Alkylation of the ambident indole ion in ionic liquids (original) (raw)
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Alkylation of ambident indole anion in ionic liquids
Central European Journal of Chemistry, 2007
Alkylation of indole salts in different ionic liquids is reported. Ionic liquids increase the alkylation reaction rate of ambident indole anion and reduce the effects of counter ions and/or additives, the alkylation reaction rates being independent of the presence of small amounts of protic solvents or water.
Alkylation of the 2-hydroxypyridine anion in ionic liquid media
Chemistry of Heterocyclic Compounds, 2008
The alkylation reaction of the ambident 2-hydroxypyridine anion was examined in ionic liquid media. Ionic liquids increase the alkylation reaction rate in comparison with molecular liquids, as well as the level of impact on the reaction rates of the counter ion and/or additives, and the distribution of isomers of the reaction products in trans-formations of the ambident 2-hydroxypyridine anion.
ChemInform, 2010
A novel synthetic method using an ionic liquid (IL) for a six-membered ring-closure cyclization is described. The ring-closure cyclization by nucleophilic C-alkylation was achieved with various haloand alkanesulfonyloxyalkyl aromatic compounds in high yields with minimal byproducts using ILs as the reaction media in the absence of any catalyst. For example, the cyclization of 2-(3-methanesulfonyloxy-propoxy)naphthalene (1a) to 2,3-dihydro-1H-naphtho[2,1-b]pyran (2) in IL [bmim] [PF 6 ] proceeded selectively at 150°C for 24 h in 85% yield.
Organic & Biomolecular Chemistry, 2012
All reactions were monitored by thin-layer chromatography with silica gel 60 F254 precoated aluminium plates (0,25mm). Melting points of solid compounds were measured on an Electrothermal IA 9000 melting point apparatus (compounds 3 and 4) or a STUART apparatus advanced SMP3 with a precision of ±0.5°C (compounds 1, 2, 5-9) and are uncorrected. IR spectra were recorded on a PerkinElmer Spectrum 100 Series FT-IR spectrometer. Liquids and solids were applied on the Single Reflection Attenuated Total Reflectance (ATR) Accessories. Absorption bands are given in cm-1 .
The Effect of Hydrogen Bonding on Allylic Alkylation and Isomerization Reactions in Ionic Liquids
Chemistry - A European Journal, 2003
Neutral allylic alkylation reactions, in which a base is generated in situ and which hence require no external bases, can significantly be retarded when carried out in the ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][BF 4 ]). Evidence suggests that the base or base precursor enters into hydrogen bonding with the imidazolium cation and is thus made less readily available for deprotonation of pre-nu-cleophiles. However, the reaction proceeds well in the presence of stronger bases that are capable of deprotonation. Whilst the phenomenon of hydrogen bonding in ionic liquids can be detrimental to reactions such as allylic alkylation, it can be exploited to suppress unwanted allylic isomerization.
HETEROCYCLES, 2003
4-Chloromethylpyrazoles are shown to react readily with amides, carbamates, ureas and azoles under neutral conditions giving the corresponding N-monoalkylated derivatives with moderate yields. Alkylation of alcohols and thiols occurs under the same conditions. The procedure described may provide a convenient and easy method for the introduction of a 4-pyrazolylmethyl group into molecules containing functional groups with weak nucleophilic character. N-Alkylation of amides is known to be a difficult process due to their low nucleophilic character. 1 Nevertheless, these reactions have been acomplished using different alkylating agents such as, electrophilic alkenes, 2 alcohols, 3 aldehydes or ketones 4 and alkyl halides. 5 Generally, the N-alkylated amides are obtained treating the starting amide with a strong base in an inert solvent followed by reaction with alkyl halide. However, under neutral conditions the direct alkylation using alkyl halides rarely leads exclusively to N-alkylated products. Instead, a mixture of both O-and N-alkylated isomers is normally isolated. Only at high temperatures the corresponding N-alkylated amides are obtained. In this work we report a convenient procedure for the alkylation of aliphatic and aromatic amides which results exclusively in the N-alkylation products. The method uses 4-chloromethylpyrazoles as alkylating agents. Chloromethyl derivatives (1a-b) were synthesized by reaction of the corresponding pyrazoles (2a-b) with paraformaldehyde (Scheme 1). 6 Compound (2a) was obtained from 3-phenyl-5-methylpyrazole 7 using methods previously described by our laboratory. 8 Pyrazole (2b) is a commercial compound.