Enaminones in Heterocyclic Synthesis

Lue, Ping; Greenhill, John V.

doi:10.1016/s0065-2725(08)60072-0

Cited by 153 publications

(89 citation statements)

References 395 publications

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“…Enaminones, 1 such as β-dimethylamino derivatives of α,β-unsaturated ketones, esters, and nitriles, are an important class of compounds, which have been used extensively for the preparation of a variety of heterocyclic systems 1,2 including some natural products and analogues. 3 Recently, β-dimethylamino-α,β-unsaturated ketones and nitriles have been transformed into pyridine, isoquinoline, 4 pyrazole, isoxazole, pyrimidine, 5 and pyranone derivatives.…”

Section: Introductionmentioning

confidence: 99%

Transformations of (Z)-2-benzoylamino-4-dimethylamino-2-oxo-3-butene and (E)-3-benzoylamino-4-cyano-2-oxo-3-butene into pyrimidine, pyrazole and isoxazole derivatives

Bratusek¹,

Meden²,

Svete³

et al. 2003

Arkivoc

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Reaction of (Z)-2-Benzoylamino-4-dimethylamino-2-oxo-3-butene 1 with amidines 2a-e afforded pyrimidines 3a-e. Acid-catalysed treatment of 1 with potassium cyanide gave (E)-3-benzoylamino-4-cyano-2-oxo-3-butene 4. 1,3-Dipolar cycloadditions of nitrile imines and 2,4,6-trimethoxybenzonitrile oxide 7a to compound 4 afforded the corresponding pyrazole derivatives 6a-d and the isoxazole-4-carbonitrile 8a. In the reaction of 4 with 2,4,6-trimethylbenzonitrile oxide 7b, bis-cycloadduct 9 was formed and its structure was also determined by X-Ray analysis.

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Section: Introductionmentioning

confidence: 99%

Transformations of (Z)-2-benzoylamino-4-dimethylamino-2-oxo-3-butene and (E)-3-benzoylamino-4-cyano-2-oxo-3-butene into pyrimidine, pyrazole and isoxazole derivatives

Bratusek¹,

Meden²,

Svete³

et al. 2003

Arkivoc

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“…Ever since, enaminones and related compounds (enaminoesters, enaminonitriles,…) have become very useful synthons in organic synthesis. [2][3][4][5][6][7][8] A privileged status among them have cyclic enaminones and their derivatives. 9,10 They can, in principle, be divided into three structural types I-III (Fig.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of [1,2-a]-fused tricyclic dihydroquinolines by palladium-catalyzed intramolecular C–N cross-coupling of polarized heterocyclic enamines

Brož¹,

Růžičková²,

Šimůnek³

2016

Arkivoc

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A simple methodology for [1,2-a]-fused tricyclic dihydroquinolines is established. The key step of the methodology is an intramolecular Buchwald-Hartwig amination reaction of suitable halogenated (both bromo and chloro) cyclic enaminoketones, enaminoesters and enaminonitriles with various ring size (from five-to seven-membered). Optimal reaction conditions (palladium source, base, ligand) depend on the ring size of the starting enamine, giving 65-98% yield of the tricyclic product. A treatment of the products with perchloric acid gives respective quinolinium perchlorates.

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“…1 In this context, the aza-annulation reaction of cyclic and acyclic enaminones has been extensively used in the preparation of a broad spectrum of nitrogencontaining compounds, 2 mainly in alkaloids 3 and conformationally constrained peptide analogues. 4 Because of these applications several protocols for the synthesis of enaminones have been developed.…”

Section: Introductionmentioning

confidence: 99%

“…5 Among them, the solid support method developed by Braibante and co-workers 6 and its systematic use in the synthesis of pyrazoles and isoxazoles derivatives is noteworthy. 7 While the reaction of methoxymethylene Meldrum's acid (1) with cyclic enaminones has been documented (Scheme 1, reactions 1-4), 8 much less study has been carried out with 1 and acyclic enaminones. There is only a single paper describing two examples of reaction of 1 with enaminones 11 and 13a (Scheme 1, reactions 5-6).…”

Section: Introductionmentioning

confidence: 99%

“…8 However, the aza-annulation of derivatives 12 and 14a under pyrolysis conditions (Scheme 1, reaction 7) is not synthetically efficient because mixture of products and poor yields are obtained. In search for a general method of synthesis of derivatives 12 to 14 we undertook a study concerning the reactions of acyclic enaminones and methoxymethylene Meldrum's acid (1). In this paper we report the results of this study with emphasis on synthetic, mechanistic and structural implications.…”

Section: Introductionmentioning

confidence: 99%

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Reaction of acyclic enaminones with methoxymethylene meldrum's acid: synthetic and structural implications

Cunha¹,

Silva²,

Napolitano³

et al. 2003

J. Braz. Chem. Soc.

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A reação de enaminonas com o derivado metoximetilênico do ácido de Meldrum forneceu N-adutos e/ou C-adutos das enaminonas, em rendimentos moderados a bons. A regioquímica da reação se revelou dependente do substituinte do nitrogênio da enaminona, e o C-aduto formado é precursor para 2-piridonas. A análise da difração de raios X de dois N-adutos revelou que estes adutos possuem a configuração Z-s-Z.The reaction of acyclic enaminones with methoxymethylene Meldrum's acid afforded N-adduct and/or C-adduct of enaminones in moderate to good yields. The regiochemistry of this reaction depends on the N-amino substituent of the enaminone. The C-adduct is a precursor to 2-pyridones. X-ray analysis of two N-adducts were investigated and the Z-s-Z configuration assigned. Keywords: enaminones, Meldrum's acid, aza-annulation, 2-pyridone IntroductionThe fascinating chemistry of enaminones and their derivatives has attracted the attention of numerous researchers due to their ambiphilic and ambident properties and their potential in the synthesis of heterocyclic compounds.1 In this context, the aza-annulation reaction of cyclic and acyclic enaminones has been extensively used in the preparation of a broad spectrum of nitrogencontaining compounds, 2 mainly in alkaloids 3 and conformationally constrained peptide analogues. 4 Because of these applications several protocols for the synthesis of enaminones have been developed. 5 Among them, the solid support method developed by Braibante and co-workers 6 and its systematic use in the synthesis of pyrazoles and isoxazoles derivatives is noteworthy. 7While the reaction of methoxymethylene Meldrum's acid (1) with cyclic enaminones has been documented (Scheme 1, reactions 1-4), 8 much less study has been carried out with 1 and acyclic enaminones. There is only a single paper describing two examples of reaction of 1 with enaminones 11 and 13a (Scheme 1, reactions 5-6). However, the aza-annulation of derivatives 12 and 14a under pyrolysis conditions (Scheme 1, reaction 7) is not synthetically efficient because mixture of products and poor yields are obtained. In search for a general method of synthesis of derivatives 12 to 14 we undertook a study concerning the reactions of acyclic enaminones and methoxymethylene Meldrum's acid (1). In this paper we report the results of this study with emphasis on synthetic, mechanistic and structural implications. Results and DiscussionEnaminones may act as an ambident nucleophile by reaction at the nitrogen and at the β-carbon. The reactions of enaminones and methoxymethylene Meldrum's acid depend on the N-amino substituent, Scheme 1. C-Adducts are obtained with NR 2 substituent (R = alkyl) and N-adducts with the NH 2 group. However, when we attempted the reaction of enaminone 13a with 1 under the literature condition 8 a low yield of the N-adduct 14a was obtained (36%, instead of the reportedly obtained 60% yield). Additionally, a small quantity of the C-adduct 18a was isolated (3.2% yield, Scheme 2), which was not previously reported. The spectral dat...

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Enaminones in Heterocyclic Synthesis

Cited by 153 publications

References 395 publications

Transformations of (Z)-2-benzoylamino-4-dimethylamino-2-oxo-3-butene and (E)-3-benzoylamino-4-cyano-2-oxo-3-butene into pyrimidine, pyrazole and isoxazole derivatives

Transformations of (Z)-2-benzoylamino-4-dimethylamino-2-oxo-3-butene and (E)-3-benzoylamino-4-cyano-2-oxo-3-butene into pyrimidine, pyrazole and isoxazole derivatives

Synthesis of [1,2-a]-fused tricyclic dihydroquinolines by palladium-catalyzed intramolecular C–N cross-coupling of polarized heterocyclic enamines

Reaction of acyclic enaminones with methoxymethylene meldrum's acid: synthetic and structural implications

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