A novel atom-economic synthesis of functionalized imidazolidines through copper(I)-catalyzed domino three-component coupling and cyclization reactions

Article abstract of DOI:10.1016/j.tet.2014.03.063

An interesting approach to functionalized imidazolidines is described. These compounds are obtained in a copper(I)-catalyzed domino three-component coupling and cyclization reaction involving two formaldehyde-derived imine units and a terminal alkyne. Alternatively, imidazolidines can be obtained from propargylamines and formaldehyde-derived imines. This strategy provides a straightforward and atom-economic pathway to construct imidazolidines with high yields and benefits from readily available starting materials, convenient one-pot operations.

Full text of DOI:10.1016/j.tet.2014.03.063

Tetrahedron 70 (2014) 3134e3140
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A novel atom-economic synthesis of functionalized imidazolidines
through copper(I)-catalyzed domino three-component coupling and
cyclization reactions
,
a
a
a
a
b,
Yufeng Li a , Zhengguang Wu , Jie Shi , Hongzhong Bu , Jiachao Gu , Yi Pan
*
*
a College of Sciences, Nanjing Tech University, Nanjing 211816, PR China
b School of Chemistry and Chemical Engineering, Nanjing University, 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An interesting approach to functionalized imidazolidines is described. These compounds are obtained in
copper(I)-catalyzed domino three-component coupling and cyclization reaction involving two
formaldehyde-derived imine units and a terminal alkyne. Alternatively, imidazolidines can be obtained
from propargylamines and formaldehyde-derived imines. This strategy provides a straightforward and
atom-economic pathway to construct imidazolidines with high yields and benefits from readily available
starting materials, convenient one-pot operations.
Received 10 January 2014
Received in revised form 9 March 2014
Accepted 19 March 2014
Available online 25 March 2014
a
Keywords:
Alkynes
Ó 2014 Elsevier Ltd. All rights reserved.
Cyclization
Imines
Multicomponent reactions
Nitrogen heterocycles
1. Introduction
Unlike traditional multistep processes, these reactions allow for-
mation of several bonds via a cascade of irreversible chemical re-
Heterocyclic compounds embedded with nitrogen have attrac-
ted considerable interest over the years because they form the core
structures, and are key intermediates, of natural products, such as
alkaloids.1 Among the nitrogen heterocycles, imidazolidine nucleus
is a prominent motif that exists in numerous natural products and
synthetic bioactive compounds.2 One of the conventional methods
for the synthesis of imidazolidines relies upon the condensation of
aldehydes with 1, 2-diamines.3 Imidazolidines can also be prepared
by dipolar cycloaddition of azomethine ylides and imines.4 The
main two routes to imidazolidines have some defects, such as
limited source of starting materials, limited diversity of the target
molecules, harsh reaction conditions, and cumbersome operation,
etc. Therefore, more efficient methods to acquire such heterocycles,
in particular highly functionalized imidazolidines, remains an at-
tractive goal.
actions in a single step with greater efficiency and atom economy.
Our efforts are recently directed toward the development of
atom-economical reactions (multicomponent domino reactions
and hydroamination6) for the efficient construction of heterocycles.
During our work in assembling acetylides with aldimines into
synthetically versatile propargylamines from which an array of
nitrogen compounds can be accessed,7 an interesting product, (E)-
methyl 2-(1,3-diphenylimidazolidin-4-ylidene)acetate (4a) was
unexpectedly obtained in 87% yield calculating from 1a (Scheme 1).
Treatment of N-methyleneaniline (1a, 1.0 equiv) with methyl pro-
piolate (2a, 1.0 equiv) in the presence of copper(I) chloride
(0.2 equiv) in toluene at rt gave neat 4a without the attempted 3a
observed. The yield of 4a was so excellent that a simple solvent
rinsing is enough to provide the analytic sample. This reaction
would involve a coupling reaction of alkyne 2a with imine 1a to
form propargylamine 3a, and under the help of cationic Cu(I),
a subsequent cyclization of another 1a molecule with activated 3a
to form 4a (Scheme 1). To the best of our knowledge, this one-pot
three-component reaction is the first route to imidazolidines from
two imines and one alkyne. Thereby, a copper-catalyzed domino
three-component reaction is established by us for substituted
imidazolidines synthesis.
In recent years, multicomponent reactions (MCRs) have become
an efficient means for assembling heterocyclic frameworks from
simple starting materials by virtue of their convergent nature.5
* Corresponding authors. Tel./fax: þ86 025 58139483; e-mail address: yufengli@
njtech.edu.cn (Y. Li).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.03.063

Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
3135
With the optimal conditions in hand (0.2 equiv CuCl, CH2Cl2, rt,
12 h), the scope of imines was investigated (Table 2). Aromatic
imines 1b, 1deg containing electron-donating groups on the ben-
zene ring reacted all smoothly with 2a to give 4b (98% yield), 4d
(95% yield), 4e (90% yield), 4f (75% yield), and 4g (89% yield), re-
spectively (Table 2, entries 2, and 4e7). The reaction was also ap-
plicable to 1c bearing an electron-withdrawing halogen atom on
the benzene ring to provide 4c in 93% yield (Table 2, entry 3). The
lowered yield of 4f seemly indicates that ortho-bulky groups on
imines exert a slightly adverse effect on the reaction. Then aliphatic
imines were also examined for this process. Imines 1h and 1i were
successfully converted into the corresponding products (Table 2,
entries 8 and 9), which really illustrates N-alkylformaldimines are
also tolerant for this reaction. Next, we investigated the scope of
terminal alkynes. To our delight, the electron-deficient alkynes,
such as ethyl propiolate (2b) and 3-butyn-2-one (2c), were both
applicable for this reaction to afford the imidazolidines 4jen in
high yields (Table 2, entries 10e14). When phenylacetylene (2d)
and trimethylsilylacetylene (2e) were employed instead of 2a, only
the propargylamine intermediates were found without generation
of desired imidazolidines. Among obtained imidazolidines, the fine
crystal of 4b was carefully cultivated through volatilization of its
dichloromethane solution for X-ray crystallography, and the result
confirmed well the structure of 4b as E configuration shown in
Fig. 1. The decreased steric effect between Ha with Hb well explains
the thermodynamic stability of the E configuration prior to the Z
configuration (Scheme 2).
Scheme 1. A sequential copper(I)-catalyzed coupling and cyclization reaction for the
synthesis of imidazolidines.
2. Results and discussion
With imine 1a and methyl propiolate 2a as model substrates,
the original reaction conditions (1a, 1.0 equiv; 2a, 1.0 equiv; CuCl,
0.2 equiv) were optimized, and the loading of 2a was increased to
2.0 equiv giving 4a with a comparable yield (89%). We then ex-
amined the process with various catalysts and solvents, and the
results are described in Table 1. A variety of copper salts were ex-
amined for this reaction in toluene at rt (Table 1, entries 1e5). CuCl,
CuBr, and CuCl2 were effected to generate the corresponding
products in moderate to good yields, but CuCl gave the best result
(Table 1, entries 1 and 2, 4). However, no desired 4a was observed in
the presence of CuI or CuSO4. AgCl, or Ag2CO3 was also used
exhibiting no activation on this reaction (Table 1, entries 6 and 7).
Subsequently, we tried to improve the yields by examining differ-
ent solvents. Toluene, CH2Cl2, dioxane, N,N-dimethylformamide
(DMF), and acetonitrile (MeCN) were all tolerant for this reaction,
whereas CH2Cl2 proved to be the best one (Table 1, entries 1, 8e11).
Furthermore, the control experiments revealed that no product was
formed in the absence of CuCl (Table 1, entry 12).
Table 2
Copper(I)-catalyzed reaction of imines and alkynesa
Entry
R1
R
4
Yieldb (%)
1c
2c
3c
4c
5
6
7
8
9
10
11
12
13
14
15
16
1a: Ph
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2a: COOMe
2b: COOEt
2b: COOEt
2c: COMe
2c: COMe
2c: COMe
2d: Ph
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
d
d
93
98
93
95
90
75
89
86
85
88
90
87
88
85
0
1b: 4-MeOC6H4
1c: 4-ClC6H4
1d: 4-MeC6H4
1e: 3-MeC6H4
1f : 2-MeC6H4
1g: 3,5-(Me)2C6H3
1h: benzyl
1i: cyclohexyl
1a: Ph
1b: 4-MeOC6H4
1a: Ph
Table 1
Optimization of reaction conditionsa
1b: 4-MeOC6H4
1c: 4-ClC6H4
1a: Ph
1a: Ph
2e: Me3Si
0
a
Reaction conditions: imine 1 (10.0 mmol), alkyne 2 (5.0 mmol), CuCl (1.0 mmol),
CH2Cl2 (15 mL), under an ambient atmosphere.
Entry
Catalyst
Solvent
Yieldb (%)
b
Yield of isolated product.
No chromatographic procedures were required for purification of the product.
1
2
3
4
5
6
7
8
CuCl
CuBr
CuI
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
CH2Cl2
Dioxane
DMF
89
84
0
70
0
c
CuCl2
CuSO4
AgCl
AgCO3
CuCl
CuCl
CuCl
CuCl
d
As a matter of course, the imine scope was tentatively extended
to other aldimines. When imine 5a (2.0 equiv) was treated with
methyl propiolate 2a (1.0 equiv) under the optimal conditions, only
a propargylamine adduct 6a was obtained just as the literature
described (Scheme 3).8 Even after refluxing for 24 h, imidazolidine
formation was still not observed. It is probably the steric hindrance
and/or the low reactivity of imine 5a that inhibit the following
cyclization of 5a with 6a. Prompted by the proposed mechanism,
we wondered whether N-methyleneaniline (1a) could perform the
cyclization with the propargylamine 6a. Thus, 6a was isolated and
0
0
93
88
65
53
0
9
10
11
12
MeCN
CH2Cl2
a
Reaction conditions: imine 1a (10.0 mmol), methyl propiolate 2a (5.0 mmol),
catalyst (1.0 mmol), solvent (15 mL), under an ambient atmosphere.
b
Isolated yield based on imine 1a.

3136
Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
Table 3
Imidazolidines from two different imines and one alkynea
Entry
Imine 1: R1
Imine 5: R2, R3
Alkyne
7, yieldb (%)
1c
2c
3c
4c
5
1a: Ph
5a: Ph, Ph
5a: Ph, Ph
5a: Ph, Ph
5a: Ph, Ph
5a: Ph, Ph
5a: Ph, Ph
5b: 4-MeOC6H4, Ph
5b: 4-MeOC6H4, Ph
5c: 4-MeC6H4, Ph
5d: Ph, 4-ClC6H4
5e: Ph, 4-MeC6H4
5f : Ph, 2-furyl
5g: Ph, 2-thienyl
5a: Ph, Ph
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2b
2c
7a, 90
7b, 98
7c, 91
7d, 95
7e, 88
7f, 88
7g, 86
7h, 93
7i, 94
7j, 87
7k, 89
7l, 88
7m, 85
7n, 88
7o, 85
1b: 4-MeOC6H4
1c: 4-ClC6H4
1d: 4-MeC6H4
1g: 3,5-(Me)2C6H3
1i: cyclohexyl
1j: isopropyl
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
6
7
Fig. 1. X-ray crystal structure for 4b.
8c
9c
10
11
12
13
14
15
1a: Ph
1a: Ph
1a: Ph
5a: Ph, Ph
a
Reaction conditions: imine
5 (10.0 mmol), CuCl (1.0 mmol), alkyne 2
(10.0 mmol), CH2Cl2 (15 mL), 12 h, imine 1 (10.0 mmol), 12 h, under an ambient
atmosphere.
b
Yield of isolated product.
No chromatographic procedures were required for purification of the product.
Scheme 2. The thermodynamic stability of the
configuration.
E configuration prior to the Z
c
process. When N-arylbenzaldimines 5bee were utilized, the re-
actions proceeded well to produce 7hek in excellent yields (Table
3, entries 8e11). Imines 5f and 5g can also be employed for this
reaction to furnish 7l and 7m both in excellent yields (Table 3,
entries 12e13). It is noteworthy that the halide and methoxyl
groups on these products offer the opportunity for further func-
tionalization.10 Electron-deficient alkynes 2b and 2c were also
adopted to give the corresponding imidazolidines 7n and 7o in
good yields (Table 3, entries 14 and 15). The structure of 7f was
confirmed unambiguously by X-ray diffraction analysis (Fig. 2),
which was in accordance with 1H NMR, 13C NMR, and HRMS
spectra.
treated with imine 1a in the presence of CuCl in CH2Cl2 at rt for
12 h, and 7a was successfully obtained with 90% yield (Scheme 3).
Next, a control experiment was carried out and revealed that no
reaction was observed in the absence of CuCl (Scheme 3). This
newly-discovered method is of great value because it can not only
allow us to achieve high molecular diversity of imidazolidines, but
also give a credible exemplification on the proposed mechanism
(Scheme 1). Although the cyclization of propargylamines to form
heterocycles has been widely reported,7c,9 the reaction of prop-
argylamines with imines to assemble substituted imidazolidines is
disclosed for the first time.
Scheme 3. Imidazolidine from propargylamine and formaldimine.
To expand the reaction scope, a variety of formaldimines
were treated with propargylamine 6, and the results are shown in
Table 3. Five N-arylformaldimines (1aed, and 1g), no matter the
electron nature of substituents on the benzene ring, reacted
smoothly to give the corresponding imidazolidines 7aee in excel-
lent yields (Table 3, entries 1e5). Especially, the above-mentioned
reactions generated no any observable undesired byproduct from
TLC analysis. Notably, when N-alkylformaldimine 1i and 1j were
used as the substrates, good yields of desired 7f and 7g were ob-
tained (Table 3, entries 6 and 7). Then, with 1a fixed as the second
imine moiety, imines 5beg were checked for this copper-catalyzed
Fig. 2. X-ray crystal structure for 7f.
3. Conclusion
In conclusion, we have developed a novel and efficient method
for the preparation of functionalized imidazolidines through
copper(I)-catalyzed domino three-component reactions of alkynes
and imines. During the reaction, one carbonecarbon bond and two
carbonenitrogen bonds are formed with 100% atom economy.

Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
3137
Readily available starting materials, operational simplicity, and
mild conditions make it very promising for both experimental
synthesis and large-scale preparation. In addition, a new stereo-
center is generated in the imidazolidine ring (7aeo) in this metal-
catalyzed procedure, which offers the opportunity for further
asymmetric investigation. Furthermore, the presented method is
another exemplification of alkynes as increasingly attractive
building blocks for developing MCRs.11 Studies in this direction are
also underway in our laboratory.
according to this procedure and the spectral data of these com-
pounds were given below.
4.3. Characterization
4.3.1. (E)-Methyl
(4a). White solid, mp: 132e133 ꢀC, 1.37 g, 4.65 mmol, 93% yield. 1H
NMR (400 MHz, CDCl3):
7.47 (t, J¼7.7 Hz, 2H), 7.40e7.27 (m, 5H),
6.85 (t, J¼7.3 Hz,1H), 6.66 (d, J¼8.0 Hz, 2H), 5.08 (s, 2H), 5.01 (s, 1H),
4.87 (s, 2H), 3.66 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
169.32,
2-(1,3-diphenylimidazolidin-4-ylidene)acetate
d
d
4. Experimental section
4.1. General
158.32, 144.86, 138.57, 129.88, 129.54, 127.14, 124.83, 118.15, 112.13,
80.92, 70.03, 53.59, 50.48 ppm. HRMS (EIþ) 294.1368 (calcd for
C18H18N2O2 294.1368).
All the reagents were purchased from commercial suppliers, and
were used without further purification. Column chromatography
was carried out on silica gel. The 1H NMR and 13C NMR spectra were
performed with a Varian Unity Plus spectrometer in CDCl3 using
TMS as internal standard. Chemical shifts are expressed in parts per
4.3.2. (E)-Methyl 2-(1,3-bis(4-methoxyphenyl)imidazolidin-4-
ylidene)acetate (4b). Light yellow solid, mp: 159e160 ꢀC, 1.74 g,
4.9 mmol, 98% yield. 1H NMR (400 MHz, CDCl3):
d 7.26e7.23 (m,
2H), 6.99e6.94 (m, 2H), 6.89 (d, J¼9.0 Hz, 2H), 6.60 (d, J¼9.0 Hz,
2H), 4.96 (s, 2H), 4.80 (s, 3H), 3.84 (s, 3H), 3.78 (s, 3H), 3.64 (s, 3H)
million (
d
) using residual solvent protons as internal standards (
d
ppm; 13C NMR (101 MHz, CDCl3):
d 169.40, 159.67, 158.65, 152.55,
7.26 for 1H,
d
77.0 for 13C). Coupling constants (J) are reported in
139.73, 131.10, 126.87, 115.12, 113.30, 79.97, 71.20, 55.80, 55.57,
54.19, 50.38 ppm. HRMS (EIþ) 354.1582 (calcd for C20H22N2O4
354.1580).
Hertz (Hz). Splitting patterns are designated as s (singlet), d (dou-
blet), t (triplet), m (multiplet). Melting points were measured on
microscopic melting point apparatus. High-resolution mass spec-
tral analysis (HRMS) data were recorded by Electro-Spray Ioniza-
tion (ESI).
4.3.3. (E)-Methyl 2-(1,3-bis(4-chlorophenyl)imidazolidin-4-ylidene)
acetate (4c). White solid, mp: 177e178 ꢀC, 1.68 g, 4.65 mmol, 93%
yield. 1H NMR (400 MHz, CDCl3):
d
7.44 (d, J¼8.8 Hz, 2H), 7.29 (d,
4.2. General procedures for the synthesis of imidazolidines
J¼8.8 Hz, 2H), 7.25 (d, J¼7.5 Hz, 2H), 6.56 (d, J¼8.9 Hz, 2H), 5.00 (d,
J¼7.2 Hz, 3H), 4.82 (d, J¼0.9 Hz, 2H), 3.66 (s, 3H) ppm; 13C NMR
4.2.1. General procedures for the preparation of imidazolidines
(4aen). Procedures for the synthesis of 4aed: CuCl (1.0 mmol) was
added to a solution of imine 1 (10.0 mmol) and alkyne 2 (5.0 mmol)
in dichloromethane (15 mL), and the reaction mixture was stirred
at rt for 12 h. Then the reaction mixture was filtered and the solvent
was removed under vacuum to give white or light yellow solid,
which was rinsed with n-hexane to give analysable imidazolidines
4. Compounds 4aed were synthesized according to this procedure
and the spectral data of these compounds were given below.
Procedures for the synthesis of 4een: CuCl (1.0 mmol) was
added to a solution of imine 1 (10.0 mmol) and alkyne 2 (5.0 mmol)
in dichloromethane (15 mL), and the reaction mixture was stirred
at rt for 12 h. After filtration of the CuCl, the crude product was
concentrated in vacuo and purified by chromatography on silica gel
(hexane/ethyl acetate 10:1e5:1) yielding the imidazolidine 4.
Compounds 4een were synthesized according to this procedure
and the spectral data of these compounds were given below.
(101 MHz, CDCl3): d 168.03, 156.55, 142.23, 135.94, 131.61, 129.08,
128.39, 124.98, 122.30, 112.16, 80.81, 68.77, 52.49, 49.58 ppm. HRMS
(EIþ) 362.0591 (calcd for C18H16Cl2N2O2 362.0589).
4.3.4. (E)-Methyl
(4d). White solid, mp: 120e121 ꢀC, 1.53 g, 4.75 mmol, 95% yield. 1H
NMR (400 MHz, CDCl3):
2-(1,3-di-p-tolylimidazolidin-4-ylidene)acetate
d
7.26 (d, J¼2.7 Hz, 2H), 7.24e7.20 (m, 2H),
7.11 (d, J¼8.2 Hz, 2H), 6.57 (d, J¼8.5 Hz, 2H), 5.01 (s, 2H), 4.92 (s,1H),
4.82 (s, 2H), 3.64 (s, 3H), 2.38 (s, 3H), 2.28 (s, 3H) ppm; 13C NMR
(101 MHz, CDCl3):
d 169.42, 158.88, 142.90, 137.18, 135.90, 130.41,
130.03, 127.37, 124.85, 112.24, 80.38, 70.46, 53.84, 50.41, 21.11,
20.38 ppm. HRMS (EIþ) 322.1679 (calcd for C20H22N2O2 322.1681).
4.3.5. (E)-Methyl
(4e). Light yellow solid, mp: 134e135 ꢀC, 1.45 g, 4.5 mmol, 90%
yield. 1H NMR (400 MHz, CDCl3):
7.37e7.30 (m, 1H), 7.23e7.09 (m,
2-(1,3-di-m-tolylimidazolidin-4-ylidene)acetate
d
4H), 6.67 (d, J¼7.5 Hz, 1H), 6.49 (s, 1H), 6.45 (d, J¼8.0 Hz, 1H), 5.05
(s, 2H), 4.98 (s, 1H), 4.85 (d, J¼1.1 Hz, 2H), 3.66 (s, 3H), 2.39 (s, 3H),
4.2.2. General procedures for the synthesis of functionalized imida-
zolidines (7aeo). Procedures for the synthesis of 7aed and 7hei:
CuCl (1.0 mmol) was added to a solution of imine 5 (10.0 mmol) and
alkyne 2 (10.0 mmol) in dichloromethane (15 mL). The reaction
mixture was stirred at rt for 12 h. Then imine 1 (10.0 mmol) was
added and the mixture was stirred at rt for 12 h. After filtration of
the CuCl, the crude product was concentrated in vacuo to yield
a white or yellow solid, which was washed with n-hexane to ana-
lysable imidazolidines 7. Compounds 7aed and 7hei were syn-
thesized according to this procedure and the spectral data of these
compounds were given below.
2.34 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
d 169.43, 158.56,
144.94, 139.95, 139.44, 138.47, 129.63, 129.37, 127.96, 125.38, 121.87,
119.06, 112.94, 109.28, 80.63, 70.15, 53.66, 50.46, 21.74, 21.41 ppm.
HRMS (EIþ) 322.1679 (calcd for C20H22N2O2 322.1681).
4.3.6. (E)-Methyl
(4f). Viscous liquid, 1.21 g, 3.75 mmol, 75% yield. 1H NMR
(400 MHz, CDCl3):
2-(1,3-di-o-tolylimidazolidin-4-ylidene)acetate
d
7.27 (dd, J¼6.2, 3.7 Hz, 3H), 7.22e7.13 (m, 3H),
7.04 (dd, J¼17.2, 7.4 Hz, 2H), 4.81 (dd, J¼28.3, 10.9 Hz, 4H), 4.37 (s,
1H), 3.61 (s, 3H), 2.39 (s, 3H), 2.19 (s, 3H) ppm; 13C NMR (101 MHz,
CDCl3):
d 169.51, 160.95, 148.21, 136.91, 136.28, 131.67, 128.58,
Procedure for the synthesis of 7eeg and 7jeo: CuCl (1.0 mmol)
was added to a solution of imine 5 (10.0 mmol) and alkyne 2
(10.0 mmol) in dichloromethane (15 mL). The reaction mixture was
stirred at rt for 12 h. Then imine 1 (10.0 mmol) was added and the
mixture was stirred at rt for 12 h. After filtration of the CuCl, the
crude product was concentrated in vacuo and purified by chro-
matography on silica gel (hexane/ethyl acetate 10:1e5:1) yielding
the imidazolidine 7. Compounds 7eeg and 7jeo were synthesized
127.58, 127.16, 126.77, 123.59, 118.53, 79.81, 74.00, 57.49, 50.32,
19.26, 17.69 ppm. HRMS (EIþ) 322.1679 (calcd for C20H22N2O2
322.1681).
4.3.7. (E)-Methyl 2-(1,3-bis(3,5-dimethylphenyl)imidazolidin-4-
ylidene)acetate (4g). Light yellow solid, mp: 159e159 ꢀC, 1.56 g,
4.45 mmol, 89% yield. 1H NMR (400 MHz, CDCl3):
d
6.94 (d,
J¼4.6 Hz, 3H), 6.50 (s, 1H), 6.29 (s, 2H), 5.02 (s, 2H), 4.97 (s, 1H), 4.83

3138
Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
(d, J¼1.1 Hz, 2H), 3.66 (s, 3H), 2.34 (s, 6H), 2.30 (s, 6H) ppm; 13C
2H), 4.83 (s, 2H), 2.05 (s, 3H) ppm; 13C NMR (75 MHz, CDCl3):
195.66, 157.45, 143.19, 133.07, 130.20, 129.38, 126.31, 123.27, 113.17,
92.07, 69.52, 54.26, 30.62 ppm. HRMS (EIþ) 346.0643 (calcd for
18H16Cl2N2O 346.0640).
NMR (101 MHz, CDCl3):
d
169.51, 158.74, 145.02, 139.64, 139.27,
d
138.38, 128.87, 122.42, 120.09, 110.12, 80.36, 70.25, 53.74, 50.44,
21.60, 21.31 ppm. HRMS (EIþ) 350.1997 (calcd for C22H26N2O2
350.1994).
C
4.3.15. (E)-Methyl 2-(1,3,5-triphenylimidazolidin-4-ylidene)acetate
4.3.8. (E)-Methyl
2-(1,3-dibenzylimidazolidin-4-ylidene)acetate
(7a). White solid, mp: 161e165 ꢀC, 3.33 g, 9.0 mmol, 90% yield. 1H
(4h). Viscous liquid, 1.39 g, 4.3 mmol, 86% yield. 1H NMR (300 MHz,
NMR (400 MHz, CDCl3):
d
7.56 (d, J¼7.3 Hz, 2H), 7.48e7.42 (m, 2H),
CDCl3):
d
7.40e7.27 (m, 7H), 7.21 (d, J¼7.2 Hz, 3H), 4.75 (s, 1H), 4.28
7.37 (d, J¼7.4 Hz, 2H), 7.31 (d, J¼7.2 Hz, 2H), 7.23e7.16 (m, 4H), 6.72
(t, J¼7.3 Hz, 1H), 6.66 (d, J¼8.0 Hz, 2H), 6.56 (s, 1H), 5.28 (d,
J¼4.4 Hz, 1H), 5.21 (dd, J¼4.3, 1.1 Hz, 1H), 5.03 (s, 1H), 3.54 (s, 3H)
(d, J¼20.4 Hz, 4H), 4.03 (s, 2H), 3.70 (s, 2H), 3.62 (s, 3H) ppm; 13C
NMR (126 MHz, CDCl3):
d 169.36, 161.12, 137.81, 135.52, 128.75,
128.56, 128.39, 127.65, 127.33, 127.19, 78.16, 73.00, 59.20, 58.89,
50.07, 48.56 ppm. HRMS (EIþ) 322.1684 (calcd for C20H22N2O2
322.1681).
ppm; 13C NMR (101 MHz, CDCl3):
d 167.88, 160.64, 143.36, 140.48,
138.68, 130.00, 129.36, 128.22, 127.63, 126.95, 124.72, 117.96, 112.39,
82.89, 69.10, 64.75, 50.45 ppm. HRMS (EIþ) 370.1677 (calcd for
C24H22N2O2 370.1681).
4.3.9. (E)-Methyl 2-(1,3-dicyclohexylimidazolidin-4-ylidene)acetate
(4i). Viscous liquid, 1.31 g, 4.25 mmol, 85% yield. 1H NMR
4 . 3 . 16 . ( E ) - M e t h y l 2 - ( 3 - ( 4 - m e t h o x y p h e n y l ) - 1, 5 -
diphenylimidazolidin-4-ylidene)acetate (7b). White solid mp:
147e148 ꢀC, 3.92 g, 9.8 mmol, 98% yield. 1H NMR (400 MHz, CDCl3):
(300 MHz, CDCl3):
d
4.50 (s, 1H), 4.06 (d, J¼4.0 Hz, 4H), 3.59 (s, 3H),
3.32 (s, 1H), 2.21 (s, 1H), 1.76 (dd, J¼47.1, 18.5 Hz, 10H), 1.26 (dd,
J¼25.6, 8.0 Hz, 10H) ppm; 13C NMR (126 MHz, CDCl3):
d
169.54,
d
7.61e7.52 (m, 2H), 7.35e7.28 (m, 4H), 7.19 (dd, J¼8.6, 7.6 Hz, 3H),
160.68, 76.22, 67.12, 61.70, 56.72, 53.90, 49.95, 31.28, 29.47, 25.79,
25.49, 24.46 ppm. HRMS (EIþ) 306.2309 (calcd for C18H30N2O2
306.2307).
6.99 (d, J¼8.9 Hz, 2H), 6.72 (t, J¼7.3 Hz, 1H), 6.64 (d, J¼7.9 Hz, 2H),
6.54 (s, 1H), 5.22 (s, 2H), 4.78 (s, 1H), 3.84 (s, 3H), 3.53 (s, 3H) ppm;
13C NMR (101 MHz, CDCl3):
d 167.91, 161.94, 158.72, 143.32, 140.53,
131.08, 129.33, 128.22, 127.58, 127.06, 117.84, 115.25, 112.31, 81.71,
4.3.10. (E)-Ethyl
(4j). White solid, mp: 127e129 ꢀC, 1.36 g, 4.4 mmol, 88% yield. 1H
NMR (300 MHz, CDCl3):
2-(1,3-diphenylimidazolidin-4-ylidene)acetate
69.78, 64.73, 55.61, 50.35 ppm. HRMS (EIþ) 400.1789 (calcd for
C25H24N2O3 400.1787).
d
7.47 (t, J¼7.6 Hz, 2H), 7.41e7.28 (m, 5H),
6.85 (t, J¼7.2 Hz, 1H), 6.66 (d, J¼7.9 Hz, 2H), 5.07 (s, 2H), 5.01 (s, 1H),
4.3.17. (E)-Methyl 2-(3-(4-chlorophenyl)-1,5-diphenylimidazolidin-
4.87 (s, 2H), 4.13 (q, J¼7.1 Hz, 2H), 1.26 (t, J¼7.1 Hz, 3H) ppm; 13C
4-ylidene)acetate (7c). Light yellow solid, mp: 137e138 ꢀC, 3.68 g,
NMR (75 MHz, CDCl3):
d
168.87, 158.11, 144.87, 138.62, 129.81,
9.1 mmol, 91% yield. 1H NMR (400 MHz, CDCl3):
d
7.54 (d, J¼7.3 Hz,
129.46, 127.03, 124.83, 118.07, 112.08, 81.36, 69.95, 58.88, 53.54,
2H), 7.47e7.42 (m, 2H), 7.36e7.27 (m, 4H), 7.25e7.17 (m, 3H), 6.74
(t, J¼7.3 Hz, 1H), 6.66 (d, J¼8.0 Hz, 2H), 6.54 (s, 1H), 5.27 (d,
J¼4.2 Hz, 1H), 5.20 (dd, J¼4.2, 1.1 Hz, 1H), 5.01 (s, 1H), 3.56 (s, 3H)
14.55 ppm. HRMS (EIþ) 308.1527 (calcd for C19H20N2O2 308.1525).
4.3.11. (E)-Ethyl 2-(1,3-bis(4-methoxyphenyl)imidazolidin-4-ylidene)
acetate (4k). White solid, mp: 141e142 ꢀC, 1.66 g, 4.5 mmol, 90%
ppm; 13C NMR (101 MHz, CDCl3):
d 167.69, 160.26, 143.26, 140.34,
137.28, 132.25, 130.17, 129.39, 128.36, 128.07, 127.73, 125.85, 118.13,
112.43, 83.68, 68.95, 64.63, 50.56 ppm. HRMS (EIþ) 404.1288 (calcd
for C24H21ClN2O2 404.1292).
yield. 1H NMR (300 MHz, CDCl3):
d
7.25 (d, J¼8.6 Hz, 2H), 6.96 (d,
J¼8.8 Hz, 2H), 6.88 (d, J¼8.9 Hz, 2H), 6.59 (d, J¼8.9 Hz, 2H), 4.94 (s,
2H), 4.79 (s, 3H), 4.10 (dd, J¼14.2, 7.1 Hz, 2H), 3.80 (d, J¼19.2 Hz,
6H), 1.24 (t, J¼7.1 Hz, 3H) ppm; 13C NMR (75 MHz, CDCl3):
d
168.96,
4.3.18. (E)-Methyl 2-(1,5-diphenyl-3-(p-tolyl)imidazolidin-4-ylidene)
159.46, 158.61, 152.52, 139.75, 131.15, 126.86, 115.09, 113.25, 80.41,
71.12, 58.75, 55.62, 54.14, 14.56 ppm. HRMS (EIþ) 368.1739 (calcd
for C21H24N2O4 368.1736).
acetate (7d). Light yellow solid, mp: 124e126 ꢀC, 3.65 g, 9.5 mmol,
95% yield. 1H NMR (400 MHz, CDCl3):
d 7.59e7.53 (m, 3H), 7.29 (t,
J¼7.5 Hz, 3H), 7.23e7.14 (m, 5H), 6.71 (dd, J¼8.9, 5.7 Hz,1H), 6.64 (d,
J¼7.9 Hz, 2H), 6.54 (s, 1H), 5.24 (d, J¼4.4 Hz, 1H), 5.20 (dd, J¼4.4,
4.3.12. (E)-1-(1,3-Diphenylimidazolidin-4-ylidene)propan-2-one
1.4 Hz, 1H), 4.93 (d, J¼0.6 Hz, 1H), 3.53 (s, 3H), 2.38 (s, 3H) ppm; 13
C
(4l). Yellow solid, mp: 107e108 ꢀC, 1.21 g, 4.35 mmol, 87% yield. 1H
NMR (101 MHz, CDCl3): d 167.93, 161.12, 143.35, 140.52, 137.15,
NMR (300 MHz, CDCl3):
6.84 (t, J¼7.3 Hz,1H), 6.66 (d, J¼8.0 Hz, 2H), 5.47 (s, 1H), 5.07 (s, 2H),
4.90 (s, 2H), 2.06 (s, 3H) ppm; 13C NMR (75 MHz, CDCl3)
195.51,
d
7.51 (t, J¼7.6 Hz, 2H), 7.42e7.27 (m, 5H),
135.93, 130.57, 129.34, 128.22, 127.59, 124.91, 117.87, 112.34, 82.31,
69.34, 64.76, 50.39, 21.13 ppm. HRMS (EIþ) 384.1832 (calcd for
d
C25H24N2O2 384.1838).
158.10, 144.75, 129.90, 129.47, 127.43, 125.02, 118.06, 112.09, 91.53,
69.74, 54.31, 30.55 ppm. HRMS (EIþ) 278.1416 (calcd for C18H18N2O
278.1419).
4 . 3 .19 . ( E ) - M e t h y l 2 - ( 3 - ( 3 , 5 - d i m e t h y l p h e n y l ) - 1, 5 -
diphenylimidazolidin-4-ylidene)acetate (7e). White solid, mp:
161e162 ꢀC, 3.5 g, 8.8 mmol, 88% yield. 1H NMR (400 MHz, CDCl3):
4.3.13. (E)-1-(1,3-Bis(4-methoxyphenyl)imidazolidin-4-ylidene)
d
7.59e7.53 (m, 2H), 7.31 (t, J¼7.5 Hz, 2H), 7.21 (td, J¼8.7, 7.5 Hz, 3H),
propan-2-one (4m). Light yellow solid, mp: 148e150 ꢀC, 1.49 g,
7.00 (s, 2H), 6.95 (s, 1H), 6.73 (t, J¼7.3 Hz, 1H), 6.66 (d, J¼7.9 Hz, 2H),
6.54 (s,1H), 5.28 (d, J¼4.4 Hz,1H), 5.21 (dd, J¼4.4,1.4 Hz,1H), 4.98 (d,
J¼0.7 Hz, 1H), 3.55 (s, 3H), 2.35 (s, 6H) ppm; 13C NMR (101 MHz,
4.4 mmol, 88% yield. 1H NMR (300 MHz, CDCl3):
d 7.30e7.23 (m,
2H), 7.00 (d, J¼8.9 Hz, 2H), 6.89 (d, J¼8.9 Hz, 2H), 6.60 (d, J¼9.0 Hz,
2H), 5.27 (s, 1H), 4.94 (s, 2H), 4.83 (s, 2H), 3.85 (s, 3H), 3.77 (s, 3H),
CDCl3): d 167.95,160.88,143.37,140.57,139.83,138.43,129.32,128.79,
2.02 (s, 3H) ppm; 13C NMR (75 MHz, CDCl3):
d
195.31,159.41,158.83,
128.22, 127.58, 122.40, 117.83, 112.33, 82.51, 69.27, 64.79, 50.40,
152.51, 139.63, 130.88, 126.90, 115.13, 113.25, 90.95, 70.90, 55.64,
54.93, 30.45 ppm. HRMS (EIþ) 338.1633 (calcd for C20H22N2O3
338.1630).
21.33 ppm. HRMS (EIþ) 398.1990 (calcd for C26H26N2O2 398.1994).
4.3.20. (E)-Methyl 2-(3-cyclohexyl-1,5-diphenylimidazolidin-4-
ylidene)acetate (7f). White solid, mp: 151e152 ꢀC, 3.31 g,
4.3.14. (E)-1-(1,3-Bis(4-chlorophenyl)imidazolidin-4-ylidene)
8.8 mmol, 88% yield. 1H NMR (400 MHz, CDCl3):
d
7.41 (d, J¼7.3 Hz,
propan-2-one (4n). White solid, mp: 180e182 ꢀC,1.47 g, 4.25 mmol,
2H), 7.23 (d, J¼7.7 Hz, 2H), 7.17 (dd, J¼10.6, 5.2 Hz, 3H), 6.69 (t,
J¼7.3 Hz, 1H), 6.60 (d, J¼8.1 Hz, 2H), 6.43 (s, 1H), 4.99 (dd, J¼4.5,
1.5 Hz, 1H), 4.89 (d, J¼4.6 Hz, 1H), 4.63 (s, 1H), 3.56 (s, 3H), 2.14 (d,
85% yield. 1H NMR (300 MHz, CDCl3):
(dd, J¼18.9, 8.8 Hz, 4H), 6.55 (d, J¼8.8 Hz, 2H), 5.44 (s, 1H), 4.99 (s,
d
7.47 (d, J¼8.6 Hz, 2H), 7.27

Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
3139
J¼12.0 Hz, 1H), 2.06 (d, J¼11.7 Hz, 1H), 1.92 (t, J¼12.8 Hz, 2H), 1.76
(d, J¼13.0 Hz, 1H), 1.60 (qd, J¼12.3, 3.4 Hz, 2H), 1.50e1.31 (m, 3H),
8.8 mmol, 88% yield. 1H NMR (400 MHz, CDCl3):
d
7.47 (t, J¼7.8 Hz,
2H), 7.40 (dd, J¼8.5, 1.2 Hz, 2H), 7.30 (d, J¼7.4 Hz, 1H), 7.24e7.20 (m,
3H), 6.81e6.70 (m, 4H), 6.55 (d, J¼3.0 Hz, 1H), 6.26 (dd, J¼3.2,
1.8 Hz,1H), 5.22 (d, J¼4.2 Hz,1H), 5.18 (dd, J¼4.2, 1.0 Hz,1H), 4.99 (s,
1.29e1.20 (m, 1H) ppm; 13C NMR (101 MHz, CDCl3):
d 167.97, 161.26,
143.26, 140.35, 129.23, 128.11, 127.38, 117.52, 112.15, 78.69, 64.93,
63.67, 54.15, 50.24, 30.50, 28.37, 25.75, 25.56, 25.43 ppm. HRMS
(EIþ) 376.2151 (calcd for C24H28N2O2 376.2151).
1H), 3.59 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
d 168.10, 158.39,
151.76, 143.26, 141.87, 138.80, 129.92, 129.27, 127.11, 125.08, 118.47,
112.88, 110.07, 109.29, 82.11, 68.81, 58.66, 50.47 ppm. HRMS (EIþ)
360.1472 (calcd for C22H20N2O3 360.1474).
4.3.21. (E)-Methyl 2-(3-isopropyl-1-(4-methoxyphenyl)-5-
phenylimidazolidin-4-ylidene)acetate (7g). Light yellow solid, mp:
180e181 ꢀC, 3.15 g, 8.6 mmol, 86% yield. 1H NMR (400 MHz, CDCl3):
4.3.27. (E)-Methyl 2-(1,3-diphenyl-5-(thiophen-2-yl)imidazolidin-4-
d
7.42e7.35 (m, 2H), 7.24 (dd, J¼8.5, 4.6 Hz, 2H), 7.19e7.13 (m, 1H),
ylidene)acetate (7m). Light yellow solid, mp: 144e145 ꢀC, 3.20 g,
6.80e6.72 (m, 2H), 6.62e6.54 (m, 2H), 6.38 (s, 1H), 4.92 (dd, J¼4.7,
1.7 Hz, 1H), 4.78 (d, J¼4.7 Hz, 1H), 4.65 (s, 1H), 4.01e3.92 (m, 1H),
3.69 (s, 3H), 3.55 (s, 3H), 1.41 (d, J¼6.7 Hz, 3H), 1.30 (d, J¼6.6 Hz, 3H)
8.5 mmol, 85% yield. 1H NMR (400 MHz, CDCl3):
d 7.41e7.36 (m,
2H), 7.32e7.27 (m, 3H), 7.23e7.16 (m, 3H), 7.08 (dd, J¼5.1, 1.1 Hz,
1H), 6.98 (s, 1H), 6.85 (dd, J¼5.1, 3.6 Hz, 1H), 6.74 (t, J¼7.4 Hz, 1H),
6.65 (d, J¼7.8 Hz, 2H), 5.18 (d, J¼4.6 Hz, 1H), 5.05 (dd, J¼4.5, 1.1 Hz,
1H), 5.01 (s, 1H), 3.58 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
ppm; 13C NMR (75 MHz, CDCl3):
d 168.07, 161.47, 152.30, 140.27,
138.28, 128.10, 127.35, 114.91, 113.94, 79.06, 66.01, 63.45, 55.67,
50.20, 45.76, 19.96, 18.12 ppm. HRMS (EIþ) 366.1940 (calcd for
d
168.16, 160.03, 143.08, 142.67, 138.64, 129.96, 129.45, 127.00,
C
22H26N2O23 366.1943).
126.45, 124.78, 118.61, 113.01, 82.85, 68.11, 60.51, 50.59 ppm. HRMS
(EIþ) 376.1247 (calcd for C22H20N2O2S 376.1245).
4.3.22. (E)-Methyl 2-(1-(4-methoxyphenyl)-3,5-diphenylimidazolidin-
4-ylidene)acetate (7h). White solid, mp: 148e149 ꢀC, 3.72 g,
4.3.28. (E)-Ethyl
(7n). White solid, mp: 108e110 ꢀC, 3.38 g, 8.8 mmol, 88% yield. 1H
NMR (300 MHz, CDCl3):
2-(1,3,5-triphenylimidazolidin-4-ylidene)acetate
9.3 mmol, 93% yield. 1H NMR (400 MHz, CDCl3):
d 7.55e7.50 (m, 2H),
7.50e7.44 (m, 2H), 7.41e7.36 (m, 2H), 7.30 (ddd, J¼7.3, 4.8, 1.4 Hz,
3H), 7.22 (dd, J¼8.3, 6.4 Hz, 1H), 6.83e6.76 (m, 2H), 6.71e6.64 (m,
2H), 6.49 (s, 1H), 5.19 (s, 2H), 5.06 (d, J¼0.7 Hz, 1H), 3.72 (s, 3H), 3.54
d
7.59 (d, J¼7.3 Hz, 2H), 7.49 (t, J¼7.6 Hz,
2H), 7.41 (d, J¼7.4 Hz, 2H), 7.32 (t, J¼7.3 Hz, 3H), 7.27e7.16 (m, 3H),
6.82e6.65 (m, 3H), 6.61 (s, 1H), 5.28 (dd, J¼22.1, 3.8 Hz, 2H), 5.05 (s,
1H), 4.04 (dd, J¼8.7, 7.3 Hz, 2H), 1.17 (t, J¼7.1 Hz, 3H) ppm; 13C NMR
(s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
d 168.02, 160.74, 152.74,
140.17, 138.85, 138.61, 129.95, 128.21, 127.60, 126.82, 124.63, 114.96,
114.61, 82.82, 69.96, 66.23, 55.67, 50.43 ppm. HRMS (EIþ) 400.1783
(calcd for C25H24N2O3 400.1787).
(75 MHz, CDCl3): d 167.46, 160.43, 143.43, 140.51, 138.75, 129.92,
129.29, 128.14, 127.52, 126.80, 124.67, 117.91, 112.39, 83.32, 69.04,
64.65, 58.87, 14.43 ppm. HRMS (EIþ) 384.1835 (calcd for
C25H24N2O2 384.1838).
4.3.23. (E)-Methyl 2-(3,5-diphenyl-1-(p-tolyl)imidazolidin-4-
ylidene)acetate (7i). White solid, mp: 159e160 ꢀC, 3.61 g,
4.3.29. (E)-1-(1,3,5-Triphenylimidazolidin-4-ylidene)propan-2-one
9.4 mmol, 94% yield. 1H NMR (400 MHz, CDCl3):
d
7.54 (d, J¼7.5 Hz,
(7o). White solid, mp: 166e168 ꢀC, 3.01 g, 8.5 mmol, 85% yield. 1H
2H), 7.47 (t, J¼7.7 Hz, 2H), 7.39 (d, J¼7.7 Hz, 2H), 7.30 (t, J¼7.4 Hz,
3H), 7.21 (t, J¼7.3 Hz, 1H), 7.01 (d, J¼8.1 Hz, 2H), 6.59 (d, J¼8.2 Hz,
2H), 6.53 (s, 1H), 5.24 (dd, J¼22.8, 4.1 Hz, 2H), 5.04 (s, 1H), 3.55 (s,
NMR (300 MHz, CDCl3):
d
7.62 (d, J¼7.4 Hz, 2H), 7.54 (t, J¼7.7 Hz,
2H), 7.46e7.30 (m, 5H), 7.21 (t, J¼7.8 Hz, 3H), 6.78e6.65 (m, 4H),
5.46 (s, 1H), 5.37e5.22 (m, 2H), 1.94 (s, 3H) ppm; 13C NMR (75 MHz,
3H), 2.21 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
d
167.95, 160.76,
CDCl3): d 193.87, 160.20, 143.21, 140.33, 138.47, 129.99, 129.26,
141.38, 140.47, 138.78, 129.93, 128.22, 127.59, 127.28, 126.87, 124.68,
112.72, 82.81, 69.36, 65.13, 50.45, 20.36 ppm. HRMS (EIþ) 384.1834
(calcd for C25H24N2O2 384.1838).
128.16,127.36,124.94,117.85,112.29, 92.31, 68.95, 64.98, 30.87 ppm.
HRMS (EIþ) 354.1735 (calcd for C24H22N2O 354.1732).
Supplementary data
4.3.24. (E)-Methyl 2-(5-(4-chlorophenyl)-1,3-diphenylimidazolidin-4-
ylidene)acetate (7j). White solid, mp: 149e150 ꢀC, 3.52 g,
Experimental procedures, characterization data, and copies of
the 1H NMR and 13C NMR spectra for the products are available.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.03.063.
8.7 mmol, 87% yield. 1H NMR (400 MHz, CDCl3):
d 7.55e7.45 (m, 4H),
7.41e7.35 (m, 2H), 7.34e7.27 (m, 2H), 7.27e7.24 (m, 1H), 7.21 (dd,
J¼8.6, 7.4 Hz, 2H), 6.76 (t, J¼7.4 Hz,1H), 6.63 (d, J¼7.9 Hz, 2H), 6.52 (s,
1H), 5.30 (d, J¼4.4 Hz, 1H), 5.23 (dd, J¼4.3, 1.5 Hz, 1H), 5.02 (d,
J¼0.8 Hz, 1H), 3.56 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
d 167.88,
References and notes
160.27, 143.10, 139.11, 138.52, 133.37, 130.05, 129.49, 128.49, 127.08,
124.66, 118.23, 112.38, 83.02, 69.09, 64.10, 50.52 ppm. HRMS (EIþ)
404.1295 (calcd for C24H21ClN2O2 404.1292).
1. (a) Iinuma, Y.; Kozawa, S.; Ishiyama, H.; Tsuda, M.; Fukushi, E.; Kawabata, J.;
Fromont, J.; Kobayashi, J. J. Nat. Prod. 2005, 68, 1109e1110; (b) Lewis, J. C.;
Bergman, R. G.; Ellman, J. A. Acc. Chem. Res. 2008, 41, 1013e1025; (c) Zhang, C.;
De, C. K.; Mal, R.; Seidel, D. J. Am. Chem. Soc. 2008, 130, 416e417; (d) Gil, C.;
Brase, S. J. Comb. Chem. 2009, 11, 175e197; (e) Bhandari, M. R.; Yousufuddin, M.;
Lovely, C. J. Org. Lett. 2011, 13, 1382e1385; (f) Chattopadhyay, B.; Gevorgyan, V.
Angew. Chem., Int. Ed. 2012, 51, 862e872; (g) Gulevich, A. V.; Dudnik, A. S.;
Chernyak, N.; Gevorgyan, V. Chem. Rev. 2013, 113, 3084e3213.
4.3.25. (E)-Methyl 2-(1,3-diphenyl-5-(p-tolyl)imidazolidin-4-
ylidene)acetate (7k). White solid, mp: 157e158 ꢀC, 3.42 g,
8.9 mmol, 89% yield. 1H NMR (400 MHz, CDCl3):
d 7.53e7.42 (m,
4H), 7.39 (d, J¼7.4 Hz, 2H), 7.30 (t, J¼7.3 Hz, 1H), 7.20 (t, J¼7.9 Hz,
2H), 7.11 (d, J¼7.9 Hz, 2H), 6.73 (t, J¼7.3 Hz, 1H), 6.66 (d, J¼8.0 Hz,
2H), 6.52 (s, 1H), 5.30 (d, J¼4.3 Hz, 1H), 5.25e5.17 (m, 1H), 5.02 (s,
1H), 3.55 (s, 3H), 2.28 (s, 3H) ppm; 13C NMR (101 MHz, CDCl3):
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d
167.91, 160.83, 143.35, 138.73, 137.52, 137.25, 129.97, 129.33,
129.03, 128.01, 126.89, 124.69, 117.86, 112.39, 82.76, 69.01, 64.48,
50.44, 21.20 ppm. HRMS (EIþ) 384.1842 (calcd for C25H24N2O2
384.1838).
4.3.26. (E)-Methyl 2-(5-(furan-2-yl)-1,3-diphenylimidazolidin-4-
ylidene)acetate (7l). Light yellow solid, mp: 141e142 ꢀC, 3.17 g,

3140
Y. Li et al. / Tetrahedron 70 (2014) 3134e3140
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