138 Organometallics, Vol. 29, No. 1, 2010
Boronat et al.
were recorded on Varian XR300 and Bruker 200 spectrometers.
Chemical shifts are referenced to tetramethylsilane (internal
standard). Optical rotation values were measured at the
sodium-D line (589 nm) with a Perkin-Elmer 241 MC polari-
meter. Gas chromatography analysis was performed using a
Hewlett-Packard 5890. The enantiomeric excess was measured
by HPLC (Agilent 1200) using chiral column chiralcel OD
(diethyl 2-benzylidene succinate (λ: 254 nm, hexane/iPrOH.
95:5, 0.5 mL/min) and chiralcel AD-H (diethyl itaconate, λ:
230 nm, hexane/iPrOH, 98:2, 0.4 mL/min.).
CH2CH2Npro; CH2CH2CH); 1.11 (9H, s, C(CH3)3). 13C NMR
(CDCl3, ppm): δ 174.35 (CdO); 158.65 (Cpy); 152.66 (Cpy); 141.71
(Cmes); 138.69 (NCHN); 138.65 (Cpy); 134.61 (Cmes); 131.15 (Cmes);
130.26 (Cmes); 124.74 (Cimi); 123.72 (Cpy); 123.12 (Cpy); 122.88
(Cimi); 67.86 (CH2CHNpro); 61.44 (CCH2Npro); 55.56 (CH2-
CH2Npro); 54.25 (NimCH2C); 50.31 (C(CH3)3); 31.30 (CH2-
CH2Npro); 29.00 (C(CH3)3); 24.39 (CH2CH2CH); 21.48 (p-CH3);
18.01 (o-CH3). EM (m/z, %): 460 (Mþ - Br, 100).
1-(2,6-Diisopropylphenyl)-3-{[6-(amine-1-ylmethyl)pyridin-2-yl]-
methyl}-1H-imidazol-3-ium Bromide ([4]Br)}. 3-{[6-(Bromo-
methyl)pyridin-2-yl]methyl}-1-(2,6-diisopropylphenyl)-1H-imida-
zol-3-ium Bromide. A mixture of 2,6-bis(bromomethyl)pyridine
(11.32 mmol, 3 g) and 1-(2,6-diisopropylphenyl-1H-imidazole
(7.59 mmol, 1.73 g) in acetone was refluxed for 18 h. The crude
product was purified by chromatography on silica gel eluting
with acetone/ethanol (10:1) to yield a white solid (1.49 g, 40%).
Mp = 200.5-202.0 °C. Anal. Calcd for C22H27N3Br2 (493): C:
53.5; H: 5.7; N: 8.5. Found: C: 53.1; H: 5.2; N: 8.1. IR (KBr,
cm-1): ν 3047 (CHCdC.); 1594, 1574, 1546 (CdC, CdN); 1458
(C-C). 1H NMR (CDCl3, ppm): δ = 10.08 (1H, NCHN); 8.16
(1H, Himi); 7.84 (1H, Hpy, d, J = 7.7 Hz), 7.71 (1H, t, Hpy, J =
7.60, 7.7 Hz); 7.48 (1H, Harom, t, J = 7.8, 7.7 Hz), 7.35 (1H, d,
Hpy, J = 7.5 Hz); 7.26-7.22 (2H, m, Harom,); 7.10 (1H, Himi);
6.21 (2H, s, NimCH2C); 4.39 (2H, s, CH2Br); 2.34-2.21 (2H, m,
CHiPr); 1.18, 1.15 (6H, d, J = 6.8 Hz, CH3); 1.09, 1.07 (6H, d,
J = 6.8 Hz, CH3). 13C NMR (CDCl3, ppm): δ 156.30 (Cpy);
152.10 (Cpy); 144.93 (NCHN); 138.27 (Cpy); 137.71 (Carom);
131.45 (Carom); 129.63 (Carom); 124.20 (Carom); 123.64 (CHimi);
123.03 (Cpy); 122.91 (CHimi); 53.07 (NimCH2C); 32.87 (CH2Br);
28.13 (CHiPr); 23.84, 23.78 (CH3). EM (m/z, %): 413 (Mþ- Br,
100).
Preparation of Precursors. 1-Mesityl-3-{[6-(amine-1-ylmethyl)-
pyridin-2-yl]methyl}-2,3-dihydro-1H-imidazol-3-ium Bromide
([3]Br). 3-{[6-(Bromomethyl)pyridin-2-yl]methyl}-1-mesityl-
1H-imidazol-3-ium Bromide.
A mixture of 2,6-bis(bromo-
methyl)pyridine (6 mmol, 1.59 g) and 1-mesityl-1H-imidazole
(4 mmol, 750 mg) in acetone was refluxed for 16 h. The crude
product was purified by chromatography on silica gel eluting
with acetone/ethanol (6:1) to yield a white solid (706 mg, 40%).
Mp = 207.5-209.0 °C. Anal. Calcd for C19H21N3Br2 (451): C:
50.4; H: 4.9; N: 9.3. Found: C: 50.3; H: 4.8; N: 9.4. IR (KBr,
cm-1): ν 3158, 3086 (CHCdC); 1591, 1565, 1549 (CdC, CdN);
1458 (C-C). 1H NMR (CDCl3, ppm): δ 10.20 (1H, NCHN); 8.06
(1H, d, J = 1.7 Hz, Himi); 7.60 (2H, Hpy, d, J = 7.57 Hz, J = 7.82
Hz, J = 0.74Hz); 7.71(1H, t, Hpy); 7.10(1H, d, J = 1.7Hz, Himi);
6.99 (2H, s, Hmes); 6.18 (2H, s, NimCH2C); 4.41 (2H, s, CH2Br);
2.30 (3H, s, p-CH3); 2.08 (6H, s, o-CH3). 13C NMR (CDCl3,
ppm): δ 156.69 (Cpy); 152.48 (Cpy); 141.19 (NCHN); 138.59
(Cpy); 137.99 (Cmes); 134.22 (Cmes); 130.57 (Cmes); 129.69
(Cmes); 123.96 (CHimi); 123.35 (Cpy); 123.11 (CHimi); 122.44
(Cpy); 53.42 (NimCH2C); 33.27 (CH2Br); 20.97 (p-CH3); 17.55
(o-CH3). EM (m/z, %): 370 (Mþ, 100).
1-Mesityl-3-{[6-(pyrrolidin-1-ylmethyl)pyridin-2-yl]methyl}-1H-
imidazol-3-ium Bromide ([3a]Br). A mixture of 1-[(6-bromopyr-
idin-2-yl)methyl]-3-mesityl-1H-imidazol-1-ium bromide (5 mmol,
2.25 g), sodium carbonate (75 mmol, 7.9 g), and pyrrolidine
(6 mmol, 0.5 mL) in acetone was stirred at room temperature
for 12 h. The crude product was washed with diethyl ether to
afford the product as a beige solid (1.65 g, 75%). Mp =
148.0-151.0 °C. Anal. Calcd for C23H29N4Br (441): C: 62.6; H:
6.6; N: 12.7. Found: C: 62.4; H: 6.5; N: 12.5. IR (KBr, cm-1):
1-(2,6-Diisopropylphenyl)-3-((6-(pyrrolidin-1-ylmethyl)pyridin-
2-yl)methyl)-1H-imidazol-3-ium Bromide ([4a]Br). A mixture of
3-{[6-(bromomethyl)pyridin-2-yl]methyl}-1-(2,6-diisopropyl-
phenyl)-1H-imidazol-3-ium bromide (1 mmol, 493 mg), potas-
sium carbonate (12 mmol, 1.66 g), and pyrrolidine (1 mmol,
82 μL) in acetone was stirred at room temperature for 24 h. The
crude product was washed with diethyl ether to afford the
product as a beige solid (362 mg, 75%). Mp = 165-168 °C.
Anal. Calcd for C26H35N4Br (483.5): C: 64.6; H: 7.3; N: 11.6.
Found: C: 64.1; H: 7.0; N: 11.2. IR (KBr, cm-1): ν 3050
(CHarom.); 1593.6, 1574.7, (CdC, CdN). 1H NMR (CDCl3,
ppm): δ 10.20 (1H, NCHN); 8.16 (1H, Himi); 7.80 (1H, Hpy, d,
1
ν 3050 (CHarom.); 1700, 1663 (CdC, CdN). H NMR (CDCl3,
ppm): δ 10.11 (1H, br s, NCHN); 8.10 (1H, d, J = 1.7 Hz, Himi);
7.73 and 7.62 (2H, d, Hpy, J = 7.66 Hz, J = 7.42 Hz,); 7.31 (1H, t,
Hpy); 7.10 (1H, d, J = 1.7 Hz, Himi); 6.92 (2H, s, Hmes); 5.99 (2H, s,
NimCH2C); 3.73 (2H, s, CCH2Npyrr); 2.55 (2H, s, CH2pyrr); 2.25
(3H, s, p-CH3); 2.06 (6H, s, o-CH3); 1.80 (2H, s, CH2pyrr). 13C
NMR (CDCl3, ppm): δ 157.13 (Cpy); 149.98 (Cpy); 139.43
(NCHN); 137.20 (Cpy); 136.11 (Cmes); 132.34 (Cmes); 132.11
(Cmes); 127.94 (Cmes); 122.12 (Cimi); 121.43 (Cpy); 120.64 (Cimi);
120.52 (Cpy); 59.77 (CCH2Npyrr); 52.02 (CH2pyrr); 51.44
(NimCH2C); 21.65 (CH2pyrr); 19.18 (p-CH3); 15.71 (o-CH3). EM
(m/z, %): 361 (Mþ - Br, 100).
J = 7.8 Hz), 7.70 (1H, t, Hpy, J = 7.82, 7.57 Hz); 7.48 (1H, Harom
,
t, J = 7.81, 7.81 Hz), 7.35 (1H, d, Hpy, J = 7.82 Hz); 7.26-7.20
(2H, m, Harom,); 7.04 (1H, Himi); 6.14 (2H, s, NimCH2C); 3.66
(2H, s, CH2pyrr); 2.48 (2H, s, CH2pyrr); 2.32-2.14 (2H, m, CHiPr);
1.73 (2H, s, CH2pyrr), 1.16 (6H, d, J = 6.84 Hz, CH3); 1.07 (6H, d,
J = 6.80 Hz, CH3). 13C NMR (CDCl3, ppm): δ 158.56 (Cpy);
152.94 (Carom); 150.85 (Cpy); 144.36 (NCHN); 137.15(Carom);
137.09 (Cpy); 130.90 (Carom); 129.16 (Carom); 123.66 (Carom);
123.11 (CHimi); 122.44 (CHimi); 122.14 (Cpy); 121.37 (Cpy);
60.97 (CCH2Npyrr); 53.29 (NCH2Pyrr); 52.92; (NimCH2C); 27.58
(CHiPr); 23.36, 23.20(CH2Pyrr); 23.00;22.52 (CH3). EM (m/z, %):
403 (Mþ - Br, 100).
(S)-3-((6-((2-(tert-Butylcarbamoyl)pyrrolidin-1-yl)methyl)-
pyridin-2-yl)methyl)-1-(2,6-diisopropylphenyl)-1H-imidazol-3-ium
Bromide ([4b]Br). A mixture of 3-{[6-(bromomethyl)pyridin-2-
yl]methyl}-1-(2,6-diisopropylphenyl)-1H-imidazol-3-ium bro-
mide (1 mmol, 493 mg), potassium carbonate (12 mmol, 1.66
g), and (S)-(tert-butyl)prolinamide (1 mmol, 169.2 mg) in
acetone was stirred at room temperature for 24 h. The crude
was washed with diethyl ether to afford the product as beige
solid (460 mg, 80%). Mp = 110-113 °C. Anal. Calcd for
C31H44N5BrN5O (582.6): C: 63.9; H: 7.6; N: 12.0. Found: C:
63.5; H: 7.2; N: 11.5. IR (KBr, cm-1): ν 3050 (CHarom.); 1664.3
(CdO); 1593.8, 1574.8, (CdC, CdN). 1H NMR (CDCl3, ppm):
δ 10.42 (1H, NCHN); 8.26 (1H, Himi); 7.85 (1H, Hpy, d, J = 7.8
Hz), 7.74 (1H, t, Hpy, J = 7.80, 7.41 Hz); 7.51 (1H, Harom, t, J =
7.80, 7.80 Hz), 7.29 (1H, d, Hpy, J = 7.41 Hz); 7.24-7.23 (2H, m,
(S)-3-((6-((2-(tert-Butylcarbamoyl)pyrrolidin-1-yl)methyl)pyridin-
2-yl)methyl)-1-mesityl-1H-imidazol-3-ium Bromide ([3b]Br). A mix-
ture of 1-[(6-bromopyridin-2-yl)methyl]-3-mesityl-1H-imidazol-1-
ium bromide (5 mmol, 2.25 g), sodium carbonate (10 mmol,
1.06 g), and (S)-(tert-butyl)prolinamide (5 mmol, 846 mg) in acetone
was stirred at room temperature for 12 h. The crude product was
washed with diethyl ether to afford the product as a yellow solid
(2.16 g, 80%). Mp = 121.0-126.0 °C. Anal. Calcd for C28H38-
N5OBr (540.5): C: 62.2; H: 7.1; N: 13.0. Found: C: 62.4; H: 7.0; N:
12.6. IR (KBr, cm-1): ν 3433 (CHarom.); 1666 (CdC, CdN).
UV-vis (λ, nm): 261, 252. 1H NMR (CDCl3, ppm): δ 10.39 (1H,
NCHN); 8.12 (1H, d, JCHimi Himi =1.74Himi);7.87(2H,d,J=7.35
,
Hz, J = 0.76 Hz, Hpy); 7.73 (1H, t, Hpy); 7.30 (1H, d, J = 7.73 Hz,
Hpy); 7.08 (1H, br s, Himi); 6.99 (2H, s, Hmes); 6.10 (2H, d, J = 14.79
Hz, NimCH2C); 3.72 (2H, d, J = 13.0 Hz, CCH2Npro); 3.17 (1H, q,
J = 3.6 Hz, CH2CHNpro); 3.13-3.09 (1H, m, CH2CH2Npro);
2.51-2.40 (1H, m, CH2CH2Npro); 2.32 (3H, s, p-CH3); 2.19-2.00
(1H, m, CH2CH2Npro); 1.98 (9H, s, o-CH3); 1.84-1.61 (3H, m,