Niobium Pentachloride-mediatedNucleophilic Additions to Cyclic<i>N</i>-AcyliminiumIons

Kleber, Carlos; Andrade, Z.; Matos, Ricardo Alexandre F.

doi:10.1055/s-2003-39902

Cited by 16 publications

(8 citation statements)

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“…2,3 Recently, the use of niobium pentachloride as a novel and efficient Lewis acid in nucleophilic additions to cyclic N-acyliminium ions was reported by us. 4,5 Now we wish to report our preliminary results on the diastereoselectivity control in these reactions. 6 The enantiomerically pure substrate 1 was prepared in 3 steps, as a diastereomeric mixture, from commercially available (S)-malic acid, according to a known procedure.…”

Section: Introductionmentioning

confidence: 99%

Studies on the niobium pentachloride-mediated nucleophilic additions to an enantiopure cyclic N-acyliminium ion derived from (S)-malic acid

Andrade¹,

Rocha²,

Russowsky³

et al. 2005

J. Braz. Chem. Soc.

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A adição nucleofílica de vários nucleófilos (alilsilano, silil enol éter da acetofenona, indol e Nsulfonilindol) ao íon N-acilimínio enantiopuro 1a, derivado do ácido (S)-málico, promovida por pentacloreto de nióbio é descrita. Os produtos foram obtidos em bons rendimentos e em diastereosseletividades variáveis dependendo do volume estérico do nucleófilo. Os melhores resultados foram obtidos com a adição de indóis. The nucleophilic addition of several nucleophiles (allyltrimethylsilane, silyl enol ether from acetophenone, indole and N-sulfonylindole) to the enantiopure cyclic N-acyliminium ion 1a, derived from (S)-malic acid, promoted by niobium pentachloride is described. The products were obtained in good yields and in variable diastereoselectivities depending on the steric bulkiness of the nucleophile. The best results were obtained with the addition of indoles.

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Section: Introductionmentioning

confidence: 99%

Studies on the niobium pentachloride-mediated nucleophilic additions to an enantiopure cyclic N-acyliminium ion derived from (S)-malic acid

Andrade¹,

Rocha²,

Russowsky³

et al. 2005

J. Braz. Chem. Soc.

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“…Other Lewis acids such as InCl 3 , CeCl 3 . 7H 2 O, TaCl 5 and GdCl 3 were also used but NbCl 5 was found to be the best catalyst for this conversion.…”

Section: Synthesis Of β β β β-Keto Estersmentioning

confidence: 99%

“…Other works immediately followed including intramolecular ene reactions [2], nucleophilic additions to cyclic N -acyliminium ions [3], and aldol reactions [4]. Other works immediately followed including intramolecular ene reactions [2], nucleophilic additions to cyclic N -acyliminium ions [3], and aldol reactions [4].…”

Section: Introductionmentioning

confidence: 99%

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Recent Applications of Niobium Catalysts in Organic Synthesis

Rocha¹

2006

MROC

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Niobium catalysts generally possess a good Lewis acidity and have received increased attention in recent years. The applications of niobium pentachloride as Lewis acid in organic synthesis have been recently reviewed. Since then, there has been an increasing number of examples on the use of niobium catalysts in organic reactions such as Biginelli reactions, Friedel-Crafts acylation and Sakurai-Hosomi reactions of acetals, Knoevenagel condensation, acetylation of alcohols and phenols, among others. Also, chiral niobium complexes have been reported to give high enantiomeric excesses in asymmetric Mannich-type reactions.In this review, recent applications of these versatile reagents in organic synthesis, including our own results, will be disclosed.

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“…[23][24][25] Em seguida daríamos início ao estudo do uso de NbCl 5pentacloreto de nióbio como ácido de Lewis em reações de abertura de epóxidos, devido ao fato de que este reagente vem apresentando comportamento de ácido de Lewis em alguns tipos de reações. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Como o objetivo do projeto é de desenvolver métodos sintéticos que possam efetivamente ser usados por químicos orgânicos, propomos também desenvolver métodos práticos, e tão simples quanto possíveis, para manipular adequadamente os reagentes, tendo então, certeza de que dominamos todas as variáveis do processo, o tornando eficiente e facilmente aplicável.…”

Section: Plano De Pesquisaunclassified

"Pentacloreto de nióbio como ácido de Lewis em síntese orgânica".

Júnior¹

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AgradecimentosUm dos melhores momentos do processo de escrever uma tese é aquele em que o autor tem a oportunidade de agradecer àqueles que o ajudaram, porque raramente (e neste caso certamente não) um pesquisador faz seu trabalho sozinho. Meus sinceros agradecimentos: Ao Prof. Dr. Mauricio Gomes Constantino, meu orientador e também educador, que soube estimular, aconselhar, criticar e orientar de forma segura este trabalho até a sua conclusão, respeitando a minha liberdade e forma de trabalhar. Ao Prof. Dr. Gil Valdo José da Silva, pela colaboração e interesse com que acompanhou este trabalho. Vladimir e outros que tenha esquecido). À Virgínia, pelo profissionalismo na obtenção dos espectros de RMN contidos nesta tese. Ao Djalma, pelos espectros de IV e massas. Aos amigos da DIRETORIA Daniel Frederico (Cobra Criada), Adilson Beatriz (Bugrão), Felipe Augusto (Pancinha), Álvaro, Cláudio, Paulo (Mion) e o Kleber (Gozadô), pelas ricas discussões sobre síntese orgânica, ressonância magnética nuclear e pela convivência agradável. Aos funcionários do Departamento de Química que direta ou indiretamente colaboraram para a realização deste trabalho.A todas as pessoas que de alguma forma contribuíram para a realização deste trabalho.

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Niobium Pentachloride-mediatedNucleophilic Additions to CyclicN-AcyliminiumIons

Abstract: Niobium chloride promoted the nucleophilic addition of allyltrimethylsilane, ethyl acetoacetate, indole and the silyl enol ether derived from acetone to cyclic N-acyliminium ions. The products were obtained in good yields.

Cited by 16 publications

References 2 publications

Studies on the niobium pentachloride-mediated nucleophilic additions to an enantiopure cyclic N-acyliminium ion derived from (S)-malic acid

Studies on the niobium pentachloride-mediated nucleophilic additions to an enantiopure cyclic N-acyliminium ion derived from (S)-malic acid

Recent Applications of Niobium Catalysts in Organic Synthesis

"Pentacloreto de nióbio como ácido de Lewis em síntese orgânica".

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