Conformational preferences of α-functionalised keten-S,N-acetals: Potential role of SO and SS interactions in solution

Dixit, A. N.; Reddy, K. Venodhar; Deshmukh, A. R. A. S.; Rajappa, S.; Ganguly, Bishwajit; Chandrasekhar, Jayaraman

doi:10.1016/0040-4020(94)01023-s

Cited by 25 publications

(14 citation statements)

References 30 publications

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“…Thus, enaminothiones react through sulfur, while enaminones react through Cα or N. Diphenylcyclopropenone reacted with enaminothiones and afforded 4,5-dimethylene cyclopentenone derivatives, in which the sulfur atom of enaminothiones acted as a nucleophile at the phenyl group [3]. Enaminothione exists exclusively in the intramolecularly hydrogen bonded E-configuration in nonpolar solvents like benzene and chloroform, while in polar solvents there is a significant population of the Z-isomers [157].…”

Section: Reactions Of Enaminones With Organometallicsmentioning

confidence: 98%

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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Section: Reactions Of Enaminones With Organometallicsmentioning

confidence: 98%

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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“…Analogous compounds were reported to show this behavior 19 . The calculated heat of formation of the enaminone E is lower than those of enaminone Z and β-keto-2-oxazoline molecules, in agreement with the experimental evidence.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of enaminones with stationary stereochemistry

Wisniewski¹,

Oliveira²,

Cunha³

et al. 1999

J. Braz. Chem. Soc.

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“…Of course, the s-cis orientation about the C2-C3 bond minimizes unfavourable steric interaction between S4 and the methyl groups centred on C8 and C9 which is present in the other possible conformation. In this geometry, the arrangement of three atoms C6-S4···O3, like similar part in another molecules (Dixit et al, 1995;Ángyán et al, 1987;Hamilton & LaPlaca, 1964), is almost linear (the measure angle of C6-S4-O3 is 178.5 (1)°).…”

Section: Mohammad Hassan Ghorbani Commentmentioning

confidence: 93%

“…For related structures and SÁ Á ÁO interactions, see: Á ngyá n et al (1985,1987); Dixit et al (1995); Hamilton & LaPlaca (1964). For van der Waals radii, see: Á ngyá n et al (1987).…”

Section: Related Literaturementioning

confidence: 97%

“…This co-planarity not only, facilitates conjugation of the S lone pairs, the C=C, and the C=O but also, make possible the attractive S···O interaction between S4 and O3 atoms (Ángyán et al, 1987). Due to this attraction the intramolecular S4···O3 non-bonded distance [2.726 (2) Å] is shorter than the sum of the corresponding van der Waals radii (3.25 Å) and the molecule adopts s-trans/s-cis conformational arrangement for S4-C1 and C2-C3 bonds, respectively (Ángyán et al, 1985;Dixit et al, 1995). Of course, the s-cis orientation about the C2-C3 bond minimizes unfavourable steric interaction between S4 and the methyl groups centred on C8 and C9 which is present in the other possible conformation.…”

Section: Mohammad Hassan Ghorbani Commentmentioning

confidence: 97%

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Methyl 2,2-dimethoxy-5,5-bis(methylsulfanyl)-3-oxopent-4-enedithioate

Ghorbani

2012

Acta Cryst E

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In the title molecule, C10H16O3S4, a short intramolecular S⋯O(=C) distance [2.726 (2) Å] indicates the presence of a nonbonding attractive interaction. In the crystal, molecules are linked into centrosymmetric dimers via weak intermolecular C—H⋯O and S⋯S [3.405 (3) Å] interactions. These dimers are linked by further weak C—H⋯O interactions into columns along the a axis.

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Conformational preferences of α-functionalised keten-S,N-acetals: Potential role of SO and SS interactions in solution

Cited by 25 publications

References 30 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

Synthesis of enaminones with stationary stereochemistry

Methyl 2,2-dimethoxy-5,5-bis(methylsulfanyl)-3-oxopent-4-enedithioate

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