Preparation of beta-enamino carbonylic compounds using microwave radiation/K-10

Braibante, Hugo T. S.; Braibante, Mara Elisa Fortes; Rosso, Giovanni; Oriques, Daniela Alves

doi:10.1590/s0103-50532003000600016

Cited by 43 publications

(22 citation statements)

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“…Initially, 1,3-diketonatoboron difluorides were prepared in good yields by treatment of the corresponding 1,3-diketones with B F 3 • O E t 2 at room temperature [53]. The reaction of cyclic, acyclic and α-c h l o r o -s u b s t i t u t e d -β-dicarbonyl compounds with amines or their corresponding ammonium acetates was carried out using K-10 as solid support and a domestic microwave oven as the radiation source to give β-e n a m i n o carbonylic compounds in good yields [54]. Due to the variety of nucleophilic and electrophilic sites in the enaminone system, enaminone esters possess great potential as reaction intermediates and medicinal compounds.…”

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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

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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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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

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“…The more straightforward way to obtain β-enamino ketones is a direct condensation of β-dicarbonyl compounds with ammonia, primary or secondary amines. As water is produced by the condensation reaction, the syntheses present in literature show a variety of methods to remove it, by use of azeotropical distillation of the solvent 7 or in the presence of drying agents as montmorillonite together with microwawes 8 3 as a reusable catalyst in aqueous media. 13 Analogously the preparation of β-enamino esters proceeds in the same way, but presents some drawbacks as the aminolysis of the ester function 14 and in some cases the formation of the β-enamino amide byproduct.…”

Section: Condensationmentioning

confidence: 99%

Chemo- and stereoselective reduction of enaminones for the preparation of biologically active compounds

Palmieri¹,

Cimarelli²

2006

Arkivoc

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The chemistry of the preparation of β-enamino ketones and β-enamino esters and their use as useful starting materials in reductive procedures for the preparation of biologically active natural products is described.Enaminones are very stable compounds and can be easily prepared, starting from cheap and easily available starting materials. Therefore they constitute also excellent starting materials in organic synthesis. Several chemo-and regioselective methodologies for their preparation have been developed also recently. The possibility to use enantiopure chiral amines for the preparation of enamino ketones and enamino esters makes available useful starting materials for the preparation of enantiopure biologically active compounds. Moreover, it is possible to obtain more complex enaminones by regio-and stereoselective functionalization of the more accessible ones.Recently numerous methodologies for the chemo-and stereoselective reduction of enaminones have been developed, that constitute useful alternative pathways to the numerous literature procedures for the preparation of γ-amino alcohols, β-amino acids, aminoalkyl phenols and their derivatives. γ-Aminoalcohols and aminoalkylphenols are a class of very stable compounds that find useful applications in asymmetric catalysis as chelant for the preparation of chiral enantiopure metallic catalysts.

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“…Focaremos nosso trabalho na grande área da química orgânica e como pode ser visto na Figura 2, a evolução no número de publicações vem crescendo exponencialmente. 16,17 O primeiro relata os resultados obtidos para preparação de b-enaminas a partir de compostos dicarbonílicos pela utilização de resina K-10 sob irradiação de micro-ondas (Sanyo EM-700T, 700 W, doméstico) com tempos de reação que variam de 2 a 7 min com rendimentos na faixa de 70 a 90% (Esquema 1). 16 Ainda em 2003, Vasconcellos e colaboradores utilizaram um micro-ondas doméstico (Panasonic, 700 W) na reação de BaylisHillman catalisada por DMAP.…”

Section: Introductionunclassified

“…16,17 O primeiro relata os resultados obtidos para preparação de b-enaminas a partir de compostos dicarbonílicos pela utilização de resina K-10 sob irradiação de micro-ondas (Sanyo EM-700T, 700 W, doméstico) com tempos de reação que variam de 2 a 7 min com rendimentos na faixa de 70 a 90% (Esquema 1). 16 Ainda em 2003, Vasconcellos e colaboradores utilizaram um micro-ondas doméstico (Panasonic, 700 W) na reação de BaylisHillman catalisada por DMAP. 17 Segundo relato dos autores foi possível observar uma grande diminuição nos tempos reacionais quando comparadas as reações sob aquecimento convencional para uma grande variedade de aldeídos (Tabela 2).…”

Section: Introductionunclassified

Irradiação de micro-ondas aplicada à síntese orgânica: uma história de sucesso no Brasil

Souza¹,

Miranda²

2011

Quím. Nova

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A tecnologia de irradiação de micro-ondas começou a ser desenvolvida na década de 40, possuindo um campo de aplicação bastante restrito, sendo utilizada principalmente na indústria de alimentos e polímeros. A sua utilização como ferramenta pelos químicos orgâni-cos só aconteceu em meados da década de 80, tendo como ponto de partida os trabalhos de Gedye 1 e Guiguere. 2 Nesses artigos os autores descrevem os resultados obtidos através da utilização de aparelhos de micro-ondas domésticos em reações de esterificação e ciclo-adição, respectivamente. A parte experimental é bastante peculiar, pois descreve detalhadamente todas as precauções tomadas para evitar explosões dos frascos reacionais.Já no meio da década de 90, a entrada no mercado de aparelhos de micro-ondas desenvolvidos especificamente para a síntese orgânica permitiu ao químico orgânico sintético controle de todos os parâme-tros reacionais (temperatura, pressão, potência) e, com isso, maior reprodutibilidade e segurança nos experimentos realizados. Hoje em dia, com as diferentes configurações de equipamentos presentes no mercado é possível realizar quase todos os tipos de reação sob irradiação de micro-ondas, desde condições criogênicas (reações até -80 °C) até reações sob pressão de 20 bar, incluindo reatores especiais para scale-up, fluxo contínuo e para reações em batelada. Desde os primeiros experimentos feitos por Gedye e Guiguere foi possível observar que a tecnologia de micro-ondas promovia um aumento da velocidade de reação e redução de formação de produtos colaterais, quando comparada com experimentos sob aquecimento convencional.Este aquecimento promovido pela irradiação de micro-ondas pode ser obtido basicamente por dois mecanismos: polarização dipolar e condução iônica. Desta maneira, quando uma reação é irradiada com micro-ondas, os dipolos ou íons presentes na mistura reacional alinham-se ao campo elétrico aplicado. Como o campo elétrico oscila, os dipolos ou íons tendem a se realinhar ao campo elétrico oscilante e neste processo perdem energia sob a forma de calor, devido aos choques moleculares e perdas dielétricas.As micro-ondas são formadas por ondas eletromagnéticas com frequência entre 0,3 e 300 GHz, correspondendo a comprimentos de onda da ordem de 1 cm a 1 m e encontram-se na região do espectro eletromagnético entre o infravermelho e as radiofreqüências, 4 Figura 1.No que diz respeito à energia associada a esta onda eletromagnética, pode-se observar na Tabela 1 que as micro-ondas possuem uma energia associada muito baixa, diferentemente do observado para a radiação ultravioleta, utilizada nos processos fotoquímicos.

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Preparation of beta-enamino carbonylic compounds using microwave radiation/K-10

Cited by 43 publications

References 9 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

Chemo- and stereoselective reduction of enaminones for the preparation of biologically active compounds

Irradiação de micro-ondas aplicada à síntese orgânica: uma história de sucesso no Brasil

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