802
D. Fang et al.
1
in 94% as a colorless liquid. H NMR (300MHz): ꢀ ¼ 2.01
(q, J ¼ 7.2Hz, 2H, –C–CH2–C–SO3), 2.40 (t, J ¼ 7.5 Hz, 2H,
–C–C–C–CH2–SO3), 3.04 (s, 3H, –CH3), 3.35(t, J ¼ 7.1 Hz,
2H, –N–CH2–C–C–SO3), 3.44–3.51 (m, 4H, –N–CH2–C–
OH), 3.85–3.91 (m, 4H, –N–C–CH2–OH) ppm; MS: m=z
(%) ¼ 225.98 (Mþ ꢁ 1, 100), 453.00.
(aqueous medium containing catalyst) was reused in
the next run without further purification. As shown in
Fig. 1, the catalyst can be reused at least six times
without appreciable decrease in yield and reaction rate.
In conclusion, it was demonstrated that the readily
available zwitterionic liquids could behave as novel
recyclable catalysts for the Knoevenagel conden-
sation between aldehydes or ketones with active
methylene compounds offering a procedure with
generality, which is environmentally benign, and is
of practical convenience in the product separation
from the reaction system.
3-Hydroxyethylammonium-n-propanesulfonate
(HEAPS, C5H13NO4S)
This compound was prepared in analogy to THEAPS, with 1 h
reaction time at room temperature. The product was obtained
in 90% as a white solid. Mp 155–157ꢀC; 1H NMR (300 MHz):
ꢀ ¼ 1.98 (q, J ¼ 7.5 Hz, 2H, –C–CH2–C–SO3), 2.48 (t, J ¼
7.5 Hz, 2H, –C–C–C–CH2–SO3), 3.08 (s, 6H, –CH3), 3.41 (t,
J ¼ 4.2Hz, 2H, –N–CH2–C–C–SO3), 3.55 (t, J ¼ 4.2 Hz, 2H,
–N–CH2–C–OH), 3.83 (s, 2H, –N–C–CH2–OH) ppm; MS:
m=z (%) ¼ 183.89 (Mþ þ 1, 100), 366.90.
Experimental
Melting points were determined by X6-Data microscope
apparatus. 1H NMR spectra were recorded on Bruker DRX300
(300 MHz). Mass spectra were obtained with automated
FININIGAN TSQ QUANTUM ULTRA AM (Thermal) LC=
MS spectrometer. Thermal analysis was determined by Mettler
Toledo spectrometer (10ꢀC=min heating rate under nitrogen).
All chemicals (AR grade) were commercially available and
used without further purification.
General procedure for the Knoevenagel condensation
in the ZILs=H2O system
To 1.06g benzaldehyde (10 mmol) and 1.13 g ethyl cyanoace-
tate (10 mmol) in 6 cm3 H2O was added 1.0 mmol ZILs under
stirring. The mixture was typically allowed to proceed for a
length of time at room temperature with the vigorous stirring.
After TLC indicated that the starting materials has disap-
peared, the resulting mixture was filtered (solid product) or
decanted (liquid product) and then the crude product was
purified by recrystallization or chromatography (silica gel,
petroleum ether:ethyl acetate ¼ 5:1). The filtrate containning
the ZILs could be reused directly in the next run without
further purification. The products were identified by 1H NMR,
and physical data (mp or bp) with those reported in literature.
Synthesis of hydroxyl functionalized zwitterionic liquids
(ZILs)
All used HO-functionalized zwitterionic liquids were synthe-
sized according to our previous method [17d] with some
changes.
3-Trihydroxyethylammonium-n-propanesulfonate
(E)-Ethyl 2-cyano-3-phenylacrylate (3a, C12H11NO2)
1
(THEAPS, C7H21NO6S)
White crystals; mp 51ꢀC; H NMR (300 MHz, CDCl3): ꢀ ¼
To a solution of 13.3 cm3 triethanolamine (0.10 mol) in 20cm3
1,2-dichloroethane was added 12.2 g 1,3-propanesultone
(0.10 mol) in portions within 30 min, and then the mixture
was stirred under nitrogen for 2 h at 45–50ꢀC. A biphasic
mixture was then formed, the product (bottom phase) was
obtained by decantation of the solvent (upper phase), and then
washed repeatedly with a mixture of chloroform, petroleum
ether, and ethanol to remove the unreacted material and dried
in a vacuum at 60ꢀC. A yield of 92% of a colorless liquid
product was obtained, its melting point was not observed in
the DSC curve when heated from ꢁ60ꢀC to 50ꢀC. The TGA
analysis showed that THEAPS is thermally stable up to 240ꢀC
and this zwitterionic liquid was entirely miscible with water.
1H NMR (300MHz): ꢀ ¼ 2.13 (q, J ¼ 3.9 Hz, 2H, –C–CH2–
C–SO3), 2.88 (t, J ¼ 14.1Hz, 2H, –C–C–C–CH2–SO3),
3.34 (t, J ¼ 5.1 Hz, 2H, –N–CH2–C–C–SO3), 3.54–3.64 (m,
2Hþ 4H, –N–CH2–C–OH), 3.83–3.95 (m, 6H, –N–C–CH2–
OH) ppm; MS: m=z (%) ¼ 274.19, 272.07 (Mþþ1), 194.11,
150.09 (100), 132.
1.40 (t, J ¼ 6.9 Hz, 3H, CH3), 4.39 (q, J ¼ 6.9 Hz, 2H, CH2),
7.48–7.60 (m, 3H, Ar-H), 8.01 (d, J ¼ 7.2 Hz, 2H, Ar-H), 8.25
(s, 1H, CH¼) ppm; MS: m=z (%) ¼ 201.00 (Mþ, 100).
Acknowledgements
We are grateful to the Educatison Commission of Jiangsu
Province (07 KJD530238), Jiangsu Provincial Key Lab
of Coast wetland Bioresource and Environment Protection
(JLCBE07020), and Nanjing University of Science and Tech-
nology (No. 2006001) for financial support. Z.-H. Fei was
funded by ‘‘qing-lan’’ project and ‘‘333’’ project of Jiangsu
Province.
References
1. a) Trost BM (1991) In: Comprehensive Organic Synthesis,
vol.2.PergamonPress,Oxford,p341;b)BalalaieS,Sheikh-
Ahmadi M, Bararjanian M (2007) Catal Commun 8:1724
2. Khan AT, Parvin T, Choudhury LH (2007) Tetrahedron
63:5593
3-Dihydroxyethylammonium-n-propanesulfonate
(DHEAPS, C7H17NO5S)
3. Kantevari S, Bantu R, Nagarapu L (2007) J Mol Catal A:
Chemical 269:53
This compound was prepared in analogy to THEAPS, with 2 h
reaction time at room temperature. The product was obtained