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au:"Silva Jr., Luiz F."

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Iodine - catalyzed prins cyclization of aliphatic and aromatic ketones
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Reddy, K. R. Kishore K.

; Silva Jr, Luiz F.

Journal of the Brazilian Chemical Society

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sep 2013, Volume 24 N. 9 Pages 1414 - 1419

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

A ciclização de Prins catalisada por iodo entre álcoois homoalílicos e cetonas foi investigada. Condições anidras e atmosfera inerte não são necessárias neste protocolo ausente de metais. A reação do 2-(3,4-di-hidronaftalen-1-il)propan-1-ol com seis cetonas simétricas alifáticas levou ao produto desejado em 67-77% de rendimento.A ciclização foi realizada com quatro cetonas alifáticas assimétricas, levando aos correspondentes piranos em 66-76% de rendimento. A ciclização de Prins também foi alcançada com quatro cetonas aromáticas com 37-66% de rendimento. Finalmente, a ciclização de Prins do monoterpeno isopulegol e acetona foi realizada com sucesso.

Iodine-catalyzed Prins cyclization of homoallylic alcohols and ketones was investigated. Anhydrous conditions and inert atmosphere are not required in this metal-free protocol. The reaction of 2-(3,4-dihydronaphthalen-1-yl)propan-1-ol with six aliphatic symmetric ketones gave the desired products in 67-77% yield. Cyclization was performed with four aliphatic unsymmetric ketones, leading to corresponding pyrans in 66-76% yield. Prins cyclization was also accomplished with four aromatic ketones in 37-66% yield. Finally, Prins cyclization of the monoterpene isopulegol and acetone was successfully achieved.

https://doi.org/10.5935/0103-5053.20130178 1724 downloads

Estudo por espectrometria de massas de soluções de hidróxi(tosilóxi)iodobenzeno: propostas para mecanismos de desproporção
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Vasconcelos, Ramon S.

; Silva Jr, Luiz F.

; Lopes, Norberto P.

Química Nova

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2012, Volume 35 N. 8 Pages 1593 - 1599

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

Solutions of [hydroxy(tosyloxy)iodo]benzene (HTIB or Koser's reagent) in acetonitrile were analyzed using high resolution electrospray ionization mass spectrometry (ESI-MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) under different conditions. Several species were characterized in these analyses. Based on these data, mechanisms were proposed for the disproportionation of the iodine(III) compounds in iodine(V) and iodine(I) species.

2437 downloads

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes
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Siqueira, Fernanda A

; Ishikawa, Eloisa E

; Fogaça, André

; Faccio, Andréa T

; Carneiro, Vânia M. T

; Soares, Rafael R. S

; Utaka, Aline

; Tébéka, Iris R. M

; Bielawski, Marcin

; Olofsson, Berit

; Silva Jr, Luiz F

Journal of the Brazilian Chemical Society

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sep 2011, Volume 22 N. 9 Pages 1795 - 1807

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

Um protocolo livre de metais foi desenvolvido para sintetizar indanos através da contração de anel de 1, 2-di-hidronaftalenos promovida por PhI(OH)OTs (HTIB ou reagente de Koser). Este rearranjo oxidativo pode ser realizado em diversos solventes (MeOH, CH3CN, 2 , 2, 2-trifluoroetanol (TFE), 1 , 1, 1, 3, 3, 3-hexafluoroisopropanol (HFIP), e uma mistura 1:4 de TFE:CH2Cl2) em condições brandas. A contração de anel fornece indanos trans-1, 3-dissubstituídos diastereosseletivamente, os quais são difíceis de obter em química orgânica sintética

A metal-free protocol was developed to synthesize indanes by ring contraction of 1, 2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser's reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH3CN, 2 , 2, 2-trifluoroethanol (TFE), 1 , 1, 1, 3, 3, 3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH2Cl2) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1, 3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry

5636 downloads

Reações de oxidação de derivados de cis-octalinas promovidas por trinitrato de tálio (TTN)
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Ferraz, Helena M. C.

; Carneiro, Vânia M. T.

; Vieira, Tiago O.

; Silva Jr., Luiz F.

Química Nova

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2008, Volume 31 N. 4 Pages 781 - 787

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

The reaction of ten cis-octalins and cis-octalones with thallium trinitrate (TTN) leads to different products, depending mainly on the substitution pattern of the substrate. Functionalized cis-hydrindanes were obtained from the reaction of 1,2,3,4,4a,5,8,8a-octahydro-4a-methylnaphthalene and of 1,2,3,4,4a,5,8,8a-octahydro-4a,7-dimethylnaphthalene with TTN in acetonitrile, whereas a cyclic ether was formed treating 1,2,3,4,4a,5,8,8a-octahydro-6,8a-dimethylnaphthalen-1-ol with TTN in trimethylorthoformate (TMOF).

1780 downloads

Helena Ferraz e Química Nova: um exemplo de relacionamento
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Silva Jr., Luiz F.

; Aguilar, Andrea M.

; Cunha, Silvio do Desterro

Química Nova

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2008, Volume 31 N. 4 Pages 725 - 725

Abstract: Pt | Text: Pt | PDF: Pt

1808 downloads

A mild procedure for a,a-dichlorination of cyclic aryl ketones using commercial bleach
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Quintiliano, Samir A. P.

; Silva Jr., Luiz F.

Journal of the Brazilian Chemical Society

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2007, Volume 18 N. 6 Pages 1281 - 1284

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

Aril cetonas cíclicas a,a-dicloradas foram obtidas pelo tratamento de uma solução metanólica da correspondente cetona com cândida comercial em condições ambiente com rendimentos que variaram de 61 a 92%. A reação ocorre em cetonas contendo tanto grupos doadores quanto retiradores de elétrons, mas parece ser sensível a efeitos estéricos. Além disso, aril-cicloalcanonas com anéis de cinco, seis e sete membros podem ser utilizadas como substrato.

a,a-Dichloro-cyclic aryl ketones were obtained treating a methanolic solution of the corresponding ketone with commercial bleach at ambient conditions in yields varying from 61 to 92%. Electron-donating and -withdrawing groups in the starting ketone are tolerated but the reaction appears to be sensitive to steric effects. Moreover, five-, six-, and seven-membered aryl-cycloalkanones can be used as substrate.

2016 downloads

Oxidation of tertiary homoallylic alcohols by thallium trinitrate: fragmentation vs. ring contraction
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Silva Jr., Luiz F.

; Quintiliano, Samir A. P.

; Ferraz, Helena M. C.

; Santos, Leonardo S.

; Eberlin, Marcos N.

Journal of the Brazilian Chemical Society

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oct 2006, Volume 17 N. 5 Pages 981 - 988

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

A oxidação de álcoois homoalílicos terciários com trinitrato de tálio (TTN) foi investigada. Os álcoois que possuem uma metila na posição alílica perdem uma molécula de acetona via uma reação de fragmentação, levando a uma mistura de álcoois alílicos isoméricos como principais produtos, juntamente com os correspondentes derivados acetilados. Por outro lado, o tratamento com TTN de álcoois terciários análogos, sem a metila na posição alílica, fornece indanos, através de uma reação de contração de anel.

The oxidation of tertiary homoallylic alcohols with thallium trinitrate (TTN) was investigated. The alcohols bearing an allylic methyl group lose a molecule of acetone via a fragmentation reaction that leads to isomeric secondary allylic alcohols as major products, together with their corresponding acetylated derivatives. On the other hand, treating analogous tertiary alcohols without the allylic methyl group with TTN gives indans, through a ring contraction reaction.

1346 downloads

Rearrangement of beta,gamma-unsaturated esters with thallium trinitrate: synthesis of indans bearing a beta-keto ester moiety
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Silva Jr., Luiz F.

; Pedrozo, Eliane C.

; Ferraz, Helena M. C.

Journal of the Brazilian Chemical Society

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feb 2006, Volume 17 N. 1 Pages 200 - 205

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

O rearranjo de ésteres beta,gama-insaturados, tais como 2-(3,4-di-hidronaftalen-1-il)-propionato de etila, com trinitrato de tálio (TTN) em ácido acético leva a 3-indan-1-il-2-metil-3-oxo-propionatos de etila com bom rendimento, através de uma reação de contração de anel. Os novos indanos assim obtidos possuem uma unidade beta-ceto éster, a qual pode ser útil para transformações posteriores.

The rearrangement of beta,gamma-unsaturated esters, such as 2-(3,4-dihydronaphthalen-1-yl)-propionic acid ethyl ester, with thallium trinitrate (TTN) in acetic acid leads to 3-indan-1-yl-2-methyl-3-oxo-propionic acid ethyl ester in good yield, through a ring contraction reaction. The new indans thus obtained feature a beta-keto ester moiety, which would be useful for further functionalization.

2812 downloads

Thallium trinitrate-mediated ring contraction of 1,2-dihydronaphthalenes: the effect of electron-donating and electron-withdrawing groups
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Silva Jr., Luiz F.

; Sousa, Raquel M. F.

; Ferraz, Helena M. C.

; Aguilar, Andrea M.

Journal of the Brazilian Chemical Society

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dec 2005, Volume 16 N. 6a Pages 1160 - 1173

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

A oxidação de uma série de 1,2-diidronaftalenos, substituídos no anel aromático, foi investigada com trinitrato de tálio (TTN) em metanol ou em trimetilortoformiato (TMOF) como solvente. Em todos os casos, indanos foram formados, embora o rendimento tenha variado de excelente a baixo, dependendo da estrutura do substrato. A presença de um grupo doador de elétrons no substrato favorece o rearranjo, enquanto que uma quantidade significativa de derivados glicólicos, bem como naftalenos, foi obtida na oxidação de 1,2-diidronaftalenos com um grupo retirador de elétrons, tais como Br e NO2. Mecanismos para a formação de cada um destes produtos foram propostos.

The oxidation of a series of 1,2-dihydronaphthalenes substituted in the aromatic ring was investigated with thallium trinitrate (TTN) in methanol or in trimethylorthoformate (TMOF) as solvent. In all cases, indans are produced, although the yield varied from excellent to poor, depending on the structure of the substrate. The presence of an electron-donating group in the substrate favors the rearrangement, whereas significant amounts of glycolic derivatives, as well as naphthalenes, were obtained in the oxidation of 1,2-dihydronaphthalenes bearing electron-withdrawing groups, such as Br and NO2. Mechanisms for the formation of each of these products are proposed.

2918 downloads

10.

Síntese de indanos: uma seleção de métodos gerais e eficientes
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Ferraz, Helena M. C.

; Aguilar, Andrea M.

; Silva Jr., Luiz F.

; Craveiro, Marcus V.

Química Nova

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aug 2005, Volume 28 N. 4 Pages 703 - 712

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

The indan ring system is present in several compounds with important pharmacological properties. In this account recent examples of selected methods (Friedel-Crafts acylation, cycloaddition reactions, ring contraction, cyclization and resolution) for the synthesis of indans are discussed.

3956 downloads

11.

The reaction of 1-tetralones with thallium trinitrate supported on clay: ring contraction vs alpha-oxidation
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Ferraz, Helena M. C.

; Silva Jr., Luiz F.

; Aguilar, Andrea M.

; Vieira, Tiago O.

Journal of the Brazilian Chemical Society

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oct 2001, Volume 12 N. 5 Pages 680 - 684

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

A reação de uma série de 1-tetralonas com trinitrato de tálio adsorvido em Montmorilonita K-10 forneceu produtos de contração de anel (1-indanocarboxilatos de metila) e/ou alfa-oxidação (2-metóxi-1-tetralonas), em rendimentos bastante variáveis.

The reaction of a series of 1-tetralones with thallium trinitrate supported on Montmorillonite K-10 clay led to products of ring contraction (methyl indan-1-carboxylates) and/or alpha-oxidation (2-methoxy-1-tetralones), in variable yields.

1813 downloads

12.

Thallium trinitrate mediated ring contraction of cis-2-decalones
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Ferraz, Helena M. C.

; Silva Jr., Luiz F.

Journal of the Brazilian Chemical Society

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aug 2001, Volume 12 N. 4 Pages 548 - 551

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

A reação de uma série de cis-2-decalonas com TTN em CH2Cl2 à temperatura ambiente foi investigada. As reações de contração de anel ocorreram com bons rendimentos, porém a regio- e a diastereosseletividade foram baixas. A influência de grupos alquílicos na regioquímica da reação depende da sua posição no anel decalínico.

The reaction of some cis-2-decalones with TTN in CH2Cl2 at room temperature was investigated. The ring contraction reactions occurred in good yields, however the regio- and diastereoselectivity were low. The effect of the alkyl groups in the regiochemistry of the reaction depends on their position at the decalone ring system.

1477 downloads

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