Clean procedure for the synthesis of A-aminophosphonates catalyzed by choline-based ionic liquid

Article abstract of DOI:10.1002/hc.21251

A sulfated choline-based ionic liquid [Ch-OSO₃H] was prepared and used as a novel catalyst for the synthesis of α-aminophosphonates via a one-pot three-component reaction with aldehydes, amines, and triethyl phosphite/diethyl phosphite at room temperature under solvent-free conditions or in aqueous media. The reaction was completed in short times and products could be simply separated from the reaction mixture in good to excellent yields. The catalyst could be recycled and reused for several times without noticeably reducing catalytic activity.

Full text of DOI:10.1002/hc.21251

Heteroatom Chemistry
Volume 00, Number 00, 2014
Clean Procedure for the Synthesis of
A-Aminophosphonates Catalyzed by
Choline-Based Ionic Liquid
Huan Peng,1 Siyu Sun,1 Yulin Hu,1 Rong Xing,1 and Dong Fang1,2
1School of Chemistry and Chemical Engineering, Yancheng Normal University, Yancheng 224002,
People’s Republic of China
2Jiangsu Provincial Key Laboratory of Coast Wetland Bioresources and Environment Protection,
Yancheng 224002, People’s Republic of China
Received 12 August 2014; revised 24 October 2014
INTRODUCTION
ABSTRACT: A sulfated choline-based ionic liquid
[Ch-OSO3H] was prepared and used as a novel catalyst
for the synthesis of α-aminophosphonates via a one-
pot three-component reaction with aldehydes, amines,
and triethyl phosphite/diethyl phosphite at room tem-
perature under solvent-free conditions or in aqueous
media. The reaction was completed in short times and
products could be simply separated from the reaction
mixture in good to excellent yields. The catalyst could
be recycled and reused for several times without no-
With the increasing public concern over environ-
mental degradation and the future of fossil fuels
resources, it has become increasingly necessary to
develop the alternative clean and green methods
in the organic process in lab and factory. The use
of nonhazardous and renewable materials, the
energy conservation involving atom economy, and a
decrease in the synthetic steps are the fundamental
factors of green chemistry [1].
ꢀC
ticeably reducing catalytic activity. 2014 Wiley Peri-
α-Aminophosphonates are pharmacologically
important compounds, which have been exhibiting
versatile biological activities such as antibacte-
rial agents, pharmacogenic agents, antitumor
agents, enzyme inhibitors, inhibitors of UDP-
galactopyranose mutase, and antiviral agents [2].
The development of suitable synthetic methodolo-
gies for these compounds has been a topic of great
interest in these years because of their widespread
biological and chemical applications. Among them,
the Kabachnik–Fields reaction appears to be still
one of the simplest and most efficient method.
The reaction proceeds via the imine formed from
carbonyl compounds and amines, which then
converted to the corresponding aminophosphonates
by the reaction with triethyl phosphite or diethyl
phosphite [3–9]. Many efforts have been made
to develop efficient methods for the synthesis of
α-aminophosphonates, including the one-pot mul-
ticomponent reaction (MCR)of aldehydes, amines,
odicals, Inc. Heteroatom Chem. 00:1–9, 2014; View
this article online at wileyonlinelibrary.com. DOI
10.1002/hc.21251
Correspondence to: Fang Dong; e-mail: fang-njust@hot
mail.com.
Contract grant sponsor: Ministry of Science and Technology of
the P.R. China.
Contract grant number: 11C26213201395.
Contract grant sponsor: Nature Science Foundation of Jiangsu
Province.
Contract grant number: BK20141257.
Contract grant sponsor: Key Laboratory of Organic Synthesis
of Jiangsu Province.
Contract grant number: KJS1112.
Contract grant number: Professional Elite Foundation of
Yancheng Normal University.
ꢀC
2014 Wiley Periodicals, Inc.
1

2
Peng et al.
SCHEME 1
SCHEME 2
and triethyl phosphite/diethyl phosphite, catalyzed
by Lewis/Brønsted acids [4,5], solid acids [6], surfac-
tants [7], metal salts [8], or metal oxides [9]. Many
of these works used one kind of P-reagents, triethyl
phosphite, or diethyl phosphite, respectively, though
a fewer used both of P-reagents [4a]. However, the
search for new readily available and green catalysts
for this reaction is still actively ongoing.
superiority properties such as inexpensive, nontoxic,
environmentally benign, and nonflammable [18].
In continuation of our efforts for environmen-
tally benign protocol for various organic trans-
formations [19], the sulfated choline-based IL
[Ch-OSO3H]HSO4 (Scheme 1) was synthesized to
be used as a novel catalyst for the one-pot three-
component synthesis of α-aminophosphonates with
triethyl phosphite or diethyl phosphite (Scheme 2).
In this decade ionic liquids (ILs) have been
explored to be promising alternative catalysts for
green chemistry purpose, some of them such
as [bmim]BF4/[bmim]PF6 [10], sulfonic acid ILs
[11], [bnmim][HSO4] [12], ethyl ammonium ni-
trate [13], [bmim][HCl] [14], and [emim]Br [15]
have been used to catalyze the synthesis of α-
aminophosphonates. However, ILs with imidazole
as the cation are relatively expensive, which might
hinder the future large-scale applications. Fur-
thermore, some typical ILs with some halogen
anions (such as [PF6]−, [BF4]−, [CF3SO3]−, or
[(CF3SO2)2N]−) were confirmed to be less “green-
ness” [16]. To overcome the problems, choline-
based catalysts (choline-based ionic liquids (CILs))
have emerged promptly and exhibited significant
activity in organic syntheses; in recent years,
Jayaram and co-workers reported the synthesis
of α-aminophosphonates with diethyl phosphite
in the presence of some kinds of IL, choline
chloride·2ZnCl2 [17]. It is generally accepted that
CILs are promising in catalytic processes due to their
RESULTS AND DISCUSSION
The preparation of the sulfated choline-based IL
[Ch-OSO3H]HSO4 was made up of two steps re-
action in a one-pot apparatus. The new catalyst
[Ch-OSO3H]HSO4 is a somewhat viscous, color-
less liquid at room temperature, entirely miscible
with water and soluble or partly soluble in organic
solvents. The biodegradable IL [Ch-OSO3H]HSO4
that bears a sulfated cholinium cation showed good
biodegradation performance and could be biode-
graded by the activated sludge process.
The one-pot three-component reaction between
benzaldehyde (10 mmol), aniline (10 mmol), and
triethyl phosphite (10 mmol) was employed as a
model reaction. The reaction completed at room
temperature for a length of time was optimized
using [Ch-OSO3H]HSO4 as a catalyst (Table 1). Al-
though the Kabachnik–Fields reaction was reported
to be carried out at 50°C for 1–8 h without a catalyst
Heteroatom Chemistry DOI 10.1002/hc

Clean Procedure for the Synthesis of A-Aminophosphonates Catalyzed by Choline-Based Ionic Liquid
3
TABLE 1 Effect of the Different Catalysts on the Synthesis
of α-Aminophosphonatesa
Entry
Catalyst (mmol)
Catalyst free
Time (min) Isolated Yield (%)
1
2
3
4
5
6
7
8
9
120
20
20
20
20
20
20
20
20
20
–
55
62
70
90
95
95
95
94
92b
[Ch-OSO3H]HSO4 (0.1)
[Ch-OSO3H]HSO4 (0.2)
[Ch-OSO3H]HSO4 (0.4)
[Ch-OSO3H]HSO4 (0.6)
[Ch-OSO3H]HSO4 (1.0)
[Ch-OSO3H]HSO4 (1.2)
[Ch-OSO3H]HSO4 (1.4)
[Ch-OSO3H]HSO4 (1.6)
[Ch-OSO3H]HSO4 (1.0)
FIGURE 1 The recycling performance of the catalyst.
10
a10 mmol benzaldehyde, 10 mmol aniline, 10 mmol triethyl phosphite,
r.t.
b0.5 mL H2O medium.
complished under solvent-free conditions in good
yield. Among the selected reaction media, this MCR
was accomplished preferably in polar solvents, in-
cluding CH3CN, EtOH, and EtOH/H2O. For green
chemistry and economic reasons, it will facilitate to
overcome the volatile organic compounds (VOCs)
problems with both solvent-free conditions and
aqueous medium reactions.
It is important to note that the [Ch-
OSO3H]HSO4 was recycled after the reaction. Under
solvent-free condition, after the reaction, 1 mL water
was added to the reaction mixture flask, stirred, and
then filtrated; the catalyst was reused after the ex-
traction with CH2Cl2, washed with ether, and dried
at 80°C under vacuum in each cycle.
TABLE 2 [Ch-OSO3H]HSO4-Catalyzed Model Reaction in
Different Solventsa
Entry
Solvent
Time (min)
Isolated Yield (%)
1
2
3
4
5
6
H2O
EtOH
CH3CN
CH2Cl2
C6H6
20
20
20
20
20
20
92
86
85
31
45
95
Solvent Free
a10 mmol benzaldehyde, 10 mmol aniline, 10 mmol triethyl phosphite,
r.t. 1.0 mmol catalyst.
and solvent [20], we could not detect the product
at room temperature (entry 1). It was observed that
initially the reaction mixture was clear and after 2–3
min the solid mud mixture formation started. Nearly
quantitative conversion of the starting material was
obtained using 10 mol% of the catalyst (entries 6
and 10). Additionally, the reaction could be carried
out either in aqueous media or under solvent-free
conditions with nearly the same yield (entries 6 and
10). A further increase in the catalyst loading did
not improve the yield (entries 7–9).
The next reaction was carried out with an equal
molar ratio of reactants in the same scale as the first
time, and the results are listed in Fig. 1 showing that
the catalyst can be reused at least six times without
a little decrease in yields.
The generality of this protocol was tested
using various aldehydes, amines, and tri/diethyl
phosphite as reactants to determine the scope of
the [Ch-OSO3H]HSO4 under the optimized reaction
conditions described above and the results are
presented in Table 3.
It is noteworthy that no desirable product could
be detected when a mixture of benzaldehyde, ani-
line, and triethyl phosphite was stirred at room tem-
perature in the absence of [Ch-OSO3H]HSO4 even
after 120 min (entry 1), which indicated that the cat-
alyst was absolutely necessary for this one-pot three-
component reaction.
To optimize the reaction conditions, different
polar solvents were then selected as a reaction
medium. In the previous literature [11], the sul-
fonic acid functionalized IL could not catalyzed such
reaction in the absence of water, but in the pres-
ence of water (1 mL) the product formed rapidly.
However, the results are different with the litera-
ture and summarized in Table 2. The reaction ac-
It can easily be seen that this one-pot three-
component MCR was accomplished within 20–50
min and the products were isolated in good
yields. First, the aromatic aldehydes carrying
either electron-donor or electron-withdrawing
substituents could give reasonable to good yields
of α-aminophosphonates (entries 2 and 13–16).
Second, both the electron-donating and electron-
withdrawing substituents (entries 3–7) would facili-
tate to this MCR in view of the anilines. Additionally,
both triethyl phosphite and diethyl phosphite could
be employed as one of the reactants in this reaction.
The comparison of the performance of [Ch-
OSO3H]HSO4 with those relatively good results have
been reported in these years (Table 4). It could be
Heteroatom Chemistry DOI 10.1002/hc

4
Peng et al.
a
TABLE 3 Synthesis of α-Aminophosphonates Catalyzed by [Ch-OSO3H]HSO4
Entry
R1
R2
C6H5
3
Time (min)
Yieldb (%)
1
2
3
4
5
6
7
8
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3C6H4
C6H5
P(OEt)3
H(O)P(OEt)2
P(OEt)3
H(O)P(OEt)2
H(O)P(OEt)2
H(O)P(OEt)2
H(O)P(OEt)2
H(O)P(OEt)2
P(OEt)3
H(O)P(OEt)2
P(OEt)3
P(OEt)3
P(OEt)3
P(OEt)3
45
50
30
50
50
50
50
50
20
30
50
30
20
20
20
20
90
92
91
93
83
80
82
80
95
91
86
89
94
95
91
90
C6H5
4-CH3C6H4
4-NO2C6H4
4-FC6H4
2,4-Cl2C6H3
4-BrC6H4
C6H5
C6H5
C6H5
3-NO2C6H4
4-NO2C6H4
C6H5
9
10
11
12
13
14
15
16
C6H5
C6H5
C6H5
2-ClC6H4
4-ClC6H4
4-HOC6H4
4-NO2C6H4
C6H5
C6H5
C6H5
P(OEt)3
P(OEt)3
Reaction conditions: a10 mmol benzaldehyde, 10 mmol aniline, 10 mmol tri/diethyl phosphite, 1 mmol catalyst, r.t. bIsolated yields.
TABLE 4 Comparison of the Results with Different Catalysts
Entry
Catalyst (mol%)
Reaction Conditions
Time
Yield (%)[Ref.]
1
2
3
4
5
6
7
ZrOCl2·8H2O (10%)
NbCl5 (5%)
TiO2 (20%)
[bnmim][HSO4] (50%)
Choline chloride·2ZnCl2 (15%)
[DDPA][HSO4] (10%)
[Ch-OSO3H]HSO4 (10%)
Solvent free/r.t
Solvent free/50°C
Solvent free/50°C
Solvent free/r.t
Solvent free/r.t
H2O/r.t
5 min
30 min
3.5 h
10 min
60 min
30 min
20 min
95 [4a]
95 [4c]
98 [9a]
96 [12]
96 [15]
95 [19b]
95 [Present work]
Solvent free/r.t
seen that the [Ch-OSO3H]HSO4 has a good efficiency
when compared with many of those reported cata-
lysts in the MCR in addition to its biodegradation.
Without a catalyst and solvent conditions, no in-
termediate formation of either an imine or a hydroxy
phosphonate was observed [20]. So, the mechanism
was somewhat similar to the reported work [11]. The
reaction might proceed through protonation of the
aldehyde, a condensation reaction with the aniline,
formation of an activated imine and a subsequent
addition of the triethyl phosphite to give a phos-
phonium intermediate, and then the reaction with
the water generated during condensation to give the
product (Fig. 2).
EXPERIMENTAL
Melting points were determined by the use of an X6-
Data microscope apparatus. The IR spectra were run
on a Bruker Vector 22 spectrometer and expressed
1
in cm−1 (KBr). H NMR spectra were recorded on
a Bruker DRX300 (300 MHz) and Bruker DRX500
(500 MHz) spectrometer. Elemental analyses were
recorded on a PerkinElmer C spectrometer. Mass
spectra were obtained with an automated Fininigan
TSQ Quantum Ultra AM (Thermal) LC-MS spec-
trometer. All chemicals (AR grade) were purchased
from Sinopharm Chemical Reagent Co., Ltd. Shang-
hai, China and used without further purification.
Synthesis of Choline-Based IL
([Ch-OSO3H]HSO4)
CONCLUSIONS
The biodegradable cholium cation IL [Ch-
OSO3H]HSO4 was synthesized according to
previous methods [18] with improvement. The IL
In summary, in this study, an efficient and clean
procedure for the synthesis of α-aminophosphonates
via a one-pot three-component reaction catalyzed by
a sulfated choline-based IL [Ch-OSO3H] was estab-
lished. The merit of this methodology is that it is
a simple postprocedure, having short reaction time,
high yields, and environmentally benign.
1
was analyzed by H NMR, 13C NMR, MS spectro-
scopes, and elemental analyses, and the spectral
data agreed with their structures (Scheme 1).
To a mixture of choline chloride (0.1 mol,
13.95 g) in hexane, 100 mL of chlorosulfonic acid
Heteroatom Chemistry DOI 10.1002/hc

Clean Procedure for the Synthesis of A-Aminophosphonates Catalyzed by Choline-Based Ionic Liquid
5
FIGURE 2 The possible mechanism for the synthesis of α-aminophosphonates
(0.10 mol, 6.65 mL) was added in portions within
30 min, and then the mixture was stirred for 1
h at 0–5°C. When HCl gas was no longer evapo-
rated, the mixture was stirred for another 1 h at
room temperature. Then, the mixture was filtered,
washed with 50 mL of hexane, and dried at room
temperature to afford intermediate N,N,N-trimethyl-
2-(sulfooxy)ethanaminium chloride. The aqueous
solution of intermediate (0.05 mol, 10.98 g) was
added dropwise into the aqueous solution of sulfuric
acid (98%) (0.05 mol, 5.0 g) at room temperature
under nitrogen atmosphere. Then, the combined
solution was washed repeatedly with diethyl ether
to remove unreacted material, and subsequently
distilled to remove the water and dried in a vacuum
again, and then the [Ch-OSO3H]HSO4 was obtained
quantitatively and in high purity as a colorless oil.
1HNMR (300 MHz, D2O): δ 3.93 (s, 9H, -CH3),
3.40–3.42 (m, 2H, -CH2-O), 3.93–3.97 (m, 2H, -CH2-
N). 13CNMR (75 MHz, D2O): δ 53.8, 53.9, 67.4. MS
(m/z): 280.30 (M+ – 1). Anal. calcd for C5H15NO8S2:
C, 21.35; H, 5.37; N, 4.98; found: C, 21.33; H, 5.38;
N, 4.97.
catalyst from the mixture, and the products were
obtained by filtration and dried under vacuum. The
products were known compounds and identified by
1H NMR (500 MHz, CDCl3), 13C NMR (125 MHz,
CDCl3), 31P (201 MHz, CDCl3), elemental analyses,
physical data (m.p.), and compared with published
studies [4c,4d,8c,9a,17].
The spectral data for compounds 4 are given in
the following.
Diethy(4-methoxyphenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 1). Col-
1
orless oil [8c], H NMR, δ: 1.04 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 1.20 (t, J = 7.0 Hz, 3H, -O-C-CH3), 3.68
(s, 3H, Ph-OCH3), 4.09–3.69 (m, 4H, -O-CH2-C),
4.72 (d, J = 24.9 Hz, 1H, P-CH), 5.20 (brs, 1H, -NH),
6.52 (t, J = 7.1 Hz, 2H, Ar-H), 6.63 (t, J = 7.1 Hz,
1H, Ar-H), 6.77 (d, J = 8.0 Hz, 2H, Ar-H), 6.99 (t,
J = 7.8 Hz, 2H, Ar-H), 7.32 (d, J = 7.8 Hz, 2H, Ar-H).
13C NMR: δ 130.1 (Ar-C), 130.0 (Ar-C), 129.5 (Ar-C),
129.4 (Ar-C), 129.3 (Ar-C), 118.6 (Ar-C), 114.4 (Ar-C),
114.3 (Ar-C), 64.0 (d, J = 7.2 Hz, O-CH2-C), 62.6 (d,
J = 7.2 Hz, O-CH2-C), 55.5 (d, J = 150.0 Hz, P-C),
55.3 (-OCH3), 16.8 (d, J = 5.7 Hz, O-C-CH3), 16.6 (d,
J = 5.7 Hz, O-C-CH3). 31P NMR: δ 20.21. Anal. calcd
for C18H24NO4P: C, 61.88; H, 6.92; N, 4.01; found:
C, 61.85; H, 6.91; N, 4.00.
General Procedure for the Synthesis of
α-Aminophosphonates (Compounds 4)
To a round-bottomed flask charged with aldehyde
(10 mmol, 1.06 g) and aniline (10 mmol, 0.93 g),
[Ch-OSO3H]HSO4 (1.0 mmol, 0.28 g) was added
under stirring. The mixture was stirred at room
temperature for 2–3 min and then triethyl phosphite
(10 mmol, 1.66 g)/or diethyl phosphite (10 mmol,
1.38 g) was added and stirred for a length of times.
On completion (monitored by thin-layer chromatog-
raphy), water (1 mL) was added to extract the
Diethy(4-methoxyphenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 2). Col-
1
orless oil [8c], H NMR, δ: 1.04 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 1.20 (t, J = 7.0 Hz, 3H, -O-C-CH3), 3.68
(s, 3H, Ph-OCH3), 4.09–3.69 (m, 4H, -O-CH2-C),
4.72 (d, J = 24.9 Hz, 1H, P-CH), 5.20 (brs, 1H, -NH),
6.52 (t, J = 7.1 Hz, 2H, Ar-H), 6.63 (t, J = 7.1 Hz,
1H, Ar-H), 6.77 (d, J = 8.0 Hz, 2H, Ar-H), 6.99 (t,
Heteroatom Chemistry DOI 10.1002/hc

6
Peng et al.
J = 7.8 Hz, 2H, Ar-H), 7.32 (d, J = 7.8 Hz, 2H, Ar-H).
13CNMR: δ 129.9 (Ar-C), 129.0 (Ar-C), 129.6 (Ar-C),
129.4 (Ar-C), 129.3 (Ar-C), 118.6 (Ar-C), 114.5 (Ar-C),
114.3 (Ar-C), 63.8 (d, J = 7.2 Hz, O-CH2-C), 62.5 (d,
J = 7.2 Hz, O-CH2-C), 55.4 (d, J = 150.0 Hz, P-C),
55.3 (-OCH3), 16.8 (d, J = 5.7 Hz, O-C-CH3), 16.7 (d,
J = 5.7 Hz, O-C-CH3).
127.6 (Ar-C), 125.4 (Ar-C), 115.5 (Ar-C), 65.0 (d,
J = 7.2 Hz, O-CH2-C), 63.9 (d, J = 7.2 Hz, O-CH2-C),
55.4 (d, J = 150.0 Hz, P-C), 55.2 (-OCH3), 16.8 (d,
J = 5.7 Hz, O-C-CH3), 16.7 (d, J = 5.7 Hz, O-C-CH3).
31P NMR: δ 21.05. Anal. calcd for C18H23FNO4P: C,
58.85; H, 6.31; N, 3.81; found: C, 58.83; H, 6.30; N,
3.80.
Diethy(4-methoxyphenyl)-N-(4-methylphenyl)
aminomethylphosphonate (Table 3, entry 3). White
solid, m.p. 97–99°C [9a], 1H NMR, δ: 1.00 (t, J = 7.0
Hz, 3H, -O-C-CH3), 1.12 (t, J = 7.0 Hz, 3H, -O-C-
CH3), 1.98 (s, 3H, Ph-CH3), 3.49 (s, 3H, Ph-OCH3),
3.99–3.60 (m, 4H, -O-CH2-C), 4.61 (d, J = 24.1 Hz,
1H, P-CH), 5.32 (brs, 1H, -NH), 6.42 (t, J = 7.2 Hz,
2H, Ar-H), 6.70 (t, J = 7.2 Hz, 2H, Ar-H), 7.25 (t,
J = 7.8 Hz, 2H, Ar-H), 7.62 (d, J = 7.8 Hz, 2H, Ar-H).
13C NMR: δ 137.0 (Ar-C), 129.7 (Ar-C), 129.5 (Ar-C),
129.4 (Ar-C), 129.3 (Ar-C), 118.6 (Ar-C), 114.5 (Ar-C),
114.3 (Ar-C), 63.9 (d, J = 7.2 Hz, O-CH2-C), 62.4 (d,
J = 7.2 Hz, O-CH2-C), 55.2 (d, J = 150.0 Hz, P-C),
55.3 (-OCH3), 24.3 (-CH3), 16.8 (d, J = 5.7 Hz,
O-C-CH3), 16.5 (d, J = 5.7 Hz, O-C-CH3). 31P NMR:
δ 20.10. Anal. calcd for C19H26NO4P: C, 62.80; H,
7.21; N, 3.85; found: C, 62.78; H, 7.20; N, 3.83.
Diethy(4-methoxyphenyl)-N-(2,4-
dicholorophenyl)aminomethylphosphonate (Table 3,
entry 6). White solid, m.p. 140–142°C [4d], 1H
NMR, δ: 1.05 (t, J = 7.0 Hz, 3H, -O-C-CH3), 1.21 (t,
J = 7.0 Hz, 3H, -O-C-CH3), 3.95 (s, 3H, Ph-OCH3),
4.03–3.65 (m, 4H, -O-CH2-C), 4.72 (d, J = 24.3 Hz,
1H, P-CH), 5.45 (brs, 1H, -NH), 6.70–7.35 (m, 7H,
Ar-H). 13CNMR: δ 157.1 (Ar-C), 141.0 (Ar-C), 136.2
(Ar-C), 129.8 (Ar-C), 129.0 (Ar-C), 128.5 (Ar-C), 128.2
(Ar-C), 127.7 (Ar-C), 125.1 (Ar-C), 115.3 (Ar-C), 64.1
(d, J = 7.2 Hz, O-CH2-C), 62.6 (d, J = 7.2 Hz,
O-CH2-C), 58.5 (d, J = 150.0 Hz, P-C), 55.3, 16.3 (d,
J = 7.6 Hz, O-C-CH3), 16.2 (d, J = 7.8 Hz, O-C-CH3).
31P NMR: δ 21.10. Anal. calcd for C18H22Cl2NO4P:
C, 51.69; H, 5.30; N, 3.35; found: C, 51.66; H, 5.29;
N, 3.33.
Diethy(4-methoxyphenyl)-N-(4-bromophenyl)
aminomethylphosphonate (Table 3, entry 7). White
solid, m.p. 106–107°C [17], 1H NMR, δ: 1.13 (t,
J = 7.0 Hz, 3H, -O-C-CH3), 1.30 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 3.69–3.72 (m,1H, -O-CH2-C), 3.93 (s, 3H,
Ph-OCH3), 3.95–3.97 (m, 1H, -O-CH2-C), 4.15–4.10
(m, 2H, -O-CH2-C), 4.63 (d, J = 24.0 Hz, 1H, P-CH),
6.48 (d, J = 7.0 Hz, 2H, Ar-H), 6.88 (t, J = 7.5 Hz, 2H,
Ar-H), 7.20–7.18 (m, 2H, Ar-H), 7.37–7.35 (m, 2H,
Ar-H). 13C NMR: δ 157.7 (Ar-C), 136.9 (Ar-C), 132.9
(Ar-C), 132.6 (Ar-C), 129.7 (Ar-C), 128.7 (Ar-C), 126.3
(Ar-C), 115.6 (Ar-C), 63.3 (d, J = 7.2 Hz, O-CH2-C),
60.9 (d, J = 7.2 Hz, O-CH2-C), 55.3 (-OCH3), 51.0 (d,
J = 150.0 Hz, P-C), 17.6 (d, J = 5.7 Hz, O-C-CH3),
17.5 (d, J = 5.7 Hz, O-C-CH3). 31P NMR: δ 20.08.
Anal. calcd for C18H23BrNO4P: C, 50.48; H, 5.41; N,
3.27; found: C, 50.46; H, 5.40; N, 3.25.
Diethy(4-methoxyphenyl)-N-(4-nitrophenyl)
aminomethylphosphonate (Table 3, entry 4). Yellow
solid, m.p. 112–114°C (112°C) [9a], 1H NMR, δ: 1.01
(t, J = 7.0 Hz, 3H, -O-C-CH3), 1.12 (t, J = 7.0 Hz,
3H, -O-C-CH3), 3.48 (s, 3H, Ph-OCH3), 3.99–3.80
(m, 4H, -O-CH2-C), 4.62 (d, J = 24.3 Hz, 1H, P-CH),
5.92 (brs, 1H, -NH), 6.41 (t, J = 7.1 Hz, 2H, Ar-H),
6.60 (t, J = 7.1 Hz, 2H, Ar-H), 7.15 (t, J = 7.8 Hz,
2H, Ar-H), 7.92 (d, J = 7.8 Hz, 2H, Ar-H). 13C NMR:
δ 153.6 (Ar-C), 141.0 (Ar-C), 133.5 (Ar-C), 129.8
(Ar-C), 129.3 (Ar-C), 127.6 (Ar-C), 124.4 (Ar-C),
114.5 (Ar-C), 65.0 (d, J = 7.2 Hz, O-CH2-C), 63.1 (d,
J = 7.2 Hz, O-CH2-C), 55.8 (d, J = 150.0 Hz, P-C),
55.3 (-OCH3), 16.8 (d, J = 5.7 Hz, O-C-CH3), 16.6 (d,
J = 5.7 Hz, O-C-CH3). 31P NMR: δ 22.25. Anal. calcd
for C18H23N2O6P: C, 54.82; H, 5.88; N, 7.10; found:
C, 54.83; H, 5.88; N, 7.11.
Diethy(4-methylphenyl)-N-(phenyl)
Diethy(4-methoxyphenyl)-N-(4-fluorophenyl)
aminomethylphosphonate (Table 3, entry 5). White
solid, m.p. 53°C [17], 1H NMR, δ: 1.03 (t, J = 7.0 Hz,
3H, -O-C-CH3), 1.20 (t, J = 7.0 Hz, 3H, -O-C-CH3),
3.60 (s, 3H, Ph-OCH3), 4.01–3.63 (m, 4H, -O-CH2-C),
4.65 (d, J = 24.3 Hz, 1H, P-CH), 5.72 (brs, 1H, -NH),
6.52 (t, J = 7.1 Hz, 2H, Ar-H), 6.70 (t, J = 7.1 Hz,
2H, Ar-H), 6.81 (d, J = 8.0 Hz, 2H, Ar-H), 7.35 (t,
J = 7.8 Hz, 2H, Ar-H). 13C NMR: δ 162.7 (Ar-C),
140.0 (Ar-C), 133.1 (Ar-C), 129.7 (Ar-C), 129.3 (Ar-C),
aminomethylphosphonate (Table 3, entry 8). White
solid, m.p. 61–62°C [9a], 1H NMR, δ: 1.01 (t, J =
7.0 Hz, 3H, -O-C-CH3), 1.12 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 2.17 (s, 3H, Ph-CH3), 4.06–3.60 (m, 4H,
-O-CH2-C), 4.73 (d, J = 24.3 Hz, 1H, P-CH), 5.90
(brs, 1H, -NH), 6.75–6.66 (m, 2H, Ar-H), 7.15–7.09
(m, 2H, Ar-H), 7.55–7.32 (m, 6H, Ar-H). 13C NMR:
δ 130.1 (Ar-C), 130.0 (Ar-C), 129.5 (Ar-C), 129.4
(Ar-C), 129.3 (Ar-C), 118.6 (Ar-C), 114.4 (Ar-C),
114.3 (Ar-C), 63.0 (d, J = 7.2 Hz, O-CH2-C), 61.2 (d,
Heteroatom Chemistry DOI 10.1002/hc

Clean Procedure for the Synthesis of A-Aminophosphonates Catalyzed by Choline-Based Ionic Liquid
7
J = 7.2 Hz, O-CH2-C), 52.2 (d, J = 150.0 Hz, P-C),
24.2 (-CH3), 16.8 (d, J = 5.7 Hz, O-C-CH3), 16.6 (d,
J = 5.7 Hz, O-C-CH3). 31P NMR: δ 19.89. Anal. calcd
for C18H24NO3P: C, 64.85; H, 7.26; N, 4.20; found:
C, 64.83; H, 7.25; N, 4.19.
δ 21.12. Anal. calcd for C17H21N2O5P: C, 56.04; H,
5.81; N, 7.69; found: C, 56.02; H, 5.80; N, 7.70.
Diethy(phenyl)-N-(4-nitrophenyl)
aminomethylphosphonate (Table 3, entry 12).
1
Yellow solid, m.p. 124–125°C [4c], H NMR, δ: 1.05
(t, J = 7.0 Hz, 3H, -O-C-CH3), 1.15 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 3.76–3.72 (m, 1H, -O-CH2-C), 3.91–3.87
(m, 1H, -O-CH2-C), 4.07–4.01 (m, 2H, -O-CH2-C),
5.12 (d, J = 24.3 Hz, 1H, P-CH), 6.85 (d, J = 7.9
Hz, 2H, Ar-H), 7.32–7.09 (m, 3H, Ar-H), 7.45 (d,
J = 8.0 Hz, 2H, Ar-H), 7.68 (d, J = 8.0 Hz, 2H,
Ar-H). 13C NMR: δ 151.8 (Ar-C), 148.2 (Ar-C), 146.3
(Ar-C), 139.0 (Ar-C), 128.2 (Ar-C), 126.2 (Ar-C),
121.4 (Ar-C), 111.3 (Ar-C), 64.0 (d, J = 7.2 Hz,
O-CH2-C), 63.3 (d, J = 7.0 Hz, O-CH2-C), 55.5 (d, J =
150.0 Hz, P-C), 16.7 (d, J = 5.8 Hz, O-C-CH3), 16.3
(d, J = 5.8 Hz, O-C-CH3). 31P NMR: δ 21.24. Anal.
calcd for C17H21N2O5P: C, 56.04; H, 5.81; N, 7.69;
found: C, 56.01; H, 5.80; N, 7.71.
Diethy(phenyl)-N-(phenyl)aminomethylphos-
phonate (Table 3, entry 9). White solid, m.p. 89–
1
90°C [lit. 8c], H NMR, δ: 1.02 (t, J = 7.0 Hz, 3H),
1.17 (t, J = 7.0 Hz, 3H), 3.36 (s, 1H), 3.72–3.64 (m,
1H), 3.90–3.82 (m, 1H), 4.09–3.99 (m, 2H), 5.02 (d,
J = 24.9 Hz, 1H), 6.52 (t, J = 7.1 Hz, 1H), 6.78 (d,
J = 8.0 Hz, 2H), 6.99 (t, J = 7.75 Hz, 2H), 7.32–7.20
(m, 3H), 7.52 (d, J = 7.2 Hz, 2H). 13C NMR: δ 146.9
(Ar-C), 146.6 (Ar-C), 136.3 (Ar-C), 129.5 (Ar-C),
128.7 (Ar-C), 128.2 (Ar-C), 118.8 (Ar-C), 114.3
(Ar-C), 64.0 (d, J = 7.2 Hz, O-CH2-C), 63.2 (d, J = 7.0
Hz, O-CH2-C), 56.5 (d, J = 150.5 Hz, P-C), 16.8 (d,
J = 5.8 Hz, O-C-CH3), 16.6 (d, J = 5.8 Hz, O-C-CH3).
31P NMR: δ 20.02. Anal. calcd for C17H22NO3P: C,
63.94; H, 6.94; N, 4.39; found: C, 63.95; H, 6.94; N,
4.40.
Diethy(2-cholorophenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 13).
White solid, m.p. 87–88°C [9a], 1H NMR, δ: 1.02
(t, J = 7.0 Hz, 3H, -O-C-CH3), 1.14 (t, J = 7.0 Hz,
3H, -O-C-CH3), 4.16–3.70 (m, 4H, -O-CH2-C), 5.13
(d, J = 24.3 Hz, 1H, P-CH), 5.99 (brs, 1H, -NH),
6.55 (t, J = 7.5 Hz, 2H, Ar-H), 6.60 (d, J = 7.5
Hz, 1H, Ar-H), 7.15–6.96 (m, 6H, Ar-H). 13C NMR:
δ 144.2 (Ar-C), 130.0 (Ar-C), 129.6 (Ar-C), 128.2
(Ar-C), 127.8 (Ar-C), 127.2 (Ar-C), 126.2 (Ar-C),
125.2 (Ar-C), 120.5 (Ar-C), 114.5 (Ar-C), 63.7 (d,
J = 7.2 Hz, O-CH2-C), 63.3 (d, J = 7.0 Hz, O-CH2-C),
55.4 (d, J = 150.0 Hz, P-C), 16.8 (d, J = 5.8 Hz,
O-C-CH3), 16.6 (d, J = 5.8 Hz, O-C-CH3). 31P NMR:
δ 20.01. Anal. calcd for C17H21ClNO3P: C, 57.72; H,
5.98; N, 3.96; found: C, 57.70; H, 5.98; N, 3.94.
Diethy(phenyl)-N-(phenyl)aminomethylphos-
phonate (Table 3, entry 10). White solid, m.p.
89–90°C [lit. 8c], 1H NMR, δ: 1.13 (t, J = 7.0 Hz,
3H, -O-C-CH3), 1.30 (t, J = 7.0 Hz, 3H, -O-C-CH3),
3.71–3.69 (m, 1H, -O-CH2-C), 3.97–3.93 (m, 1H,
-O-CH2-C), 4.16–4.10 (m, 2H, -O-CH2-C), 4.79 (d,
J = 24.3 Hz, 1H, P-CH), 5.80 (brs, 1H, -NH),
6.73–6.61 (m, 3H, Ar-H), 7.37–7.11 (m, 5H, Ar-H),
7.50–7.49 (d, J = 7.7 Hz, 2H, Ar-H). 13C NMR: δ
146.8 (Ar-C), 146.6 (Ar-C), 136.3(Ar-C), 129.6(Ar-C),
128.7(Ar-C), 128.2(Ar-C), 118.8(Ar-C), 114.3(Ar-C),
63.8 (d, J = 7.0 Hz, O-CH2-C), 63.0 (d, J = 7.0 Hz,
O-CH2-C), 56.5 (d, J = 150.5 Hz, P-C), 16.8 (d, J =
5.8 Hz, O-C-CH3), 16.6 (d, J = 5.8 Hz, O-C-CH3).
Diethy(phenyl)-N-(3-nitrophenyl)
Diethy(4-cholorophenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 11).
Yellow solid, m.p. 124–125°C [4c], H NMR, δ: 1.04
aminomethylphosphonate (Table 3, entry 14).
White solid, m.p. 57–58°C [9a], H NMR, δ: 1.15 (t,
1
1
(t, J = 7.0 Hz, 3H, -O-C-CH3), 1.17 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 3.76–3.68 (m, 1H, -O-CH2-C), 3.93–3.85
(m, 1H, -O-CH2-C), 4.09–4.02 (m, 2H, -O-CH2-C),
5.23 (d, J = 24.3 Hz, 1H, P-CH), 7.27–7.20 (m, 3H,
Ar-H), 7.33 (t, J = 7.5 Hz, 3H, Ar-H), 7.54 (d, J =
7.1 Hz, 2H, Ar-H), 7.68 (d, J = 2.0 Hz, 1H, Ar-H).
13C NMR: δ 149.9 (Ar-C), 149.6 (Ar-C), 136.3 (Ar-C),
129.5 (Ar-C), 128.7 (Ar-C), 128.2 (Ar-C), 122.5 (Ar-C),
118.8 (Ar-C), 114.3 (Ar-C), 111.2 (Ar-C), 64.3 (d,
J = 7.2 Hz, O-CH2-C), 63.5 (d, J = 7.0 Hz, O-CH2-C),
56.8 (d, J = 150.5 Hz, P-C), 16.8 (d, J = 5.8 Hz,
O-C-CH3), 16.6 (d, J = 5.8 Hz, O-C-CH3). 31P NMR:
J = 7.0 Hz, 3H, -O-C-CH3), 1.29 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 3.76–3.68 (m, 1H, -O-CH2-C), 3.83–3.76
(m, 1H, -O-CH2-C), 4.19–4.09 (m, 2H, -O-CH2-C),
4.85 (d, J = 24.5 Hz, 1H, P-CH), 5.99 (brs, 1H, -NH),
6.61 (d, J = 7.5 Hz, 2H, Ar-H), 6.71 (d, J = 7.5
Hz, 1H, Ar-H), 7.35–6.99 (m, 6H, Ar-H). 13C NMR:
δ 146.5 (Ar-C), 130.0 (Ar-C), 129.5 (Ar-C), 128.2
(Ar-C), 127.7 (Ar-C), 126.2 (Ar-C), 121.4 (Ar-C),
117.5 (Ar-C), 63.8 (d, J = 7.2 Hz, O-CH2-C), 63.3
(d, J = 7.0 Hz, O-CH2-C), 55.5 (d, J = 150.0 Hz,
P-C), 16.7 (d, J = 5.8 Hz, O-C-CH3), 16.3 (d, J = 5.8
Hz, O-C-CH3). 31P NMR: δ 20.00. Anal. calcd for
Heteroatom Chemistry DOI 10.1002/hc

8
Peng et al.
tacharya, A. K.; Raut, D. S.; Rana, K. C.; Polanki, I.
K.; Khan, M. S.; Iram, S. Eur J Med Chem 2013, 66,
146–152; (c) Yao, G.; Ye, M.; Huang, R.; Li, Y.; Pan,
Y.; Xu, Q.; Liao, Z.; Wang, H. Bioorg Med Lett 2014,
24, 501–507; (d) Kabachnik, M. I.; Medved, T. Y. Dokl
Akad Nauk SSSR 1952, 83, 689–692; (e) Fields, E. K.
J Am Chem Soc 1952, 74, 1528–1531.
C17H21ClNO3P: C, 57.72; H, 5.98; N, 3.96; found: C,
57.74; H, 5.99; N, 3.97.
Diethy(4-hydroxyphenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 15).
1
Colorless oil, [9a], H NMR, δ: 0.99 (t, J = 7.0 Hz,
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3H, -O-C-CH3), 1.09 (t, J = 7.0 Hz, 3H, -O-C-CH3),
3.76–3.71 (m, 1H, -O-CH2-C), 3.83–3.76 (m, 1H,
-O-CH2-C), 4.02–3.95 (m, 2H, -O-CH2-C), 4.69 (d, J
= 24.0 Hz, 1H, P-CH), 4.97 (s, 1H, Ph-OH), 5.49 (brs,
1H, -NH), 6.55–6.49 (m, 3H, Ar-H), 6.65 (d, J = 7.0
Hz, 2H, Ar-H), 6.87 (d, J = 7.5 Hz, 2H, Ar-H), 7.09
(d, J = 7.0 Hz, 2H, Ar-H). 13C NMR: δ 148.8 (Ar-C),
141.2 (Ar-C), 136.3 (Ar-C), 132.0 (Ar-C), 129.7 (Ar-C),
128.6 (Ar-C), 126.3 (Ar-C), 115.6 (Ar-C), 63.6 (d, J
= 7.2 Hz, O-CH2-C), 63.1 (d, J = 7.0 Hz, O-CH2-C),
52.3 (d, J = 150.0 Hz, P-C), 16.8 (d, J = 5.8 Hz,
O-C-CH3), 16.6 (d, J = 5.8 Hz, O-C-CH3). 31P NMR:
δ 21.29. Anal. calcd for C17H22NO4P: C, 60.89; H,
6.61; N, 4.18; found: C, 60.88; H, 6.60; N, 4.16.
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Diethy(4-nitrophenyl)-N-(phenyl)
aminomethylphosphonate (Table 3, entry 16).
1
Yellow solid, m.p. 123–125°C [17], H NMR, δ: 1.20
(t, J = 7.0 Hz, 3H, -O-C-CH3), 1.31 (t, J = 7.0 Hz, 3H,
-O-C-CH3), 3.91–3.89 (m, 1H, -O-CH2-C), 4.04–4.07
(m, 1H, -O-CH2-C), 4.19–4.13 (m, 2H, -O-CH2-C),
4.88 (d, J = 25.0 Hz, 1H, P-CH), 6.55 (d, J = 8.0
Hz, 2H, Ar-H), 7.28–6.74 (m, 5H, Ar-H), 8.21 (d, J =
8.5 Hz, 2H, Ar-H). 13C NMR: δ 151.6 (Ar-C), 148.3
(Ar-C), 147.6 (Ar-C), 139.0 (Ar-C), 128.2 (Ar-C),
126.0 (Ar-C), 121.3 (Ar-C), 112.3 (Ar-C), 63.9 (d, J
= 7.2 Hz, O-CH2-C), 63.3 (d, J = 7.0 Hz, O-CH2-C),
55.2 (d, J = 150.0 Hz, P-C), 16.5 (d, J = 5.8 Hz,
O-C-CH3), 16.2 (d, J = 5.8 Hz, O-C-CH3). 31P NMR:
δ 21.20. Anal. calcd for C17H21N2O5P: C, 56.04; H,
5.81; N, 7.69; found: C, 56.05; H, 5.80; N, 7.70.
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