Synthesis of fluorinated imines and carbodiimides from azides via aza-Wittig reaction

Article abstract of DOI:10.1016/j.jfluchem.2006.06.004

The Staudinger reaction of fluoroalkylazides were studied. A series of N-fluoroalkylimines were synthesized via aza-Wittig reaction of N-fluoroalkyliminophosphoranes. The N,N′-difluoroalkylated carbodiimide was also synthesized via the reaction of N-fluor

Full text of DOI:10.1016/j.jfluchem.2006.06.004

Journal of Fluorine Chemistry 127 (2006) 1152–1157
www.elsevier.com/locate/fluor
Synthesis of fluorinated imines and carbodiimides
from azides via aza-Wittig reaction
a,b
a
Yongming Wu a, , Qingrui Sun , Juan Deng , Weisheng Tian
*
a,b,**
a Key Laboratory Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
354 Fenglin Lu, Shanghai 200032, PR China
b Life and Environment Science College, Shanghai Normal University, 100 Guilin Rd., Shanghai 200234, PR China
Received 7 April 2006; received in revised form 3 June 2006; accepted 6 June 2006
Available online 9 June 2006
Abstract
The Staudinger reaction of fluoroalkylazides were studied. A series of N-fluoroalkylimines were synthesized via aza-Wittig reaction of N-
fluoroalkyliminophosphoranes. The N,N0-difluoroalkylated carbodiimide was also synthesized via the reaction of N-fluoroalkyliminophosphoranes
with carbon dioxide or carbon disulfide.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Fluoroalkylazide; N-Fluoroalkylimines; N-Fluoroalkyliminophosphoranes; N,N0-Difluoroalkylated carbodiimides; Staudinger reaction; Aza-Wittig
reaction
1. Introduction
fluoroalkylazides, in this paper we would like to report the
Staudinger reaction and aza-Wittig reaction of this kind of
azides.
The Staudinger reaction between triphenylphosphines and
alkyl azides [1] is useful in organic synthesis. Since the first
report of the synthesis of iminophosphoranes by the reaction of
a triary phosphine with organic azides [2], numerous articles
have reported on the reactions and synthetic applications of
these kind of compounds. They can be used to synthesis of
Schift base [3], imidoyl halides [4], isocyanate and isothio-
cyanate [3,5], and different kind of heterocycles [6].
2. Results and discussion
The Staudinger reaction of fluoroalkylazide proceeded very
smoothly under room temperature and the N-fluoroalkylimi-
nophosphoranes 3 was precipitated as a white solid in the
reaction mixture. The iminophosphoranes was obtained by
direct filtration without further purification (Scheme 1).
With the iminophosphoranes 1 in hand, we then studied it’s
aza-Wittig reaction with carbonyl compounds. Firstly we used
the reaction of 1a and benzaldehyde as the model reaction,
various conditions were studied and the results were listed in
Table 1. From the table it was found that when THF was used as
solvent, the imine was obtained in 53.8% yield at 50 8C after 2
days. Toluene was the best solvent, the imine could be obtained
in 62.3% yield at 80 8C.
It has been known for some time that fluorine atom can lead
to unexpected results on biological activity arising due to the
special properties of the fluorine atom, such as the highest
electronegativity of fluorine and high carbon–fluorine bond
energy [7]. To the best our knowledge there are very few reports
on the synthesis of fluorinated imine, especially for the
synthesis of N-fluoroalkyl substituted imine. During the course
of our study of the synthesis of organofluorine compounds by
fluorinated building block strategy, we developed fluorinated
alkylazides as the intermediates for synthesis of fluoroalkyl
substituted 1,2,3-triazoles [8]. To expand the utility of these
The reactions of 3 with different carbonyl compounds were
explored under the optimized reaction conditions, the results
are shown in Scheme 2 and Table 2.
From the table, it was found that different carbonyl
compounds, e.g.: arylaldehydes (entries: 1–4 and 8–11),
heterocyclic aldehydes (entries: 5, 6, 12, 13) and benzoyl
* Corresponding author. Tel.: +86 21 54925190; fax: +86 21 64166128.
** Corresponding author.
E-mail address: ymwu@mail.sioc.ac.cn (Y. Wu).
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2006.06.004

Y. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 1152–1157
1153
Table 1
aza-Wittig reaction under different conditions
Entry
Solvent
Temperature (8C)
Time (day)
Yield (%)
1
2
3
4
DMSO
THF
80
50
r.t.
80
3
2
3
3
41.5
53.8
57.2
62.3
CH2Cl2
Toluene
Table 2
Results of the aza-Wittig reaction
Entry
1
Rf
R1
Time (day)
2
Product
Yielda (%)
61.0
HCF2CF2CH2
5aa
2
3
HCF2CF2CH2
HCF2CF2CH2
HCF2CF2CH2
HCF2CF2CH2
HCF2CF2CH2
HCF2CF2CH2
CF3CH2
2
3
2
3
3
2
2
2
3
2
4
4
2
5ab
5ac
5ad
5ae
5af
78.7
64.4
65.1
62.3
57.6
62.3
41.3
82.7
66.2
85.7
29.2
30.3
78.3
4
5
6
7
5ag
5ba
5bb
5bc
5bd
5be
5bf
5bg
8
9
CF3CH2
10
11
12
13
CF3CH2
CF3CH2
CF3CH2
CF3CH2
14
CF3CH2
a
Isolated yield.

1154
Y. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 1152–1157
3. Conclusion
In conclusion, a series of N-fluoroalkylimines were
synthesis by the reaction of N-fluoroalkyliminophosphoranes
with carbonyl compounds, which may be applied in the
synthesis fluorinated organic compounds. N,N0-Difluoroalky-
lated carbodiimides could also be synthesized by the reaction
of N-fluoroalkyliminophosphoranes with carbon dioxide or
carbon disulfide. Further studies are currently in progress in
this lab.
Scheme 1. The Staudinger reaction of fluoroalkylazides.
4. Experimental
Unless otherwise noted, solvents and reagents were
1
commercial available and used as received. H NMR spectra
were recorded on a Brucker AM-300 (300 MHz) spectrometer
with Me4Si as internal standard. 19F NMR spectra were taken
on Brucker AM-300 (282 MHz) spectrometer with CFCl3 as
external standard, downfield shifts being designed as positive.
The 13C NMR spectra were measured at Brucker AM-300
(75 MHz) spectrometer with all protons decoupled, and the
chemical shifts are reported in ppm downfield of SiMe4. Mass
spectra were taken on a HP 5989a spectrometer, and accurate
mass measurements were performed on Finnigan MAT
instrument, while elemental analysis were performed by this
institute.
Scheme 2. The aza-Wittig reaction of N-fluoroalkyliminophosphoranes.
chloride (entries: 7, 14) could proceed the aza-Wittig reaction
with N-fluoroalkyliminophosphoranes 3 smoothly in good to
excellent yields. For benzoyl chloride, imidoyl chlorides were
obtained as the product. Electron-withdrawing group in the
benzene ring would raise the reaction yields (entries 2, 9 versus
entries 3, 10). Comparing with the non-fluorinated imines, N-
fluoroalkylimines were very unstable, they will hydrolyze
during flash chromatography in a silica gel column. So all the
products were purified by distillation. The imines could also be
obtained in one pot reaction started from fluoroalkylazides with
no effects on the yield.
4.1. Typical procedure for the preparation of N-
fluoroalkyliminophosphoranes (3)
To a solution of azide (30 mmol) in diethyl ether (20 mL), a
solution of PPh3 (30 mmol) in 30 mL Et2O was added
dropwised. After addition, the mixture was stirred at room
temperature for 6 h. A white solid was precipitated in the
reaction system. After filtration and dryness afford the product
3. Without further purification, the solid can be used to
following reaction.
This kind of N-fluoroalkyliminophosphoranes could also
react with carbon dioxide or carbon disulfide. Not as Trabelsl’s
reported results [5a], in our instance, no isocyanate or
isothiocyanate could be obtained, what we obtained was
N,N0-difluoroalkylated carbodiimides 7. These different results
might be due to the difference of the block group between N
atom and CF2 in N-fluoroalkyliminophosphoranes. In the
Trabelsl’s report there are two CH2 appeared in between N atom
and CF2, while in our research there was only one. The short
CH2 chain made the strong electron-withdrawing effects for the
N P bond which resulted in better reactivity for the N-
fluoroalkyliminophosphoranes (Scheme 3).
4.1.1. N-(2,2,3,3-Tetrafluoro-propyl)-iminophosphoranes
(3a)
Colorless solid; m.p.; 110–111 8C. IR (KBr) (cmꢀ1): 2825,
1143, 1098. 1H NMR (CDCl3) d 3.54 (2H, q, J = 14.0 Hz, CH2),
6.34 (1H, tt, J1 = 6.0 Hz, J2 = 54.0 Hz, H–C), 7.41–7.67 (15H,
m, Ar). 19F NMR (CDCl3) d ꢀ142.06 (2F, d, JFF = 5.4 Hz),
ꢀ124.79 (2F, m). MS: m/z (%) 391 (M+, 7.00), 390 (10.00), 290
(100.00), 262 (10.00), 183 (20.00). Anal. calcd. for
C21H18F4NP: C, 64.45; H, 4.64; N, 3.58; P, 7.91. Found: C,
64.59; H, 4.72; N, 3.37; P, 8.04.
4.1.2. N-(2,2,2-Trifluoro-ethyl)-iminophosphoranes (3b)
Colorless solid; m.p.; 155–156 8C; IR (KBr) (cmꢀ1): 2840,
1
1439, 1130. H NMR (CDCl3) d 3.571 (2H, qd, J1 = 10.0 Hz,
J2 = 22.0 Hz, CH2), 7.421–7.702 (15H, m, Ar). 19F NMR
(CDCl3) d ꢀ73.51 (3F, t, J = 10.0 Hz). MS: m/z (%) 359 (M+,
23.09), 358 (49.10), 290 (100.00), 262 (22.03), 183 (34.00).
Anal. calcd. for C20H17F3NP: C, 66.85; H, 4.77; N, 3.90; P,
8.62. Found: C, 66.91; H, 4.82; N, 3.75; P, 8.60.
Scheme 3. Preparation of carbodiimide.

Y. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 1152–1157
1155
4.2. Typical procedure for the preparation of N,N0-
difluoroalkylimines (5)
4.2.5. (4-Methoxy-benzylidene)-(2,2,3,3-tetrafluoro-
propyl)-amine (5ac)
Colorless liquid. b.p.; 73–75 8C, 17 mmHg. IR (KBr)
A solution of N-fluoroalkyliminophosphoranes 3 (10 g,
25 mmol) and carbonyl compounds 4 (2.12 g, 20 mmol) in
toluene (mL) was stirred at 80 8C. The reaction was monitored
by TLC. After completion (2–3 days), the solvent was removed
under reduced pressure and the residue was washed with
hexane (3 ꢁ 10). After removing of the solvent under reduced
pressure. The residue was purified by distillation under reduced
pressure to yield 5 as a colorless liquid.
(cmꢀ1): 1652, 1607, 1515, 1258, 1168, 1107, 1040, 831,
1
701, 678. H NMR (CDCl3) d 3.86 (3H, s, CH3), 4.06 (2H, t,
J = 14.1 Hz, CH2), 6.06 (1H, tt, J1 = 5.7 Hz, J2 = 53.4 Hz, H–
C), 6.94 (2H, d, J = 9.0 Hz, Ar), 7.70 (2H, d, J = 8.7 Hz, Ar),
8.26 (1H, s, H–C ). 19F NMR (CDCl3) d ꢀ139.62 (2F, d,
J
FF = 5.1 Hz), ꢀ122.61 (2F, m). MS: m/z (%) 249 (M+, 25.78),
230 (1.87), 148 (42.22), 121 (100.00), 51 (23.43). Anal. calcd.
for C11H11F4NO: C, 53.02; H, 4.45; N, 5.62. Found: C, 53.05;
H, 5.45; N, 4.44.
4.2.1. N-(2,2,3,3-Tetrafluoro-propyl)-iminophosphoranes
(3a)
4.2.6. (4-Chloro-benzylidene)-(2,2,3,3-tetrafluoro-propyl)-
amine (5ad)
Colorless solid; m.p.; 110–111 8C. IR (KBr) (cmꢀ1): 2825,
1143, 1098. 1H NMR (CDCl3) d 3.54 (2H, q, J = 14.0 Hz, CH2),
6.34 (1H, tt, J1 = 6.0 Hz, J2 = 54.0 Hz, H–C), 7.41–7.67 (15H,
m, Ar). 19F NMR (CDCl3) d ꢀ142.06 (2F, d, JFF = 5.4 Hz),
ꢀ124.79 (2F, m). MS: m/z (%) 391 (M+, 7.00), 390 (10.00), 290
(100.00), 262 (10.00), 183 (20.00). Anal. calcd. for
C21H18F4NP: C, 64.45; H, 4.64; N, 3.58; P, 7.91. Found: C,
64.59; H, 4.72; N, 3.37; P, 8.04.
Colorless liquid. b.p.; 60–63 8C, 18 mmHg. IR (KBr)
(cmꢀ1): 1652, 1597, 1573, 1186, 1110, 1040, 828, 749, 679.
1H NMR (CDCl3) d 4.09 (2H, t, J = 12.9 Hz, CHz, CH2), 6.05
(1H, tt, J1 = 3.9 Hz, J2 = 53.4 Hz, H–C), 7.42 (2H, d,
J = 10.8 Hz, Ar), 7.70 (2H, d, J = 6.6 Hz, Ar), 8.30 (1H, s,
H–C ). 19F NMR (CDCl3) d ꢀ139.47 (2F, d, JFF = 43.98 Hz),
ꢀ122.25 (2F, m). MS: m/z (%) 253 (M+, 13.35), 234 (2.17), 218
(1.86), 152 (73.09), 125 (100.00), 51 (32.61). Anal. calcd. for
C10H8F4NCl: C, 47.36; H, 3.18; N, 5.52. Found: C, 47.74; H,
3.18; N, 5.71.
4.2.2. N-(2,2,2-Trifluoro-ethyl)-iminophosphoranes (3b)
Colorless solid; m.p.; 155–156 8C; IR (KBr) (cmꢀ1): 2840,
1
1439, 1130. H NMR (CDCl3) d 3.571 (2H, qd, J1 = 10.0 Hz,
J2 = 22.0 Hz, CH2), 7.421–7.702 (15H, m, Ar). 19F NMR
(CDCl3) d ꢀ73.51 (3F, t, J = 10.0 Hz). MS: m/z (%) 359 (M+,
23.09), 358 (49.10), 290 (100.00), 262 (22.03), 183 (34.00).
Anal. calcd. for C20H17F3NP: C, 66.85; H, 4.77; N, 3.90; P,
8.62. Found: C, 66.91; H, 4.82; N, 3.75; P, 8.60.
4.2.7. (2,2,3,3-Tetrafluoro-propyl)-thiophen-2-
ylmethylene-amine (5ae)
Colorless liquid. b.p.; 63–65 8C, 14 mmHg. IR (KBr)
(cmꢀ1): 1640, 1433, 1184, 1107, 1047, 833, 763, 717. 1H
NMR (CDCl3) d 4.05 (2H, q, J = 12.3 Hz, CH2), 6.04 (1H, tt,
J1 = 5.4 Hz, J2 = 54 Hz, H–C), 7.10 (1H, q, J = 3.6 Hz, H–C ),
7.39 (1H, d, J = 3.6 Hz, H–C ), 7.48 (1H, d, J = 4.8 Hz, H–
C ), 8.43 (1H, s, H–C ). 19F NMR (CDCl3) d ꢀ139.84 (2F, d,
4.2.3. Benzylidene-(2,2,3,3-tetrafluoro-propyl)-amine
(5aa)
Colorless liquid. b.p.; 66–68 8C, 16 mmHg. IR (KBr)
J
FF = 45.90 Hz), ꢀ122.55 (2F, m). MS: m/z (%) 225 (M+,
1
(cmꢀ1): 1651, 1582, 1453, 1105, 1038, 1829, 757, 693. H
13.76), 206 (1.75), 124 (55.91), 110 (5.64), 97 (100.00), 51
(27.93). Anal. calcd. for C8H7F4NS: C, 42.67; H, 3.13; N, 6.22.
Found: C, 42.84; H, 3.14; N, 6.12.
NMR (CDCl3) d 4.09 (2H, t, J = 13.6 Hz, CH2), 6.07 (1H, tt,
J1 = 5.4 Hz, J2 = 53.4 Hz, H–C), 7.40–7.51 (3H, m, Ar),
7.74–7.77 (2H, m, Ar), 8.34 (1H, s, H–C ). 19F NMR
(CDCl3) d ꢀ139.75 (2F, d, JFF = 43.71 Hz), ꢀ122.25 (2F, m).
MS: m/z (%) 219 (M+, 12.87), 200 (3.29), 142 (0.89), 118
(72.86), 91 (100.00), 77 (13.29), 51 (27.30). Anal. calcd. for
C10H9F4N: C, 54.80; H, 4.14; N, 6.39. Found: C, 54.67; H,
4.07; N, 6.17.
4.2.8. Furan-2-ylmethylene-(2,2,3,3-tetrafluoro-propyl)-
amine (5af)
Colorless liquid. b.p.; 56–60 8C, 13 mmHg. IR (KBr)
(cmꢀ1): 1660, 1486, 1275, 1103, 1039, 836, 755, 695. 1H
NMR (CDCl3) d 4.07 (2H, q, J = 12.6 Hz, CH2), 6.04 (1H, tt,
J1 = 5.4 Hz, J2 = 54 Hz, H–C), 6.52 (1H, q, J = 1.5 Hz, H–C ),
6.88 (1H, d, J = 3.6 Hz, H–C ), 7.57 (1H, d, J = 0.9 Hz, H–
C ), 8.140 (1H, s, H–C ). 19F NMR (CDCl3) d ꢀ139.42 (2F, d,
4.2.4. (4-Nitro-benzylidene)-(2,2,3,3-tetrafluoro-propyl)-
amine (5ab)
Colorless liquid. b.p.; 86–89 8C, 18 mmHg. IR (KBr)
(cmꢀ1): 1650, 1604, 1527, 1352, 1188, 856, 746, 703. 1H
NMR (CDCl3) d 4.16 (2H, t, J = 14.1 Hz, CH2), 6.05 (1H, tt,
J1 = 4.8 Hz, J2 = 53.4 Hz, H–C), 7.94 (2H, d, J = 8.4 Hz, Ar),
8.29 (2H, d, J = 8.1 Hz, Ar), 8.44 (1H, s, H–C ). 19F NMR
(CDCl3) d ꢀ139.47 (2F, d, JFF = 49.68 Hz), ꢀ122.25 (2F, m).
MS: m/z (%) 265 (M+, 6.16), 264 (M+, 3.70), 248 (4.49), 217
(5.50), 163 (100.00), 117 (94.12), 51 (37.60). Anal. calcd. for
C10H8F4N2O2: C, 45.46; H, 3.05; N, 10.60. Found: C, 45.86; H,
2.92; N, 10.67.
J
FF = 5.1 Hz), ꢀ122.22 (2F, m). MS: m/z (%) 209 (M+, 13.77),
190 (2.48), 108 (100.00), 101 (2.13), 81 (88.15), 51 (42.84).
Anal. calcd. for C8H7F4NO: C, 45.94; H, 3.37; N, 6.70. Found:
C, 45.90; H, 3.37; N, 6.50.
4.2.9. N-(2,2,3,3-Tetrafluoro-propyl)-benzimidoylchloride
(5ag)
Colorless liquid. b.p.; 65–67 8C, 14 mmHg. IR (KBr)
(cmꢀ1): 1666, 1449, 1190, 1104, 1035, 910, 833, 783, 688.
1H NMR (CDCl3) d 4.16 (2H, t, J = 13.5 Hz, CH2), 6.09 (1H, tt,

1156
Y. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 1152–1157
J1 = 4.8 Hz, J2 = 53.4 Hz, H–C), 7.25–7.54 (3H, m, Ar), 7.99–
8.02 (2H, m, Ar). 19F NMR (CDCl3) d ꢀ139.04 (2F, m),
ꢀ121.81 (2F, m). MS: m/z (%) 254 (M+, 12.09), 234 (2.20), 218
(100.00), 124 (0.63), 77 (27.14), 51 (50.40). Anal. calcd. for
C10H8F4N2O2: C, 47.36; H, 3.18; N, 5.52. Found: C, 47.42; H,
3.29; N, 5.46.
(CDCl3) d 4.09 (2H, q, J = 9.0 Hz, CH2), 7.10 (1H, t,
J = 4.2 Hz, H–C ), 7.41 (1H, d, J = 3.3 Hz, H–C ), 7.49
(1H, d, J = 5.1 Hz, H–C ), 8.44 (1H, s, H–C ). 13C NMR
(CDCl3) d 61.24, 122.58, 127.56, 130.61, 132.28, 146.67,
159.86. 19F NMR (CDCl3) d ꢀ70.86 (3F, t, JFF = 9.025 Hz).
MS: m/z (%) 193 (M+, 45.01), 174 (0.81), 110 (14.23), 97
(100.00), 83 (26.14), 69 (21.68), 51 (7.32). HRMS calcd. for
C7H6NF3NS: 193.0173; found: 193.0175.
4.2.10. Benzylidene-(2,2,2-trifluoro-ethyl)-amine (5ba)
Colorless liquid. b.p.; 65–66 8C, 15 mmHg. IR (KBr)
(cmꢀ1): 1651, 1583, 1265, 1140, 1044, 828, 756, 670. 1H
NMR (CDCl3) d 4.12 (2H, q, J = 9.1 Hz, CH2), 7.40–7.51 (3H,
m, Ar), 7.77–7.80 (2H, m, Ar), 8.35 (1H, s, H–C ). 13C NMR
(CDCl3) d 61.60, 122.74, 126.40, 128.65, 128.75, 129.03,
131.73, 135.14, 166.85. 19F NMR (CDCl3) d ꢀ70.87 (3F, t,
4.2.15. Furan-2-ylmethylene-(2,2,2-trifluoro-ethyl)-amine
(5bf)
Colorless liquid. b.p.; 50–52 8C, 15 mmHg. IR (KBr)
(cmꢀ1): 1651, 1485, 1265, 1142, 1046, 845, 754, 678. H
1
NMR (CDCl3) d 4.08 (2H, q, J = 9.3 Hz, CH2), 6.52 (1H, t,
J = 1.8 Hz, H–C ), 6.90 (1H, d, J = 3.3 Hz, H–C ), 7.58
(1H, s, H–C ), 8.15 (1H, s, H–C ). 13C NMR (CDCl3) d
61.24, 112.14, 116.29, 122.54, 126.22, 129.89, 145.83,
150.68, 154.89. 19F NMR (CDCl3) d ꢀ70.84 (3F, t,
J
FF = 9.0 Hz). MS: m/z (%) 187 (M+, 26.30), 118 (67.21), 110
(6.19), 91 (100.00), 83 (17.35), 77 (26.33), 51 (28.80). HRMS
calcd. for C9H8NF3: 187.0609; found: 187.0616.
4.2.11. (4-Nitro-benzylidene)-(2,2,2-trifluoro-ethyl)-amine
(5bb)
J
FF = 9.0 Hz). MS: m/z (%) 177 (M+, 45.30), 108 (100.00),
97 (18.66), 94 (12.96), 83 (49.96), 70 (51.78), 51
(21.98). HRMS calcd. for C7H6NF3NO: 177.0401; found:
177.0400.
Colorless liquid. b.p.; 81–83 8C, 17 mmHg. IR (KBr)
(cmꢀ1): 1650, 1524, 1345, 1155, 1043, 846, 737, 670, 557.
1H NMR (CDCl3) d 4.19 (2H, q, J = 7.5 Hz, CH2), 7.98 (2H, d,
J = 8.7 Hz, Ar), 8.31 (2H, t, J = 8.4 Hz, Ar), 8.45 (1H, s, H–
C ). 19F NMR (CDCl3) d ꢀ70.69 (3F, t, JFF = 9.0 Hz). MS: m/z
(%) 232 (M+, 32.68), 213 (1.14), 185 (14.87), 163 (100.00), 136
(17.53), 110 (15.37), 83 (30.73). Anal. calcd. for C9H7F3N2O2:
C, 46.56; H, 3.04; N, 12.07. Found: C, 47.09; H, 3.20; N, 11.78.
4.2.16. N-(2,2,2-Trifluoro-ethyl)-benzimidoylchloride
(5bg)
Colorless liquid. b.p.; 59–62 8C, 14 mmHg. IR (KBr)
(cmꢀ1): 1668, 1582,1449, 1288, 1131, 911, 840, 767, 688.
1H NMR (CDCl3) d 4.18 (2H, q, J = 9.3 Hz, CH2), 7.41–7.53
(3H, m, Ar), 8.03–8.06 (2H, m, Ar). 19F NMR (CDCl3) d
ꢀ71.00 (3F, t, JFF = 10.7 Hz). MS: m/z (%) 221 (M+, 0.82), 186
(100.00), 146 (3.18), 104 (40.54), 89 (3.48), 77 (24.15). Anal.
calcd. for C9H7F3N: C, 48.78; H, 3.18; N, 6.32. Found: C,
48.88; H, 3.19; N, 6.30.
4.2.12. (4-Methoxy-benzylidene)-(2,2,2-trifluoro-ethyl)-
amine (5bc)
Colorless liquid. b.p.; 70–71 8C, 16 mmHg. IR (KBr)
(cmꢀ1): 1650, 1606, 1515, 1259, 1141, 1110, 1049, 836,
671. 1H NMR (CDCl3) d 3.86 (3H, s, CH3), 4.08 (2H, t,
J = 9.6 Hz, CH2), 6.94 (2H, d, J = 8.1 Hz, Hz, Ar), 7.73 (2H, d,
J = 8.1 Hz, Ar), 8.27 (1H, s, H–C ). 19F NMR (CDCl3) d
ꢀ70.96 (3F, m). MS: m/z (%) 217 (M+, 63.98), 198 (1.98), 148
(41.42), 121 (100.00), 83 (11.07), 51 (18.34). Anal. calcd. for
C10H10F3NO: C, 55.30; H, 4.64; N, 6.45. Found: C, 55.47; H,
4.63; N, 6.51.
4.3. Preparation of N,N0-difluoroalkylated carbodiimide 7
CO2 gas was bubbled into a solution of 3b (2 mmol) and
Et2O (20 mL), a white was appeared in the reaction system. The
reaction was monitored by TLC. After completion, the solvent
was removed under reduced pressure. The residue was purified
by flash chromatography on a silicon gel column with
petroleum ether/ethyl acetate (v/v = 10:1) as eluent.
4.2.13. (4-Chloro-benzylidene)-(2,2,2-trifluoro-ethyl)-
amine (5bd)
Colorless liquid. b.p.; 59–60 8C, 15 mmHg. IR (KBr)
(cmꢀ1): 1653, 1597, 1492, 1278, 1143, 1048, 834, 670, 573.
1H NMR (CDCl3) d 4.12 (2H, q, J = 8.1 Hz, CH2), 7.42 (2H, t,
J = 6.9 Hz, Ar), 7.74 (2H, t, J = 6.9 Hz, Ar), 8.31 (1H, s, H–
C ). 19F NMR (CDCl3) d ꢀ70.86 (3F, t, JFF = 9.3 Hz). MS: m/z
(%) 221 (M+, 53.78), 186 (1.45), 152 (69.22), 125 (100.00), 110
(9.62), 102 (8.01), 89 (28.84), 75 (28.02), 41 (4.66). Anal.
calcd. for C9H7F3NCl: C, 48.78; H, 3.18; N, 6.32. Found: C,
48.81; H, 3.25; N, 6.19.
4.3.1. N,N0-Difluoroalkylated carbodiimide (7)
Colorless liquid. IR (KBr) (cmꢀ1): 3593, 2951, 2164, 1106.
1H NMR (CDCl3) d 3.80 (4H, t, J = 14.0 Hz, CH2), 5.90 (2H, tt,
J1 = 4.0 Hz, J2 = 53 Hz, H–C). 19F NMR (CDCl3) d ꢀ137.63
(4F, d, JFF = 53.0 Hz), ꢀ122.32 (4F, t, J = 14.0 Hz). MS: m/z
(%) 270 (M+, 7.00), 251 (9.02), 169 (100.00), 51 (25.03). Anal.
calcd. for C7H6F8N2: C, 31.13; H, 2.24; N, 10.37. Found: C,
31.13; H, 2.34; N, 10.38.
Acknowledgment
4.2.14. Thiophen-2-ylmethylene-(2,2,2-trifluoro-ethyl)-
amine (5be)
The authors thank the National Natural Science Foundation
of China (NNSFC) (Nos. 20472104 and 20532040) for
financial support.
Colorless liquid. b.p.; 54–57 8C, 15 mmHg. IR (KBr)
1
(cmꢀ1): 1640, 1434, 1264, 1150, 1051, 845, 714. H NMR

Y. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 1152–1157
1157
¨
[5] (a) H. Trabelsli, E. Bollens, M.A. Jouani, M. Gaysinski, F. Szonyl, A.
References
Cambon, Phosphorous Sulfur Silicon 90 (1994) 185–191;
(b) P. Molina, M. Alajarin, A. Arques, Synthesis (1982) 596–597.
´
[6] (a) F. Palacios, C. Alonso, M. Rodrrguez, E.M. de Marigorta, G. Rubiales,
[1] (a) F.A. Cambon, Synth. Commun. 24 (1994) 2653–2660;
(b) D.E. Shalev, S.M. Chiacchiera, J. Org. Chem. 61 (1996) 1689–1701;
(c) E. Patonay-Peli, G. Litkei, Synthesis (1990) 511–514.
[2] H. Staudinger, J. Meyer, Helv. Chim. Acta 2 (1919) 635–646.
[3] (a) A.R. Katritzky, J. Jiang, Synthesis (1990) 565–567;
(b) A.R. Katritzky, J.L. Jiang, J.V. Greenhill, J. Org. Chem. 58 (1993)
1987–1988.
Eur. J. Org. Chem. (2005) 1795–1984;
(b) J.F. Chang, C. Xie, M.W. Ding, H.W. He, Synthesis (2005) 2544–3548.
[7] J.T. Welch, Tetrahedron 43 (1987) 3123–3197.
[8] (a) Y.M. Wu, J. Deng, X. Fang, Q.Y. Chen, J. Fluorine Chem. 125 (2004)
1415–1423;
(b) Y.M. Wu, J. Deng, Y. Li, Q.Y. Chen, Synthesis (2005) 1314–1318;
(c) J. Deng, Y.M. Wu, Q.Y. Chen, Synthesis (2005) 2730–2738;
(d) Y.M. Wu, J. Deng, Q.Y. Chen, Synlett (2006) 645–647.
[4] B.G. Van den Hoven, H. Alper, J. Am. Chem. Soc. 123 (2001) 10214–
10220.