Synthesis of novel room temperature chiral ionic liquids: application as reaction media for the heck arylation of aza-endocyclic acrylates

Abstract

Novos líquidos iônicos aquirais e quirais foram preparados utilizando-se rotas sintéticas inéditas e/ou otimizadas. Estas séries de líquidos iônicos do tipo imidazolínico, imidazólico e piridínico foram totalmente caracterizadas, incluindo-se análises por calorimetria diferencial de varredura (DSC). O desempenho desses líquidos iônicos (LIs) foi demonstrado empregando-se a arilação de Heck de aza-acrilato endocíclicos com sais de arenodiazônio ou iodetos de arila. As arilações de Heck realizadas na presença destas entidades iônicas quirais, seja como um solvente ou um aditivo, foram eficazes levando à completa conversão do substrato, em bons a excelentes rendimentos do aduto de Heck na maioria dos casos, apesar de não ser observada indução assimétrica em nenhum dos casos estudados. Dois novos complexos quirais de paládio do tipo carbeno N-heterocíclico foram preparados em bons rendimentos a partir de um sal imidazólico quiral e suas estruturas caracterizadas por difração de raios-X. De modo geral, a arilação de Heck empregando tetrafluoroboratos de arenodiazônio em líquidos iônicos demonstrou ser mais eficiente do que os protocolos tradicionais em termos de reatividade e rendimentos de reação.New achiral and chiral RTILs were prepared using novel and/or optimized synthetic routes. These new series of imidazolinium, imidazolium, pyridinium and nicotine-derived ionic liquids were fully characterized including differential scanning calorimetry (DSC) analysis. The performance of these achiral and chiral room temperature ionic liquids (RTILs) was demonstrated by means of the Heck arylation of endocyclic acrylates employing arenediazonium salts and aryl iodides. The Heck arylations performed in the presence of these ionic entities, either as a solvent or as an additive, were effective leading to complete conversion of the substrate and good to excellent yield of the Heck adduct. In spite of the good performances, no asymmetric induction was observed in any of the cases studied. Two new diastereoisomeric NHC-palladium complexes were prepared in good yields from a chiral imidazolium salt and their structure characterized by X-ray diffraction. Overall, the Heck arylations employing arenediazonium tetrafluoroborates in RTILs were more effective than the traditional protocols employing aryl iodides in terms of reactivity and yields.

A New Approach to CO2Capture and Conversion Using Imidazolium Based-Ionic Liquids as Sorbent and Catalyst

“…It was observed that the reaction time reduction from 6 up to 2 h (entry [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], provided a decreases in yield, curiously the increase in reaction time from 6 to 8 h (entry 4-21) decreases the yield. The reaction time of 6 h was ideal for this the system.…”

“…They are more environmentally friendly when compared to conventional organic solvents exhibiting the possibility of the catalyst separation and recycling. 6,[13][14][15][16] Peng and Deng 10 reported the synthesis of propylene carbonate from CO 2 6 ] and demonstrated that the catalytic activity of an ionic liquid depends on the nature of the cation and the anion. For the anions, the activity decreased in the order bmim + > bpy + and BF 4 − > Cl − > PF 6 − .…”

Heterocyclic Carbene–Metal-catalyzed Csp2–Csp2 and Csp–Csp2 Couplings Using Nonmetallic Substrates

“…The research group of Correia has employed different room-temperature ionic liquids (RTILs) based on imidazole and imidazolidine in combination with palladium(II) acetate in order to perform the coupling between 4-fluorobenzenediazonium tetrafluoroborate and methyl N-phenoxycarbonyl-1,2,3,6-tetrahydropyridine-3-carboxylate for the synthesis of an intermediate in the paroxetine synthesis. 72 Thus, the formation of a NHC ligand can be expected in the course of the reaction, which can help in the stabilization of the palladium(0) species.…”

Novel chiral ionic liquid (CIL) assisted selectivity enhancement to (L)-proline catalyzed asymmetric aldol reactions

“…1,2 Since the first example of chiral ionic liquid reported by Howarth et al 3 in 1997, a large number of CILs bearing chiral cations, anions or seldom both were reported by other groups. 4,5 Previous studies have shown that in many asymmetric reactions the use of CILs as reaction media or catalyst can enhance the yield and/or selectivity significantly. [6][7][8] As most of the asymmetric reactions were carried out using metal/chiral catalysts as chiral sources, which are relatively expensive or environmental unfriendly, searching for a catalyst which is easy to obtain and environmentally benign for the asymmetric reactions is of great significance.…”