1-Butyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid
COMMUNICATIONS
77, 65; IR (KBr): n 3368, 2942, 1619, 1518, 1448, 1328, 1257,
1158, 1085, 808 cmÀ1; anal. calcd. for C21H22N2O2S (366.47): C
68.82, H 6.05, N 7.64, S 8.74; found: C 68.87, H 6.09, N 7.69, S,
8.79.
both cation and anion play an important role as the
reaction media. The scope and generality of this process
is illustrated with respect to various aziridines and
arylamines and the results are presented in Table 1. The
use of [bmim]BF4 ionic liquid as reaction media for this
transformation avoids the use of heavy metal Lewis
acids or acidic promoters and also avoids aqueous work-
up to isolate the products. The simple experimental and
product isolation procedures combined with the ease of
recovery and reuse of the novel reaction medium is
expected to contribute to the development of a green
strategy for the synthesis of 1,2-diamines.
In summary, this paper describes a novel and efficient
method for the synthesis of 1,2-diamines by regioselec-
tive ring opening of aziridines with arylamines using
imidazolium-based ionic liquids as novel reaction media
as well as promoters. This method is also useful for the
preparation of b-azidoamines from aziridines and
sodium azide. The notable features of this procedure
are mild reaction conditions, simplicity in operation,
improved yields and reaction rates, cleaner reaction
profiles and recyclability of ionic liquids which make it a
simple, convenient and user-friendly process for the
synthesis of 1,2-diamines.
1
4e: solid, mp 98 1008C; H NMR (400 MHz, CDCl3): d
7.78 (d, 2H, J 8.2 Hz), 7.23 (d, 2H, J 8.2 Hz), 7.07 (t, 2H, J
8.0 Hz), 6.65 (t, 1H, J 8.0 Hz), 6.43 (d, 2H, J 8.2 Hz), 5.38
(brd, J 5.7 Hz, 1H), 3.30 3.45 (m, 2H), 2.38 (s, 3H), 2.08
2.25 (m, 2H), 1.60 1.85 (m, 2H), 1.20 1.35 (m, 2H); EIMS: m/
z 330 [M ], 175, 132, 120, 91, 56; IR (neat): n 3378, 2967,
1621, 1538, 1448, 1332, 1156, 1098, 824, 677 cmÀ1; anal. calcd.
for C18H22N2O2S (330.44): C 65.42, H 6.70, N 8.47, S 9.70; found:
C 65.47, H 6.73, N 8.51, S 9.75.
4 h: solid, mp 152 1548C; 1H NMR (400 MHz, CDCl3): d
7.70 (d, 2H, J 8.3 Hz), 7.30 (d, 2H, J 8.3 Hz), 7.08 (t, 2H, J
8.0 Hz), 6.65 (t, 1H, J 8.0 Hz), 6.40 (d, 2H, J 8.3 Hz), 4.84
(brd, J 5.5 Hz, 1H), 3.40 (brs, 1H), 3.10 (ddd, J 3.9, 10.0,
10.0 Hz, NCH, 1H), 2.95 (ddd, J 4.0, 10.0, 10.0 Hz, NCH, 1H),
2.45 (s, 3H), 2.03-2-20 (m, 2H), 1.65 1.70 (m, 2H), 1.23 1.38
(m, 3H), 0.99 1.05 (m, 1H); EIMS: m/z 344 [M ], 189, 172,
141, 96, 91, 65; IR (neat): n 3400, 2958, 1620, 1528, 1423, 1324,
1092, 824, 732 cmÀ1; anal. calcd. for C19H24N2O2S (344.47): C
66.24, H 7.01, N 8.12, S 9.30; found: C 66.29, H 7.05, N 8.16, S
9.35.
1
3 m: solid, mp 68 708C; H NMR (200 MHz, CDCl3): d
7.78 (d, 2H, J 8.0 Hz), 7.20 (d, 2H, J 8.3 Hz), 7.05 (t, 2H, J
7.8 Hz), 6.70 (t, 1H, J 7.8 Hz), 6.40 (d, 2H, J 8.0 Hz), 5.15
(m, 1H, NH), 4.20 (dd, 1H, J 4.0, 9.8 Hz), 3.15 (ddd, 1H, J
4.0, 9.8, 10.0 Hz), 3.0 (ddd, 1H, J 3.5, 9.8, 10.0 Hz), 2.43 (s,
3H), 1.38 1.50 (m, 2H), 1.08 1.20 (m, 4H), 0.80 (t, 3H, J
Experimental Section
6.8 Hz); EIMS: m/z 346 [M ], 162, 106, 91, 65; IR (KBr): n
Melting points were recorded on Buchi R-535 apparatus and
are uncorrected. IR spectra were recorded on a Perkin-Elmer
FT-IR 240-c spectrophotometer using KBr optics. 1H and
13C NMR spectra were recorded on Gemini-200 spectrometer
in CDCl3 using TMS as internal standard. Mass spectra were
recorded on a Finnigan MAT 1020 mass spectrometer operat-
ing at 70 eV. [Bmim]BF4 and [bmim]PF6 ionic liquids were
prepared according to the procedures reported in the liter-
ature.[13]
3268, 2930, 1602, 1508, 1433, 1318, 1158, 1089, 966, 815,
751 cmÀ1; anal. calcd. for C19H26N2O2S (346.48): C 65.85, H
7.56, N 8.09, S 9.25; found: C 65.89, H 7.59, N 8.11, S 9.29.
Acknowledgements
BVS and KP thank CSIRNew Delhi, for the award of
fellowships.
General Procedure
References and Notes
A mixture of aziridine (1 mmol), arylamine (1 mmol), in
[bmim]BF4 or [bmim]PF6 (2 mL) was stirred at room temper-
ature for the appropriate time (Table 1). After completion of
the reaction, as indicated by TLC, the reaction mixture was
washed with diethyl ether (3 Â 10 mL). The combined ether
extracts were concentrated under vacuum and the resulting
product was directly charged onto a small silica gel column and
eluted with a mixture of ethyl acetate:n-hexane (1:9) to afford
the pure 1,2-diamine. The remaining ionic liquid was further
washed with ether and dried at 808C under reduced pressure to
retain its activity in subsequent runs. In the case of solids, the
products were purified by recrystallization in an appropriate
solvent.
[1] a) D. Tanner, Angew. Chem. Int. Ed. Engl. 1994, 33, 599;
b) W. McCoull, F. A. Davis, Synthesis 2000, 1347.
[2] a) A. Dureault, I. Tranchepain, J. C. Depezay, J. Org.
Chem. 1989, 54, 5324; b) D. Tanner, H. M. He, Tetrahe-
dron 1992, 48, 6079.
[3] T. Hudlicky, H. Luna, J. D. Price, F. Rulin, J. Org. Chem.
1990, 55, 4683.
[4] a) A. R. Katritzky, C. W. Rees, Comprehensive Hetero-
cylic Chemistry, Pergamon Press, Oxford, 1984, Vol. 7,
pp. 47; b) J. E .G. Kump, Comprehensive Organic Syn-
thesis, (Eds.: B. M. Trost, I. Fleming), Pergamon Press,
Oxford, 1991, Vol. 7, pp. 469.
[5] a) Drugs of the Future 1999, 24, 1175; b) P. W. Smith,
S. L. Sollis, P. D. Howes, P. C. Cherry, I. D. Starkey, K. N.
Cobley, H. Weston, J. Scicinski, A. Merritt, A. Whitting-
ton, P. Wyatt, N. Taylor, D. Green, R. C. Bethell, S.
Madar, R. J. Fenton, P. J. Morley, T. Patemann, A.
2a: solid, mp 150 1528C; 1H NMR (200 MHz, CDCl3): d
7.78 (d, 2H, J 8.0 Hz), 7.58 7.63 (m, 1H), 7.20 7.38 (m, 6H),
7.05 (t, 2H, J 7.8 Hz), 6.60 (t, 1H, J 7.8 Hz), 6.40 (d, 2H, J
8.0 Hz), 5.25 (brd, 1H, J 6.5 Hz), 4.30 (dd, 1H, J 4.0, 9.8 Hz),
3.18 (ddd, 1H, J 4.0, 9.8, 10.0 Hz), 3.0 (ddd, 1H, J 3.7, 9.8,
10.0 Hz), 2.40 (s, 3H); EIMS: m/z 366 [M ], 180, 155, 104, 91,
Adv. Synth. Catal. 2003, 345, 948 952
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