Synthesis of enaminones with stationary stereochemistry

“…The double bond is stabilized in the configuration E, due to the internal hydrogen bond, either in the solid state or in non-polar solvents. From the analysis of bond orders, 13 C chemical shifts, and C=O, C=C stretching frequencies, it was possible to detect an extensive delocalization of the lone electron pairs of the enaminone nitrogen and oxygen atoms over the adjacent vinyl and carbonyl π sistem [29].Several enantiomerically pure β'-hydroxy-β-enaminoketones were prepared from the corresponding isoxazolic carbinols, which were obtained by enzymatic kinetic resolution of the racemic β-hydroxy-isoxazoles catalyzed by commercial lipases, such as, Pseudomonas cepacia lipase, P o rcine pancreatic lipase, Candida cylindracea l i p a s e , Candida antarctica lipase and A s p e rgillus niger l i p a s e [4,30]. The enzymatic transesterification of racemic alcohols was studied with respect to the influence of experimental variables such as the enzyme used, the acylating agent or the solvent on the enantioselectivity of the reaction.…”

mentioning

confidence: 99%

Recent development in preparation reactivity and biological activity of enaminoketones and enaminothiones and their utilization to prepare heterocyclic compounds

Negri

Kascheres

2004

Journal of Heterocyclic Chem

179

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Enaminoketones and esters are gaining increased interest, particularly cyclic-β-enaminoesters, which are known as important intermediates for the synthesis of heterocycles and natural products, because the enantioselective preparation of highly functionalized compounds is of central importance in synthetic chemistry. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. Enaminoketones and enaminonitriles have proven to be versatile building blocks for the synthesis of various heterocycles such as pyridine, pyrimidine and pyrrole derivatives. Enaminones systems have "enone" character, and may act as acceptors in both 1,2 and 1,4-additions. In this way the enaminone serves as a scaffold for annulation, and can gain access to systems such as pyrroles indolizidines, quinolizidines and perhydroindoles, all of which are common motifs in alkaloid structures. Enaminones are frequently employed as building blocks for the preparation of a variety of bicyclic compounds of biological interest and have been recently recognized as potential anticonvulsant compounds. Since a large number of developments in the use of enaminones in heterocyclic synthesis have occurred, a review of the recent developments in the synthetic approaches, covering the literature since 1995 until 2004, to these interesting molecules and their useful chemical transformations and biological activity can be considered of considerable value.J. Heterocyclic Chem., 41, 461 (2004).Enaminoketones. Introduction.The term enaminone was introduced by Greenhill to define the enamine of a 1,3-diketone, β-ketoester or similar 1,3-difunctional reagents, and is used to indicate any compound containing the conjugated system N-C=C-C=O [1]. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. The chemistry of the enaminocarbonyl group 1 is potentially an area of considerable scope when one considers that there are present in this moiety, three nucleophilic sites (a, c and e) and two electrophilic sites (b and d) [2][3][4] (Figure 1).Theorically, primary and secondary acyclic enaminones can exist in three tautomeric forms: ketamino form, iminoenol form and oxoimino form [1][2][3]. There is also evidence that cyclic enaminones exist primarily in the enaminoketo form. A study of cyclic enaminoketones shows that these compounds have a significant steric fator in the six-membered ring. The six-membered ring enaminoketones are only slightly stronger bases than the saturated amines, whereas five-and-seven membered rings are much stronger bases than saturated amines. This has been attributed to a large steric strain present in six-membered enaminoketones [5].β-Aminoenones or enaminoketones can exist in four conformations owing to restricted rotations around the C=C double and C-C=O single bonds [3]. Enaminones with primary or secondary amino groups can exist in both Z-and E-forms. If there is a...

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“…They are typical push-pull systems in which the amine group pushes and the carbonyl pulls electron density and have the ability to function both as ambident nucleophiles and as ambident electrophiles (Michael et al, 1999;Almazroa1 et al, 2004;Ruffino and Zanetti, 2009). The carbonyl group, conjugated with the enamine moiety, gives this system enough stability to be easily prepared, isolated and stored under atmospheric conditions at room temperature (Junior et al, 1999;Shawali, 2010). Enaminones are known to possess a variety of medicinal properties including anticonvulsant, antimalarial, antiinflamatory, antitumor and cardiovascular effects (Chaaban et al, 1979;Purnami et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of the Proton Transfer in Enaminones

Elias¹

2012

American Journal of Applied Sciences

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Problem statement: Hydrogen bonding has a vital rule to unrevealed the nature of many different interactions both in gas phase and condensed media thus it is one of the most important concepts in chemistry. Enaminoes with their ability to form intrahydrogen bonded cheated rings represent one of the suitable compounds to study such concept. Approach: The three possible tautomers of eneminones were fully optimized at several theoretical levels including B3LYP with the 6-31+G(d,p), 6-311++G(d,p) and aug-cc-pVDZ basis sets as well as MP2/6-311++G(d,p) level of theory. Then a search for the possible transition state between the two most stable tautomers; the ketamine and the enolimine was done at the B3LYP/6-311++G(d,p) level of theory. Results: The ketamine is the most stable while the diketo is the less stable within the tautomeric mixture and the proton transfer occurs through a transition state that is energetically resemble the enolimine tautomer. Conclusion:The interconversion of the tautomers is preferable in the enolimine → ketamine direction.

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Synthesis of enaminones with stationary stereochemistry

Abstract: Cinco enaminonas 4a-e, derivadas da reação do ânion da 2,4,4-trimetil-2-oxazolina com acetato de etila, benzoato de etila, ciclohexanoato de etila, hexanoato de etila e p-metil benzoato de etila,

Cited by 11 publications

References 8 publications

Recent Development in Preparation Reactivity and Biological Activity of Enaminoketones and Enaminothiones and Their Utilization to Prepare Heterocyclic Compounds

Recent Development in Preparation Reactivity and Biological Activity of Enaminoketones and Enaminothiones and Their Utilization to Prepare Heterocyclic Compounds

Recent development in preparation reactivity and biological activity of enaminoketones and enaminothiones and their utilization to prepare heterocyclic compounds

Theoretical Study of the Proton Transfer in Enaminones

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