DE102008014028A1 - Preparing imidazolium salts, preferably 1,3-disubstiuted imidazolium salts, useful e.g. as precursors of N-heterocyclic carbenes, comprises reducing 1,3-disubstituted-2-alkoxyimidazolium salts with hydrides and/or hydride donors - Google Patents

Abstract

Preparing imidazolium salts (II) comprises reducing 1,3-disubstituted-2-alkoxyimidazolium salts (I) with hydrides and/or hydride donors. Preparing imidazolium salts of formula (II) comprises reducing 1,3-disubstituted-2-alkoxyimidazolium salts of formula (I) with hydrides and/or hydride donors. Either R1-R5 : H, 1-20C-alkyl, 2-20C-alkenyl with one or more double bonds, 2-20C-alkynyl with one or more triple bonds or optionally partially or completely saturated 3-10C-cycloalkyl (optionally substituted with 1-10C-alkyl); or R1R2, R1R3 or R3R4 bounded by single-, double- or triple-bonds : 3-8-membered ring to form bi-, tri- or poly-cyclic cations, where R1-R5 in any position are partially or completely substituted by halogen (preferably F, Cl, Br or I) or in any position is partially substituted by CN or NO 2, a carbon atom of one or more substituents of R1-R5 is optionally substituted by atom and/or atom groups comprising -O-, -C(O)-, -C(O)O-, -S-, -S(O)-, -SO 2-, -SO 3-, -N=, -N=N-, -NH-, -NR1a-, -PR1a-, -P(O)R1a, -P(O)R1a-O-, -O-P(O)R1a-O- or -P(R1a) 2=N-, and R1a is not fluorinated, partially or perfluorinated 1-6C-alkyl, saturated or partially unsaturated 3-7C-cycloalkyl, optionally substituted phenyl or optionally substituted heterocycle; A ->F ->, Cl ->, Br ->, I ->, CN ->, [ClO 4] ->, [BF 4] ->, [BF zR(f) 4 - z] ->, [BF z(CN) 4 - z] ->, [B(CN) 4] ->, [B(C 6F 5) 4] ->, [B(OR6) 4] ->, [N(CF 3) 2] ->, [N(CN) 2] ->, [AlCl 4] ->, [SbF 6] ->, [SiF 6] ->, [R6SO 3] ->, [R(f)SO 3] ->, [(R(f)SO 2) 2N] ->, [(R(f)SO 2) 3C] ->, [(FSO 2) 3C] ->, [R6CH 2OSO 3] ->, [R6C(O)O] ->, [R(f)C(O)O] ->, [CCl 3C(O)O] ->, [(CN) 3C] ->, [(CN) 2CR6] ->, [(R6O(O)C) 2CR6] ->, [P(C nF 2 n + 1 - mH m) yF 6 - y] ->, [P(C 6F) yF 6 - y] ->, [R6 2P(O)O] ->, [R6P(O)O 2] 2> ->, [(R6O) 2P(O)O] ->, [(R6O)P(O)O 2] 2> ->, [(R6O)(R6)P(O)O] ->, [R(f) 2P(O)O] ->or [R(f)P(O)O 2] 2> ->, where A ->contains at least two substituents R(f), and at least two R6, in which R(f) are bounded together by single or double bonds to form 3-8 membered ring, and R6 are bounded together by single or double bonds to form 3-8 membered ring; R(f) : perfluorinated and optionally branched 1-20C-alkyl, perfluorinated and optionally branched 2-20C-alkenyl with one or more double bonds, perfluorinated phenyl and optionally partially or completely saturated 3-7C-cycloalkyl, which is optionally substituted by perfluoroalkyl, where a carbon atom or two non-adjacent carbon atoms of R(f) are optionally substituted by atoms and/or atom groups comprising -O-,-C(O)-, -S-,-S(O)-,-SO 2-, -N=, -N=N-,-NR1a-, -PR1a-, -P(O)R1a, R1a-O-SO 2- or R1a-OC(O)-; R6 : H, linear or branched 1-20C-alkyl, 2-20C-alkenyl with one or more double bonds, 2-20C-alkynyl with one or more triple bonds or optionally partially or completely saturated 3-10C-cycloalkyl, which is optionally substituted with 1-10C-alkyl, where R6 is partially substituted by CN ->or NO 2-, F ->, Cl ->, Br ->or I ->, and a carbon atom of R6 are optionally substituted by atoms and/or atom groups comprising -O-, -C(O)-, -C(O)O-, -S-, -S(O)-, -SO 2-, -SO 3-, -N=, -N=N-, -NH-, -NR1a-, -PR1a- and -P(O)R1a, -P(O)R1a-O- or -O-P(O)R1a-O-, -P(R1a) 2=N-, -C(O)NH-, -C(O)NR1a, -SO 2NH- or -SO 2NR1a-; n : 1-20; m, z : 0-3; and y : 0-4. [Image].

Description

The The present invention relates to a process for producing 1,3-disubstituted Imidazolium salts by reduction of 1,3-disubstituted 2-Alkoxyimidazoliumsalzen and the use of the imidazolium salts thus prepared.

imidazolium and their preparation are known from the literature. It deals These are important connections, on the one hand as Ionian Liquids are used, on the other hand, as a precursor of N-heterocyclic carbenes and their metal complexes serve. The carbenes themselves can act as nucleophilic organ catalysts be used. Metal complexes of N-heterocyclic carbenes can be used as metal catalysts.

Ionic liquids or liquid salts are ionic species consisting of an organic cation and usually an inorganic anion. They contain no neutral molecules and usually have a melting point less than 373 K. The prior art discloses a large number of compounds which are used as ionic liquids. For example, solvent-free ionic liquids have been disclosed in a number of US patents, including U.S. Patent Nos. 3,846,675, 4,769,865, 4,348,859, 3,748,859, 3,748,865, and 3,700,657 US 2,446,331 . US 2,446,339 and US 2,446,350 ,

Development in the field of ionic liquids has progressed further in recent years and some reviews have been published on this topic ( Ionic Liquids: R. Sheldon "Catalytic Reactions in Ionic Liquids", Chem. Commun. 2001, 2399-2407 ; MJ Earle, KR Seddon "Ionic liquids. Green solvent for the future ", Pure Appl. Chem. 2000, 72, 1391-1398 ; P. Wasserscheid, W. Keim "Ionic Liquids - Novel Solutions for Transition-Metal Catalysis," Angew. Chem. 2000, 112, 3926-3945 ; T. Welton "Room temperature ionic liquids. Solvents for synthesis and catalysis ", Chem. Rev. 1999, 99, 2071-2083 , N-Heterocyclic Carbenes: AJ Arduengo, III "Looking for Stable Carbenes: The Difficulty in Starting Anew", Acc. Chem. Res. 1999, 32, 913-921 ; D. Bourissou; O. Guerret, FP Gabbaï, G. Bertrand, "Stable Carbenes" Chem. Rev. 2000, 100, 39-91 , Organ catalysis: V. Nair, S. Bindu, V. Sreekumar, Angew. Chem. 2004, 116, 5240-5245 , Catalysis with N-Heterocyclic Carbene Metal Complexes: WA Herrmann, "N-Heterocyclic Carbenes: A New Approach in Organometallic Catalysis," Angew. Chem. 2002, 114, 1342-1363 .)

The Preparation of unsymmetrically substituted imidazolium salts is already described in the literature, however, is a targeted and simple Production possibility of in particular asymmetrical diaryl-substituted imidazolium salts are still difficult.

Chen at al. describe in Organometallics, 2000, 19, 5133 the preparation of imidazolium salts by two-fold substitution on the nitrogen atoms starting from imidazole. However, this is only possible if the second substituent is an alkyl radical. An arylation of 1-aryl or 1-alkylimidazole has only been observed in strongly electron-deficient aromatics under drastic conditions (150-180 ° C).

The preparation starting from bisimines by introduction of a Cl fragment, however, is described in three different ways: on the one hand by the use of carcinogenic (α-chloromethyl) ethyl ether ( Arduengo III et al. in Tetrahedron, 1999, 55, 14523 ), on the other hand by means of expensive silver salts as in WO 2004/007465 A1 disclosed or with formaldehyde under acidic conditions ( Jafarpour et al. in J. Organomet. Chem. 2000, 606, 49 ). However, the targeted preparation of unsymmetrically substituted 1,2-diarylbisimines still poses major problems until today, since in the synthesis a statistical distribution of the various substituents on the nitrogen atoms occurs.

So will in US 5,077,414 discloses the one-pot synthesis of paraformaldehyde, primary amine and glyoxal under acidic conditions. However, in the case of two different amines, this course of the reaction yields a random mixture of the N-substituted imidazolium salts.

For example, another way to prepare the imidazolium salts is described Wanzlick et al. in Angew. Chem. 1968, 80, 154 or Pesch et al. in Eur. J. Org. Chem. 2004, 9, 2025 , These are the desulfurization of imidazoline-2-thiones by acidic oxidation with nitric acid or peracids. A disadvantage of these synthetic routes is that they can only be carried out with insensitive substrates.

Also known is the reduction of alkylthioimidazolium salts to imidazolium salts ( Morel in Syn. Lett. 2003, 14, 2167 ).

adversely however, in the two last-mentioned synthetic routes, that is generally the synthesis unfavorable starting from 1,3-diarylimidazole-2-thionen is, as mixed-substituted 1,3-diarylimidazole-2-thiones by Simple arylamination reactions can not be produced.

Fürstner et al. in a 6-step synthesis also unsymmetrical diaryl-substituted representatives ( Fürstner et al. in Chem. Commun. 2006, 2176 ). However, this method is not generally applicable, since, for example, Dipyridoimidzoliumsalze and other fused Imidazoliumsalze are not representable in this way. In addition, all substituents must be used as primary amines. In the synthesis of compounds containing several imidazolium units, very polar, salt-like compounds are thus already obtained in an early synthesis step, which can be problematic for the solubility and further reactions.

Next The disadvantages already mentioned are those described in the literature Process for the preparation of imidazolium salts to the disadvantage that the synthesis routes are expensive and in particular the production unsymmetrically substituted, for example asymmetrically 1,3-diarylsubstituierter Imidazolium salts not possible or only with enormous effort is. Therefore, there is a constant need for one as possible general, d. H. regardless of the type of if necessary different substituents, and simple methods of preparation of imidazolium salts, which also in principle on an industrial scale can be used.

The Object of the present invention was therefore a simple and generally applicable, d. H. regardless of the type of optionally different substituents, process for the preparation of imidazolium salts. In particular, the invention was The object of the invention is a method of producing unbalanced substituted imidazolium salts such as unsymmetrical 1,3-diaryl substituted imidazolium salts to provide, which in particular the disadvantages of the previously described Does not have methods.

worin,
die Substituenten R¹, R², R³, R⁴ und R⁵ jeweils unabhängig voneinander die Bedeutung von Wasserstoff, geradkettiges oder verzweigtes Alkyl mit 1-20 C-Atomen, geradkettiges oder verzweigtes Alkenyl mit 2-20 C-Atomen und einer oder mehreren Doppelbindungen, geradkettiges oder verzweigtes Alkinyl mit 2-20 C-Atomen und einer oder mehreren Dreifachbindungen, oder
gesättigtes, teilweise oder vollständig ungesättigtes Cycloalkyl mit 3-10 C Atomen, welches mit Alkylgruppen mit 1-10 C-Atomen substituiert sein kann, haben,
wobei ein oder mehrere Substituenten R¹, R², R³, R⁴ oder R⁵ teilweise in beliebiger Position oder vollständig durch Halogen oder teilweise in beliebiger Position durch CN oder NO₂ substituiert sein können,
und Halogen ausgewählt ist aus F, Cl, Br und I,
wobei im Falle der genannten aliphatischen Substituenten die Substituenten R¹ und R², R¹ und R³ sowie R³ und R⁴ auch jeweils unabhängig voneinander durch Einfach-, Doppel- oder Dreifachbindungen miteinander verbunden sein können, sodass sie jeweils gemeinsam unabhängig voneinander einen drei- bis achtgliedrigen Ring bilden und dass bi-, tri- oder polycyclische Kationen entstehen,
und wobei ein Kohlenstoffatom eines oder mehrerer Substituenten R¹, R², R³, R⁴ und R⁵, durch Atome und/oder Atomgruppierungen, ausgewählt aus der Gruppe -O-, -C(O)-, -C(O)O-, -S-, -S(O)-, -SO₂-, -SO₃-, -N=, -N=N-, -NH-, -NR'-, -PR'-, -P(O)R', -P(O)R'-O-, -O-P(O)R'-O-, und -P(R')₂=N- ersetzt sein können, wobei R' nicht fluoriertes, teilweise oder perfluoriertes Alkyl mit 1-6 C-Atomen, gesättigt oder teilweise ungesättigtes Cycloalkyl mit 3-7 C-Atomen, unsubstituiertes oder substituiertes Phenyl oder unsubstituierter oder substituierter Heterocyclus ist,
und
A^– ausgewählt wird aus der Gruppe bestehend aus:
F^–, Cl^–, Br^–, I^–, CN^–, [ClO₄]^–, [BF₄]^–, [BF_zR^F _4-z]^–, [BF_z(CN)_4-z]^–, [B(CN)₄]^–, [B(C₆F₅)₄]^–, [B(OR⁶)₄]^–, [N(CF₃)₂]^–, [N(CN)₂]^–, [AlCl₄]^–, [SbF₆]^–, [SiF₆]^–, [R⁶SO₃]^–, [R^FSO₃]^–, [(R^FSO₂)₂N)]^–, [(R^FSO₂)₃C)]^–, [(FSO₂)₃C]^–, [R⁶CH₂OSO₃]^–, [R⁶C(O)O]^–, [R^FC(O)O]^–, [CCl₃C(O)O]^–, [(CN)₃C]^–, [(CN)₂CR⁶]^–, [(R⁶O(O)C)₂CR⁶], [P(C_nF_2n+1-mH_m)_yF_6-y]^–, [P(C₆F)_yF_6-y]^–, [R⁶ ₂P(O)O]^–, [R⁶P(O)O₂]^2–, [(R⁶O)₂P(O)O]^–, [(R⁶O)P(O)O₂]^2–, [(R⁶O)(R⁶)P(O)O]^–, [R^F ₂P(O)O]^–, [R^FP(O)O₂]^2–,
wobei die Substituenten R^F jeweils unabhängig voneinander die Bedeutung von perfluoriertes und geradkettiges oder verzweigtes Alkyl mit 1-20 C-Atomen, perfluoriertes und geradkettiges oder verzweigtes Alkenyl mit 2-20 C-Atomen und einer oder mehreren Doppelbindungen, perfluoriertes Phenyl und gesättigtes, teilweise oder vollständig ungesättigtes Cycloalkyl mit 3-7 C-Atomen, das mit Perfluoralkylgruppen substituiert sein kann,
wobei in einem Anion A^–, das mindestens zwei Substituenten R^F enthält, die Substituenten R^F durch Einfach- oder Doppelbindungen miteinander verbunden sein können, sodass sie gemeinsam einen drei- bis achtgliedrigen Ring bilden,
und
wobei ein Kohlenstoffatom oder zwei nicht benachbarte Kohlenstoffatome des Substituenten R^F durch Atome und/oder Atomgruppierungen, ausgewählt aus der Gruppe -O-, -C(O)-, -S-, -S(O)-, -SO₂-, -N=, -N=N-, -NR'-, -PR'- und -P(O)R'- ersetzt sein können oder eine Endgruppe R'-O-SO₂- oder R'-OC(O)-besitzen können, wobei R' die zuvor genannte Bedeutung hat
und
wobei die Substituenten R⁶ jeweils unabhängig voneinander die Bedeutung von Wasserstoff, geradkettiges oder verzweigtes Alkyl mit 1-20 C-Atomen,
geradkettiges oder verzweigtes Alkenyl mit 2-20 C-Atomen und einer oder mehreren Doppelbindungen,
geradkettiges oder verzweigtes Alkinyl mit 2-20 C-Atomen und einer oder mehreren Dreifachbindungen,
gesättigtes, teilweise oder vollständig ungesättigtes Cycloalkyl mit 3-7 C-Atomen, das durch Alkylgruppen mit 1-6 C-Atomen substituiert sein kann,
wobei die Substituenten R⁶ teilweise durch CN^–, NO₂ ^–, F^–, Cl^–, Br^– oder I^– substituiert sein können,
wobei in einem Anion A^–, das mindestens zwei Substituenten R⁶ enthält, die Substituenten R⁶ durch Einfach- oder Doppelbindungen miteinander verbunden sein können, sodass sie gemeinsam einen drei- bis achtgliedrigen Ring bilden,
und
wobei ein Kohlenstoffatom des R⁶, durch Atome und/oder Atomgruppierungen, ausgewählt aus der Gruppe -O-, -C(O)-, -C(O)O-, -S-, -S(O)-, -SO₂-, -SO₃-, -N=, -N=N-, -NH-, -NR'-, -PR'- und -P(O)R'-, -P(O)R'O-, -OP(O)R'O-, -PR'₂=N-, -C(O)NH-, -C(O)NR'-, -SO₂NH- oder -SO₂NR'- ersetzt sein können, wobei R' die zuvor genannte Bedeutung hat
und die Variablen n, m, y und z jeweils ganze Zahlen sind, und
n 1 bis 20,
m 0, 1, 2 oder 3,
y 0, 1, 2, 3 oder 4,
z 0, 1, 2 oder 3 bedeuten.These objects are achieved by a process for the preparation of imidazolium salts of the general formula (II) by reduction of 1,3-disubstituted 2-alkoxyimidazolium salts of the general formula (I) with hydrides and / or hydride transfer agents,

wherein,
the substituents R ¹ , R ² , R ³ , R ⁴ and R ⁵ each independently represent the meaning of hydrogen, straight-chain or branched alkyl having 1-20 C atoms, straight-chain or branched alkenyl having 2-20 C atoms and one or a plurality of double bonds, straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, or
saturated, partially or completely unsaturated cycloalkyl having 3-10 C atoms which may be substituted by alkyl groups having 1-10 C atoms,
wherein one or more substituents R ¹ , R ² , R ³ , R ⁴ or R ^{5 may be} partially substituted in any position or completely by halogen or partially in any position by CN or NO ₂ ,
and halogen is selected from F, Cl, Br and I,
wherein in the case of said aliphatic substituents, the substituents R ¹ and R ² , R ¹ and R ³ and R ³ and R ⁴ may each be independently connected to each other by single, double or triple bonds, so that they each independently together form a three- to eight-membered ring and that bi-, tri- or polycyclic cations are formed,
and wherein a carbon atom of one or more substituents R ¹ , R ² , R ³ , R ⁴ and R ^{5 is} substituted by atoms and / or atomic groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'-, -P (O) R ', -P (O) R'-O-, -OP (O) R'-O-, and -P (R') ₂ = N- may be substituted, where R 'is not fluorinated, partially or perfluorinated alkyl having 1-6 C atoms, saturated or partially unsaturated cycloalkyl having 3-7 C atoms, unsubstituted or substituted phenyl or unsubstituted or substituted hetero cyclus is,
and
A ^{- is} selected from the group consisting of:
F ^-, Cl ^-, Br ^-, I ^-, CN ^-, [ClO _4] ^-, [BF _4] ^-, [BF _z R ^F _4-z] ^-, [BF _z (CN) _4-z] ^-, [B (CN) ₄ ] ^- , [B (C ₆ F ₅ ) ₄ ] ^- , [B (OR ⁶ ) ₄ ] ^- , [N (CF ₃ ) ₂ ] ^- , [N (CN) ₂ ] ^- , [AlCl ₄ ] ^- , [SbF ₆ ] ^- , [SiF ₆ ] ^- , [R ⁶ SO ₃ ] ^- , [R ^F SO ₃ ] ^- , [(R ^F SO ₂ ) ₂ N)] ^- , [(R ^F SO ₂ ) ₃ C)] ^- , [(FSO ₂ ) ₃ C] ^- , [R ⁶ CH ₂ OSO ₃ ] ^- , [R ⁶ C (O) O] ^- , [R ^F C (O) O] ^-, [CCl ₃ C (O) O] ^-, [(CN) ₃ C] ^- ([(R ⁶ O (O) C) ₂ CR ^6], [P ^-, [(CN) ₂ CR ^6] C _n F _{2n + 1-m} H _m ) _y F _6-y ] ^- , [P (C ₆ F) _y F _6-y ] ^- , [R ⁶ ₂ P (O) O] ^- , [R ⁶ P (O) O ₂ ] ^2- , [(R ⁶ O) ₂ P (O) O] ^- , [(R ⁶ O) P (O) O ₂ ] ^2- , [(R ⁶ O) (R ⁶ ) P (O) O] ^- , [R ^F ₂ P (O) O] ^- , [R ^F P (O) O ₂ ] ^2- ,
where the substituents R ^F each independently represent the meaning of perfluorinated and straight-chain or branched alkyl having 1-20 C atoms, perfluorinated and straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, perfluorinated phenyl and saturated, in part or completely unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by perfluoroalkyl groups,
in an anion A ^- which contains at least two substituents R ^F , the substituents R ^F may be linked to each other by single or double bonds so that they together form a three- to eight-membered ring,
and
wherein one or two non-adjacent carbon atoms of the substituent R ^{F are} substituted by atoms and / or atomic groups selected from the group -O-, -C (O) -, -S-, -S (O) -, -SO ₂ -, -N =, -N = N-, -NR'-, -PR'- and -P (O) R'- may be replaced or an end group R'-O-SO ₂ - or R'-OC (O) may have, where R 'has the meaning given above
and
wherein the substituents R ⁶ each independently of one another denote the meaning of hydrogen, straight-chain or branched alkyl having 1-20 C atoms,
straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds,
straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds,
saturated, partially or completely unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms,
wherein the substituents R ⁶ in part by CN ^-, NO ₂ ^-, F ^-, Cl ^-, Br ^- or I ^- may be substituted,
wherein in an anion A ^- which contains at least two substituents R ⁶ , the substituents R ⁶ may be linked together by single or double bonds so that they together form a three- to eight-membered ring,
and
wherein a carbon atom of R ⁶ , by atoms and / or atomic groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'- and -P (O) R'-, -P (O) R'O- , -OP (O) R'O-, -PR ' ₂ = N-, -C (O) NH-, -C (O) NR'-, -SO ₂ NH- or -SO ₂ NR' - be replaced can, where R 'has the meaning given above
and the variables n, m, y and z are each integers, and
n 1 to 20,
m 0, 1, 2 or 3,
y is 0, 1, 2, 3 or 4,
z is 0, 1, 2 or 3.

Under become fully unsaturated substituents in the context of the present invention also aromatic substituents Understood.

In detail, the collective terms given for the different radicals R have the following meaning:
straight-chain or branched alkyl having 1-20 C atoms: straight-chain or branched hydrocarbon radicals having up to 20 C atoms, preferably C ₁ -C ₁₂ -alkyl, such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert Butyl, pentyl, 1-, 2- or 3-methylbutyl, 1,1-, 1,2- or 1,3-dimethylpropyl, 1-ethylpropyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl and dodecyl and their isomers. Particular preference is given to alkyl radicals having 1-8 C atoms.
straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds: unsaturated, straight-chain or branched hydrocarbon radicals having at least one double bond in any position, preferably C ₂ -C ₁₂ -alkenyl, such as ethenyl, 1- or 2-propenyl, 1-methylethenyl, 1-, 2- or 3-butenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 1-, 2-, 3- or 4-pentenyl , 1-, 2-, 3-, 4- or 5-hexenyl, as well as their isomers and the isomers of heptenyl, octenyl, nonenyl, decenyl, undecenyl and dodecenyl. Particularly preferred are alkenyl radicals having 2-8 C atoms.
straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds: unge saturated, straight-chain or branched hydrocarbon radicals having at least one triple bond in any position, preferably C ₂ -C ₁₂ alkynyl, such as ethynyl, 1- or 2-propynyl, 1-, 2- or 3-butynyl, 1-methyl-2-propynyl , 1-, 2-, 3- or 4-pentynyl, 1-, 2-, 3-, 4- or 5-hexynyl, as well as their isomers and the isomers of heptynyl, octynyl, nonynyl, decynyl, undecynyl and dodecynyl. Particularly preferred are alkynyl radicals having 2-8 C atoms.
saturated, partially or fully unsaturated cycloalkyl having 3 to 10 carbon atoms, which may be substituted by alkyl groups having 1 to 10 carbon atoms: monocyclic, saturated, partially or completely unsaturated, ie aromatic hydrocarbon group having 3 to 10 carbon ring members, preferably with 3 to 7 carbon ring members such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclopenta-1,3-dienyl, cyclohexenyl, cyclohexa-1,3-dienyl, cyclohexa-1,4-dienyl, phenyl, cycloheptenyl, cyclohepta-1 , 3-dienyl, cyclohepta-1,4-dienyl or cyclohepta-1,5-dienyl, which may be substituted by C ₁ -C ₁₀ alkyl groups.

The individual substituents, as described above, independently of one another at any position, may be partially or completely substituted by halogen or partially by CN or NO ₂ , where halogen is selected from the group consisting of F, Cl, Br and I. For example, the number of halogen atoms is in a substituent a maximum of 8, preferably a maximum of 5, more preferably a maximum of 3, most preferably a maximum of 1 and in particular the substituent is not substituted by halogen atoms. The number of CN and NO ₂ groups in a substituent is for example at most 4, preferably at most 2, very particularly preferably at most 1, and in particular the substituent is not substituted by CN or NO ₂ groups.

If the abovementioned substituents are aliphatic substituents, the substituents R ¹ and R ² , R ¹ and R ³ , as well as R ³ and R ^{4 may} also be linked together by single, double or triple bonds, so that they each independently together form a three- to eight-membered, preferably a five- to seven-membered and more preferably a five- to six-membered ring and that bi-, tri- or polycyclic cations arise. These rings may be saturated, unsaturated, conjugated unsaturated or aromatic, preferably the rings are conjugated unsaturated or aromatic.

According to the invention, a carbon atom of one or more substituents R ¹ , R ² , R ³ , R ⁴ and R ^{5 is} substituted by atoms and / or atom groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'-, -P (O) R ', -P (O) R'-O-, -OP (O) R'-O-, and -P (R') ₂ = N-, where R 'is non-fluorinated, partially or perfluorinated Alkyl having 1-6 C atoms, saturated or partially unsaturated cycloalkyl having 3-7 C atoms, unsubstituted or substituted phenyl or unsubstituted or substituted heterocycle, wherein the terms alkyl and cycloalkyl have the abovementioned meaning. Heterocycle is understood as meaning five- to nine-membered, preferably five- to six-membered, oxygen, nitrogen and / or sulfur-containing ring systems, for example 2- or 3-furyl, 2- or 3-thienyl, 1-, 2- or 3-pyrrolyl , 1-, 2-, 4- or 5-imidazolyl, 3-, 4- or 5-pyrazolyl.

According to the invention, the salt contains an anion selected from the group consisting of F ^-, Cl ^-, Br ^-, I ^-, CN ^-, [ClO _4] ^-, [BF _4] ^-, [BF _z R ^F _4-z ] ^- , [BF _z (CN) _4-z ] ^- , [B (CN) ₄ ] ^- , [B (C ₆ F ₅ ) ₄ ] ^- , [B (OR ⁶ ) ₄ ] ^- , [N (CF ₃ ) ₂ ] ^- , [N (CN) ₂ ] ^- , [AlCl ₄ ] ^- , [SbF ₆ ] ^- , [SiF ₆ ] ^- , [R ⁶ SO ₃ ] ^- , [R ^F SO ₃ ] ^- , [ (R ^F SO ₂ ) ₂ N)] ^- , [(R ^F SO ₂ ) ₃ C)] ^- , [(FSO ₂ ) ₃ C] ^- , [R ⁶ CH ₂ OSO ₃ ] ^- , [R ⁶ C ( O) ^- , [R ^F C (O) O] ^- , [CCl ₃ C (O) O] ^- , [(CN) ₃ C] ^- , [(CN) ₂ CR ⁶ ] ^- , [(R ⁶ O (O) C) ₂ CR ^6], [P (C _n F _{2n + 1-m} H _{m) y} F _6-y] ^-, [P (C ₆ F) _y F _6-y] ^-, [ R ⁶ ₂ P (O) O] ^- , [R ⁶ P (O) O ₂ ] ^2- , [(R ⁶ O) ₂ P (O) O] ^- , [(R ⁶ O) P (O) O ₂ ] ^2- , [(R ⁶ O) (R ⁶ ) P (O) O] ^- , [R ^F ₂ P (O) O] ^- , [R ^F P (O) O ₂ ] ^2- .

Preferred anions A ^- are F ^- , Cl ^- , Br ^- , I ^- , CN ^- , [ClO ₄ ] ^- , [BF ₄ ] ^- , R ⁶ CH ₂ OSO ₃ ] ^- , [SbF ₆ ] ^- , [PF ₆ ] ^-, and particularly preferably Cl ^-, Br ^-, I ^-, [BF _4] ^-, [PF _6] ^-.

The substituents R ^F can each independently of one another denote the meaning of perfluorinated and straight-chain or branched alkyl having 1-20 C atoms, perfluorinated and straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, perfluorinated phenyl and saturated, in part or fully unsaturated cycloalkyl having 3-7 C atoms which may be substituted by perfluoroalkyl groups, wherein the terms alkyl, alkenyl and cycloalkyl have the abovementioned meaning.

In principle, it is possible that an anion A ^- , which contains at least two substituents R ^F , the substituents R ^F may be connected to each other by single or double bonds, so that they are together a three- to eight-membered, preferably a five- to seven-membered and more preferably form a five- to six-membered ring.

Furthermore, a carbon atom or two non-adjacent carbon atoms of the substituent R ^F can be selected from atoms and / or atomic groups selected from the group -O-, -C (O) -, -S-, -S (O) -, -SO ₂ -, -N =, -N = N-, -NR'-, -PR'- and -P (O) R'- be replaced or an end group R'-O-SO ₂ - or R'-OC (O) - may have, where R 'has the meaning given above.

The substituents R ⁶ can each independently of one another denote the meaning of hydrogen, straight-chain or branched alkyl having 1-20 C atoms, straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms, be. The terms alkyl, alkenyl, alkynyl and cycloalkyl have the abovementioned meaning.

Furthermore, the substituents R ^{6 can be} partially substituted by CN ^- , NO ₂ ^- and halogen ^- , wherein halogen has the abovementioned meaning.

In principle, it is possible that an anion A ^- containing at least two substituents R ⁶ , the substituents R ⁶ may be connected to each other by single or double bonds, so that they are together a three- to eight-membered, preferably a five- to seven-membered and more preferably form a five- to six-membered ring.

Furthermore, a carbon atom of the substituent R ⁶ can be selected from atoms and / or atomic groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'- and -P (O) R'-, -P (O) R'O- , -OP (O) R'O-, -PR ' ₂ = N-, -C (O) NH-, -C (O) NR'-, -SO ₂ NH- or -SO ₂ NR' - be replaced where R 'has the meaning given above.

The Variables n, m, y and z are each integers, where n is 1 to 20, m is 0, 1, 2 or 3, y is 0, 1, 2, 3 or 4 and z is 0, 1, 2 or 3 is.

The Reduction of the compound of general formula (I) is done by Hydrides such as lithium hydride, sodium hydride, potassium hydride, Calcium hydride, borohydride where hydrides are also complex hydrides such as sodium borohydride, zinc borohydride, sodium cyanoborohydride, Sodium trimethoxyborohydride, tetramethylammonium triacetoxyborohydride, Lithium tri (sec-butyl) borohydride (L-Selectride), sodium tri (sec-butyl) borohydride (Na-Selectride), potassium tri (sec-butyl) borohydride (K-Selectride), alkali metal aluminum hydrides such as lithium aluminum hydride, lithium tri (tert-butoxy) aluminum hydride or aluminum hydrides such as diisobutylaluminum hydride, but especially sodium borohydride and sodium trimethoxyborohydride. Other hydride carriers such as diisopinocampheyl chloroborane, Alpine borane or Hantzsch esters are possible. Of course can also be any mixtures of said hydrides and hydride transfer agents are used. Prefers However, only a hydride or a hydride is used.

In the methods according to the invention are customary 1 to 10 equivalents per mole of a compound of formula (I) used on reducing agent per transferable hydride. Usually the addition of the reducing agent takes place in one or more small portions, but it can also be done continuously.

The preparation of uronium salts from ureas is in WO 2004/106287 A1 described. This document with its complete disclosure is explicitly referenced at this point.

The simple, targeted representation of unsymmetrical diaryl-substituted imidazoline-2-ones is after T. Hafner, D. Kunz, Synthesis 2007, 1403 possible.

Usually the process according to the invention takes place in one suitable solvents. Such solvents are, for example, nitriles having 2 to 4 carbon atoms, alcohols with 1 to 5 C atoms, water, ethers, cyclic ethers and mixtures the said solvent. Preferably, the inventive Procedure, however, carried out only in a solvent.

The Reaction temperature is for example from -50 to 80 ° C, preferably at -35 to 30 ° C.

The Reaction is usually at atmospheric pressure carried out. Of course, the reaction can also carried out under vacuum or at overpressure become.

According to the method according to the invention, simple and generally applicable, ie. h un depending on the nature of the substituents, produce both symmetrically and asymmetrically substituted imidazolium salts.

In a particular embodiment of the invention Process become asymmetrically 1,3-disubstituted imidazolium salts produced. In particular, it is by the invention Process possible, unsymmetrical 1,3-diarylsubstituierte To produce imidazolium salts.

One Another object of the present invention is the use produced by the process according to the invention Imidazolium salts as ionic liquids and as precursors to carbenes.

The following examples are intended to illustrate the invention but not to limit it to these examples:
The preparative work was carried out partly with exclusion of oxygen and moisture in an inert gas atmosphere using the Schlenk technique. The protective gas used was argon 4.6 (Messrs. Messer Group GmbH), which was finely purified with activated charcoal, a heated CuO catalyst (BASF SE) and 4 Å molecular sieve. The glassware used was heated before use in a fine vacuum (<10 ^-3 mbar) with a hot air blower and then fumigated with argon. Solvents used were prepared according to standard methods ( WLF Armarego, CLL Chai, "Purification of Laboratory Chemicals", 5th Ed., Butterworth-Heinemann (Elsevier), Amsterdam, 2003 ), degassed and saturated with argon. Solvent transfer was by septum cannula technique. The degassing of the deuterated solvent was carried out by freezing the substance with liquid nitrogen and evacuating the supernatant gas space. Glass frits or Celite columns were used to filter suspensions. The handling of solids was carried out in a filled with nitrogen as an inert gas glove box from MBraun. Commercially available chemicals were purchased from Acros, Sigma Aldrich and Fisher Scientific.

The nuclear resonance spectra were recorded on a Bruker ARX250, Broker DRX300 or Bruker DRX500 spectrometer. The calibration of the ¹ H-NMR spectra is carried out internally by the residual proton signals of the deuterated solvents: [D ₇ ] -THF δ = 1.73, 3.58, [D ₂ ] -acetonitrile δ = 1.93, [D ₅ ] -DMSO δ = 2.49, [D ₁ ] -dichloromethane δ = 5.32. ¹³ C NMR spectra were recorded with broadband decoupling. Here the calibration is carried out by the displacement of the solvent signals: [D ₈ ] -THF δ = 25.5, 67.7, [D ₆ ] -DMSO δ = 39.5, [D ₃ ] acetonitrile δ = 1.39, 118.7, [D ₂ ] -dichloromethane δ = 54.0. Abbreviations for the fine structures of the signals: s = singlet, d = doublet, t = triplet, q = quartet and their combinations, and m = multiplet. The suffix br indicates a broad signal. The assignment of the signals was carried out by means of suitable 2D experiments. Infrared spectra were recorded on a Bruker Equinox 55 FT-IR spectrometer. Abbreviations used for the intensity of the bands: vs = very strong, s = strong, m = middle, w = weak. The elemental analyzes were carried out by the Microanalytical Laboratory of the Chemical Institutes of Heidelberg University. MS spectra were recorded on a Jeol JMS-700 instrument, a Finnigan TSQ 700 triple quadrupole mass spectrometer, or on a Bruker Apex Qe Apollo II FT-ICR instrument by the mass spectrometry department of the University of Heidelberg's Institute of Organic Chemistry. The determination of the melting and decomposition points was carried out in a glass capillary in a melting point determination apparatus (Melting Point B 540) from Büchi (Dr. Tottoli. The values are not corrected.

example 1

Synthesis of 6-dimethylamino-2,10-di-tert-butyl-dipyrido [1,2-c; 2 ', 1'-e] imidazolium chloride (1a)

In a heated three-necked flask with stirrer and pressure relief valve under protective gas atmosphere 100 ml of abs. Submitted toluene. Under ice-cooling, 4.75 ml (4.49 g, 61.5 mmol) of N, N-dimethylformamide (DMF) and 4.80 ml (7.09 g, 55.9 mmol) of oxalyl chloride were added. When gas evolution ceased, 15.0 g (55.9 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine was added. The mixture turned color immediately yellow and it fell out after a short time a green solid. After 20 minutes, 3.9 ml (2.8 g, 28 mmol) of triethylamine were added. The dark green suspension was stirred for one hour at 0 ° C and then warmed to room temperature. The solid was filtered off immediately, washed with 1000 ml of toluene and then dried in vacuo. The color changed from green to yellow. The storage of the crude product is carried out under inert gas.

For purification, the solid was dissolved in about 300 ml of water and adjusted with ice cooling with cold, aqueous concentrated sodium hydroxide solution to pH = 11. The precipitated starting material 4,4'-di-tert-butyl-2,2'-bipyridine was extracted three times with 750 ml of diethyl ether and could be used again for the reaction. The aqueous phase was adjusted to pH = 5 with dilute hydrochloric acid and the solvent was removed on a rotary evaporator. Subsequently, the solid was dried in an oil pump vacuum. To remove the inorganic components, the product was dissolved several times in acetone, filtered, and the solvent was removed to give the product as a yellow solid, which was stored under inert gas.

Yield: 15.9 g (79%) of 1a. 2.84 g (15%) of 4,4'-di-tert-butyl-2,2'-bipyridine could be reisolated.

¹ H-NMR (250 MHz, DMSO-d ₆ ): δ = 1.39 (s, 18H, C (CH ₃ ), 3.11 (s, 6H, N (CH ₃ ) ₂ ), 7.63 (br d, ³ J = 7.4 Hz, 2H, H-3, H-9), 8.60 (m, 4H, H-1, H-4, H-8, H-11) ¹³ C-NMR (75 MHz, DMSO-d ₆ ) : δ = 30.1 (C ( C H ₃ )), 35.0 ( C (CH ₃ )), 39.7 (N (CH ₃ ) ₂ ), 113.4 (C-1, C-11), 118.6 (C-11a, C -11b), 119.3 (C-3, C-9), 120.5 (C-4, C-8), 125.6 (C-6), 144.5 (C-2, C-10).

Melting point: 145 ° C (decomposition)

Mass (HR-ESI ⁺ ):
For C ₂₁ H ₃₀ N ₃ : calculated m / z 324.24342; found m / z 324.24346 [M-Cl] ⁺ .

Elemental analysis:
For C ₂₁ H ₃₀ N ₃ Cl.H ₂ O:
calculates C = 66.73; H = 8.53; N = 11.12.
found C = 66.69; H = 8.50; N = 10.84.

IR (KBr): ν ~ = 3022 (m), 2963 (s), 2867 (m), 1761 (w), 1656 (s), 1624 (m), 15.46 (m), 1477 (m), 1367 ( m), 1302 (m), 1260 (s), 1095 (s), 1052 (s), 804 (m) cm ^-1 .

Crystallization: from THF / hexane Synthesis of 2,10-di-tert-butyl-dipyrido [1,2-c; 2 ', 1'-e] imidazol-6-one (2a)

10.0 g (27.8 mmol) 2,10-di-tert-butyl-6-dimethylamino-dipyrido [1,2-c; 2 ', 1'-e] imidazolium chloride (1a) were dissolved in 200 ml of water and 16.6 g (415 mmol) Added sodium hydroxide. The dark brown solution was Heated under reflux for 1.5 hours. The educated red solid (2a) was after cooling the suspension filtered off immediately, washed with plenty of water and in an oil pump vacuum dried.

4,4'-di-tert-butyl-2,2'-bipyridine, which was obtained as a byproduct, could by sublimation in vacuo separated at 100 ° C and again for the synthesis of 2,10-di-tert-butyl-6-dimethylamino-dipyrido [1,2-c; 2 ', 1'-e] imidazolium chloride (1a) are used.

The residual solid was dissolved in toluene, dried over sodium sulfate, and recrystallized from hot toluene to give product 2a in the form of deep red crystals. Storage takes place under a protective gas atmosphere.

Yield: 6.10 g (74%) of 2a. 1.5 g (15%) of 4,4'-di-tert-butyl-2,2'-bipyridine could be reisolated.

In another approach, the unpurified guanidinium salt 1a was further reacted immediately. A total of 69% of product 2a was obtained over 2 stages and 28% of 4,4-di-tert-butyl-2,2'-bipyridine were reisolated.

¹ H-NMR (300 MHz, THF-d ₈ ): δ = 1.28 (s, 18H, C (CH ₃ ) ₃ ), 6.51 (dd, ³ J = 7.8 Hz, ⁴ J = 1.8 Hz, 2H, H- 3, H-9), 7.31 (br s, 2H, H-1, H-11), 7.65 (dd, ³ J = 7.8 Hz, ⁵ J = 1.8 Hz, 2H, H-4, H-8). ¹³ C-NMR (75 MHz, THF-d ₈ ): δ = 30.3 (C ( C H ₃ ) ₃ ), 35.2 ( C (CH ₃ ) ₃ ), 111.7 (C-1, C-11), 111.8 ( C-2, C-10), 112.0 (C-3, C-9), 121.1 (C-4, C-8), 139.4 (C-6), signal C11a, C11b was not observed.

Melting point: 199 ° C (decomposition)

Elemental analysis:
calculated: C = 76.99; H = 8.16; N = 9.45.
found: C = 76.71; H = 8.20; N = 9.44.

IR (KBr): ν ~ = 3050 (br w), 2959 (m), 2903 (w), 2867 (w), 1679 (vs, C = O), 1443 (m), 1418 (m), 1369 ( m), 1348 (m), 1257 (w), 1126 (w), 661 (m) cm ^-1 .

Crystallization: from hot toluene.

Synthesis of 2,10-di-tert-butyl-6-ethoxy-dipyrido [1,2-c; 2 ', 1'-e] imidazolium tetrafluoroborate (3a)

Into a Schlenk tube, 500 mg (1.69 mmol) of 2,10-di-tert-butyl-dipyrido [1,2-c; 2 ', 1'-e] -imidazol-6-one (2a) in 20 ml of cold acetonitrile ( abs.) Suspended. Then 320 mg (1.69 mmol) of triethyloxonium tetrafluoroborate were added under an inert gas atmosphere and the reaction mixture was stirred at room temperature overnight. The color changed from bright red to dark green. The solvent was removed in an oil pump vacuum, and 2,10-di-tert-butyl-6-ethoxy-dipyrido [1,2-c; 2 ', 1'-e] imidazolium tetrafluoroborate (3a) crystallized as dark green, air and moisture sensitive Solid off.

Yield: 676 mg (97%)

¹ H-NMR (250 MHz, CD ₃ CN): δ = 1.38 (s, 18H, C (CH ₃ ) ₃ ), 1.60 (t, ³ J = 7.0 Hz, 3H, CH ₃ ), 4.68 (q, ³ J = 7.0 Hz, 2H, OCH ₂ ), 7.53 (dd, ³ J = 7.5 Hz, ⁴ J = 1.7 Hz, 2H, H-3, H-9), 8.21 (s, 2H, H-1, H11) , 8.30 (d, ³ J = 7.5 Hz, 2H, H-4, H-8). ¹³ C-NMR (75 MHz, CD ₃ CN): δ = 30.9 (C ( C H ₃ ) ₃ ), 36.5 ( C (CH ₃ ) ₃ ), 76.8 (OCH ₂ ), 113.7 (C-1, C-) 11), 118.1 (C11a, C11b), 119.7 (C-4, C-8), 120.8 (C-3, C-9), 130.0 (C-6), 146.0 (C-2, C-10).

Melting point: 75 ° C (decomposition)

Mass (HR-ESI ⁺ ):
For C ₂₁ H ₂₉ N ₂ O: calculated m / z 325.22744; found m / z 325.22755 [M-BF ₄ ] ⁺ .

Elemental analysis:
For C ₂₁ H ₂₉ N ₂ OBF ₄ .CH ₃ CN:
calculates C = 60.94; H = 7.11; N = 9.27.
found C = 60.90; H = 7.41; N = 9.31.

IR (KBr) ν ~ = 3088 (br w), 2964 (m), 2869 (w), 1681 (s, CO), 1632 (m), 1562 (s), 1125 (s), 1084 (vs), 1033 (s) cm ^-1 .

Crystallization: from acetonitrile

Synthesis of 2,10-di-tert-butyldipyrido [1,2-c; 2 ', 1'-e] imidazolium tetrafluoroborate (4a)

1.84 g (4.45 mmol) of 2,10-di-tert-butyl-6-ethoxy-dipyrido [1,2-c; 2 ', 1'-e] imidazolium tetrafluoroborate (3a) were dissolved in 80 ml of acetonitrile in a round-bottom flask and cooled to -35 ° C. After addition of 42.1 mg (1.11 mmol) of sodium borohydride NaBH ₄ , the color of the reaction solution changed from dark green to yellow-orange within one minute. The mixture was allowed to stand overnight at -35 ° C in the freezer. Subsequently, another 42.1 mg (1.11 mmol) of sodium borohydride was added to the mixture and this was slowly warmed to room temperature. The reaction control was performed ¹ H-NMR by sampling every 8 hours after the addition of NaBH. ₄ If necessary, an additional 42.1 mg (1.11 mmol) of sodium borohydride was added at low temperatures. The solid was filtered off and after removal of the solvent in vacuo, the yellow-orange crude product was dissolved in about 10 ml of acetone and precipitated by the addition of n-hexane. To completely separate the inorganic components, the imidazolium salt was dissolved in 50 ml of dichloromethane and filtered. The solvent was removed in vacuo and product 4a was obtained as a pale yellow solid.

Yield: 830 mg (49%) of 4a. 450 mg (38%) of 4,4'-di-tert-butyl-2,2'-bipyridine could be reisolated.

¹ H-NMR (300 MHz, CD ₃ CN): δ = 1.41 (s, 18H, C (CH ₃ ) ₃ ), 7.58 (d, ³ J = 7.5 Hz, ⁴ J = 1.8 Hz, 2H, H-3 , H-9), 8.30 (s br, 2H, H-1, H-11), 8.56 (dd, ³ J = 7.5 Hz, ⁵ J = 0.9 Hz, 2H, H-4, H-8), 9.54 (s, 1H, H-6). ¹³ C-NMR (75 MHz, CD ₃ CN): δ = 30.4 (C ( C H ₃ ) ₃ ), 36.1 ( C (CH ₃ ) ₃ ), 113.9 (C-1, C-11), 114.5 (C -6), 121.3 (C-3, C-9), 123.4 (C-4, C-8), 147.8 (C-2, C-10).

Melting point: 200 ° C

Mass (ESI ⁺ in CH ₃ CN):
m / z = 280.5 [M-BF ₄ ] ⁺ (100), 266.5 [M-BF ₄ -CH ₃ ] ⁺ (6), 251.5 [M-BF ₄ -2CH ₃ ] ⁺ (4).

Elemental analysis:
For C ₁₉ H ₂₅ N ₂ BF ₄ :
calculated C = 61.98; H = 6.84; N = 7.61.
found C = 61.88; H = 7.05; N = 7.54.

IR (KBr) ν = 3138 (w), 2961 (m), 2869 (w), 1663 (w), 1487 (w), 1369 (w), 1261 (w), 1124 (s), 1084 (vs ), 1053 (s), 1012 (m) cm ^-1 .

Crystallization: from hot ethanol

Example 2

Synthesis of 2-ethoxy-3-phenyl-1-p-tolyl-imidazolium tetrafluoroborate (3b)

In a heated Schlenk tube, 100 mg (0.340 mmol) of 3-phenyl-1-p-tolyl-1,3-dihydroimidazol-2-one (2b) (prepared according to T. Hafner, D. Kunz, Synthesis 2007, 1403 .) And 76.0 mg (0.340 mmol) Triethyloxoniumtetrafluoroborat weighed and 3.0 ml abs. Dichloromethane added. The mixture was stirred at room temperature for three days and the solvent removed in vacuo. What remained was a highly viscous brown oil, which still contained small amounts of solvent.

Yield: quantitative (lt. ¹ H-NMR)

¹ H-NMR (300 MHz, CD ₃ CN): δ = 1.03 (t, ³ J (HH) = 7.0 Hz, 3H, CH ₃ ), 2.45 (s, 3H, CH ₃ -Tol), 4.07 (q, ³ J (HH) = 7.0 Hz, 2H, OCH ₂ ), 7.39 (m, 2H, H-4/5), 7.46 (m, 4H, m-Tol), 7.51 (m, 4H, o-Tol), 7.64 (br m, 5H, o / m / p-Ph). ¹³ C NMR (75 MHz, CD ₃ CN): δ = 15.3 (CH ₃ ), 21.3 (CH ₃ -Tol), 77.0 (OCH ₂ ), 119.5 / 119.7 (C-4/5), 126.0 (o-) Tol), 126.3 (o-Ph), 128.6 (p-Ph), 131.3 (m-Tol), 131.7 (m-Ph), 134.5 (i-Ph), 142.4 (p-Tol), 147.7 (C-2 ). The signal i-Tol is not observed.

Mass (HR-ESI ⁺ ):
For C ₁₈ H ₁₉ N ₂ O: calculated m / z 279.14919; found m / z 279.14943 [M-BF ₄ ] ⁺

IR (KBr): ν ~ = 3157 (w), 3032 (w), 2964 (w), 2920 (w), 2858 (w), 1687 (vs), 1598 (m), 1518 (s), 1502 ( s), 1456 (m), 1427 (s), 1299 (w), 1278 (m), 1225 (m), 1084 (vs br), 919 (m), 819 (m), 758 (m), 693 (m), 664 (m) cm ^-1 .

Synthesis of 1-phenyl-3- (4'-tolyl) imidazolium tetrafluoroborate (4b)

In a 100 ml round bottom flask, 228 mg (0.620 mmol) of 2-ethoxy-3-phenyl-1-p-tolyl-imidazolium tetrafluoroborate were dissolved in 30 ml of acetonitrile and cooled to -35 ° C. Subsequently, 6.5 mg (0.16 mmol) of sodium borohydride were added and slowly warmed to room temperature. Another four portions (6.5 mg each time, 0.16 mmol) of NaBH _{4 were} again added at -35 ° C. each time and heated slowly. The reaction was monitored by ¹ H NMR spectroscopy and depending on the needs further sodium borohydride had to be added in small portions at low temperatures. After complete conversion of the uronium salt, the yellow suspension was filtered and the solvent removed on a rotary evaporator. Subsequently, the residue was washed four times with 30 ml of hot toluene. The crude product is finally extracted with methylene chloride, filtered with a syringe filter and then freed from the solvent for 16 hours in an oil pump vacuum. The product remained as a light brown solid.

Yield: 67 mg (34%)

¹ H-NMR (300 MHz, DMSO-d ₆ ): δ = 2.42 (s, 3H, CH ₃ ), 7.50 (d, ³ J (HH) = 8.0 Hz, 2H, m -tol), 7.63 (m, 1H, p-Ph), 7.71 (m, 2H, m-Ph), 7.79 (m, 2H, o-Ph), 7.90 (d, ³ J (HH) = 8.0 Hz, 2H, o-Tol), 8:53 and 8.55 (2 t, ⁴ J (HH) = 1.6 Hz, 2H, H-4/5), 10.28 (t, ⁴ J (HH) = 1.6 Hz, 2H, H-2). ¹³ C-NMR (75 MHz, DMSO-d ₆ ): δ = 20.6 (CH ₃ -Tol), 121.8 (o-Tol), 121.9 (C-4/5), 122.0 (o-Ph), 130.0 (p-Ph), 130.1 (m-Ph), 130.5 (m-Tol), 132.3 (i-Tol), 134.3 (C-2), 134.7 (i-Ph), 139.9 (p-Tol).

¹ H-NMR (300 MHz, CD ₃ CN): δ = 2.45 (s, 3H, CH ₃ -Tol), 7.47 (m, 2H, m-Tol), 7.49 (m, 2H, o-Tol), 7.67 (m, 5H, o / m / p-Ph), 7.93 (2 t, ⁴ J (HH) = 1.8 Hz, 2H, H-4/5), 9.25 (t, ⁴ J (HH) = 1.8 Hz, 2H, H-2). ¹³ C-NMR (75 MHz, CD ₃ CN): δ = 20.3 (CH ₃ -Tol), 123.5 (o-Tol), 123.6 (C-4/5), 123.7 (o-Ph), 131.5 (m-) Ph), 131.7 (p-Ph), 131.9 (m-Tol), 133.4 (i-Tol), 134.7 (C-2), 135.8 (i-Ph), 142.4 (p-Tol).

Melting point: 135 ° C

Mass (HR-ESI ⁺ ):
For C ₁₆ H ₁₅ N ₂ : calculated m / z 235.12297; found m / z 235.12314 [M-BF ₄ ] ⁺

IR (KBr): ν ~ = 3138 (m), 3100 (m), 3051 (m), 2963 (m), 2923 (m), 2855 (w), 1597 (m), 1553 (s), 1515 ( m), 1495 (m), 1464 (m), 1342 (w), 1306 (m), 1259 (s), 1084 (br vs), 821 (s), 762 (s), 689 (m) cm ^{- 1} .

Elemental analysis:
For C ₁₆ H ₁₅ N ₂ BF _4. 0.8 H ₂ O:
calculates C = 57.11; H = 4.97; N = 8.32.
found C = 57.15; H = 5.22; N = 8.39.

Example 3

2-ethoxy-1,3,4,5-tetramethylimidazolium tetrafluoroborate (3c)

1.40 g (10.0 mmol) of 1,2,3,4-tetramethylimidazolin-2-one (2c) ( Synthesis according to J. Akester, J. Cui, G. Fraenkel, J. Org. Chem. 1997, 62, 431 or T. Kondo, S. Kotachi, Y. Watanabe, J. Chem. Soc., Chem. Commun. 1992, 1318 ) were dissolved in 50 ml of dichloromethane and treated at 0 ° C with 1.89 g (10.0 mmol) of triethyloxonium tetrafluoroborate. The mixture was allowed to warm to room temperature and stir for a further 12 h. Subsequently, the solvent was removed and the residue was recrystallized from hot dichloromethane. After filtering off and drying in an oil pump vacuum and working up the mother liquor, the product 3c was obtained in the form of pink crystals with a yield of 1.94 g (76%).

¹ H NMR (250 MHz, CD ₃ CN): δ = 4.42 (q, ³ J _HH = 7.0 Hz, 2H, OC H ₂ CH ₃ ), 3.66 (s, 6H, NC H ₃ ), 2.13 (s, 6H, = CC H ₃ ), 1.45 (t, ³ J _HH = 7.0 Hz, 3H, OCH ₂ C H ₃ ).

¹ H-NMR (300 MHz, CD ₂ Cl ₂ ): δ = 4.48 (q, ³ J = 7.0 Hz, 2H, OC H ₂ CH ₃ ), 3.52 (s, 6H, NC H ₃ ), 2.16 (s, 6H, = CC H ₃ ), 1.51 (t, ³ J = 7.0 Hz, 3H, OCH ₂ C H ₃ ). ¹³ C-NMR (75 MHz, CD ₂ Cl ₂ , 298 K): δ = 146.3 (C2), 122.2 (C4, C5), 76.0 (O C H ₂ CH ₃ ), 30.5 (N C H ₃ ), 15.4 (OCH ₂ C H ₃ ), 8.3 (= C C H ₃ ).

Elemental analysis:
calculated: C: 42.22 H: 6.69 N: 10.94
Found: C: 42.24 H: 6.80 N: 10.91

1,3,4,5-tetramethylimidazolium tetrafluoroborate (4c)

512 mg (2.00 mmol) of 2-ethoxy-1,3,4,5-tetramethylimidazolium tetrafluoroborate (3c) were suspended with 75.6 mg (2.00 mmol) of sodium borohydride in 10 ml of acetonitrile, where rapid decolorization of the pink suspension was observed. The mixture was stirred for 12 h at room temperature and filtered from the remaining solid. The filtrate was concentrated to dryness and the white solid suspended in 10 ml of dichloromethane. It was filtered from the insoluble salts and the filtrate completely freed from the solvent. This resulted in 105 mg (25%) of the imidazolium salt 4c as a colorless solid.

¹ H-NMR (250 MHz, CD ₂ Cl ₂ ): δ = 9.24 (s, 1H, NC H N), 3.78 (s, 6H, NC H ₃ ), 2.22 (s, 6H, = CC H ₃ ).
¹ H-NMR (250 MHz, CD ₃ CN): δ = 8.30 (s, 1H, NC H N), 3.68 (s, 6H, NCH ₃ ), 2.20 (s, 6H, = CC H ₃ ).

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

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Claims (8)

Process for the preparation of imidazolium salts of general formula (II) by reduction of 1,3-disubstituted 2-alkoxyimidazolium salts of general formula (I) with hydrides and / or hydride transfer agents,

wherein, the substituents R ¹ , R ² , R ³ , R ⁴ and R ^{5 are} each independently the meaning of hydrogen, straight-chain or branched alkyl having 1-20 C atoms, straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, or saturated, partially or fully unsaturated cycloalkyl having 3-10 C atoms, which may be substituted by alkyl groups having 1-10 C atoms , wherein one or more substituents R ¹ , R ² , R ³ , R ⁴ or R ^{5 may be} partially substituted in any position or completely by halogen or partially in any position by CN or NO ₂ , and halogen is selected from F , Cl, Br and I, wherein in the case of said aliphatic substituents, the substituents R ¹ and R ² , R ¹ and R ^3, and R ³ and R ^{4 are} each independently represented by single, double or triple bonds n may be connected together so that they each independently form a three- to eight-membered ring and that bi-, tri- or polycyclic cations formed, and wherein a carbon atom of one or more substituents R ¹ , R ² , R ³ , R ⁴ and R ⁵ , by atoms and / or atomic groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'-, -P (O) R ', -P (O) R'-O-, -OP (O) R'-O-, and -P (R ') ₂ = N- can be replaced, where R' is not fluorinated, partially or perfluorinated alkyl having 1-6 C atoms, saturated or partially unsaturated cycloalkyl with 3- 7 C atoms, unsubstituted or substituted phenyl or unsubstituted or substituted heterocycle, and A ^- is selected from the group consisting of: F ^-, Cl ^-, Br ^-, I ^-, CN ^-, [ClO _4] ^-, [BF ₄ ] ^- , [BF _z R ^F _4-z ] ^- , [BF _z (CN) _4-z ] ^- , [B (CN) ₄ ] ^- , [B (C ₆ F ₅ ) ₄ ] ^- , [B (OR ⁶ ) ₄ ] ^- , [N (CF ₃ ) ₂ ] ^- , [N (CN) ₂ ] ^- , [AlCl ₄ ] ^- , [SbF ₆ ] ^- , [SiF ₆ ] ^- , [R ⁶ SO ₃ ] ^- , [R ^F SO ₃ ] ^- , [(R ^F SO ₂ ) ₂ N)] ^- , [(R ^F SO ₂ ) ₃ C)] ^- , [(FSO ₂ ) ₃ C] ^- , [R ⁶ CH ₂ OSO ₃ ] ^- , [R ⁶ C (O) O] ^- , [R ^F C (O) O] ^- , [CCl ₃ C (O) O] ^- , [(CN) ₃ C] ^- , [(CN) ₂ CR ⁶ ] ^-, [(R ⁶ O (O) C) ₂ CR ^6], [P _y F _6-y (C _n F _{2n + 1-m} H _{m n)]} ^-, [P (C ₆ F) _y F _{6- y} ] ^- , [R ⁶ ₂ P (O) O] ^- , [R ⁶ P (O) O ₂ ] ^2- , [(R ⁶ O) ₂ P (O) O] ^- , [(R ⁶ O) P (O) O ₂ ] ^2- , [(R ⁶ O) (R ⁶ ) P (O) O] ^- , [R ^F ₂ P (O) O] ^- , [R ^F P (O) O ₂ ] ^2- , wherein the substituents R ^{F are} each independently the meaning of perfluorinated and straight-chain or branched alkyl having 1-20 C atoms, perfluorinated and straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, perfluorinated phenyl and saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by perfluoroalkyl groups, wherein i n is an anion A ^- containing at least two substituents R ^F , the substituents R ^F may be linked to each other by single or double bonds so that they together form a three- to eight-membered ring, and wherein one or two non-adjacent carbon atoms of the substituent R ^{F is represented} by atoms and / or atom groups selected from the group -O-, -C (O) -, -S-, -S (O) -, -SO ₂ -, -N =, -N = N-, -NR'-, -PR'- and -P (O) R'- may be replaced or may have an end group R'-O-SO ₂ - or R'-OC (O) -, wherein R 'is the abovementioned Each of the substituents R ⁶ is independently of one another the meaning of hydrogen, straight-chain or branched alkyl having 1-20 C atoms, straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms, wherein the substituents R ⁶ in part by CN ^-, NO ₂ -, F ^-, Cl ^-, Br ^- or I ^- may be substituted, in which an anion a ^-, which contains at least two substituents R ^6, the substituents R ⁶ by single or double bonds with each other may be joined together to form a three- to eight-membered ring, and wherein one carbon atom of R ⁶ is substituted by atoms and / or atomic groups selected from the group -O-, -C (O) -, -C (O) O-, -S-, -S (O) -, -SO ₂ -, -SO ₃ -, -N =, -N = N-, -NH-, -NR'-, -PR'- and -P (O) R'-, -P (O) R'O-, -OP (O) R'O-, -PR _'2 = N-, -C (O) NH-, -C (O) NR' -, -SO ₂ NH- or -SO ₂ NR '- may be replaced, wherein R' has the meaning mentioned above, and the variables n, m, y and z respectively are integers, and n is 1 to 20, m is 0, 1, 2 or 3, y is 0, 1, 2, 3 or 4, z is 0, 1, 2 or 3. Process for the preparation of compounds 4a, 4b or 4c. Process according to Claims 1 to 2, characterized in that 1 to 1 mol of the compound of the formula (I) 4 equivalents of reducing agent can be used. Process according to claims 1 to 3, characterized characterized in that the addition of the reducing agent in one or several small portions as well as continuously. Process according to claims 1 to 4, in which as reducing agent sodium borohydride or sodium trimethoxyborohydride be used. Process according to claims 1 to 5, in which as solvent nitriles with 2 to 4 carbon atoms, alcohols with 1 to 5 C atoms, water, ethers, cyclic ethers and mixtures these solvents are used. Process according to Claims 1 to 6, characterized characterized in that the temperature is between -50 and + 80 ° C lies. Process according to Claims 1 to 7, characterized characterized in that the reaction time is between 10 min and 5 days is.