Synthesis and crystal structures of non-symmetric 1,3-di(alkyloxy)imidazolium salts

Z. Naturforsch. 2017; aop

Markus Jochriem, Christian G. Kirchler, Gerhard Laus*, Klaus Wurst, Holger Kopacka,

Thomas Müller and Herwig Schottenberger

Synthesis and crystal structures of non-symmetric

1

,3-di(alkyloxy)imidazolium salts

https://doi.org/10.1515/znb-2017-0089

2

Results and discussion

Received May 31, 2017; accepted June 29, 2017

Abstract: A series of non-symmetric 1,3-di(alkyloxy)imi- In order to obtain non-symmetric 1,3-di(alkyloxy)imida-

dazolium salts were synthesized by stepwise alkylation zolium salts, a modified strategy was required in con-

of 1-hydroxyimidazole-3-oxide. The quaternary salts were trast to symmetric 1,3-di(alkyloxy)imidazolium salts [1],

subsequently functionalized by bromination in 2-position. namely a stepwise alkylation. The key step was mono-

A 2-azidoimidazolium salt and an imidazoline-2-thione alkylation of 1-hydroxyimidazole-3-oxide by an alkyl

were prepared exemplarily. Crystal structures of two halide (ethyl, allyl, butyl, and benzyl). Thus, one equiva-

2

-bromo-1-alkyloxy-3-methyloxyimidazolium tribromides lent of ethyl bromide converted 1-hydroxyimidazole-3-ox-

and a mercury(II)-thione complex have been determined ide to 1-ethyloxyimidazole-3-oxide (1). Treatment of the

by X-ray diffraction.

resulting zwitterionic liquid 1 with NH PF yielded the

4

6

solid 1-hydroxyimidazolium salt 1a. So far, 1,3-dihydroxy-

Keywords: imidazolium salt; ionic liquid; mercury;

thione; tribromide.

imidazolium salts [3, 4] and 1-alkyl-3-hydroxyimidazolium

[

3] have been described. Salt 1a is therefore a representa-

tive of the new class of 1-alkyloxy-3-hydroxyimidazolium

salts. In the same manner the new liquid N-oxides 2 and

3 were prepared. The intermediate 1-benzyloxyimida-

zole-3-oxide (4) was mentioned in an earlier paper but

1

Introduction

In continuation of our interest in N-(alkyloxy)imi- not isolated [5]. The 1-alkyloxyimidazole-3-oxides 1–4

dazolium salts [1–3], a series of new non-symmetric were subsequently alkylated to yield the non-symmetric

,3-di(alkyloxy)imidazolium salts were synthesized. 1,3-di(alkyloxy)imidazolium salts (Scheme 1). Employing

1

Beside the additional synthetic challenge, the primary dialkyl sulfates or alkyl halides for the second alkyla-

motivation for this endeavor was the high likelihood of tion step, the imidazolium alkyl sulfates 5a, 7, 8, 9a, 10,

such compounds, due to their non-symmetric substitu- and 11a or halides 6a and 12 were obtained. According to

tion patterns, to exhibit lower melting points than their NMR the quaternary salts tend to tenaciously retain water

symmetric congeners and therefore qualify as true Ionic and residual solvents even after prolonged treatment in

Liquids (ILs), even at room temperature. In addition, the vacuum. In fact, this hygroscopic nature of the ILs pre-

quaternary salts and their 2-bromo derivatives would be vented the aquisition of meaningful elemental analyses.

valuable intermediates for further synthetic modifica- In several cases, isolation and purification was accom-

tion. The preparation and structural characterization of plished by ion metathesis of the crude primary product

a transition metal complex with 1,3-di(alkyloxy)imida- to the corresponding crystalline hexafluoridophosphates

zoline-2-thione ligands was also conceived and could be 5b, 6b and 9b. This anion was chosen because the salts

successfully accomplished.

crystallize more readily and are less hygroscopic than the

halides or alkyl sulfates. The hexafluoridophosphate 11b

was obtained directly when the respective Meerwein’s

reagent was used. Ion metathesis also yielded the hydro-

phobic ILs 5c and 11c containing the weakly coordinating

bis(trifluoromethanesulfonyl)amide (‘triflimide’) anion.

Allyl substituents, as in 7, 8, 12, evoke the scenario of

presumable polymerization. However, the reactivity of

N-allyl-functionalized ILs has not yet been explored to

any degree of satisfaction. It seems obvious to continue

the investigation of N-allylimidazolium salts [6] before

*

Corresponding author: Gerhard Laus, Faculty of Chemistry and

Pharmacy, University of Innsbruck, 6020 Innsbruck, Austria,

Fax: +43 512 507 57099, E-mail: gerhard.laus@uibk.ac.at

Markus Jochriem, Christian G. Kirchler, Klaus Wurst,

Holger Kopacka, Thomas Müller and Herwig Schottenberger:

Faculty of Chemistry and Pharmacy, University of Innsbruck,

6020 Innsbruck, Austria

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ꢀ^ꢀ^ꢀ^ꢀ^ꢁꢀM. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium salts

1

2

Scheme 1:ꢀ(a) KOH, MeOH, R X; (b) R X; (c) NH PF , H O; (d) LiTf N, H O-CH Cl ; (e) Br , MeOH-H O, Na CO ; (f) NaN , acetone; (g) S , pyridine,

4

6

2

3

8

Et N; (h) HgCl , MeOH.

3

2

tackling the more challenging N-allyloxyimidazolium the pertinent C–Brꢀ·ꢀ·ꢀ·ꢀBr and Brꢀ·ꢀ·ꢀ·ꢀBr–C angles which

salts. This topic therefore will be deferred to a subsequent are summarized in Table 2. In addition, other red areas

scientific discourse. The quaternary salts described here of the Hirshfeld surface [10] indicate C–Hꢀ·ꢀ·ꢀ·ꢀBr contacts

are N-heterocyclic carbene precursors and are readily which according to Hirshfeld analysis account for 81%

converted to imidazoline-2-thiones [7]. Bromination of the of the total surface of one of the two tribromide anions

hexafluoridophosphates 5b and 9b in aqueous methanol in compound 13a (Fig. 3b), 63% in the second. In 15,

gave 2-bromo derivatives as before [1, 2], but the products C–Hꢀ·ꢀ·ꢀ·ꢀBr contacts amount to 77 and 78% of the total

bear two different alkyloxy groups and appear as crys- surface of the anions. A fingerprint plot shows the char-

talline tribromides 13a and 15. It is noteworthy that 6b acteristic Brꢀ·ꢀ·ꢀ·ꢀBr, Brꢀ·ꢀ·ꢀ·ꢀC and Brꢀ·ꢀ·ꢀ·ꢀH intermolecular

remained a hexafluoridophosphate after conversion to contacts (Fig. 3c). These electrostatic interactions are not

the 2-bromo compound 14, presumably due to lower solu- obvious from a conventional inspection of short contacts.

bility. Exemplarily, the 2-azido derivative 16, the imida- The tribromide ions deviate only slightly from linearity

zoline-2-thione 17, and the mercury(II) complex 18 were with Br3–Br4–Br5 and Br6–Br7–Br8 angles of 179.3 and

prepared.

175.2° in 13a, and 176.7 and 178.6° in 15, respectively. The

The crystal structures of three representative deriva- Br–Br bonds are unsymmetrical, their lengths ranging

tives have been determined by single-crystal X-ray dif- from 2.479 to 2.622 Å. Whereas there are numerous crystal

fraction. Crystallographic data and refinement details structures of networks of polybromides [11], including

are summarized in Table 1. In the crystal structures of tribromides, in the Cambridge Structural Database [12],

2

-bromo-1-ethyloxy-3-methyloxyimidazolium tribromide only a limited number of structures display interactions

(

13a, Fig. 1) and 2-bromo-1-butyloxy-3-methyloxyimidazo- between tribromides and carbon-bound bromine [13–21].

lium tribromide (15, Fig. 2), the two independent ion pairs As expected, the geometry of these Brꢀ·ꢀ·ꢀ·ꢀBr contacts is

exhibit typical Brꢀ·ꢀ·ꢀ·ꢀBr contacts which involve negative determined by the anisotropic distribution of the electron

ring domains and positive end cap domains (‘σ holes’) of density.

Br atoms (Fig. 3a) due to their polarizability [8, 9]. The

Conformational syn and anti isomers of

cations have been

direction of a Brꢀ·ꢀ·ꢀ·ꢀBr contact can then be judged from 1,3-di(alkyloxy)imidazolium

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M. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium saltsꢂ^ꢁ^ꢀ^ꢀ^ꢀꢂ3

Table 1:ꢀCrystallographic data and structure refinement details.

Compound

ꢁꢂa

ꢁ5

ꢁ8

Formula

C H BrN O ꢁ·ꢁBr

C H N O S ꢁ·ꢁCl Hg

ꢆ

ꢃ

ꢄꢅ

ꢆ

ꢇ

ꢈ

ꢄꢉ

ꢆ

ꢇ

ꢆꢉ ꢉꢅ

ꢄꢆꢇꢊ.ꢈꢃ

ꢈ

ꢉ

M_r

ꢉꢃꢄ.ꢈꢅ

ꢉꢈꢊ.ꢈꢋ

Crystal size, mm^ꢇ

ꢅ.ꢄꢃꢁ×ꢁꢅ.ꢄꢋꢁ×ꢁꢅ.ꢄꢉ

ꢅ.ꢇꢄꢁ×ꢁꢅ.ꢄꢋꢁ×ꢁꢅ.ꢅꢇ

ꢅ.ꢄꢋꢁ×ꢁꢅ.ꢄꢄꢁ×ꢁꢅ.ꢅꢌ

Crystal system

Triclinic

Monoclinic

Tetragonal

Space group

Pꢄ

̅

Pꢆ /n

Iꢉ

̅

ꢄ

a, Å

ꢃ.ꢊꢄꢋꢇ(ꢆ)

ꢄꢉ.ꢄꢌꢊꢋ(ꢋ)

ꢄꢉ.ꢋꢄꢇꢉ(ꢌ)

ꢊꢈ.ꢋꢈꢅ(ꢆ)

ꢄꢅꢇ.ꢌꢉꢌ(ꢆ)

ꢄꢅꢅ.ꢊꢋꢅ(ꢆ)

ꢄꢇꢆꢈ.ꢌꢄ(ꢊ)

ꢉ

ꢄꢃ.ꢄꢇꢈꢃ(ꢌ)

ꢄꢅ.ꢌꢊꢄꢌ(ꢇ)

ꢄꢊ.ꢃꢄꢉꢃ(ꢈ)

ꢊꢅ

ꢄꢇ.ꢄꢅꢉꢃ(ꢉ)

b, Å

c, Å

ꢆꢇ.ꢌꢄꢊ(ꢄ)

ꢊꢅ

α, °

β, °

ꢄꢄꢇ.ꢈꢅꢇ(ꢆ)

ꢊꢅ

γ, °

V, Å^ꢇ

Z

ꢇꢄꢆꢋ.ꢃ(ꢆ)

ꢈ

ꢉꢅꢌꢇ.ꢇ(ꢇ)

ꢉ

D_c_a_l_c_d, g cm ^ꢇ

−

ꢆ.ꢇꢄ

ꢆ.ꢅꢈ

ꢆ.ꢅꢆ

−

ꢄ

μ(MoK ), mm

ꢄꢆ.ꢄ

ꢄꢅ.ꢇ

ꢈ.ꢄ

α

F(ꢅꢅꢅ), e

hkl range

ꢈꢃꢉ

ꢄꢈꢋꢃ

ꢆꢇꢈꢉ

−ꢈꢁ≤ꢁhꢁ≤ꢁꢈ

−ꢄꢈꢁ≤ꢁhꢁ≤ꢁꢄꢊ

−ꢄꢆꢁ≤ꢁkꢁ≤ꢁꢄꢆ

−ꢆꢇꢁ≤ꢁlꢁ≤ꢁꢆꢇ

ꢅ.ꢋꢊ

−ꢄꢋꢁ≤ꢁhꢁ≤ꢁꢄꢋ

−ꢄꢋꢁ≤ꢁkꢁ≤ꢁꢄꢋ

−ꢆꢌꢁ≤ꢁlꢁ≤ꢁꢆꢈ

ꢅ.ꢃꢅ

−

ꢄꢌꢁ≤ꢁkꢁ≤ꢁꢄꢌ

ꢄꢌꢁ≤ꢁlꢁ≤ꢁꢄꢌ

−

(

(sinθ)/λ)_m_a_x, Å⁻^ꢄ

ꢅ.ꢃꢆ

ꢈꢊꢆꢋ

Reflections collected

Independent reflections/R_i_n_t

Reflections [Iꢁ>ꢁꢆ σ(I)]

Parameters

ꢄꢌ ꢅꢈꢄ

ꢉꢌ ꢊꢇꢆ

ꢇꢌꢄꢈ/ꢅ.ꢅꢇꢉ

ꢆꢈꢋꢄ

ꢋꢄꢌꢆ/ꢅ.ꢅꢉꢇ

ꢇꢊꢆꢆ

ꢆꢋꢋ

ꢅ.ꢅꢉꢋ/ꢅ.ꢄꢅꢄ

ꢅ.ꢅꢃꢌ/ꢅ.ꢄꢄꢄ

ꢄ.ꢅꢉ

ꢅ.ꢌꢄ/–ꢅ.ꢌꢃ

ꢄꢉꢌꢇꢄꢇꢋ

ꢋꢉꢈꢆ/ꢅ.ꢅꢌꢈ

ꢇꢊꢅꢇ

ꢇꢄꢈ

ꢆꢆꢈ

R /wR indices [Iꢁ>ꢁꢆ σ(I)]

ꢅ.ꢅꢋꢃ/ꢅ.ꢄꢇꢄ

ꢅ.ꢅꢈꢉ/ꢅ.ꢄꢉꢉ

ꢄ.ꢅꢃ

ꢅ.ꢅꢆꢊ/ꢅ.ꢅꢋꢆ

ꢅ.ꢅꢉꢇ/ꢅ.ꢅꢋꢋ

ꢄ.ꢄꢇ

ꢄ

ꢆ

R /wR indices (all data)

ꢄ

ꢆ

Goodness-of-fit on F

−

ꢇ

Δρ_m_a_x_/_m_i_n, e Å

ꢅ.ꢌꢅ/−ꢄ.ꢄꢉ

ꢄꢉꢌꢇꢄꢇꢃ

ꢅ.ꢆꢊ/–ꢅ.ꢌꢄ

ꢄꢉꢌꢇꢄꢇꢌ

CCDC No.

Fig. 1:ꢀCrystal structure of 2-bromo-1-ethyloxy-3-methyloxyimidazo-

lium tribromide (13a). Dashed lines indicate Brꢁ·ꢁ·ꢁ·ꢁBr interactions.

Fig. 2:ꢀCrystal structure of 2-bromo-1-butyloxy-3-methyloxyimidazo-

lium tribromide (1ꢃ). Dashed lines indicate Brꢁ·ꢁ·ꢁ·ꢁBr interactions.

described previously [2] and corroborated by theoreti- structure of 13a adopt both syn and anti conformations.

cal calculations [22]. Interestingly, the alkyloxy sub- The C–Oꢀ·ꢀ·ꢀ·ꢀO–C dihedral angle in the syn conformer is

stituents of the two independent cations in the crystal 1°, whereas in the anti conformer it is 172° (Fig. 4). In

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ꢀ^ꢀ^ꢀ^ꢀ^ꢁꢀM. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium salts

Fig. 4:ꢀConformational isomers identified in the crystal structure of

3a, exhibiting (a) a syn dihedral angle of 1° and (b) an anti dihedral

angle of 172°.

1

The crystal structure of complex 18 was refined as a

-component inversion twin. There were two independ-

2

ent quarter molecules in the asymmetric unit. Mercury

atoms were located at fourfold rotoinversion axes in the

c direction and exhibited distorted tetrahedral coordi-

nation geometries. Four thione groups surround each

mercury(II) ion with Hg1–S1 and Hg2–S2 bond lengths

of 2.563 and 2.576 Å, respectively. To our knowledge, this

is the first crystal structure of a mercury-thione complex

with a 1:4 metal-to-thione ratio. The distorted geometry

Fig. 3:ꢀ(a) Preferred geometry for Brꢁ·ꢁ·ꢁ·ꢁBr interactions. (b) Hirshfeld is reflected by S1–Hg1–S1 angles of 107.1 and 114.3°, and

surface of one of the tribromide ions in 13a. (c) Hirshfeld fingerprint

S2–Hg2–S2 angles of 103.8 and 112.4°. The thione ligand at

Hg1 exhibits a slight positional disorder (not solved) and

shows increased anisotropic displacement parameters for

non-H atoms. The other ligand at Hg2 shows a 3:2 posi-

tional disorder for all atoms, where O, N and C atoms were

ꢁ5 refined isotropically. Only the major component is shown

in Fig. 5. The alkyloxy substituents adopt anti confor-

plot showing characteristic intermolecular contacts.

Table 2:ꢀGeometric parameters of the Brꢁ·ꢁ·ꢁ·ꢁBr contacts (Å, deg).

Compound

ꢁꢂa

Brꢄꢁ·ꢁ·ꢁ·ꢁBrꢇ

ꢇ.ꢇꢈꢌ(ꢄ)

ꢇ.ꢇꢈꢈ(ꢄ)

ꢄꢃꢇ.ꢉ(ꢆ)

ꢌꢈ.ꢈ(ꢄ)

ꢄꢃꢉ.ꢆ(ꢆ)

ꢌꢌ.ꢈ(ꢄ)

ꢇ.ꢇꢅꢉ(ꢄ)

ꢇ.ꢇꢆꢌ(ꢄ)

^m^a^tⁱ^oⁿ^s^wⁱ^t^h^t^o^r^sⁱ^oⁿ^aⁿ^g^l^e^s^o^f¹⁷⁰^aⁿ^d¹⁷²^°^.^T^h^e^H^g^C^l4²

−

Brꢆꢁ·ꢁ·ꢁ·ꢁBrꢃ

Cꢄ–Brꢄꢁ·ꢁ·ꢁ·ꢁBrꢇ

Brꢄꢁ·ꢁ·ꢁ·ꢁBrꢇ–Brꢉ

ꢄꢃꢉ.ꢄ(ꢆ) counter ions are well ordered, exhibiting interatomic

ꢈꢅ.ꢃ(ꢄ)

distances of Hg3–Cl1 and Hg4–Cl2 of 2.461 and 2.499 Å,

a

b

Cꢈ (ꢊ) –Brꢆꢁ·ꢁ·ꢁ·ꢁBrꢃ

Brꢆꢁ·ꢁ·ꢁ·ꢁBrꢃ–Brꢌ

ꢄꢌꢅ.ꢄ(ꢆ)

respectively. The distorted tetrahedral anions display

ꢈꢇ.ꢉ(ꢄ)

Cl1–Hg3–Cl1 angles of 107.1 and 114.3°, and Cl2–Hg4–Cl2

a

b

For 13a; for 1ꢃ.

angles of 106.6 and 115.4°. Crystal structures of other Hg–

imidazolinethione complexes have been reported previ-

contrast, the cations of 15 adopt two different anti con- ously [23–25], they typically involve a 1:2 metal-to-thione

formations in the crystal structure with torsion angles of ratio and additional ligands such as chloride, triflimide or

1

57 and 176°.

acetate.

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M. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium saltsꢂ^ꢁ^ꢀ^ꢀ^ꢀꢂꢃ

νꢀ=ꢀ3071 (m), 2982 (m), 1683 (m), 1538 (s), 1479 (m), 1386

(

m), 1361 (m), 1301 (s), 1148 (s), 1117 (m), 1085 (m), 1007

s), 855 (m), 776 (m), 741 (s), 722 (s), 666 (m), 633 (m), 582

−1

s), 500 (m) cm . – HRMS ((ꢀ+)-ESI): m/zꢀ=ꢀ129.0665 (calcd.

+

1

29.0659 for C H N O , [Mꢀ+ꢀH] ).

5

9

2

3.2 1-Butyloxyimidazole-3-oxide (2)

1

-Hydroxyimidazole-3-oxide (5.0 g, 50 mmol) was sus-

pended in MeOH (50 mL) and cooled to 0°C. KOH (4.3 g,

5 mmol) was added slowly. The resulting solution was

allowed to warm to room temperature, and BuI (5.7 mL,

6

5

2

0 mmol) was added. The solution was refluxed for

0 h and turned red-brown. The white precipitate was

filtered off, the solvent evaporated and the residue sus-

pended in CH Cl . The mixture was filtered again and

2

then evaporated, and the residue was dried in vacuum

to yield orange-brown liquid 1-butyloxyimidazole-3-ox-

1

ide. Yield: 6.7 g (86%). – H NMR (300 MHz, [D ]DMSO):

6

δꢀ=ꢀ0.91 (t, Jꢀ=ꢀ7.3 Hz, 3H), 1.40 (m, 2H), 1.61 (m, 2H), 4.25

Fig. ꢃ:ꢀCrystal structure of Hg(II)-thione complex 1ꢄ.

(

t, Jꢀ=ꢀ6.5 Hz, 2H), 7.08 (t, Jꢀ=ꢀ2 Hz, 1H), 7.58 (t, Jꢀ=ꢀ2 Hz,

1

3

1

H), 8.74 (t, Jꢀ=ꢀ2 Hz, 1H) ppm. – C NMR (75 MHz, [D₆]

DMSO): δꢀ=ꢀ14.4, 19.1, 29.9, 81.3, 115.1, 119.2, 123.5 ppm. –

HRMS (ESI): m/zꢀ=ꢀ157.0983 (calcd. 157.0972 for C H N O ,

3

Experimental section

7

13

2

+

[

Mꢀ+ꢀH] ).

1-Hydroxyimidazole-3-oxide [CAS-RN 35321-46-1] was pre-

pared as previously described [26]. NMR spectra were

recorded with a Bruker AC 300 spectrometer. IR spectra

were obtained using a Nicolet 5700 FT spectrometer in 3.3 1-Allyloxyimidazole-3-oxide (3)

ATR mode. High-resolution mass spectra were measured

with a Finnigan MAT 95 spectrometer. Commercial chemi- Potassium hydroxide (85%, 4.3 g, 65 mmol) was added

cals were used as received.

to an ice-cooled solution of 1-hydroxyimidazole-3-oxide

5.0 g, 50 mmol) in MeOH (50 mL). The ice-bath was

(

removed when the solution was clear, and allyl bromide

(97%, 6.2 g, 50 mmol) was added during 2 min. The

reaction mixture was refluxed for 23 h. The solution

3

.1 1-Ethyloxyimidazole-3-oxide (1)

Potassium hydroxide (85%, 4.3 g, 65 mmol) was added was filtered, and the filter cake was washed with MeOH

to an ice-cooled solution of 1-hydroxyimidazole-3-oxide (2ꢀ×ꢀ40 mL). The solvent was evaporated, and the residue

(

5

5.0 g, 50 mmol) in MeOH (50 mL), and EtBr (5.5 g, was resuspended in CH CN. Removal of precipitate, evap-

3

0 mmol) was added during 2 min. The reaction mixture oration of solvent and drying yielded 1-allyloxyimidazole-

1

was refluxed for 48 h. The solution was filtered, and 3-oxide as a brown liquid. Yield: 5.4 g (86%). – H NMR

the filter cake was washed with MeOH (2ꢀ×ꢀ40 mL). The (300 MHz, [D ]methanol): δꢀ=ꢀ4.74 (d, Jꢀ=ꢀ6.6 Hz, 2H), 5.33–

4

solvent was evaporated, and the residue was resus- 5.40 (m, 2H), 5.95–6.08 (m, 1H), 7.06 (t, Jꢀ=ꢀ2.0 Hz, 1H), 7.54

pended in CH Cl . Removal of precipitate, evaporation (t, Jꢀ=ꢀ2.0 Hz, 1H), 8.70 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – IR (neat):

2

of solvent and drying yielded 1-ethyloxyimidazole-3-ox- νꢀ=ꢀ3090 (m), 3016 (m), 2981 (m), 2941 (m), 2882 (m), 1681

1

ide as orange-brown oil. Yield: 4.0 g (63%). – H NMR (m), 1564 (m), 1539 (s), 1497 (m), 1451 (m), 1422 (m), 1352

(

300 MHz, [D ]DMSO): δꢀ=ꢀ1.23 (t, Jꢀ=ꢀ7.1 Hz, 3H), 4.29 (q, (m), 1301 (s), 1195 (w), 1142 (s), 1077 (m), 1003 (s), 934 (s),

6

Jꢀ=ꢀ7.0 Hz, 2H), 7.13 (t, Jꢀ=ꢀ2.0 Hz, 1H), 7.62 (t, Jꢀ=ꢀ2.0 Hz, 895 (s), 754 (s), 726 (s), 679 (m), 627 (m), 581 (m), 505 (w)

1

3

−1

1

H), 8.84 (t, Jꢀ=ꢀ1.9 Hz, 1H) ppm. – C NMR (75 MHz, [D ] cm . – HRMS (ESI): m/zꢀ=ꢀ141.0668 (calcd. 141.0659 for

6

+

DMSO): δꢀ=ꢀ12.9, 76.8, 115.0, 118.3, 124.0 ppm. – IR (neat): C H N O , [Mꢀ+ꢀH] ).

6

9

2

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ꢀ^ꢀ^ꢀ^ꢀ^ꢁꢀM. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium salts

(

1

q, Jꢀ=ꢀ6.9 Hz, 2H), 8.26 (t, Jꢀ=ꢀ2.3 Hz, 1H), 8.31 (t, Jꢀ=ꢀ2.3 Hz,

3.4 1-Benzyloxyimidazole-3-oxide (4)

1

3

H), 10.27 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR (75 MHz, [D ]

6

Potassium hydroxide (85%, 4.3 g, 65 mmol) was added DMSO): δꢀ=ꢀ12.9, 52.9, 69.5, 78.3, 117.1, 117.8, 129.9 ppm. – IR

to an ice-cooled solution of 1-hydroxyimidazole-3-oxide (neat): νꢀ=ꢀ3116 (m), 3085 (m), 2995 (m), 2952 (m), 1725 (m),

(

5.0 g, 50 mmol) in MeOH (50 mL). The ice-bath was 1651 (m), 1553 (m), 1448 (m), 1390 (w), 1251 (s), 1174 (s),

removed when the solution was clear, and benzyl bromide 1044 (m), 1001 (s), 947 (m), 859 (m), 759 (m), 611 (m), 580

−1

(

6.0 mL, 50 mmol) was added during 2 min. The reaction (s), 436 (m) cm .

mixture was refluxed for 1 h. The solution was filtered,

and the filter cake was washed with MeOH (2ꢀ×ꢀ40 mL).

The solvent was evaporated, and the residue was redis- 3.7 1-Ethyloxy-3-methyloxyimidazolium

solved in CH CN. Removal of precipitate, evaporation of

3

hexafluoridophosphate (ꢃb)

solvent and drying yielded 1-benzyloxyimidazole-3-oxide

1

as a brown liquid. Yield: 7.9 g (83%) – H NMR (300 MHz, To a solution of 1-ethyloxy-3-methyloxyimidazolium

[

D ]DMSO): δꢀ=ꢀ5.28 (s, 2H), 7.04 (t, Jꢀ=ꢀ1.9 Hz, 1H), 7.37–7.43 methyl sulfate (5a; 0.27 g, 1.1 mmol) H O (1 mL) and NH PF

6

2

4

6

(

m, 5H), 7.45 (t, Jꢀ=ꢀ1.9 Hz, 1H), 8.64 (t, Jꢀ=ꢀ1.9 Hz, 2H) ppm. (0.18 g, 1.1 mmol) were added. Two layers were formed.

1

3

–

C NMR (75 MHz, [D ]DMSO): δꢀ=ꢀ81.9, 114.4, 118.3, 122.9, After drying in high vacuum the brown oily residue was

6

1

28.6 (2C), 129.5, 129.8 (2C), 133.1 ppm. – IR (neat): νꢀ=ꢀ3149 redissolved in acetone. Removal of precipitate and evapo-

(

m), 3064 (m), 3031 (m), 1681 (w), 1565 (m), 1540 (m), 1496 ration of solvent yielded 1-ethyloxy-3-methyloxyimidazo-

m), 1454 (m), 1374 (m), 1300 (m), 1212 (w), 1141 (m), 1082 lium hexafluoridophosphate as brown oily liquid (0.23 g,

(

1

(

w), 1005 (m), 952 (w), 907 (m), 845 (w), 735 (s), 696 (s), 74%). H NMR (300 MHz, [D ]DMSO): δꢀ=ꢀ1.33 (t, Jꢀ=ꢀ7.1 Hz,

6

−

1

6

28 (m), 582 (m), 557 (w), 496 (w) cm . – HRMS (ESI): 3H), 4.26 (s, 3H), 4.50 (q, Jꢀ=ꢀ6.9 Hz, 2H), 8.26 (t, Jꢀ=ꢀ2.3 Hz,

+

m/zꢀ=ꢀ191.0831 (calcd. 191.0815 for C H N O , [Mꢀ+ꢀH] ).

1H), 8.30 (t, Jꢀ=ꢀ2.3 Hz, 1H), 10.28 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm.

10

11

2

3

1

–

P NMR (121 MHz, [D ]DMSO): δꢀ=ꢀ−143.1 (sept, Jꢀ=ꢀ711 Hz)

6

ppm.

3

.ꢃ 1-Ethyloxy-3-hydroxyimidazolium

hexafluoridophosphate (1a)

3

.ꢄ 1-Ethyloxy-3-methyloxyimidazolium

1

-Ethyloxyimidazole-3-oxide (1; 0.33 g, 2.6 mmol) was

bis(trifluoromethanesulfonyl)amide (ꢃc)

added to a saturated aqueous solution of NH PF (0.42 g,

4

6

2

.6 mmol) and stirred for 3 h. The precipitate was collected 1-Ethyloxy-3-methyloxyimidazolium methyl sulfate (5a;

by filtration and dried in vacuum to yield 1-ethyloxy-3-hy- 1.0 g, 3.9 mmol) was dissolved in H O (10 mL) and CH Cl

2

droxyimidazolium hexafluoridophosphate (0.69 g, 98%), (10 mL) was added. To this mixture Li Tf N (1.8 g, 6.3 mmol)

2

1

mp. >240°C. H NMR (300 MHz, [D ]DMSO): δꢀ=ꢀ1.26 (t, was added while stirring. After 5 min the organic layer

6

Jꢀ=ꢀ7.1 Hz, 3H), 4.33 (q, Jꢀ=ꢀ7.0 Hz, 2H), 7.17 (br s, 1H), 7.26 was separated and the aqueous phase was extracted

13

(

s, 1H), 7.71 (s, 1H), 8.99 (s, 1H) ppm. – C NMR (75 MHz, with CH Cl (10 mL). The combined organic fractions were

2 2

31

[

D ]DMSO): δꢀ=ꢀ12.9, 77.0, 115.2, 118.3, 124.2 ppm. – P NMR evaporated and the liquid residue dried in vacuum. Yield:

6

1

(

121 MHz, [D ]DMSO): δꢀ=ꢀ−143.6 (sept, Jꢀ=ꢀ711 Hz) ppm. – IR 1.2 g (72%). – H NMR (300 MHz, [D ]methanol): δꢀ=ꢀ1.43

6

4

neat): νꢀ=ꢀ3334 (w), 3170 (w), 2991 (w), 1550 (w), 1445 (m), (t, Jꢀ=ꢀ6.9 Hz, 3H), 4.32 (s, 3H), 4.55 (q, Jꢀ=ꢀ6.9 Hz, 2H), 7.99

1

319 (w), 1143 (w), 1011 (m), 816 (s), 740 (s), 723 (m), 671 (t, Jꢀ=ꢀ2.0 Hz, 1H), 8.02 (t, Jꢀ=ꢀ2.0 Hz, 1H), 9.93 (t, Jꢀ=ꢀ2.0 Hz,

−1

13

(m), 627 (m), 590 (m), 553 (s) cm .

1H) ppm. – C NMR (75 MHz, [D ]methanol): δꢀ=ꢀ13.4, 70.6,

4

8

0.5, 118.6, 119.3, 123.5, 131.0 ppm.

3

.6 1-Ethyloxy-3-methyloxyimidazolium

methyl sulfate (ꢃa)

3

.9 1-Butyloxy-3-ethyloxyimidazolium

iodide (6a)

1-Ethyloxyimidazole-3-oxide (1; 0.65 g, 5.1 mmol) was

stirred with dimethyl sulfate (0.77 g, 6.1 mmol) overnight 1-Ethyloxyimidazole-3-oxide (1; 1.0 g, 7.8 mmol) was

at ambient conditions. Removal of volatiles yielded 1-eth- stirred with BuI (0.89 mL, 7.8 mmol) for 24 h at ambient

yloxy-3-methyloxyimidazolium methyl sulfate as brown conditions. Removal of volatiles yielded 1-butyloxy-

1

liquid. Yield: 1.1 g (87%). – H NMR (300 MHz, [D ]DMSO): 3-ethyloxyimidazolium iodide as a brown viscous liquid.

6

1

δꢀ=ꢀ1.32 (t, Jꢀ=ꢀ6.9 Hz, 3H), 3.38 (s, 3H), 4.26 (s, 3H), 4.50 Yield: 2.4 g (99%). – H NMR (300 MHz, [D ]methanol):

4

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δꢀ=ꢀ1.01 (m, 3H), 1.44 (m, 3H), 1.53 (m, 2H), 1.78 (m, 2H), DMSO): δꢀ=ꢀ12.8, 15.1, 61.2, 78.3, 82.2, 117.8, 118.0, 124.7,

1

3

4

.59 (m, 4H), 8.07 (s, 2H) ppm. – C NMR (75 MHz, [D ] 129.7, 130.5 ppm. – IR (neat): νꢀ=ꢀ3307 (w), 3137 (w), 2983

4

methanol): δꢀ=ꢀ13.6, 14.1, 19.8, 30.7, 80.6, 84.5, 119.2, (w), 1651 (m), 1445 (w), 1391 (w), 1150 (m), 1031 (s), 997 (s),

19.4 ppm. – HRMS (ESI): m/zꢀ=ꢀ185.1300 (calcd. 185.1285 920 (m), 864 (m), 792 (m), 653 (m), 621 (m), 581 (m), 444

1

+

−1

for C H N O , [M] ).

(m) cm .

9

17

2

3

.10 1-Butyloxy-3-ethyloxyimidazolium

hexafluoridophosphate (6b)

3.13 1-Butyloxy-3-methyloxyimidazolium

methyl sulfate (9a)

To 1-butyloxy-3-ethyloxyimidazolium iodide (6a; 2.4 g, 1-Butyloxyimidazole-3-oxide (3; 5.2 g, 33 mmol) was

7

.9 mmol) was added a solution of NH PF (1.5 g, 9.4 mmol) cooled to 0°C and dimethyl sulfate (3.8 mL, 40 mmol) was

4 6

in H O (4 mL). After stirring overnight the solution was added. Stirring for 20 h and removal of volatiles yielded

2

extracted with CH Cl . Evaporation of the organic phase 1-butyloxy-3-methyloxyimidazolium methyl sulfate as

2

1

and drying in vacuum yielded 1-butyloxy-3-ethyloxyimi- brown liquid. Yield: 9.3 g (99%). – H NMR (300 MHz, [D ]

4

1

dazolium hexafluoridophosphate. Yield: 1.8 g (69%). – H methanol): δꢀ=ꢀ1.01 (m, 3H), 1.52 (m, 2H), 1.79 (m, 2H), 3.67

NMR (300 MHz, [D ]methanol): δꢀ=ꢀ1.00 (m, 3H), 1.43 (m, (m, 3H), 4.32 (m, 3H), 4.52 (m, 2H), 7.08 (m, 2H), 9.99 (m,

4

1

3

H) 1.52 (m, 2H), 1.79 (m, 2H), 4.54 (m, 4H), 7.98 (s, 2H) 1H) ppm. – C NMR (75 MHz, [D ]methanol): δꢀ=ꢀ14.1, 19. 8,

4

ppm.

30.7, 55.2, 70.7, 84.5, 118.6, 119.2, 131.0 ppm.

3

.11 1-Allyloxy-3-methyloxyimidazolium

methyl sulfate (7)

3.14 1-Butyloxy-3-methyloxyimidazolium

hexafluoridophosphate (9b)

1

-Allyloxyimidazol-3-oxide (2; 0.60 g, 4.3 mmol) was 1-Butyloxy-3-methyloxyimidazolium methyl sulfate (9a;

stirred with dimethyl sulfate (0.65 g, 5.2 mmol) for 3 d at 5 g, 17.7 mmol) and a solution of NH PF (3.5 g, 21.3 mmol)

4

6

ambient conditions. Removal of volatiles yielded 1-ally- in H O (9 mL) were stirred overnight. Then the heavier

2

loxy-3-methyloxyimidazolium methyl sulfate as brown phase was separated and dried in vacuum to yield

1

oily liquid (1.1 g, 99%). H NMR (300 MHz, [D ]DMSO): 1-butyloxy-3-methyloxyimidazolium hexafluoridophos-

6

1

δꢀ=ꢀ3.39 (s, 3H), 4.25 (s, 3H), 4.96 (d, Jꢀ=ꢀ6.6 Hz, 2H), 5.44– phate (4.03 g, 72%). H NMR (300 MHz, [D ]methanol):

4

5

.50 (m, 2H), 5.99–6.12 (m, 1H), 8.23 (t, Jꢀ=ꢀ2.3 Hz, 1H), 8.31 δꢀ=ꢀ1.00 (m, 3H), 1.51 (m, 2H), 1.78 (m, 2H), 4.32 (s, 3H),

13

(

1

t, Jꢀ=ꢀ2.2 Hz, 1H), 10.26 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR 4.51 (m, 2H), 7.96 (m, 2H), 9.84 (m, 1H) ppm. – C NMR

75 MHz, [D ]DMSO): δꢀ=ꢀ53.0, 69.6, 82.3, 117.1, 118.1, 124.7, (75 MHz, [D ]methanol): δꢀ=ꢀ14.0, 19.7, 30.6, 70.6, 84.5,

6

4

29.8, 130.1 ppm. – IR (neat): νꢀ=ꢀ3114 (m), 3085 (m), 3008 118.5, 119.1, 130.8 ppm.

(

8

m), 2951 (m), 1717 (m), 1647 (m), 1553 (m), 1454 (m), 1427

m), 1371 (w), 1247 (s), 1202 (s), 1056 (m), 1001 (s), 945 (m),

−1

84 (m), 757 (s), 611 (m), 581 (s), 435 (m) cm .

3.1ꢃ 1-Benzyloxy-3-methyloxyimidazolium

methyl sulfate (10)

3

.12 1-Allyloxy-3-ethyloxyimidazolium ethyl 1-Benzyloxyimidazole-3-oxide (4; 0.71 g, 3.8 mmol) was

stirred with dimethyl sulfate (0.47 g, 3.8 mmol) overnight

at ambient conditions. Removal of volatiles yielded

sulfate (ꢄ)

1

-Allyloxyimidazole-3-oxide (2; 0.49 g, 3.5 mmol) was 1-benzyloxy-3-methyloxyimidazolium methyl sulfate as

1

stirred with diethyl sulfate (0.55 g, 3.5 mmol) overnight at brown oil (1.2 g, 99%). H NMR (300 MHz, [D ]DMSO):

6

ambient conditions. Removal of volatiles yielded 1-ally- δꢀ=ꢀ4.22 (s, 3H), 4.26 (s, 3H), 5.49 (s, 2H), 7.32–7.48 (m,

loxy-3-ethyloxyimidazolium ethyl sulfate as brown oil 5H), 8.20 (t, Jꢀ=ꢀ2.3 Hz, 1H), 8.29 (t, Jꢀ=ꢀ2.3 Hz, 1H), 10.20

1

(

1.0 g, 99%). H NMR (300 MHz, [D ]DMSO): δꢀ=ꢀ1.10 (t, (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – IR (neat): νꢀ=ꢀ3087 (m), 2951 (w),

6

Jꢀ=ꢀ7.1 Hz, 3H), 1.31 (t, Jꢀ=ꢀ7.1, 3H), 3.74 (q, Jꢀ=ꢀ7.1 Hz, 2H), 4.50 1722 (m), 1552 (w), 1497 (w), 1455 (m), 1212 (s), 1056 (m),

q, Jꢀ=ꢀ6.9 Hz, 2H), 4.96 (d, Jꢀ=ꢀ6.9 Hz, 2H), 5.43–5.49 (m, 2H), 1001 (s), 946 (m), 909 (w), 869 (w), 845 (m), 754 (m), 698

.00–6.13 (m, 1H), 8.26 (t, Jꢀ=ꢀ2.3 Hz, 1H), 8.29 (t, Jꢀ=ꢀ2.3 Hz, (m), 652 (m), 618 (m), 576 (m), 551 (m), 496 (w), 464 (w),

(

6

13

−1

1

H), 10.27 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR (75 MHz, [D ] 438 (m) cm .

6

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DMSO): δꢀ=ꢀ12.6, 78.3, 83.4, 117.8, 117.9, 119.5 (q, Jꢀ=ꢀ321 Hz,

C), 128.9 (2C), 130.1, 130.2 (2C), 130.4, 131.9 ppm.

3

.16 1-Benzyloxy-3-ethyloxyimidazolium

2

ethyl sulfate (11a)

1

-Benzyloxyimidazole-3-oxide (4; 0.50 g, 2.6 mmol) was

stirred with diethyl sulfate (0.42 g, 2.6 mmol) for 4 h at 3.19 1-Allyloxy-3-benzyloxyimidazolium

ambient conditions. Removal of volatiles yielded 1-benzy-

loxy-3-ethyloxyimidazolium ethyl sulfate as brown liquid

bromide (12)

1

(

0.88 g, 99%). H NMR (300 MHz, [D ]DMSO): δꢀ=ꢀ1.10 (t, A solution of allyl bromide (97%, 0.14 g, 1.1 mmol) in CH Cl₂

6

2

Jꢀ=ꢀ7.1 Hz, 3H), 1.25 (t, Jꢀ=ꢀ7.1 Hz, 3H), 3.74 (q, Jꢀ=ꢀ7.1 Hz, 2H), (5 mL) was added dropwise to 1-benzyloxyimidazole-3-ox-

4

.44 (q, Jꢀ=ꢀ7.1 Hz, 2H), 5.51 (s, 2H), 7.38–7.49 (m, 5H), 8.23– ide (4; 0.21 g, 1.1 mmol). The reaction mixture was stirred

13

8

.29 (m, 2H), 10.15 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR (75 MHz, at 50°C for 1 h to obtain 1-allyloxy-3-benzyloxyimidazolium

[

D ]DMSO): δꢀ=ꢀ12.7, 15.1, 61.2, 78.2, 83.3, 117.8, 117.9, 128.9 bromide as brown oil which was freed from volatiles under

6

1

(

2C), 130.1, 130.2 (2C), 130.4, 131.9 ppm. – IR (neat): νꢀ=ꢀ3068 reduced pressure (0.35 g, 99%). H NMR (300 MHz, [D ]

6

(

m), 2980 (m), 2901 (m), 1683 (m), 1551 (m), 1497 (w), 1455 DMSO): δꢀ=ꢀ4.92 (d, Jꢀ=ꢀ6.9 Hz, 2H), 5.33 (s, 2H), 5.38–5.44

(m), 1387 (m), 1213 (s), 1111 (m), 1059 (m), 1016 (s), 915 (s), (m, 2H), 5.88–6.11 (m, 1H), 7.47 (s, 5H), 8.25 (s, 1H), 8.26 (s,

−1

8

47 (m), 762 (s), 702 (m), 621 (m), 579 (m), 419 (w) cm .

1H), 10.27 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – IR (neat): νꢀ=ꢀ3326 (w),

153 (m), 3034 (m), 1677 (m), 1548 (w), 1496 (w), 1424 (m),

401 (m), 1314 (w), 1214 (w), 1141 (w), 1083 (m), 1012 (m),

3

1

9

3

.17 1-Benzyloxy-3-ethyloxyimidazolium

−1

39 (m), 825 (s), 741 (s), 699 (s), 626 (w), 554 (s) cm .

hexafluoridophosphate (11b)

1

-Benzyloxyimidazol-3-oxide (4; 0.05 g, 0.3 mmol) was 3.20 2-Bromo-1-ethyloxy-3-methyloxyimida-

added to a solution of triethyloxonium hexafluoridophos-

phate (0.07 g 0.3 mmol) in CH Cl . The precipitate was

zolium tribromide (13a)

2

collected by filtration and dried in vacuum to yield 1-ben- 1-Ethyloxy-3-methyloxyimidazolium hexafluoridophos-

zyloxy-3-ethyloxyimidazolium

hexafluoridophosphate phate (5b; 1.0 g, 3.5 mmol) was suspended in MeOH (1.5 mL)

1

as liquid (0.10 g, 99%). H NMR (300 MHz, [D ]DMSO): and H O (3.0 mL). Then bromine (0.18 mL, 3.5 mmol) was

6

2

δꢀ=ꢀ1.25 (t, Jꢀ=ꢀ7.1 Hz, 3H), 4.44 (q, Jꢀ=ꢀ6.9 Hz, 2H), 5.50 (s, 2H), added and the mixture was stirred for 24 h. After this time

.39–7.47 (m, 5H), 8.22 (t, Jꢀ=ꢀ2.2 Hz, 1H), 8.25 (t, Jꢀ=ꢀ2.3 Hz, Na CO (369 mg, 3.5 mmol) and again bromine (0.18 mL,

7

2

3

1

3

1

H), 10.15 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR (75 MHz, [D ] 3.5 mmol) were added. After stirring again for 24 h the

6

DMSO): δꢀ=ꢀ12.7, 78.3, 83.4, 117.8, 117.9, 128.9 (2C), 130.1, 130.2 orange precipitate was filtered off, dissolved in hot MeOH

3

1

(

2C), 130.4, 132.9 ppm. – P NMR (121 MHz, [D ]DMSO): (5 mL) and precipitated again by addition of Et O (60 mL)

6

2

δꢀ=ꢀ−146,5 (sept, Jꢀ=ꢀ711 Hz) ppm. – IR (neat): νꢀ=ꢀ3153 (m), and cooling to −20°C. Filtration and drying in air yielded

1

(

554 (w), 1457 (w), 1390 (w), 1087 (w), 1012 (m), 825 (s), 756 2-bromo-1-ethyloxy-3-methyloxyimidazolium tribromide

m), 701 (m), 598 (m), 555 (s), 497 (m) cm .

−1

1

as bright orange crystals. Yield: 0.7 g (45%). – H NMR

(

300 MHz, [D ]methanol): δꢀ=ꢀ1.49 (t, Jꢀ=ꢀ6.9 Hz, 3H), 4.33

4

s, 3H), 4.58 (q, Jꢀ=ꢀ6.9 Hz, 2H), 8.27 (d, Jꢀ=ꢀ3.0 Hz, 1H), 8.29

3

.1ꢄ 1-Benzyloxy-3-ethyloxyimidazolium

1

3

d, Jꢀ=ꢀ3.0 Hz, 1H) ppm. – C NMR (75 MHz, [D ]metha-

4

bis(trifluoromethanesulfonyl)amide (11c)

nol): δꢀ=ꢀ13.7, 70.1, 80.3, 119.8, 120.7, 161.0 ppm. – IR (neat):

νꢀ=ꢀ3129 (m), 3098 (m), 3078 (m), 2997 (m), 2940 (m), 1683

HCl (37%, 0.06 g, 1.7 mmol) and Li Tf N (0.48 g, 1.7 mmol)

2

(

8

5

w), 1547 (m), 1446 (m), 1391 (m), 1352 (w), 1319 (w), 1263

w), 1192 (w), 1152 (w), 1111 (m), 1040 (s), 1003 (s), 933 (s),

43 (s), 754 (w), 723 (s), 678 (w), 633 (s), 604 (s), 558 (m),

27 (w), 463 (m), 428 (w) cm .

was added to 1-benzyloxy-3-ethyloxyimidazolium ethyl

sulfate (11a; 0.56 g, 1.7 mmol). The product was partitioned

betweenH O(5mL)andCH Cl (5mL)bystirringthemixture

2

−1

for 3 h. After separation of the organic layer the solvent was

evaporated. Drying in vacuum yielded 1-benzyloxy-3-ethy-

loxyimidazolium bis(trifluoromethanesulfonyl)amide as

brown liquid (0.77 g, 91%). H NMR (300 MHz, [D ]DMSO):

δꢀ=ꢀ1.26 (t, Jꢀ=ꢀ6.9 Hz, 3H), 4.44 (q, Jꢀ=ꢀ6.9 Hz, 2H), 5.50 (s,

3

.21 2-Bromo-1-ethyloxy-3-methyloxyimida-

1

6

zolium hexafluoridophosphate (13b)

2

H), 7.47 (s, 5H), 8.22 (t, Jꢀ=ꢀ2.3 Hz, 1H), 8.25 (t, Jꢀ=ꢀ2.3 Hz, 2-Bromo-1-ethyloxy-3-methyloxyimidazolium

tribro-

1

3

1

H), 10.15 (t, Jꢀ=ꢀ2.0 Hz, 1H) ppm. – C NMR (75 MHz, [D ] mide (13a; 300 mg, 0.65 mmol) was suspended in H O

6

2

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M. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium saltsꢂ^ꢁ^ꢀ^ꢀ^ꢀꢂ9

and NH PF (127 mg, 7.8 mmol) was added. After stirring

3

.24 2-Azido-1-ethyloxy-3-methyloxyimida-

4

6

for 24 h the white precipitate was filtered off and washed

zolium hexafluoridophosphate (16)

with H O. Drying in vacuum yielded 2-bromo-1-ethyloxy-

2

3

-methyloxyimidazolium hexafluoridophosphate as 2-Bromo-1-ethyloxy-3-methyloxyimidazolium hexafluori-

yellowish powder, mp. 101°C. Yield: 220 mg (92%). – IR dophosphate (13b; 110 mg, 0.3 mmol) and sodium azide

(

neat): νꢀ=ꢀ3169 (w), 3149 (w), 1704 (w), 1557 (w), 1458 (w), (20 mg, 0.3 mmol) were suspended in acetone (2 mL)

397 (w), 1357 (w), 1064 (m), 1001 (w), 994 (w), 821 (s), and stirred for 71 h. The precipitate was filtered off and

1

7

−1

26 (m), 680 (w), 645 (w), 619 (w), 555 (s), 456 (w) cm .

the solvent evaporated. Drying of the residue in vacuum

yielded 2-azido-1-ethyloxy-3-methyloxyimidazolium hex-

afluoridophosphate as slightly brownish powder, mp.

1

60°C (decomposition). Yield: 26 mg (26%). – IR (neat):

3

.22 2-Bromo-1-butyloxy-3-ethyloxyimida-

zolium hexafluoridophosphate (14)

νꢀ=ꢀ3171 (w), 2164 (w), 1684 (w), 1604 (w), 1481 (w), 1434

(

w), 1261 (w), 1095 (w), 1070 (w), 1026 (m), 999 (w), 952

w), 834 (s), 742 (m), 692 (m), 660 (w), 609 (w), 556 (m), 529

w), 509 (w), 494 (m) cm .

1

-Butyloxy-3-ethyloxyimidazolium hexafluoridophosphate

−1

(

6b; 1.77 g, 5.4 mmol) was dissolved in MeOH (2.3 mL) and

H O (4.6 mL) and bromine (0.28 mL, 5.4 mmol) was added

slowly. The solution was stirred for 66 h and then Na CO₃

2

3.2ꢃ 1-Ethyloxy-3-methyloxyimidazoline-

2

(

570 mg, 5.4 mmol) and bromine (0.28 mL, 5.4 mmol)

2

-thione (17)

were added. The solution was stirred again overnight, the

resulting red oil was separated from the yellow solution 1-Ethyloxy-3-methyloxyimidazolium methylsulfate (5a;

1

and dried in vacuum (1.06 g, 48%). H NMR (300 MHz, [D ] 1.0 g, 3.9 mmol) was dissolved in pyridine and sulfur

4

methanol): δꢀ=ꢀ1.01 (m, 3H), 1.46 (m, 3H) 1.58 (m, 2H), 1.83 (127 mg, 3.9 mmol) and triethylamine (0.6 mL, 4.3 mmol)

13

(

[

m, 2H), 4.59 (m, 4H), 8.21 (s, 2H) ppm. – C NMR (75 MHz, were added. After heating to 70°C for 2 h the solvent was

D ]methanol): δꢀ=ꢀ13.8, 14.2, 19.9, 30.9, 80.4, 84.2, 120.5, evaporated. The residue was dissolved in EtOAc and washed

4

1

20.7 ppm. – IR (neat): νꢀ=ꢀ3121 (w), 2960 (w), 2873 (w), 1745 with H O (2ꢀ×ꢀ100 mL) and HCl (1 M, 2ꢀ×ꢀ25 mL). Evaporation

2

(

w), 1551 (w), 1456 (w), 1387 (w), 1115 (w), 1042 (m), 1003 of solvent and drying yielded 1-ethyloxy-3-methyloxymida-

m), 929 (w), 836 (s), 713 (w), 636 (w), 631 (w), 557 (m), 453 zoline-2-thione as oil that solidified at room temperature

−

1

w) cm .

after shock-cooling with liquid N , mp. 63°C. Yield: 189 mg

2

1

(

28%). – H NMR (300 MHz, [D ]methanol): δꢀ=ꢀ1.35 (t,

4

Jꢀ=ꢀ6.9 Hz, 3H), 4.06 (s, 3H), 4.36 (q, Jꢀ=ꢀ6.9 Hz, 2H), 7.22 (m,

13

2

H) ppm. – C NMR (75 MHz, [D ]methanol): δꢀ=ꢀ13.6, 66.0,

4

3

.23 2-Bromo-1-butyloxy-3-methyloxyimida-

zolium tribromide (1ꢃ)

7

5.1, 112.9, 114.2, 155.1 ppm. – HRMS (ESI): m/zꢀ=ꢀ175.0551

+

(

calcd. 175.0536 for C H N O S, [Mꢀ+ꢀH] ).

6

11

2

1-Butyloxy-3-methyloxyimidazolium hexafluoridophos-

phate (9b; 3.5 g, 10.9 mmol) was dissolved in MeOH 3.26 Tetrakis(1-ethyloxy-3-methyloxy-

(

4.6 mL) and H O (9.2 mL) and bromine (0.56 mL,

2

imidazoline-2-thione)mercury(II)

tetrachloridomercurate(II) (1ꢄ)

1

0.9 mmol) was added slowly. The solution was stirred

for 66 h and then Na CO (1.2 g, 10.9 mmol) and bromine

2

3

(

0.56 mL, 10.9 mmol) were added. The solution was 1-Ethyloxy-3-methyloxymidazoline-2-thione (17; 75 mg,

stirred again overnight, and the resulting red oil sepa- 0.43 mmol) was dissolved in MeOH and mercury(II)

rated from the yellow solution and dried in vacuum chloride (58.4 mg, 0.215 mmol) was added. After stirring

1

(

2.94 g, 55%). H NMR (300 MHz, [D ]methanol): δꢀ=ꢀ1.03 for 30 min the solvent was evaporated and the result-

4

t, Jꢀ=ꢀ7.4 Hz, 3H), 1.58 (sext, 2H), 1.86 (m, 2H), 4.35 (s, ing brownish powder was dried in vacuum. Single crys-

H), 4.56 (t, Jꢀ=ꢀ6.6 Hz, 2H), 8.21 (d, Jꢀ=ꢀ2.6 Hz, 1H), 8.23 (d, tals suitable for X-ray characterization were grown from

3

1

3

Jꢀ=ꢀ2.6 Hz, 1H) ppm. – C NMR (75 MHz, [D ]methanol): MeOH, mp. 139°C. Yield: 132 mg (99%). – IR (neat): νꢀ=ꢀ3116

4

δꢀ=ꢀ14.1, 19.9, 30.9, 70.2, 84.3, 119.9, 120.6 ppm. – IR (neat): (m), 3062 (w), 2941 (w), 1721 (w), 1541 (s), 1439 (m), 1406

νꢀ=ꢀ3151 (w), 2960 (w), 2873 (w), 1553 (w), 1453 (w), 1383 (s), 1388 (s), 1261 (w), 1151 (w), 1123 (m), 1028 (s), 1007 (s),

(

6

w), 1123 (w), 1044 (m), 937 (m), 832 (s), 714 (w), 675 (w), 943 (s), 857 (s), 762 (m), 727 (s), 676 (m), 655 (s), 594 (m),

−1

39 (w), 611 (w), 557 (m) cm .

530 (s), 439 (w) cm .

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0ꢀ^ꢀ^ꢀ^ꢀ^ꢁꢀM. Jochriem et al.: Non-symmetric 1,3-di(alkyloxy)imidazolium salts

[

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φ and ω scans with a Nonius KappaCCD diffractometer

using MoKα radiation at 233(2) K. The crystal structures

were solved by Direct Methods and refined by full-matrix

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were assigned anisotropic displacement parameters in the

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Z. Naturforsch.ꢂ

ꢂ2017 | Volume x | Issue x(b)

Graphical synopsis

Markus Jochriem, Christian G. Kirchler,

Gerhard Laus, Klaus Wurst, Holger

Kopacka, Thomas Müller and Herwig

Schottenberger

Synthesis and crystal structures of non-

symmetric 1,3-di(alkyloxy)imidazolium

salts

https://doi.org/10.1515/znb-2017-0089

Z. Naturforsch. 2017; x(x)b: xxx–xxx

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Synthesis and crystal structures of non-symmetric 1,3-di(alkyloxy)imidazolium salts

DOI: 10.1515/znb-2017-0089

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