(5 mL per mmol of starting trialkylpyridine). The reaction
mixture was stirred at 80 ◦C until completion. The reaction
progress was followed by t.l.c. using silica gel 60 GF-254
aluminum sheets and Cl2CH2 : CH3OH (95 : 5) as eluent. The
mixture was heated under reduced pressure and the resulting IL
was washed with ethyl ether (4 ¥ 3 mL per mmol of starting
trialkylpyridine). The remaining ethyl acetate was removed by
heating under reduced pressure to afford the desired IL that was
dried by heating at (373.15 to 383.15 K) and stirring under high
vacuum (2 ¥ 10-1 Pa) for 48 h.
1-Hexyl-3,5-dimethyl-2-pentylpyridinium bromide (8). Yield
85%. H NMR (CDCl3): d 9.76 (1H, s, 6-H), 7.89 (1H, s, 4-
1
H), 4.85 (2H, dd, J1 = 6.1 Hz, J2 = 10.0 Hz, NCH2), 2.93 (2H,
dd, J1 = 5.9 Hz, J2 = 10.6 Hz, 1¢-Pen), 2.56 (3H, s, Ar-CH3),
2.51 (3H, s, Ar-CH3), 1.95 (2H, m, NCH2CH2), 1.61 (2H, m, 2¢-
Pen), 1.55–1.25 (10H, m, N(CH2)2CH2CH2CH2, 2¢,3¢,4¢-Pen),
0.90 (3H, t, J = 7.2 Hz, 5¢-Pen), 0.84 (3H, dt, J1 = 3.7 Hz, J2 =
7.1 Hz, N(CH2)5CH3). 13C NMR (CDCl3): d 152.9, 147.2, 144.4,
137.1, 136.5, 57.8, 32.1, 31.8, 31.2, 29.2, 27.6, 26.0, 22.4, 22.1,
19.4, 18.0, 13.9, 13.8. Electrospray MS (micrOTOF Focus) m/z
(%) 263 [(C18H32N) + 1]+ (18), 262.25261 ([(C18H32N)]+ requires
262.25293, 100).
1-Hexyl-2,3,5-trimethylpyridinium iodide (4). Yield 99%. 1H
NMR (CDCl3): d 9.18 (1H, s, 6-H), 7.97 (1H, s, 4-H), 4.75 (2H,
dd, J1 = 6.2 Hz, J2 = 9.8 Hz, NCH2), 2.77 (3H, s, Ar-CH3), 2.53
(3H, s, Ar-CH3), 2.51(3H, s, Ar-CH3), 1.91 (2H, m, NCH2CH2)
1.46 (2H, m, N(CH2)2CH2) 1.32 (4H, m, N(CH2)3CH2CH2) 0.86
(3H, t, J = 7.1 Hz, N(CH2)5CH3). 13C NMR (CDCl3): d 150.5,
147.1, 142.8, 138.6, 136.4, 59.7, 31.2, 30.6, 26.2, 22.5, 20.7, 18.5,
17.5, 14.0. Electrospray MS (apex-Qe) m/z (%) 1206 [(C14H24N)4
(I)3 + 1]+ (5), 1205 [(C14H24N)4 (I)3]+ (9), 541 [(C14H24N)2 (I) +
2]+ (3), 540 [(C14H24N)2(I) + 1]+ (26), 539.28492 ([(C14H24N)2
(I)]+ requires 539.28567, 100), 207 [(C14H24N) + 1]+ (6), 206
[C14H24N]+ (49).
General procedures for the synthesis of pyridinium
bis(trifluoromethanesulfonyl)imides
The tetraalkylpyridinium halide (21 mmol) was dissolved in
water (20 mL) and treated with an aqueous solution of
bis(trifluoromethane)sulfonimide lithium salt (6,64 g, 23 mmol)
in water (20 mL). The obtained solution was stirred at rt for
10 min. The product was isolated by solvent extraction using
CH2Cl2 (2 ¥ 10 mL). The extracts were dried over anhydrous
Na2SO4 and evaporated under reduced pressure to yield the
required product. The ILs obtained were dried by heating at
(343.15 to 353.15 K) and stirring under high vacuum (2 ¥ 10-1
Pa) for 48 h.
2-Ethyl-1-hexyl-3,5-dimethylpyridinium bromide (5). Yield
98%. 1H NMR (CDCl3): 1H NMR (CDCl3): d 9.47 (1H, s, 6-H),
7.99 (1H, s, 4-H), 4.76 (2H, dd, J1 = 5.7 Hz, J2 = 10.3 Hz,
NCH2), 3.02 (2H, q, J = 7.6 Hz, 2-CH2), 2.51 (3H, s, Ar-
CH3), 2.50 (3H, s, Ar-CH3), 1.91 (2H, m, NCH2CH2), 1.45 (2H
m, N(CH2)2CH2), 1.28 (7H, m, N(CH2)2CH2CH2, 2-CH2CH3),
0.81 (3H, t, J = 7.0 Hz, N(CH2)5CH3). 13C NMR (CDCl3): d
153.9, 147.2, 144.6, 136.9, 136.6, 57.9, 32.3, 31.2, 26.0, 22.7, 22.3,
19.2, 18.0, 13.9, 12.2. Electrospray MS (micrOTOF Focus) m/z
(%) 522 [(C15H26N)2 (81Br) + 1]+ (11), 521.32829 ([(C15H26N)2
(81Br)]+ requires 521.32896, 34), 520 [(C15H26N)2 (79Br) + 1]+
(12), 519.32939 ([(C15H26N)2 (79Br)]+ requires 519.33084, 28), 221
[(C15H26N) + 1]+ (18), 220 [(C15H26N)]+ (100).
1-Hexyl-2,3,5-trimethylpyridinium bis(trifluoromethanesul-
1
fonyl)imide (9). Yield 99%. H NMR (CDCl3): d 8.29 (1H, s,
6-H), 7.96 (1H, s, 4-H), 4.47 (2H, dd, J1 = 5.9 Hz, J2 = 10.3 Hz,
NCH2), 2.69 (3H, s, Ar-CH3), 2.50 (3H, s, Ar-CH3), 2.46 (3H, s,
Ar-CH3), 1.88 (2H, m NCH2CH2), 1.43 (2H, m, N(CH2)2CH2),
1.33 (4H, m, N(CH2)3CH2CH2), 0.88 (3H, t, J = 7.1 Hz,
N(CH2)5CH3). 13C NMR (CDCl3): d 150.6, 146.7, 142.2, 138.6,
136.3, 119.77 (q, JC-F = 321.4 Hz), 59.2, 31.0, 30.4, 25.9, 22.3,
19.9, 17.7, 16.1, 13.8. 19F RMN (CDCl3): d -78.92. Electrospray
MS (apex-Qe) m/z (%) 693.30 [(C14H24N)2 (C2F6NO4S2) + 1]+
(4), 692.29730 ([(C14H24N)2 (C2F6NO4S2)]+ requires 692.29849,
11), 207.19 [(C14H24N) + 1]+ (12), 206.19 [(C14H24N)]+ (100).
1-Ethyl-3,5-dimethyl-2-pentylpyridinium bromide (6). Yield
92%. 1H NMR (CDCl3): d 9.63 (1H, s, 6-H), 7.97 (1H, s, 4-H),
4.86 (2H, q, J = 7.27 Hz, NCH2), 2.94 (2H, dd, J1 = 9.45 Hz, J1 =
7.11 Hz, 1¢-Pen), 2.52 (3H, s, Ar-CH3), 2.49 (3H, s, Ar-CH3), 1.63
(3H, t, J = 7.3 Hz, NCH2CH3), 1.56 (2H, m, 2¢-Pen), 1.44 (2H,
m, 3¢-Pen), 1.34 (2H, m, 4¢-Pen), 0.89 (1H, t, J = 7.2 Hz, 5¢-Pen).
13C NMR (CDCl3): d 153.0, 147.2, 144.0, 137.2, 136.8, 53.5,
31.8, 29.2, 27.7, 22.2, 19.4, 18.0, 17.4, 13.8. Electrospray MS
(micrOTOF Focus) m/z (%) 207 [(C14H24N + 1]+ (15), 206.19012
([(C14H24N]+ requires 206.19033, 100).
2-Ethyl-1-hexyl-3,5-dimethylpyridinium bis(trifluoromethane-
sulfonyl)imide (10). Yield 97%. 1H NMR (CDCl3): d 8.36 (1H,
s, 6-H), 7.98 (1H, s, 4-H), 4.49 (2H, dd, J1 = 6.1 Hz, J2
=
10.1 Hz, NCH2), 3.05 (2H, q, J = 7.6 Hz, 2-CH2), 2.54 (3H, s, Ar-
CH3), 2.49 (3H, s, Ar-CH3), 1.93 (2H, m, NCH2CH2), 1.46 (2H,
m, N(CH2)2CH2), 1.35 (7H, m, N(CH2)3CH2CH2, 2-CH2CH3),
0.91 (3H, t, J = 6.9 Hz, N(CH2)5CH3). 13C NMR (CDCl3): d
154.6, 147.5, 142.7, 137.8, 136.7, 119.8 (q, JC-F = 321.4 Hz),
58.4, 31.8, 31.0, 26.0, 22.7, 22.3, 19.0, 17.7, 13.8, 11.7. 19F RMN
(CDCl3): d -78.92. Electrospray MS (micrOTOF Focus) m/z
(%) 722 [(C15H26N)2 (C2F6NO4S2) + 2]+ (10), 721 [(C15H26N)2
(C2F6NO4S2) + 1]+ (22), 720.32735 ([(C15H26N)2 (C2F6NO4S2)]+
requires 720.32979, 57), 637 [(C26H39F6N3O4S2) + 2]+ (2), 636
[(C26H39F6N3O4S2) + 1]+ (10), 221 [(C15H26N) + 1]+ (18), 220
[(C15H26N)]+ (100).
1-Butyl-3,5-dimethyl-2-pentylpyridinium bromide (7). Yield
1
91%. H NMR (CDCl3): d 9.64 (1H, s, 6-H), 7.96 (1H, s, 4-
H), 4.80 (2H, dd, J1 = 6.0 Hz, J2 = 9.9 Hz, NCH2), 2.92 (2H,
dd, J1 = 5.8 Hz, J2 = 10.7 Hz, 1¢-Pen), 2.52 (3H, s, Ar-CH3),
2.50 (3H, s, Ar-CH3), 1.97-1.87 (2H, m, NCH2CH2), 1.64-1.30
(m, 8H, N(CH2)2CH2, 2¢,3¢,4¢-Pen), 0.96 (3H, t, J = 7.3 Hz,
N(CH2)3CH3), 0.90 (3H, t, J = 7.2 Hz, 5¢-Pen). 13C NMR
(CDCl3): d 152.9, 147.2, 144.5, 137.1, 136.5, 57.6, 34.0, 31.8,
29.2, 27.7, 22.1, 19.7, 19.4, 18.0, 13.8, 13.6. Electrospray MS
(micrOTOF Focus) m/z (%) 235 [(C16H28N) + 1]+ (17), 234.22137
([(C16H28N)]+ requires 234.22163, 100).
1-Ethyl-3,5-dimethyl-2-pentylpyridinium bis(trifluoromethane-
sulfonyl)imide (11). Yield 89%. 1H NMR (CDCl3): d 8.39 (1H,
s, 6-H), 7.97 (1H, s, 4-H), 4.58 (2H, q, J = 7.3 Hz, NCH2), 2.98
(2H, dd, J1 = 7.2 Hz, J2 = 9.5 Hz, 1¢-Pen), 2.53 (3H, s, Ar-
CH3), 2.49 (3H, s, Ar-CH3), 1.64 (5H, m, NCH2CH3, 2¢-Pen),
2774 | Green Chem., 2011, 13, 2768–2776
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The Royal Society of Chemistry 2011
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