scholarly journals Room Temperature Ionic Liquids in Asymmetric Hetero-Ene Type Reactions: Improving Organocatalyst Performance at Lower Temperatures

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 355
Author(s):  
Fabricio R. Bisogno ◽  
Rosario Fernández ◽  
Jose María Lassaletta ◽  
Gonzalo de de Gonzalo
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Catalyst Activity ◽  
Room Temperature Ionic Liquids ◽  
Tertiary Alcohols ◽  
Tert Butyl ◽  
Keto Esters ◽  
Enantioselective Addition ◽  
Positive Effect

Room temperature ionic liquids (RTILs) have been widely used as (co)solvents in several catalytic processes modifying, in most of the cases, the catalyst activity and/or the selectivity for the studied reactions. However, there are just a few examples of their use in hydrogen bonding organocatalysis. In this paper, we show the positive effect of a set of imidazole-based ionic liquids ([bmim]BF4 and [hmim]PF6) in the enantioselective addition of formaldehyde tert-butylhydrazone to prochiral α-keto esters catalyzed by a sugar-based chiral thiourea. Reactions performed in the presence of low percentages of RTILs led to an increase of the catalyst activity, thereby making possible to work at lower temperatures. Thus, the chiral tert-butyl azomethyl tertiary alcohols could be obtained with moderate to good conversions and higher enantioselectivities for most of the studied substrates when using up to 30 vol% of [hmim]PF6 as a cosolvent in processes performed in toluene.

Ruthenium catalyzed asymmetric hydrogenation of α- and β-keto esters in ionic liquids using chiral P-Phos ligand

2005 ◽  
Vol 83 (6-7) ◽  
pp. 903-908 ◽  
Author(s):  
Kim Hung Lam ◽  
Lijin Xu ◽  
Lichun Feng ◽  
Jiwu Ruan ◽  
Qinghua Fan ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Room Temperature ◽  
Asymmetric Hydrogenation ◽  
Room Temperature Ionic Liquids ◽  
Keto Ester ◽  
Keto Esters ◽  
Simple Extraction

Chiral dipyridylphosphine ligand P-Phos was used in the Ru catalyzed asymmetric hydrogenation of α- and β-keto esters in room temperature ionic liquids (RTILs) with high conversions and good to excellent enantioselectivities. The catalyst was recycled by simple extraction and reused five times without loss of activity and enantioselectivity.Key words: ruthenium, asymmetric hydrogenation, keto ester, ionic liquids, P-Phos.

scholarly journals The role of hydrogen bonding in controlling the selectivity of Diels–Alder reactions in room-temperature ionic liquids

2002 ◽  
Vol 4 (5) ◽  
pp. 517-520 ◽  
Author(s):  
Ajay Aggarwal ◽  
N. Llewellyn Lancaster ◽  
Alick R. Sethi ◽  
Tom Welton
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Diels Alder ◽  
Room Temperature Ionic Liquids

Ruthenium- and Rhodium-catalyzed Carbenoid Reactions of Diazoesters in Hexaalkylguanidinium-based Ionic Liquids

2012 ◽  
Vol 67 (4) ◽  
pp. 347-353 ◽  
Author(s):  
Torsten Large ◽  
Tobias Müller ◽  
Helene Kunkel ◽  
Stefan Buck ◽  
Gerhard Maas
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Reaction Medium ◽  
High Yield ◽  
Room Temperature Ionic Liquids ◽  
Tert Butyl ◽  
Trans Isomerization ◽  
Intermolecular Reaction

Hexaalkylguanidinium-based room-temperature ionic liquids were investigated as solvents for the cyclopropanation of styrene with diazoacetates catalyzed by Rh2(OAc)4 or [Ru2(μ-OAc)2(CO)4]n. While the yields of the formed cyclopropanes are much lower compared to the reactions performed in dichloromethane, the diastereomeric ratio is not significantly affected by the change of the reaction medium. Immobilization of the catalysts is only partially successful. In contrast to this intermolecular reaction, the Ru-catalyzed formation of a β -lactam by an intramolecular carbenoid C-H insertion of an α-methoxycarbonyl-α-diazoacetamide occurs in high yield, similar to the Rh2(OAc)4-catalyzed reaction. The cis → trans isomerization of the resulting 1-tert-butyl-3-methoxycarbonyl-4-phenylazetidin- 2-one is accelerated in the ionic liquid N,N-dibutyl-N’ ,N’-diethyl-N’,N’-dihexylguanidinium triflate.

Solute–solvent hydrogen-bonding in room temperature ionic liquids studied by Raman spectroscopy

2012 ◽  
Vol 14 (39) ◽  
pp. 13676 ◽  
Author(s):  
Akira Kobayashi ◽  
Koji Osawa ◽  
Masahide Terazima ◽  
Yoshifumi Kimura
Keyword(s):  
Raman Spectroscopy ◽  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Room Temperature Ionic Liquids
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