Synthesis and Crystal Structures of 1-Alkoxy-3-alkylimidazolium Salts Including Ionic Liquids, 1-Alkylimidazole 3-oxides and 1-Alkylimidazole Perhydrates

Laus, Gerhard; Schwärzler, Alexander; Bentivoglio, Gino; Hummel, Michael; Kahlenberg, Volker; Wurst, Klaus; Kristeva, Elka; Schütz, Johannes; Kopacka, Holger; Kreutz, Christoph; Bonn, Günther K.; Andriyko, Yuriy O.; Nauer, Gerhard; Schottenberger, Herwig

doi:10.1515/znb-2008-0411

Cited by 33 publications

(23 citation statements)

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“…1-Methoxyimidazole and 1-methoxyimidazolium hexafluorophosphate were synthesized by catalytic hydrogenation of 1,3-dimethoxyimidazolium hexafluorophosphate [54]. The quaternary precursor salts 1,3-dimethylimidazolium iodide (1a) [9,30,66] or hexafluorophosphate (1b) [67 -69] or methylsulfate (1c) [69], 1-benzyloxy-3-methylimidazolium hexafluorophosphate (2) [70], 1,3-dimethoxyimidazolium hexafluorophosphate (4) [54], and 1,3-bis(benzylideneamino)imidazolium chloride (8) [27] were synthesized as described. No spectroscopic data of 8 have been disclosed so far, and they are therefore given here.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Crystal Structures of New 1,3-Disubstituted Imidazoline-2-thiones

Laus

Kahlenberg

Wurst

et al. 2013

Zeitschrift Für Naturforschung B

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Two methods (MeOH/K 2 CO 3 , pyridine/Et 3 N) were assessed for the introduction of sulfur into the 2-position of 1,3-disubstituted quaternary imidazolium salts 1-9 (Cl, I, BF 4 , PF 6 , CH 3 OSO 3 were used as anions) to yield nine 1,3-disubstituted imidazoline-2-thiones 10-18 (1, 10: R 1 = CH 3 , R 2 = CH 3 ; 2, 11: R 1 = OCH 2 Ph, R 2 = CH 3 ; 3, 12: R 1 = OCH 3 , R 2 = CH 3 ; 4, 13: R 1 = OCH 3 , R 2 = OCH 3 ; 5, 14: R 1 = NH 2 , R 2 = CH 2 Ph; 6, 15: R 1 = NCHPh, R 2 = CH 3 ; 7, 16: R 1 = NH 2 , R 2 = CH 3 ; 8, 17: R 1 = NCHPh, R 2 = NCHPh; 9, 18: R 1 = NH 2 , R 2 = OCH 3 ). Compounds 11-18 represent N-alkyloxy and N-amino imidazoline-2-thiones, whereas 10 served as reference compound. The first method was advantageous for the conversion 1 → 10 due to faster reaction, whereas in the reaction 2 → 11 considerable amounts of by-products were formed. Pure thiones 11, 14, 16, 17, and 18 were obtained only by the second method. Both methods worked for the synthesis of the methoxy derivatives 12 and 13 from 3 and 4, and the benzylideneamino derivative 15 from 6. 1-Amino-3-methylimidazoline-2-thione (16) was also prepared by hydrolysis of the benzylideneamino derivative 15. Crystal structures of seven 1,3-disubstituted imidazoline-2-thiones were determined by singlecrystal X-ray diffraction. Intermolecular C-H···S contacts were identified and, additionally, N-H···S interactions in aminothiones 14 and 16. The 1 H NMR shifts of 10 and 13 were satisfactorily correlated with the Kamlet-Abboud-Taft π * and β parameters in ten solvents. From the lack of correlation with the α parameter and from the C=S bond length (average 1.68Å) a significant contribution of a mesoionic imidazolium-2-thiolate resonance structure seems unlikely.

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Section: Methodsmentioning

confidence: 99%

Synthesis and Crystal Structures of New 1,3-Disubstituted Imidazoline-2-thiones

Laus

Kahlenberg

Wurst

et al. 2013

Zeitschrift Für Naturforschung B

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“…5 In contrast to six-membered N-heterocycles, imidazoles cannot be converted to the corresponding N-oxides by treatment with typical oxidizing reagents. 6 Therefore, condensations of -hydroxyimino ketones with methylidene amines (formaldehyde imines) were applied as a convenient access to 2-unsubstituted imidazole N-oxides. 5a,7 Starting with optically active primary amines, such as 1-phenylethylamine, transcyclohexane-1,2-diamine, as well as -amino acid esters, the desired enantiomerically pure imidazole N-oxides were obtained as sole products.…”

Section: Introductionmentioning

confidence: 99%

Optically active imidazole N-oxides derived from l-prolinamine1

Mlostoń

Wróblewska

Obijalska

et al. 2013

Tetrahedron: Asymmetry

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Starting with (S)-1-benzylprolinamine and alpha-hydroxyimino ketones, enantiomerically pure bisheterocyclic imidazole N-oxides bearing the (S)-configured N-benzyl(pyrrolidin-2-yl)methyl residue were prepared. These N-oxides reacted with 2,2,4,4-tetramethylcyclobutane-1,3-dithione to give the corresponding optically active imidazole-2-thione derivatives via a sulfur transfer reaction. Reduction of the N-oxides with Raney-nickel led to deoxygenation, whereas catalytic hydrogenation (Pd/C) in ethanol occurred with simultaneous deoxygenation and debenzylation, leading to optically active 1-(pyrrolidin-2-yl)methyl-1H-imidazoles. Alkylation of the prepared imidazole N-oxides and their respective imidazoles with butyl and hexyl bromide and subsequent anion exchange gave optically active N-alkoxy-and N-alkylimidazolium tetrafluoroborates, respectively, with the properties of 'room temperature ionic liquids'.

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“…Imidazolium salts with an N-O bond are rare [1,[3][4][5][6][7][8][9].Depending on the anion, e. g. triflimide [1,9] or tris(pentafluoroethyl)-trifluorophosphate (FAP) [1,10], they exhibit low melting points and mayb er egarded as 'ionic liquids'. It is known that imidazolium salts are sensitive to strong bases [11,12].…”

Section: Discussionmentioning

confidence: 99%