. Part 3 Heterogenously catalyzed reactions of synthetic interest: hydrogenation 1 - selectivity catalytic hydrogenation 2 - alkenes and dienes hydrogenation 3 - alkynes hydrogenation 4 - aromatic compounds hydrogenation 5 - carbonyl compounds hydrogenation 6 - nitrogen containing functional groups hydrogenolysis oxidation other reactions.
371 citations