英语翻译We also notice that room-temperature ionic liquids (ILs)

英语翻译
We also notice that room-temperature ionic liquids (ILs),which are recognized
as important “green” solvents,have been applied widely in multifarious
reactions and often brought about unexpected results.[13] Of course,someresearchers
have already brought ILs into the Knoevenagel reaction.For example,Harjani
et al.[14] described their Knoevenagel condensation using Lewis acidic ILs containing
AlCl3; Khan et al.[15a] reported they carried out their reaction in 1-butyl-3-
methylimidazolium hexafluorophosphate ([bmim]PF6) or 1-butyl-3-methylimidazolium
tetrafluoroborate ([bmim]BF4) with or without catalyst.Their efforts
showed many merits of the ILs,such as accelerating the reaction,making the
workup easier,and the potential for recycling.
We had synthesized an IL,1,1,3,3-tetramethylguanidium lactate,through
neutralizing 1,1,3,3-tetramethylguanidine with lactic acid.[16] It had already
been used in preparing the immobilized catalyst for heterogeneous hydrogenation
of olefins,[17] in desulfurization of simulated flue gas,[18] and particularly
in the reactions between aldehydes or acetones and the compounds with
active hydrogen,such as Henry reaction[19] and direct aldol reaction.[20] In our
continuous pursuit in this area,here we demonstrate the application of this IL
in the Knoevenagel condensation reaction.In contrast to the previous work in
which the ILs were used as solvents,[14,15,21] we observed that when this IL
was used in a catalytic amount,the Knoevenagel condensation between
ethyl cyanoacetate or malononitrile and carbonyl compounds (Scheme 1)
could be performed with high efficiency.
The reactions were conducted at room temperature.Only IL was added
into the reactants,provided the reactants could dissolve each other to form
a homogenous mixture.Ethyl acetate was added as the solvent to dissolve
the reactants,and IL was added if the reactants are inhomogeneous.Here,
the solvent was not optimized.The results are shown in Table 1.
We can see from Table 1 that the reactions using aromatic aldehydes with
various substituents,such as nitro,chloro,hydroxy,methoxy,and so on,could
be carried out smoothly (Entries 1–8,12–17).Toward terephthalaldehyde,
both of the carbonyls could react with ethyl cyanoacetate to yield a bis-condensation
product (Entry 3).In addition,furfural (Entries 9,18) and
E-cinnamaldehyde (Entries 10,19),the a,b-unsaturated aldehydes,could also
react rapidly with both of the active methylene compounds.When
ethylcyanoacetate was used as the active methylene compound,only E isomers
were obtained because of steric effects,and this was confirmed by 1H NMR.[