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Toscano, Rubén A.; Rosas, Raul; Hernández-Galindo, María del Carmen; Álvarez-Toledano, Cecilio; García-Mellado, Olivia

doi:10.1023/a:1006978622592

“…It confirmed the molecular structure of 10 b (Figure 2), the initial dihydropyridine 7 b having undergone a lactonization reaction akin to those described in Scheme 3, but involving CF 3 . As in the previous functionalized lactones, the introduced group is trans to the lactone bridge.…”

supporting

confidence: 72%

“…[3] For the purpose of comparing the two activation procedures, with methyl chloroformate or triflic anhydride, we synthesized a series of dihydropyridines subsituted by a triflyl group on the nitrogen atom. This led us to the discovery of a new, unexpected transformation of these dihydropyridines.…”

mentioning

confidence: 99%

Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride

Rudler

¹

,

Parlier

²

,

Sandoval-Chavez

³

et al. 2008

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Dihydropyridines of type 2 substituted at the C4-position by a carboxylic acid are valuable intermediates for the synthesis of new heterocyclic compounds, including tetrahydropyridinefused d-lactones 3, polysubstituted tetrahydropyridines 4, and piperidine-fused d-lactones 5 (Scheme 1).[1]The starting materials for all those transformations were differently substituted pyridines, which underwent stepwise nucleophilic addition reactions with ketene acetals 1 upon activation by methyl chloroformate. The ring-closure reaction, leading from 2 to 3, is stereospecific: only the transdiaxial-oriented functionalized lactones are formed. These transformations are part of a special class of reactions of dihydropyridines: nonbiomimetic oxidations, which do not lead, as one would expect, to pyridinium salts.[2] Indeed, the electrophiles preferentially react with one of the double bonds of the ene-carbamates 2 than with the proton at C4.The activation of the pyridinium nucleus towards carbon nucleophiles is not limited to alkyl chloroformates or acid chlorides, since several research groups have also used triflic anhydride for that purpose; in addition to the higher stability of the intermediate pyridinium salts and the general higher yields of the addition products, the absence of rotamers at room temperature is also beneficial.[3] For the purpose of comparing the two activation procedures, with methyl chloroformate or triflic anhydride, we synthesized a series of dihydropyridines subsituted by a triflyl group on the nitrogen atom. This led us to the discovery of a new, unexpected transformation of these dihydropyridines.Thus, the reaction of pyridine with ketene acetals 1 a,b (1 equiv) and then with triflic anhydride (1 equiv) at À30 8C led, as expected, after warming the mixture to room temperature and stirring for 17 h, to the same type of acid-substituted dihydropyridines 7 a,b in high yield (97 %, Scheme 2). Although the reaction of these dihydropyridines with either silica gel or an anhydrous solution of HCl in diethyl ether did not lead to the expected lactones 8 a,b, they did react with I 2 and CuBr 2 to give, as for 2, the corresponding halolactones 9 (Scheme 3). [1,4] However, further studies allowed us to discover a new transformation of these dihydropyridines. Indeed, it appeared that the yield of the dihydropyridines 7 a,b was dependent both on the reaction conditions (order of addition, time of reaction) and on the amount of triflic anhydride used with respect to the starting pyridine: no such an influence was observed when methyl chloroformate was used as the activating agent. The use of an excess of triflic anhydride, however, led to the yield of the dihydropyridines decreasing as a function of time. Surprisingly, according to TLC analysis, Scheme 1. Transformations of dihydropyridines.Scheme 2. Preparation of 7.Scheme 3. Formation of lactone 9.

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“…9,10 All chemicals were reagent-grade products from commercial suppliers and they were used without further purification.…”

Section: Methodsmentioning

confidence: 99%

“…N-Trifluoromethanesulfonyl-1-azahexa-1,3,5-trienes (TFSAT) compounds, which are highly functionalized pentametines, have been previously studied due to its interesting physical and chemical properties. 9 These compounds are especially interesting from a structural point of view for some reasons; in a neutral form, they show an extensive electronic delocalization, which give them a very particular chemical behavior. Furthermore, these pentametines can work as monodentate ligands, bidentate ligands, and even interact with metals through electrons.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, these pentametines can work as monodentate ligands, bidentate ligands, and even interact with metals through electrons. 9 Due to its planar structure, it is evident that the TFSAT molecules are excellent candidates to form new MMs in a similar way as the TTF complexes do. 6 Therefore, the aim of this work is to study the voltammetric formation of new materials by the coupling of TFSTA molecules and a magnetic anion.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical and atomic force microscopy investigations of new materials from N-trifluoromethanesulfonyl-1-azahexa-1,3,5-trienes derivatives

Rivera¹,

Álvarez-Toledano²,

Moreno³

et al. 2005

J. Braz. Chem. Soc.

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Filmes finos foram crescidos sobre a superfície de elétrodos de grafito pirolizado altamente orientado a partir de precursores p-doadores utilizando a técnica cíclica de voltametria cíclica e eletroquímica-microscopia de força atômica. Os resultados indicam que é possível a formação de novos compostos chamados materiais moleculares, estes são formados pelo acoplamento de espécies N-trifluormetanosulfonil-1-aza-hexa-1,3,5-trieno eletro-oxidadas e o anion [Cr(C 2 O 4 ) 3 ] 3-. Diferentes técnicas foram empregadas para caracterizar a morfologia e composição dos filmes formados. Os resultados indicam que os materiais novos exibiram uma resposta eletroquímica particular e uma textura diferente dependendo da composição química dos materiais de partida.Thin films have been created on the surface of highly oriented pyrolytic graphite electrodes from chemically synthesized -donor species by using the cyclic voltammetry technique and in situ electrochemistry-atomic force microscopy. Results indicate that it is possible to form new compounds called molecular materials from the coupling of electro-oxidized N-trifluoromethanesulfonyl-1-azahexa-1,3,5-triene species and a [Cr(C 2 O 4 ) 3 ] 3-anion. Different techniques such as AFM, SEM and EDS were employed to characterize the films morphology and composition. Results indicate that the new materials exhibited a particular electrochemical response and a different film texture depending on the chemical composition of the starting compounds. Keywords: thin films, electrodeposition, in situ AFM IntroductionOver the last few years, there have been an increasing number of reports regarding the formation of molecular materials (MMs) with electronic or opto electronic properties based on organic and organometallic derivatives.1,2 For example, it has been reported the formation of supramolecular building blocks with tailored pore structures by Plaud et al. to generate predictable and robust structures for specific applications.3 Moreover, recent research work has been oriented to the formation and characterization of molecular-material thin films. 4 For instance, the use of the chemical vapor deposition to grow thin films of molecular conductors such as (TTF)(TCNQ) (TTF= tetrathiafulvalene, TCNQ = tetracyanoquinodimethane) has been reported. [5][6][7][8] It has been observed, that a regular stacking of molecules such as those found in MMs allows the formation of semiconducting, conducting or superconducting thin films. These thin films exhibit in general preferential directions for electrical conductivity. The electrical conductivity of MMs is associated with an extensive delocalization of electrons that depends on their 317 Electrochemical and Atomic Force Microscopy Investigations of New Materials Vol. 16, No. 3A, 2005 planarity and the orbital overlap extension between their molecular units. N-Trifluoromethanesulfonyl-1-azahexa-1,3,5-trienes (TFSAT) compounds, which are highly functionalized pentametines, have been previously studied due to its interesting physical and chemical p...

show abstract

Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride

Rudler

¹

,

Parlier

²

,

Sandoval-Chavez

³

et al. 2008

Angewandte Chemie

6

0

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Dihydropyridines of type 2 substituted at the C4-position by a carboxylic acid are valuable intermediates for the synthesis of new heterocyclic compounds, including tetrahydropyridinefused d-lactones 3, polysubstituted tetrahydropyridines 4, and piperidine-fused d-lactones 5 (Scheme 1).[1]The starting materials for all those transformations were differently substituted pyridines, which underwent stepwise nucleophilic addition reactions with ketene acetals 1 upon activation by methyl chloroformate. The ring-closure reaction, leading from 2 to 3, is stereospecific: only the transdiaxial-oriented functionalized lactones are formed. These transformations are part of a special class of reactions of dihydropyridines: nonbiomimetic oxidations, which do not lead, as one would expect, to pyridinium salts.[2] Indeed, the electrophiles preferentially react with one of the double bonds of the ene-carbamates 2 than with the proton at C4.The activation of the pyridinium nucleus towards carbon nucleophiles is not limited to alkyl chloroformates or acid chlorides, since several research groups have also used triflic anhydride for that purpose; in addition to the higher stability of the intermediate pyridinium salts and the general higher yields of the addition products, the absence of rotamers at room temperature is also beneficial.[3] For the purpose of comparing the two activation procedures, with methyl chloroformate or triflic anhydride, we synthesized a series of dihydropyridines subsituted by a triflyl group on the nitrogen atom. This led us to the discovery of a new, unexpected transformation of these dihydropyridines.Thus, the reaction of pyridine with ketene acetals 1 a,b (1 equiv) and then with triflic anhydride (1 equiv) at À30 8C led, as expected, after warming the mixture to room temperature and stirring for 17 h, to the same type of acid-substituted dihydropyridines 7 a,b in high yield (97 %, Scheme 2). Although the reaction of these dihydropyridines with either silica gel or an anhydrous solution of HCl in diethyl ether did not lead to the expected lactones 8 a,b, they did react with I 2 and CuBr 2 to give, as for 2, the corresponding halolactones 9 (Scheme 3). [1,4] However, further studies allowed us to discover a new transformation of these dihydropyridines. Indeed, it appeared that the yield of the dihydropyridines 7 a,b was dependent both on the reaction conditions (order of addition, time of reaction) and on the amount of triflic anhydride used with respect to the starting pyridine: no such an influence was observed when methyl chloroformate was used as the activating agent. The use of an excess of triflic anhydride, however, led to the yield of the dihydropyridines decreasing as a function of time. Surprisingly, according to TLC analysis, Scheme 1. Transformations of dihydropyridines.Scheme 2. Preparation of 7.Scheme 3. Formation of lactone 9.

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Cited by 16 publications

References 7 publications

Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride

Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride

Electrochemical and atomic force microscopy investigations of new materials from N-trifluoromethanesulfonyl-1-azahexa-1,3,5-trienes derivatives

Overall “Pseudocationic” Trifluoromethylation of Dihydropyridines with Triflic Anhydride

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