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‣ Synthesis of pure stereoisomers of benzo[b]thienyl dehydrophenylalanines by Suzuki cross-coupling. Preliminary studies of antimicrobial activity

Abreu, Ana S.; Ferreira, Paula M.T.; Monteiro, Luís S.; Ferreira, Isabel C.F.R.; Calhelha, Ricardo C.; Estevinho, Leticia M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.56048%
Several benzo[b]thienyldehydrophenylalanines were synthesized from pure stereoisomers of the methyl ester of N-(tertbutoxycarbonyl)- b-bromodehydrophenylalanine as an extension of our previously reported method for the synthesis of dehydrotryptophan analogues to dehydrophenylalanine derivatives. The latter were obtained in high yields by N-deprotection and bromination of N,N-bis-(tertbutoxycarbonyl)-( Z)-dehydrophenylalanine using TFA and NBS. This was carried out in two steps or in a one pot procedure resulting in different E/Z ratios. These compounds were coupled under Suzuki cross-coupling conditions [Pd(PPh3)4, Na2CO3, DME/H2O] with several boronic benzo[b]thienyl acids in good to high yields maintaining the stereochemistry of the starting materials. The best yields were obtained when the boronic acid was in position 7 of the benzo[b]thiophene and with the E isomer of the brominated dehydrophenylalanine. In some cases it was possible to increase the lower yields by changing the Pd source to PdCl2(PPh3)2. A model dipeptide was prepared coupling a benzo[b]thienyldehydrophenylalanine with the methyl ester of alanine. Preliminary antimicrobial studies were performed with both isomers of one of the b, b-diaryldehydroalanines obtained. The results show that the compounds are selective and very active (very low MICs) against Gram positive bacteria (B. cereus and B. subtilis) the Z-isomer being more active. The compounds are also active against Candida albicans presenting similar MICs.

‣ Synthesis of β - benzo[b]thienyldehydrophenylalanine derivatives by one-pot palladium-catalyzed borylation and suzuki coupling (BSC) and metal-assisted intramolecular cyclization: studies of fluorescence and antimicrobial activity

Abreu, Ana S.; Ferreira, Paula M.T.; Queiroz, Maria João R.P.; Ferreira, Isabel C.F.R.; Calhelha, Ricardo C.; Estevinho, Leticia M.
Fonte: Wiley Interscience Publicador: Wiley Interscience
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
67.67298%
Palladium-catalyzed borylation and Suzuki coupling (BSC) in a one-pot procedure was successfully applied to the synthesis of several β-substituted dehydrophenylalanines in the benzo[b]thiophene series, with the stereochemistry of the starting materials being maintained. Bromobenzo[b]thiophenes bearing an ortho EDG (OMe or Me) were used as the components to be borylated with pinacolborane, whilst pure stereoisomers of β-bromodehydrophenylalanines were used as the other Suzuki coupling components. Treatment of the obtained methyl ester of (Z)-N-(tert-butoxycarbonyl)-β- (2,3,5-trimethylbenzo[b]thien-6-yl)dehydrophenylalanine with Pd(OAc)2 and Cu(OAc)2 in DMF at 160 °C gave two in dole derivatives (1:3), the major product resulting from isomerization and cyclization and the minor product resulting from direct cyclization (thienoindole). Carrying out the reaction at 100 °C gave the same products in similar amounts. Use of the methyl ester of (Z)-N-(tert-butoxycarbonyl)-β- (2,3,7-trimethylbenzo[b]thien-6-yl)dehydrophenylalanine as starting material gave only one product, resulting from isomerization and cyclization at 100 °C. Two of the cyclized compounds were subjected to fluorescence studies; the thienoindole could be useful as a fluorescent probe. Preliminary studies of antimicrobial activity were performed on the precursors and on the cyclized products.

‣ Reação de acoplamento Suzuki : desenvolvimento de novos catalisadores e estudos mecanísticos

Zim, Danilo
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
Português
Relevância na Pesquisa
48.170273%
Este trabalho teve como objetivo o desenvolvido de novos sistemas catalíticos, à base de Pd e Ni, capazes de promover o acoplamento de de Suzuki para uma grande gama de substratos com excelente rendimento e sob condições brandas de reação. Um novo sistema a base do ciclopaladato de enxofre [Pd(n¹-C6H4)CH2StBu-µ-Cl]2 foi desenvolvido para a reação de acoplamento de Suzuki de haletos de arila incluindo aqueles menos reativos tais como cloretos de arila contendo substituintes eletrodoadores e brometos estericamente impedidos. Este novo sistema não requ>er o uso de qualquer ligante auxiliar e a reação ocorre a temperatura ambiente, com baixas concentrações de catalisador, (tipicamente 0,2-0,5 mol%) gerando os produtos desejados, com excelentes rendimentos isolados, tipicamente, da ordem de 90%. Os sistemas catalíticos a base de Pd(OAc)2 ou PdCl2(SEt2)2 também são ativos para uma grande gama de substratos, inclusive, cloretos de arila, embora sejam mais sensíveis ao efeito do impedimento estérico e dos grupos eletrondoadores presentes nos haletos de arila. O desenvolvimento dos sistemas à base de Pd(OAc)2 ou PdCl2(SEt2)2 mostra que uma série de sistemas propostos na literatura, do tipo paládio-ligante, poderiam ser ativos mesmo na ausência de ligante auxiliar. Na maioria dos casos...

‣ Acoplamentos de Heck, Suzuki e Ullmann em compostos vinílicos: desenvolvimento de sistemas catalíticos e aplicação na síntese de fármacos

Limberger, Jones
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
Português
Relevância na Pesquisa
47.84767%
Este trabalho descreve a síntese de novas olefinas tri e tetrassubstituídas através da reação de Heck, do acoplamento de Suzuki e do acoplamento de Ullmann em substratos vinílicos. Esses compostos são intermediários sintéticos avançados na obtenção dos fármacos Z-tamoxifeno, tolterodina e atomoxetina. A reação de Heck em diarilolefinas foi estudada. A utilização de um sistema catalítico baseado em Pd(OAc)2/P(o-Tol)3 leva a triarilolefinas com rendimentos de bons a ótimos. A presença de grupamentos eletrorretiradores na porção arila da olefina influencia fortemente a regioquímica da reação. Para a reação de Heck do trans-estilbeno, os resultados de reações competitivas sugerem que a adição oxidativa não é a etapa determinante da velocidade. A reação de Heck entre o trans-estilbeno e a 2-(4-bromofenoxi)-N,N-dimetil-etanamina levou a uma olefina trissubstituída intermediária na síntese do Z-tamoxifeno com rendimento de 96% e 87% de estereosseletividade. Utilizando-se essa reação como etapa chave, o fármaco foi obtido com 64% de rendimento global e relação Z:E de 65:35. Partindo-se do cloreto de cinamila e do álcool cinâmico, brometos de vinila trissubstituídos foram obtidos com bons rendimentos e excelentes régio e estereosseletividade...

‣ Synthesis of pure stereoisomers of benzo[b]thienyldehydrophenylalanines by Suzuki cross-coupling : preliminary studies of antimicrobial activity

Abreu, Ana S.; Ferreira, Paula M. T.; Monteiro, Luís S.; Queiroz, Maria João R. P.; Ferreira, Isabel C. F. R.; Calhelha, Ricardo C.; Estevinho, Letícia M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2004 Português
Relevância na Pesquisa
47.56048%
Several benzo[b]thienyldehydrophenylalanines were synthesized from pure stereoisomers of the methyl ester of N-(tert-butoxycarbonyl)-beta-bromodehydrophenylalanine as an extension of our previously reported method for the synthesis of dehydrotryptophan analogues to dehydrophenylalanine derivatives. The latter were obtained in high yields by N-deprotection and bromination of N,N-bis-(tert-butoxycarbonyl)-(Z)-dehydrophenylalanine using TFA and NBS. This was carried out in two steps or in a one pot procedure resulting in different E/Z ratios. These compounds were coupled under Suzuki cross-coupling conditions [Pd(PPh3)4, Na2CO3, DME/H2O] with several boronic benzo[b]thienyl acids in good to high yields maintaining the stereochemistry of the starting materials. The best yields were obtained when the boronic acid was in position 7 of the benzo[b]thiophene and with the E isomer of the brominated dehydrophenylalanine. In some cases it was possible to increase the lower yields by changing the Pd source to PdCl2(PPh)2. A model dipeptide was prepared coupling a benzo[b]thienyldehydrophenylalanine with the methyl ester of alanine. Preliminary antimicrobial studies were performed with both isomers of one of the beta,beta-diaryldehydroalanines obtained. The results show that the compounds are selective and very active (very low MICs) against Gram positive bacteria (B. cereus and B. subtilis) the Z-isomer being more active. The compounds are also active against Candida albicans presenting similar MICs.; Fundação para a Ciência e Tecnologia - POCTI/1999/QUI/32689...

‣ Palladium-catalyzed borylation and Suzuki coupling (BSC) to obtain beta-substituted dehydroamino acid derivatives

Abreu, Ana S.; Silva, Natália O.; Ferreira, Paula M. T.; Queiroz, Maria João R. P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2003 Português
Relevância na Pesquisa
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Several benzo[b]thienyldehydroamino acids were prepared by one pot palladium-catalyzed borylation and Suzuki coupling (BSC) from bromobenzo[b]thiophenes containing EDG (OMe or Me), as the component to be borylated with pinacolborane, and pure stereoisomers of beta-bromodehydroamino acid derivatives. To our knowledge it is the first time that the BSC reaction involves a non aromatic system.; Fundação para a Ciência e Tecnologia - POCTI/1999/QUI/32689, SFRH/BD/4709/2001.

‣ Synthesis of beta-benzo[b]thienyldehydrophenylalanine derivatives by one pot palladium-catalyzed borylation and Suzuki coupling (BSC) and metal-assisted intramolecular cyclization : studies of fluorescence and antimicrobial activity

Abreu, Ana S.; Ferreira, Paula M. T.; Queiroz, Maria João R. P.; Ferreira, Isabel C. F. R.; Calhelha, Ricardo C.; Estevinho, Letícia M.
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
Relevância na Pesquisa
67.67298%
Palladium-catalyzed borylation and Suzuki coupling (BSC) in a one pot procedure was successfully applied to the synthesis of several beta-substituted dehydrophenylalanines in the benzo[b]thiophene series maintaining the stereochemistry of the starting materials. Bromobenzo[b]thiophenes bearing an ortho EDG (OMe or Me) were used as the components to be borylated with pinacolborane. Pure stereoisomers of beta-bromodehydrophenylalanines were used as the other Suzuki coupling component. Treatment of the methyl ester of N-(tert-butoxycarbonyl)-(Z)-beta-(2,3,5-trimethylbenzo[b]thien-6-yl)dehydrophenylalanine thus obtained, with Pd(OAc)2 and Cu(OAc)2 in DMF at 160 oC gave two indole derivatives (1:3). The major product resulting from isomerization and cyclization and the minor product resulting from direct cyclization (thienoindole). Reaction at 100 oC gave the same products in similar amounts. Using as starting material the methyl ester of N-(tert-butoxycarbonyl)-(Z)-beta-(2,3,7-trimethylbenzo[b]thien-6-yl)dehydrophenylalanine gave only one product, resulting from isomerization and cyclization at 100 oC. Two of the cyclized compounds were submitted to fluorescence studies; the thienoindole could be used as a fluorescent probe. Preliminary studies of antimicrobial activity were performed on the precursors and on the cyclized products.; Fundação para a Ciência e Tecnologia - POCTI/99/QUI/32689...

‣ Synthesis of new fluorescent 3-arylindole-2-carboxylates using beta,beta-diaryldehydroamino acids as building blocks. Fluorescence studies

Queiroz, Maria João R. P.; Abreu, Ana S.; Castanheira, Elisabete M. S.; Ferreira, Paula M. T.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /01/2007 Português
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Several new methyl 3-arylindole-2-carboxylates were synthesized in high yields using a metal-assisted [Pd(OAc)2/Cu(OAc)2, DMF, 130 oC] intramolecular C-N cyclization of beta,beta-diaryldehydroamino acids, developed by us, thus extending the scope of this reaction. The latter were obtained by a bis-Suzuki coupling of a beta,beta-dibromodehydroalanine with arylboronic acids bearing either electron-donating groups (EDGs) or electron-withdrawing groups (EWGs). We were able to establish general conditions for this coupling reaction [PdCl2dppf.CH2Cl2 1:1(20 mol%), boronic acid (5 equiv.), Cs2CO3 (1.4 equiv.), THF/H2O 1:1, 80 oC]. This strategy constitutes a novel, general and unprecedent approach to the synthesis of 3-arylindole-2-carboxylates. The fluorescence of the differently substituted indoles prepared was studied in several polar and non-polar solvents. In general the new indoles exhibit a solvent sensitive emission. The indoles with EDGs (OCH3 and SCH3) have reasonable fluorescence quantum yields in all solvents except in water. The indole with the cyano groups shows high fluorescent quantum yields in all solvents studied, despite the lower solvent sensitivity of its emission. The indole with the acetyl groups only exhibits reasonable fluorescence quantum yields in protic solvents. The fluorescence studies show that the new 3-arylindole-2-carboxylates are good candidates to be used as fluorescent probes.; Fundação para a Ciência e a Tecnologia (FCT)

‣ Synthesis of fluorescent tetracyclic lactams by a “one pot” three steps palladium-catalyzed borylation, Suzuki coupling (BSC) and lactamization. DNA and polynucleotides binding studies

Queiroz, Maria João R. P.; Castanheira, Elisabete M. S.; Lopes, Teresa C. T.; Cruz, Yvonne K.; Kirsch, G.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /03/2007 Português
Relevância na Pesquisa
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Tetracyclic lactams (benzothieno[2,3-c]quinolones) were prepared by “one pot” three steps palladium-catalyzed borylation, Suzuki coupling (BSC) and lactamization, starting from ortho-haloanilines and alkyl 3-bromobenzo[b]thiophene-2-carboxylates. The former were used as the components to be borylated with pinacolborane, and the latter as the brominated component in the Suzuki coupling. The amidation occurred with loss of the alkyl alcohol, presumably in the Suzuki coupling product, giving the corresponding tetracyclic lactam. This constitutes a novel application of the BSC reaction using sterically hindered substrates. In this work studies of absorption and fluorescence in several solvents and in presence of salmon sperm DNA or synthetic double stranded (ds) heteropolynucleotides, poly(dA-dT)•(dA-dT) and poly(dG-dC)•(dG-dC), were performed. The binding constants values (Ki = 2.6x10^5- 4.5x10^5 M^-1) point to a high affinity of the lactams to DNA. It was shown that the intercalation is the prefered mode of binding and that the substituted new lactams (with F or OMe) exhibit a higher affinity for A-T regions. Quenching experiments with iodide show that the methoxylated lactam is the more intercalative in DNA. The same type of experiments using this compound bound to heteropolynucleotides show a very low accessibility (fa = 0.07) of the lactam in poly(dG-dC)•(dG-dC) to the quencher showing a large majority of intercalative binding while the high affinity for A-T regions together with a higher accessiblity (fa = 0.25) point to the possiblity of intercalative and groove binding.; Foundation for the Science and Technology (Portugal) and FEDER for financial support through a research project POCI/QUI/59407/2004 and through Centro de Química and Centro de Física of Univ. Minho.

‣ Synthesis of 5-aryl-5´-formyl-2,2´-bithiophenes as new precursors for nonlinear optical (NLO) materials

Herbivo, Cyril; Comel, Alain; Kirsch, G.; Raposo, M. Manuela M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 08/01/2009 Português
Relevância na Pesquisa
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A series of formyl-substituted 5-aryl-2,2´-bithiophenes 5 were synthesized using two different methods: Vilsmeier-Haack-Arnold reaction (VHA) or through Suzuki coupling. The synthesis of compounds 5 through the Vilsmeier-Haack-Arnold reaction, starting from inexpensive and easily available precursors such as acetophenones, gave the title compounds in low yields after four reaction steps. On the other hand Suzuki coupling of functionalized aryl boronic acids 7 and the 5-bromo-5´-formyl-2,2´-bithiophene 6 gave compounds 5 in good yields in only one step.; Fundação para a Ciência e a Tecnologia (FCT)

‣ New 1,3-diarylureas linked by C-C Suzuki coupling to the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate moiety: synthesis and fluorescence studies in solution and in lipid membranes

Queiroz, Maria João R. P.; Peixoto, Daniela; Rodrigues, Ana Rita O.; Mendes, Pedro M. F.; Costa, Cátia N. C.; Coutinho, Paulo J. G.; Castanheira, Elisabete M. S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /03/2013 Português
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New six fluorescent 1,3-diarylureas linked by C-C Suzuki coupling to the 6-position of the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate moiety were prepared by reaction of the amino groups on the ortho or meta positions relative to the C-C bond of the Suzuki coupling products, with different para-substituted arylisocyanates (H, OMe, CN), in high to excellent yields. The fluorescence properties of the 1,3-diarylureas in solution and in lipid membranes of egg-yolk phosphatidylcholine (Egg-PC), dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) or dioctadecyldimethylammonium bromide (DODAB), with or without cholesterol (Ch), were studied. The six 1,3-diarylureas have reasonable fluorescence quantum yields in several solvents (between 0.02 and 0.69) and present a moderately solvent sensitive emission, but are not fluorescent in alcohols and water. The compounds bearing the arylurea moiety in the meta position relative to the C-C bond, especially with the OMe and CN substituents, present the better solvatochromic properties. Incorporation of the six compounds in lipid membranes indicates that all the compounds are deeply located in the hydrophobic region of the lipid bilayers, feeling the transition between the rigid gel phase and fluid phases.; To the Foundation for the Science and Technology (FCT...

‣ Estratégias para estudo das correlações de energia livre em acoplamento aril-aril de Suzuki: elucidando ciclos catalíticos através da equação de Hammett

Rosa,Gilber Ricardo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 Português
Relevância na Pesquisa
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The present work deals with the study of the correlation of free-energy developed in a catalytic system for Suzuki coupling, by way of the Hammett equation. The system presents NCP pincer palladacycle 1 as a catalyst precursor, which proved to be very efficient in the coupling of various aryl boronic acids with aryl halides in previous studies. Thus, the article presented here intends to serve as a support for further investigations and clarifications relating to cross-coupling catalytic cycles.

‣ Palladium nanoparticles supported on layered hydroxide salts and their use in carbon-carbon coupling organic reactions

Martínez,Maby; Ocampo,Rogelio; Rios,Luz Amalia; Ramírez,Alfonso; Giraldo,Oscar
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
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Palladium nanoparticles supported on zinc hydroxide salts were prepared by intercalation of [PdCl6]2- and its further reduction with ethanol under reflux. All the materials were completely characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), thermogravimetric/derivative thermogravimetric (TG/DTG) analyses, scanning electron microscopy (SEM), UV-Visible spectrometry and transmission electron microscopy (TEM). TEM analysis confirmed that the palladium nanoparticles were properly supported. The material containing supported palladium nanoparticles was used to promote Heck and Suzuki coupling reactions starting from aryl halides, with isolated yields of 98, 75 and 62% of biphenyl, cinnamic acid and 3-nitrobiphenyl, respectively.

‣ Pd complexes based on phosphine-linked cyclophosphazenes: synthesis, characterization and application in Suzuki coupling reactions

Paula,Vanderlei I. de; Sato,Cintia A.; Buffon,Regina
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2012 Português
Relevância na Pesquisa
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Palladium complexes were obtained by reaction of phosphine-linked cyclophosphazenes, (P3N3)(O-C6H4-PR2)6, where R = phenyl, i-propyl or cyclohexyl, with using a Pd/ligand molar ratio of 3/1. The (P3N3)(O-C6H4-PR2)6Pd3(dba)x complexes were characterized by elemental analyses, mass spectrometry, 31P NMR and FT-IR where a characteristic νC=C band of dba coordinated to palladium was always observed. All complexes were tested in Suzuki coupling reactions between phenylboronic acid and aryl halides. Turnover numbers as high as ca. 17,500 for the coupling of 2-bromotoluene with chlorophenylboronic acid could be obtained for R = cyclohexyl. The complex based on -PPh2 was also immobilized in silica matrixes by the sol-gel method. Preliminary experiments showed that the immobilized catalyst could be used in at least three consecutive Suzuki reactions with the same catalytic activity.

‣ Agarose-Alumina Composite Supported Palladium Catalyst for Suzuki Coupling Reactions

Wang,Peng; Cai,Jin; Chen,Junqing; Ji,Min
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 Português
Relevância na Pesquisa
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The palladium catalyst supported on agarose-alumina composite and its utilization in the Suzuki reaction have been investigated. The agarose-alumina composite was prepared and modified with organofunctional groups by reacting with the coupling reagent 3-aminopropyltriethoxysilane (APTES) through Al−O−Si bonds. Palladium was efficiently loaded on the composite by the amino groups. The Suzuki coupling reaction can proceed successfully at room temperature under air. High yields of various aryl-aryl products have been obtained. Recycling studies have shown that the catalyst can be easily recovered and reused several times. The yields decreased from 95% to 85% in five cycles.

‣ Facilitating room-temperature Suzuki coupling reaction with light: Mott-Schottky photocatalyst for C-C-coupling

Li, Xin-Hao; Baar, Moritz; Blechert, Siegfried; Antonietti, Markus
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 29/04/2013 Português
Relevância na Pesquisa
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The Suzuki coupling reaction is one of the most practiced classes of catalytic C-C bond formation. The development of new means of activating molecules and bonds over old catalysts for C-C bond formation is a fundamental objective for chemists. Here, we report the room-temperature C-C bond formation over heterogeneous Pd catalysts by light-mediated catalyst activation. We employ stimulated electron transfer at the metal-semiconductor interface from optically active mesoporous carbon nitride nanorods to Pd nanoparticles. This photocatalytic pathway is highly efficient for coupling aryl halides with various coupling partners with high activity and selectivity under photo irradiation and very mild conditions.

‣ Études vers la synthèse totale du cylindrocyclophane F et Synthèse d’hétérocycles azotés fluorescents

Constantineau-Forget, Lea
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
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Dans ce mémoire, deux principaux sujets seront présentés. Nos efforts se sont d’abord tournés vers la synthèse du cylindrocyclophane F, un [7,7]-paracyclophane naturel, puis vers l’élaboration d’une nouvelle classe d’hétérocycles fluorescents. Premièrement, la cyclopropanation, une des étapes clés de la synthèse du cylindrocyclophane F, ainsi qu’une nouvelle voie de synthèse passant par une réaction de cyclopropénation ont été revisitées. La possibilité d’employer une méthode de macrocyclisation, incluant une réaction de couplage de Suzuki sur deux centres sp3, a ensuite été étudiée sur un substrat modèle. Deuxièmement, la synthèse de benzo[a]imidazo[2,1,5-c,d]indolizines à partir de N-[(6-bromo-2-pyridinyl)méthyl]benzamides a été développée. Dans un premier temps, le tandem cyclodéshydratation/aromatisation effectué en présence de 2-méthoxypyridine a été optimisé afin d’obtenir la 5-bromo-3-phénylimidazo[1,5-a]pyridine. Puis, une arylation intramoléculaire en présence d’une quantité catalytique d’un complexe de palladium a permis d’obtenir l’hétérocycle fusionné désiré. Les propriétés photochimiques de cette nouvelle classe d’hétérocycles seront aussi présentées.; In this thesis...

‣ Tandem palladium-catalyzed borylation and suzuki coupling (BSC) to thienocarbazole precursors

Ferreira, Isabel C.F.R.; Queiroz, Maria João R.P.; Kirsch, Gilbert
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Substituted 2-methyl-2'-nitro diaryl compounds in the benzo[b]thiophene series were prepared by palladium-catalyzed, two-step, one-pot borylation/Suzuki coupling (BSC) reaction in good to high yields. The borylation reaction was performed on methylated 6-bromobenzo[b]thiophenes using pinacolborane and was followed by in situ Suzuki coupling with substituted (CF3, OMe) 2-bromonitrobenzenes. The compounds obtained were cyclized to the corresponding ring A substituted thienocarbazoles which can have biological activity or/and be used as biomarkers due to their fluorescence properties and possible DNA intercalation.

‣ Acoplamento Suzuki-Miyaura: uso de glicerol para síntese de ésteres arilboronatos e como solvente, e síntese de atropoisômeros

Nichele, Tatiana Zarichta
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
Português
Relevância na Pesquisa
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Nesta tese a reação de Suzuki-Miyaura será abordada em três diferentes enfoques: utilização de ésteres glicerolarilboronatos, emprego de glicerol como meio reacional e síntese de atropoisômeros a partir de ligantes nitrogenados N-N’ quirais. Primeiramente, a reação do glicerol com ácido fenilborônico proporcionou uma mistura de ésteres cíclicos, glicerol 1,2- fenilboronato (80 %) e glicerol 1,3-fenilboronato (20 %). Os ésteres glicerol fenilforonatos foram empregados em reações de Suzuki-Miyaura catalisadas por paládio com haletos de arila e as respectivas biarilas foram obtidas com rendimentos elevados (> 90 %). Não foi necessário utilização de excesso do composto organoborado e as reações de acoplamento Suzuki-Miyaura foram realizadas mediante precursor catalítico preparado in situ a partir de acetato de paládio e trifenilfosfina sob condições reacionais brandas. A atividade catalítica foi obtida com TON de 62.000. Posteriormente, o uso de glicerol como meio reacional foi eficaz para a o acoplamento de Suzuki-Miyaura que foi estudado. A reação entre brometos de arila e de ácidos arilborônicos, utilizando glicerol como solvente, forneceu um protocolo ambientalmente menos danoso, eficiente e prático para a síntese biarilas. O glicerol foi usado como solvente utilizando baixas quantidades de catalisador (0...

‣ Preparation of benzyne complexes of group 10 metals by intramolecular Suzuki coupling of ortho -metalated phenylboronic esters: Molecular structure of the first benzyne-palladium(0) complex.

Retboll, Mikael; Edwards, Alison; Rae, A David; Willis, Anthony; Bennett, Martin; Wenger, Eric
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
57.48205%
A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr{o-C6H4B(pin)}L2] (M = Ni, L2 = 2PPh3 (2a), 2PCy3 (2b), 2PEt3 (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L2 = 2PPh3 (3a), 2PCy3 (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KOtBu to form the corresponding benzyne complexes [M(η2-C6H4)L2] (M = Ni, L2 = 2PPh3 (4a), 2PCY3 (4b), 2PEt3 (4c), dcpe (4d); M = Pd, L2 = 2PCy3 (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KOtBu, but in this case disproportionation of the initially formed η2-C6H4 complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(μ2-C6H4)Pd(dcpe)] (6), and a 2,2′-biphenyldiyl complex, [Pd(2,2′-C6H4C6H4)-(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.