The Reaction of Enaminones with Grignard Reagents: Synthesis of α,β-Unsaturated Ketones

Fontenas, Christophe; Aït‐Haddou, Hassan; Bejan, Elena; Balavoine, G.

doi:10.1080/00397919808007005

Cited by 13 publications

(4 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Enaminones 2 7 3 dissolved in toluene reacted with Grignard reagents in tetrahydrofuran to gave selectively and with high yields of cyclic and aliphatic α,β-unsaturated ketones 275 (Figure 96). The alkylations Jul-Aug 2004 485 take place via intermediates, such as 274, which have no propensity for additional attack by nucleophiles [148]. The use of "dry"cerium (III) chloride allows the addition of organolithiums to enaminones [149].…”

Section: Reactions Of Enaminones With Organometallicsmentioning

confidence: 99%

See 1 more Smart Citation

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

176

View full text Add to dashboard Cite

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...

show abstract

Section: Reactions Of Enaminones With Organometallicsmentioning

confidence: 99%

“…Furthermore, this bifunctional moiety is present in a large number of molecules of biological relevance [148]. Enaminones 2 7 3 dissolved in toluene reacted with Grignard reagents in tetrahydrofuran to gave selectively and with high yields of cyclic and aliphatic α,β-unsaturated ketones 275 (Figure 96).…”

Section: Reactions Of Enaminones With Organometallicsmentioning

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

176

View full text Add to dashboard Cite

show abstract

“…However, β-aminopropenals seems to react with organomagnesium and organolithium compounds mainly in a 1,2-fashion at the carbonyl group, as depicted in Scheme 221b. The use of toluene as solvent when using Grignard reagents has proved to increase the yield of the obtained final enones in these type of reactions . In addition, improved stereoselectivities in the synthesis of α,β-unsaturated ketones have been achieved when the reaction is carried out with Grignard reagents in the presence of cerium(III) chloride, the starting enaminone 433 bearing a secondary amine framework (Scheme ) …”

Section: β-Acylvinyl Cationic Synthonsmentioning

confidence: 99%

“…221b The use of toluene as solvent when using Grignard reagents has proved to increase the yield of the obtained final enones in these type of reactions. 224 In addition, improved stereoselectivities in the synthesis of R,β-unsaturated ketones have been achieved when the reaction is carried out with Grignard reagents in the presence of cerium(III) chloride, the starting enaminone 433 bearing a secondary amine framework (Scheme 96). 225 In this case, a trans relationship between the introduced substituent and the carbonyl group is predominantly observed in final enone 434, probably induced by a mechanism involving cerium oxygen-nitrogen complexation and 1,2-addition followed by 1,3-carbonyl shift.…”

Section: β-Acylvinyl Cationic Synthonsmentioning

confidence: 99%