Imidazolium-Oxazoline Salts in Ruthenium-Catalyzed Reactions
O) ppm. 13C NMR (CDCl3, 75 MHz): δ = 22.9, 23.1, 25.7, 36.8,
45.5, 65.3, 74.4, 162.5 ppm.
9.2 Hz, 1 H); 6.03 (s, 2 H); 7.00 (s, 2 H); 7.14 (s, 1 H); 7.22–7.40
(m, 5 H); 7.95 (s, 1 H); 10.64 (s, 1 H) ppm. 13C NMR (CDCl3,
75 MHz): δ = 17.8, 21.5, 46.8, 69.8, 76.5, 122.9, 124.9, 126.9, 129.1,
130.1, 128.1, 131.1, 134.7, 139.9, 141.4, 162.8 ppm. HRMS (ESI)
calcd. for C22H24N3O+ [M]+ 346.1919; found 346.1915.
2-Chloromethyl-(4R)-phenyl-4,5-dihydrooxazole (3d): Yield: 83%.
1H NMR (CDCl3, 200.13 MHz): δ = 4.25 (s, 2 H, CH2-Cl masking
CH-N, m); 4.76 and 5.29 (apparent triplet, J = 9.0 Hz, 1 H each,
CHa-O); 7.29–7.39 (m, 5 H, CHarom) ppm. 13C NMR (CDCl3,
1-{[(4R)-Benzyl-4,5-dihydro-1,3-oxazol-2-yl]methyl}-3-mesityl-1H-
imidazol-3-ium Chloride (4e): Yield: 87%. 1H NMR (CDCl3,
200.13 MHz): δ = 2.08 (s, 6 H, CH3Mes); 2.37 (s, 3 H, CH3Mes);
2.72 (dd, J = 13.7, J = 6.0 Hz, 1 H, CH2Ph); 2.96 (dd, J = 13.7, J
= 5.4 Hz, 1 H, CH2Ph); 4.12 (m, 1 H, CH-N); 4.38 (m, 2 H, CH2-
O); 5.81 and 5.89 (AB, J = 14.5 Hz, 2 H, CH2-N); 7.03 (s, 2 H,
CH-Mes); 7.13–7.29 (m, 6 H, Ph, N-CH=); 7.75 (s, 1 H, =CH-N);
10.52 (s, 1 H, NCHN) ppm. 13C NMR (CDCl3, 50 MHz): δ = 17.9,
21.5, 41.7, 46.7, 67.6, 73.8, 122.9, 124.8, 126.9, 129.6, 130.1, 128.8,
131.1, 134.7, 139.8, 141.6, 161.6 ppm. HRMS (ESI) calcd. for
C23H26N3O+ [M]+ 360.2076; found 360.2070.
75 MHz):
δ = 36.8, 70.2, 76.1, 127.0, 128.3, 129.3, 141.7,
164.2 ppm.
2-Chloromethyl-(4R)-benzyl-4,5-dihydrooxazole: (3e): Yield: 85%.
1H NMR (CDCl3, 200.13 MHz): δ = 2.73 and 3.14 (dd, J = 14.7,
JЈ = 6.7 Hz, 1 H each, CH2-Ph); 4.14 (s, 2 H, CH2-Cl, masking 1
H of CH2-0); 4.34 (apparent triplet, J = 9.3 Hz, 1 H, 1 H of CHa-
O); 4.49 (m, 1 H, CH-N); 7.24–7.37 (m, 5 H, CHarom) ppm. 13C
NMR (CDCl3, 75 MHz): δ = 36.8, 41.7, 67.9, 73.2, 127.1, 129.0,
129.7, 137.7, 163.5 ppm.
General Procedure for the Synthesis of Imidazolium Chlorides 4a–e:
To a Schlenk flask equipped with a magnetic stirrer were success-
ively added under a nitrogen atmosphere, 2,4,6-trimethylphen-
ylimidazole (2.58 mmol), anhydrous DMF (3 mL) and 2-chlo-
romethyl-4,5-dihydrooxazole (2.58 mmol). The reaction mixture
was stirred at room temperature for 3 h and was heated at 80 °C
for 3 h. After cooling at room temperature, dry Et2O was added,
and a white solid precipitated. The solid was washed with dry Et2O
and filtered, and the residue was dissolved in CH2Cl2 (3 mL). Dry
Et2O was added to the solution, and the solid immediately began
to precipitate. The product was filtered and dried under vacuum.
General Procedure for the Catalytic Allylation Reaction: Into a
Schlenk tube equipped with a magnetic stirring bar and under ar-
gon were introduced oxazoline–imidazolium salt (0.03 mmol) and
tBuOK (0.03 mmol). The mixture was kept under vacuum for a
few minutes and then under argon. Dry THF (5 mL) was added,
and the mixture was stirred at 50 °C for 2 h. [Cp*Ru(MeCN)3][PF6]
(0.03 mmol) was then introduced, and the reaction was run for 2 h
under the same conditions. Then the solvent was removed under
vacuum, CH3CN (5 mL) was added, and then were added K2CO3
(1.2 mmol), cinnamyl chloride (1 mmol) and phenol (1.2 mmol).
The reaction mixture was stirred at room temperature for 16 h. The
solvent was evaporated, dichloromethane (10 mL) was added, and
the resulting solution was filtered under argon. The solution was
concentrated for fast chromatography on a column of silica (eluent:
Et2O/hexane = 1:9). The conversion and the B/L ratio of the prod-
1-{[(4R)-Ethyl-4,5-dihydro-1,3-oxazol-2-yl]methyl}-3-mesityl-1H-
imidazol-3-ium Chloride (4a): Yield: 72 %. 1H NMR (CDCl3,
200.13 MHz): δ = 0.92 (t, J = 7.1 Hz, 3 H, CH3CH2); 1.56 (m, 2
H, CH2CH3); 2.11 (s, 6 H, CH3Mes); 2.36 (s, 3 H, CH3Mes); 4.02
(m, 2 H, CH-N, CH-O); 4.45 (m, 1 H, CH-O); 5.84 (s, 2 H, NCH2);
7.02 (s, 2 H, CH,Mes); 7.16 (s, 1 H, MesN-CH=CH-N); 7.83 (s, 1
H, MesN-CH=CH-N); 10.59 (s, 1 H, NCHN) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 10.5, 17.9, 21.5, 28.9, 46.9, 68.1, 74.2, 122.7,
124.1, 134.8, 140.5, 141.8, 130.2, 161.1 ppm. HRMS (ESI) calcd.
for C18H24N3O+ [M]+ 298.1919; found 298.1921.
1
ucts were determined by H NMR spectroscopy.
General Procedure for Cross Metathesis of Allylic Ether 5: In a
Schlenk tube were introduced 5 (105 mg, 0.5 mmol), acrylic deriva-
tives 6a and 6b (2 equiv., 1 mmol), distilled toluene (5 mL) and then
Hoveyda II catalyst 7 (15.5 mg, 5 mol-%). The mixture was heated
at 80 °C for 16 h (8a) or 6 h (8b). The solution was quickly filtered
on silica (in a Pasteur pipette). The solvent was removed under
vacuum, and the product was chromatographed on silica gel, elu-
ent: petroleum ether/diethyl ether (9:1). The solvent was evaporated
to give a white solid for 8a (66.5 mg, 65%) and a transparent oil
for 8b (56 mg, 63%).
1-{[(4R)-Isopropyl-4,5-dihydro-1,3-oxazol-2-yl]methyl}-3-mesityl-
1H-imidazol-3-ium Chloride (4b): Yield: 78%. 1H NMR (CDCl3,
200.13 MHz): δ = 0.86 (t, J = 7.7 Hz, 3 H, CH3CH); 0.90 (t, J =
7.7 Hz, 3 H, CH3CH); 1.69 (m, 2 H, CHMe2); 2.10 (s, 6 H,
CH3Mes); 2.36 (s, 3 H, CH3Mes); 3.90 (m, 1 H, CH-N); 4.09 (ap-
parent triplet, J = 8.4 Hz, 1 H, CH-O); 4.42 (apparent triplet, J =
9.4 Hz, 1 H, CH-O); 5.83 (s, 2 H, CH2-N); 7.01 (s, 2 H, CHMes);
7.16 (s, 1 H) and 7.89 (s, 1 H) [MesN-CH=CH-N], 10.45 (s, 1 H,
NCHN) ppm. 13C NMR (CDCl3, 75 MHz): δ = 17.9, 18.9, 19.2,
21.5, 33.2, 46.9, 72.6, 72.7, 122.7, 124.2, 131.1, 134.8, 140.4, 141.8,
130.2, 161.1 ppm. HRMS (ESI) calcd. for C19H26N3O+ [M]+
312.2076; found 312.2073.
Compound 8a: 1HNMR (500.13 MHz. CDCl3): δ = 3.68 (s, 3 H,
OMe); 4.85 [dd, 1 H, J = 1.5 and 4.8 Hz, CH(OPh)]; 7.08 (dd, 1
H, J = 4.8 and 15.7 Hz, CH=CHCO2Me); 6.89 (dd, 1 H, J = 1.5
and 15.7 Hz, =CHCO2Me); 7.19 (m, 2 Harom); 7.27 (m, 1 Harom);
7.34 (m, 4 H) ppm. MS: m/z = 268.
1
Compound 8b: H NMR (500.13 MHz. CDCl3): δ = 5.86 [dd, J =
1-{[(4R)-Isobutyl-4,5-dihydro-1,3-oxazol-2-yl]methyl}-3-mesityl-1H-
imidazol-3-ium Chloride:(4c): Yield: 76 %. 1H NMR (CDCl3,
200.13 MHz): δ = 0.93 (d, J = 6.5 Hz, 3 H); 0.94 (d, J = 6.5 Hz, 3
H); 1.30–1.80 (m, 3 H); 2.11 (s, 6 H); 2.37 (s, 3 H); 3.95 (m, 1 H);
4.16 (m, 1 H); 4.48 (apparent triplet, J = 8.0 Hz, 1 H); 5.84 (s, 2
H); 7.03 (s, 2 H); 7.13 (s, 1 H); 7.73 (s, 1 H); 10.69 (s, 1 H) ppm.
13C NMR (CDCl3, 75 MHz): δ = 17.9, 21.51, 22.9, 23.2, 25.8, 45.5,
46.9, 65. 1, 74.9, 122.8, 124.5, 124.8, 130.2, 130.9, 131.1, 134.8,
140.2, 141.7, 143.9, 160.9 ppm.
1.5 and 7.7 Hz, 1 H, CH(OPh)]; 6.42 (ddd, J = 1.5, 7.7, 15.5 Hz, 1
H, =CH); 6.88–6.96 (m, 4 H, =CHCHO, Harom); 7.20–7.24 (m, 2
H); 7.30–7.33 (m, 1 H): 7.36–7.40 (m, 4 H) ppm. 13C NMR
(75.46 MHz,CDCl3): δ = 193.18 (CHO); 157.2 (CH=CHCHO);
154.5 (OCarom); 137.9 (=CHCHO); 131.2; 129.6; 129.1; 128.7;
126.7; 116.0; 78.8 (CHOPh) ppm. MS: m/z = 238.
Acknowledgments
1-{[(4R)-Phenyl-4,5-dihydro-1,3-oxazol-2-yl]methyl}-3-mesityl-1H-
imidazol-3-ium Chloride (4d): Yield: 85 %. 1H NMR (CDCl3,
200.13 MHz): δ = 2.07 (s, 6 H); 2.35 (s, 3 H); 4.22 (apparent triplet,
J = 8.2 Hz, 1 H); 4.79 (dd, J = 9.3, J = 8.4 Hz, 1 H); 5.22 (t, J =
The authors acknowledge Centre National de la Recherche Sci-
entifique (CNRS) and DGRSRT (project SC17802) for financial
support.
Eur. J. Inorg. Chem. 2010, 4752–4756
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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