Facile access to oxazolidin-2-imine, thiazolidin-2-imine and imidazolidin-2-imine derivatives bearing an exocyclic haloalkyliene via direct halocyclization between propargylamines, heterocumulenes and I2 (NBS)

Article abstract of DOI:10.1016/j.tet.2015.04.080

Abstract A simple, cheap, efficient, and metal-free method for one-step synthesis of a library of 1,3-diheteroatom five-membered heterocycles with exocyclic CN and CC double bonds was presented. The convenient reactions proceed via the direct three-compon

Full text of DOI:10.1016/j.tet.2015.04.080

Tetrahedron xxx (2015) 1e8
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Facile access to oxazolidin-2-imine, thiazolidin-2-imine and
imidazolidin-2-imine derivatives bearing an exocyclic haloalkyliene
via direct halocyclization between propargylamines,
heterocumulenes and I2 (NBS)
,b,
Shujian Huang a, Yinlin Shao a, Ruiting Liu a, Xigeng Zhou a
*
a Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple, cheap, efficient, and metal-free method for one-step synthesis of a library of 1,3-diheteroatom
five-membered heterocycles with exocyclic C]N and C]C double bonds was presented. The convenient
reactions proceed via the direct three-component halocyclization of propargylamines, heterocumulenes
and I2 (NBS).
Received 20 March 2015
Accepted 23 April 2015
Available online xxx
Ó 2015 Published by Elsevier Ltd.
Keywords:
Heterocycles
Metal-free
Iodocyclization
Propargylamines
1. Introduction
imidazolidin-2-ones as major products (Scheme 1).14d Further-
more, it has been found that replacement of the tosyl isocyanate by
Substituted oxazoles,1 thiazoles2 and imidazoles3 are important
structural components of a vast array of naturally occurring and
pharmacologically active molecules. Furthermore, these types of
heterocycles are also valuable intermediates4 in organic synthesis
and useful ligands5 for organometallic compounds with interesting
properties. There has been a longstanding interest in the de-
velopment of new oxazole-, thiazole- and imidazole-based struc-
tures for the fine-tuning of the biological or physical properties of
these molecules and new methods for their construction.6e8
Among a variety of oxazole, thiazole and imidazole derivatives,
oxazolidin-2-imines,9 thiazolidin-2-imines10 and imidazolidin-2-
imines11 are currently attracting considerable attention due to
their therapeutic value in diseases, such as methicillin-resistant
Staphylococcus aureus (MRSA)12 and Mycobacterium tuberculosis.13
Several synthetic approaches to substituted oxazolidin-2-imines,
thiazolidin-2-imines and imidazolidin-2-imines have recently been
reported.14,15 Recently, Campbell and Toste found that (L)AuCl/
AgNTf2 can catalyze the cyclization of the in situ generated prop-
argylamines with a tosyl isocyanate to form oxazolidin-2-imines as
major products while the application of AgOTf provided
aryl or alkyl isocyanates in the presence of Ph3PAuCl/AgOTf or Rh2þ
led to the formation of tetrasubstituted 3,4-dihydropyrimidin-
2(1H)-ones (Scheme 1). Remarkably, both chemo- and regiose-
lectivity of cyclization of propargylamines and isocyanates are de-
pendent on the catalyst, and the nature of isocyanates and
propargylamines.16 Consequently, further insights into the re-
activity of propargylamines toward isocyanates are essential. In
particular on the industrial scale for medicinal chemistry applica-
tions the catalyst- and additive-free method is highly desirable.
Vinyl halides are versatile building blocks in organic synthesis
due to their applicability toward a vast range of cross-coupling
reactions.17 Iodocyclization has been successfully employed in
synthesis of various kinds of iodo-substituted carbocycles and
heterocycles.18 Among these transformations, however, examples
that form products containing the exocyclic iodoalkylidene func-
tionality are still rare.14b,19 Very recently, one viable protocol for
synthesis of 5-iodomethyleneoxazolidin-2-imines and 5-
methylenethiazolidin-2-imines from the CuI-catalyzed multicom-
ponent, one-pot, three-step reaction between aldehyde, amine,
alkyne, iso(thio)cyanate and I2 is reported.14b Although this method
employs the readily available starting materials aldehyde, amine,
alkyne, and iso(thio)cyanate, the iodocyclization procedure suffers
from more stoichiometric amounts of I2 in the presence of large
* Corresponding author. Tel./fax: þ86 21 6564 3769; e-mail address: xgzhou@
fudan.edu.cn (X. Zhou).
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S. Huang et al. / Tetrahedron xxx (2015) 1e8
Scheme 1. Direction reaction between substituted propargylamine and isocyanate.
excess of Na2CO3, and moderate yields. Here, we describe a direct
reaction between propargylamines, I2, and heteroallenes such as
RNCO, RNCS and RN¼C¼NR, which provides an efficient method for
the synthesis of oxazolidin-2-imines, thiazolidin-2-imines and
imidazolidin-2-imines bearing an exocyclic iodoalkylidene and
significantly increase the reaction substrate scope. This methodol-
ogy is also general in preparing oxazolidin-2-imines bearing an
exocyclic bromoalkylidene.
2. Results and discussion
Fig. 1. ORTEP drawing of 3aa with 30% probability thermal ellipsoids.
In our initial screening experiments, the three-component re-
action between propargylamine 1a, phenyl isocyanate 2a and I2
was selected as the model reaction. A mixture of 1a (0.3 mmol) and
2a (0.3 mmol) in ethyl acetate (EA) was treated with molecular
iodine (0.3 mmol) at room temperature, providing the desired
product 3aa in 75% yield (Table 1, entry 1). Increasing reaction
temperature to 50 ꢀC gave 3aa in 97% yield, while a higher tem-
perature showed a little improvement (Table 1, entries 2 and 3).
Afterwards, evaluation of different solvents (dichloromethane,
acetonitrile, methanol) reveled that ethyl acetate was among the
most suitable solvents for this iodocyclization (Table 1, entries
4e7). The structure of 3aa was further confirmed by the X-ray
crystal structure analysis (Fig. 1).
On the basis of the optimized conditions, the scope of this
protocol was initially examined by applying an array of different
isocyanates 2. The results showed that aryl isocyanates bearing
electron-donating and electron-neutral groups afforded the cor-
responding oxazolidine derivatives 3abe3ae in good to excellent
yields (Table 2, entries 2e5). Products 3afe3ai bearing halogens
(fluorine, chlorine, bromine) were also obtained with excellent
yields (Table 2, entries 6e9). However, the presence of the strong
Table 2
Isocyanates scopea
Table 1
Optimization of reaction conditions for the synthesis of oxazolidine derivative 3aaa
Entry
R
Product
Yield (%)b
1
2
3
4
5
6
7
8
Ph (2a)
3aa
3ab
3ac
3ad
3ae
3af
3ag
3ah
3ai
97
92
96
93
86
99
96
90
91
88
65
4-CH3C6H4 (2b)
4-CH3OC6H4 (2c)
2-CH3OC6H4 (2d)
2-CH3C6H4 (2e)
4-FC6H4 (2f)
3-FC6H4 (2g)
4-ClC6H4 (2h)
4-BrC6H4 (2i)
4-CF3C6H4 (2j)
2-CF3C6H4 (2k)
Entry
Solvent
T/ꢀC
Time/h
Yield/%b
1
2
3
4
5
6
7
EA
EA
EA
EA
DCM
MeCN
MeOH
25
50
75
50
50
50
50
24
24
24
12
12
12
12
75
97
99
98
89
75
9
10
11
3aj
3ak
Complicated
a
a
Reactions were carried out with 1a (0.30 mmol), 2 (0.30 mmol), I2 (0.3 mmol),
Reactions were carried out with 1a (0.30 mmol), 2 (0.30 mmol), I2 (0.3 mmol) in
and solvent (3 mL).
EA (3 mL) at 50 ꢀC for 12 h.
b
b
Isolated yield.
Isolated yield.
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S. Huang et al. / Tetrahedron xxx (2015) 1e8
3
electro-withdrawing CF3 group in aryl isocyanates (Table 2, entries
10 and 11) and the substituent shift from the para-to ortho-position
(e.g., 3ab vs 3ae, 3aj vs 3ak) have a slightly negative impact on the
yields.
Given the fact that substituted thiazoles display a very promis-
ing antitumor activity,2,10 we made an extension of this protocol to
synthesis of thiazolidin-2-imines (Scheme 2). It was found that
4ae4d were suitable reactants, and desirable products 5aae5ad
were generated in good to quantitative yields.
To our delight, this protocol is also effective for the trans-
formation of variously substituted propargylamines (Table 3). In
general, the nature of N-substituents has a significant effect on the
yields. For example, N-benzyl and N-(2-phenyl)ethyl substituted
propargylamines gave the desired oxazolidine derivatives 3bc, 3bf,
and 3cc in excellent yields. In contrast, N-tert-butyl substituted
propargylamine (1d) was found to have a lower activity for iodo-
cyclization (3da and 3dc) compared to 1ae1c, due to the increased
steric hindrance. Furthermore, the results show that propargyl-
amines with an internal/terminal C^C bond are all compatible
with this protocol. Arylalkynes seem to be more reactive than
alkylalkynes (3fa and 3ff vs 3gc, 3ha and 3hc), presumably as aryl
substituents facilitate the stability of the iodonium cation in-
termediate (vide infra). Noticeably, the presence of the large ste-
rically demanding tert-butyl group at another alkyne terminus also
had a negative impact on the reaction outcomes, leading to the
decrease of yields (3ha, 3hc, and 3hf).
Scheme 2. Iodocyclization between propargylamines, isothiocyanates and I2.
Encouraged by the above results, we further explored the appli-
cation of this method in synthesis of imidazoline derivatives and
envisioned that combination of 1 with carbodiimides 6 and I2 could
subject to some tandem transformation in the current experimental
conditions. Surprisingly, no desired iodocyclization product 7aa was
obtained, when the optimal conditions described above were applied
to the cyclization between 1a, diarylcarbodiimide 6a and I2. After
adding K2CO3 as an additive, the desirable reaction proceeded
smoothly, affording 7aa in a satisfactory yield (Table 4). The slug-
gishness of such reaction likely resulted from larger steric hindrance
and weaker electrophilicity of carbodiimides compared to iso-
cyanates and isothiocyanates and the decreasing acidity of the multi-
substituted guanidine intermediate compared with the urea and
thioureas ones. Subsequently, we investigated the generality and the
Table 3
Propargylamine scopea,b
Table 4
Three-component iodocyclization between propargylamines, carbodiimides and I2a,b
a
a
Reactions were carried out with 1 (0.30 mmol), 2 (0.30 mmol), I2 (0.3
Reactions were carried out with 1 (0.36 mmol), 2 (0.30 mmol), I2 (0.36
mmol) in EA (3 mL) at 50 oC. b isolated yield.
mmol), K2CO3 (0.45 mmol) in EA (3 mL) at 25 oC; b isolated yield.
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4
S. Huang et al. / Tetrahedron xxx (2015) 1e8
scope of this transformation via variation of both propargylamines
and carbodiimides. As illustrated in Table 4, a series of propargyl-
amines 1ae1i were investigated by coupling reaction with di(p-
methylphenyl)carbodiimide 6a and I2 in the presence of 1.5 equiv of
K2CO3. To our delight, various electron-rich, electron-neutral, and
electron-deficient substituents were well tolerated, and the standard
reaction conditions were compatible to substrates with both aryl and
alkyl groups at another terminus of propargylamines. In general, the
steric effect of substituents on propargylamines has an impact on the
yield. For example, reaction of 6a with N-methyl substituted prop-
argylamine 1f gave 7fa in 97% yield, while the N-tert-butyl
substituted propargylamine 1i gave the corresponding product 7ia in
75% yield. Similarly, the introduction of sterically larger encumbered
substituents at another alkyne terminus led to the decrease of the
yield too (7ga vs 7ha). The structure of 7ha was further confirmed by
the X-ray crystal structure analysis (Fig. 2). Noticeably, the position of
the methyl group in the benzene ring has some effect on the reaction.
For example, the diarylcarbodiimide with the methyl at the para-
position (6a) gave the expected product in a higher yield than the
ortho-position isomer (6b) (7ga vs 7gb).
Based on the results described above, a plausible mechanism for
the present iodocyclization of propargylamines with isocyanates
and I2 is illustrated in Scheme 5. Initially, propargylamine reacts
with isocyanate (isothiocyanate) to form a urea (thiourea) in-
termediate (I). Next, the electrophilic addition of I2 to alkyne of I
results in the formation of a three-membered cyclic iodonium
cation (II). The isomerization of intermediate II gives intermediate
III as observed previously,19b which subsequently undergo the
intramolecular cyclization through an attack of the oxygen (sulfur)
atom upon the three-membered cyclic iodonium cation, forming
the ammonium intermediate (IV). Finally, the release of HI of IV in
the presence of base gives the corresponding iodocyclization
product. Since the addition of carbodiimides to propargylamines is
sluggish, the additive K2CO3, which is promotor for guanidination
of carbodiimides with propargylamines and sequent intra-
molecular cyclization, is required.20
Scheme 5. The plausible mechanism for the formation of 3, 5 and 7.
3. Conclusions
In summary, we have developed a simple, cheap, efficient, and
metal-free method for one-step synthesis of a library of 1,3-
diheteroatom five-membered heterocycles with exocyclic C]N
and C]C double bonds via the direct three-component iodocycli-
zation of propargylamines, heterocumulenes and I2. This method
allows access to a wide range of 5-iodoalkylidenated oxazolidin-2-
imines, thiazolidin-2-imines and imidazolidin-2-imines in moder-
ate to excellent yields under mild conditions. The present pro-
cedure is also suitable for the synthesis of 5-bromoalkylidenated
oxazolidin-2-imines from readily available propargylamines, iso-
cyanates and NBS, which are potential pharmacological interest
and synthetic potential in organometallic and organic chemistry.
The advantages of the present method are easy access to the re-
agents, simple operation, high chemo- and regioselectivity, without
the need of catalyst and additives (except carbodiimides).
Fig. 2. ORTEP drawing of 7ga with 30% probability thermal ellipsoids.
In addition, this protocol also allows the bromocyclization be-
tween propargylamines, isocyanate and N-bromosuccinimide
(NBS). As shown in Scheme 3, products 8ah and 8ac were suc-
cessfully accessed with moderate to good yields, which provides an
efficient method for bromoalkylidene-substituted oxazolidine
derivatives.
4. Experimental section
4.1. General
Scheme 3. Bromocyclization between propargylamines, isocyanates and NBS.
To shed light on the mechanism of the reaction, the following
experiments were conducted. Firstly, the reaction of propargyl-
amine 1a with PhNCO 2a gave the urea Ia in 90% yield. Sub-
sequently, the cyclization of Ia with I2 was performed under the
aforementioned conditions, giving the desired product 3aa in al-
most quantitative yield (Scheme 4).
Propargylamines21 and carbodiimides22 were prepared accord-
ing to the literature procedures. 1H NMR and 13C NMR spectra were
recorded on a JEOL ECA-400 NMR spectrometer (FT, 400 MHz for
1H; 100 MHz for 13C) in CDCl3 at room temperature. All chemical
shift values are quoted in ppm and coupling constants quoted in Hz.
GCeMS were obtained on a Focus GC-ISQ MS instrument. High
resolution mass spectrometry (HRMS) spectra were obtained on
a micro TOF II Instrument using ESI ionization source. X-ray dif-
fraction data for 3aa (CCDC no. 1047709) and 7ga (CCDC no.
1047710) were collected on a SMART APEX CCD diffractometer
(graphite-monochromated MoK
a
radiation, 4-
u scan technique,
Scheme 4. Mechanism study of stepwise reactions.
ꢀ
l¼0.71073 A). The intensity data were integrated by means of the
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S. Huang et al. / Tetrahedron xxx (2015) 1e8
5
SAINT program. SADABS was used to perform area-detector scaling
and absorption corrections. The structure was solved by direct
methods and was refined against F2 using all reflections with the
aid of the SHELXTL package. All non-hydrogen atoms were found
from the difference Fourier syntheses and refined anisotropically.
The H atoms were included in calculated positions with isotropic
thermal parameters related to those of the supporting carbon
atoms but were not included in the refinement. All calculations
were performed using the Bruker Smart program.
J¼2.8 Hz, 2H), 3.04 (s, 3H). 13C NMR (100M, CDCl3):
d
164.41, 161.98,
150.58, 150.49, 148.26, 148.26, 148.17, 129.59, 129.50, 119.46, 110.77,
110.55, 109.50, 109.29, 53.48, 49.59, 31.72. 19F NMR (376M, CDCl3):
d
114.18. HRMS (EI) (m/z): [MþH]þ Calcd for C11H11N2OFI 332.9900,
found 332.9909.
4.2.7. 4-Chloro-N-((E)-5-(iodomethylene)-3-methyloxazolidin-2-
ylidene)aniline (3ah). Dark brown oil. 1H NMR (400M, CDCl3):
d
7.21e7.19 (m, 2H), 6.97e6.95 (m, 2H), 5.67 (t, J¼2.8 Hz,1H), 4.13 (d,
J¼2.8 Hz, 2H), 3.03 (s, 3H). 13C NMR (100M, CDCl3):
d 150.62, 150.40,
4.2. General procedure for the synthesis of oxazolidine de-
rivatives 3
145.03, 128.72, 124.83, 55.83, 49.48, 31.75. HRMS (EI) (m/z):
[MþH]þ Calcd for C11H11N2OICl 348.9605, found 348.9612.
A
mixture of isocyanate (0.3 mmol) and propargylamine
4.2.8. 4-Bromo-N-((E)-5-(iodomethylene)-3-methyloxazolidin-2-
(0.3 mmol) was treated with iodine (0.3 mmol) in ethyl acetate
(3 mL). The reaction tube was stirred for 12 h at 50 ꢀC (oil bath
temperature) with the gradual formation of white precipitation.
Subsequently, the reaction was quenched with K2CO3 aqueous so-
lution to make the PH beyond 9. The mixture was extracted with EA
(3ꢁ10 mL) and the combined organic layers were dried over
Na2SO4, filtered and concentrated. Pure products 3 were obtained
by column chromatography (silica gel, with a mixture of hexane/
ethyl acetate (4:1) as eluent).
ylidene)aniline (3ai). Dark brown solid. 1H NMR (400M, CDCl3):
d
7.35e7.33 (m, 2H), 6.92e6.89 (m, 2H), 5.67 (t, J¼2.4 Hz, 1H), 4.14
(d, J¼2.4 Hz, 2H), 3.03 (s, 3H). 13C NMR (100M, CDCl3):
d 150.69,
150.39, 131.67, 125.33, 115.44, 53.54, 49.52, 31.75. HRMS (EI) (m/z):
[MþH]þ Calcd for C11H11N2OBrI 392.9099, found 392.9091.
4.2.9. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-yliden-e)-4-
(trifluoromethyl)aniline (3aj). Yellow solid. 1H NMR (400M, CDCl3):
d
7.49 (d, J¼8.3 Hz, 2H), 7.10 (d, J¼8.3 Hz, 2H), 5.69 (t, J¼2.8 Hz, 1H),
4.15 (d, J¼2.8 Hz, 2H), 3.05 (s, 3H). 13C NMR (100M, CDCl3):
d 150.70,
4.2.1. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-yliden-e)-4-
150.45,145.87,125.90,125.87,123.68,123.68, 53.49, 49.73, 31.69. 19
F
NMR (376M, CDCl3):
C12H11F3N2OI 382.9868, found 382.9862.
methylaniline (3ab). Light yellow solid. 1H NMR (400M, CDCl3):
d
ꢂ61.59. HRMS (EI) (m/z): [MþH]þ Calcd for
d
7.06 (d, J¼8.0 Hz, 2H), 6.93e6.91 (m, 2H), 5.63 (t, J¼2.8 Hz, 1H),
4.12 (d, J¼2.8 Hz, 2H), 3.06 (s, 3H), 2.30 (s, 3H). 13C NMR (100M,
CDCl3):
d
150.90, 150.08, 143.71, 132.02, 129.37, 123.24, 53.60, 49.07,
4.2.10. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-ylide-ne)-2-
31.83, 20.99. HRMS (EI) (m/z): [MþH]þ Calcd for C12H14N2OI
(trifluoromethyl)aniline (3ak). Dark brown oil. 1H NMR (400M,
329.0151, found 329.0162.
CDCl3):
d
7.56 (d, J¼8.0 Hz, 1H), 7.40 (t, J¼8.0 Hz, 1H), 7.10e7.04 (m,
2H), 5.65 (t, J¼2.8 Hz, 1H), 4.15 (d, J¼2.8 Hz, 2H), 3.06 (s, 3H). 13
C
4.2.2. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-yliden-e)-4-
NMR (100M, CDCl3): d 150.62, 150.02, 145.39, 132.12, 126.29, 126.24,
methoxyaniline (3ac). Brown solid. 1H NMR (400M, CDCl3):
125.76, 124.69, 123.04, 122.16, 55.58, 49.60, 31.66. 19F NMR (376M,
d
7.00e6.96 (m, 2H), 6.83e6.80 (m, 2H), 5.64 (t, J¼2.8 Hz, 1H), 4.11
CDCl3):
382.9868, found 382.9862.
d
62.24. HRMS (EI) (m/z): [MþH]þ Calcd for C12H11F3N2OI
(d, J¼2.8 Hz, 2H), 3.78 (s, 3H), 3.03 (s, 3H). 13C NMR (100M, CDCl3):
d
155.34, 150.90, 150.00, 139.43, 124.22, 114.02, 55.53, 53.55, 49.01,
31.83. HRMS (EI) (m/z): [MþH]þ Calcd for C12H14N2O2I 345.0100,
4.2.11. N-((E)-3-Benzyl-5-(iodomethylene)oxazolidin-2-yliden-e)-4-
found 345.0117.
methoxyaniline (3bc). Yellow solid. 1H NMR (400M, CDCl3):
d
7.41e7.35 (m, 5H), 7.08e7.06 (m, 2H), 6.87e6.85 (m, 2H), 5.66 (t,
4.2.3. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-yliden-e)-2-
J¼2.8 Hz, 1H), 4.63 (s, 3H), 3.98 (d, J¼2.8 Hz, 2H), 3.80 (s, 3H). 13
C
methoxyaniline (3ad). Light yellow solid. 1H NMR (400M, CDCl3):
NMR (100M, CDCl3): d 155.38, 151.00, 149.50,139.32, 135.95, 128.95,
d
7.01e6.89 (m, 4H), 5.58 (t, J¼2.8 Hz, 1H), 4.13 (d, J¼2.8 Hz, 2H),
128.35, 128.04, 124.28, 114.05, 55.54, 50.78, 49.21, 48.78. HRMS (EI)
3.82 (s, 3H), 3.08 (s, 3H). 13C NMR (100M, CDCl3):
d
152.15, 150.88,
(m/z): [MþH]þ Calcd for C18H18N2O2I 421.0413, found 421.0417.
150.67, 135.89, 124.16, 123.63, 120.68, 111.37, 55.88, 53.89, 48.94,
31.39. HRMS (EI) (m/z): [MþH]þ Calcd for C12H14N2O2I 345.0100,
found 345.0093.
4.2.12. N-((E)-3-Benzyl-5-(iodomethylene)oxazolidin-2-yliden-e)-4-
fluoroaniline (3bf). Yellow solid. 1H NMR (400M, CDCl3):
d
7.44e7.35 (m, 5H), 7.09e6.97 (m, 4H), 5.69 (t, J¼2.6 Hz, 1H), 4.64
4.2.4. N-((E)-5-(Iodomethylene)-3-methyloxazolidin-2-yliden-e)-2-
(s, 2H), 4.00 (d, J¼2.8 Hz, 2H) 3C NMR (100M, CDCl3):
d 160.07,
methylaniline (3ae). Light yellow solid. 1H NMR (400M, CDCl3):
157.68, 150.79, 149.82,142,23, 135.77, 129.00,128.33, 124.62,124.54,
d
7.16e6.93 (m, 4H), 5.61 (t, J¼2.8 Hz, 1H), 4.14 (d, J¼2.8 Hz, 2H),
115.37, 115.15, 50.76, 49.52, 48.72. 19F NMR (376M, CDCl3):
3.06 (s, 3H), 2.20 (s, 3H). 13C NMR (100M, CDCl3):
d
150.87, 149.34,
d
ꢂ121.80. HRMS (EI) (m/z): [MþH]þ Calcd for C17H15FN2O2I
145.19, 131.00, 130.13, 126.11, 126.11, 122.79, 63.76, 49.03, 31.87,
18.29. HRMS (EI) (m/z): [MþH]þ Calcd for C12H14N2OI 329.0151,
found 329.0152.
409.0213, found 409.0205.
4.2.13. N-((E)-5-(Iodomethylene)-3-phenethyloxazolidin-2-yli-
dene)-4-methoxyaniline (3cc). Yellow solid. 1H NMR (400M, CDCl3):
4.2.5. 4-Fluoro-N-((E)-5-(iodomethylene)-3-methyloxazolidin-2-
d 7.31e7.24 (m, 5H), 6.97e6.95 (m, 2H), 6.82e6.79 (m, 2H), 5.58 (t,
ylidene)aniline (3af). Light yellow oil. 1H NMR (400M, CDCl3):
J¼2.8 Hz, 1H), 3.93 (d, J¼2.8 Hz, 2H), 3.76 (s, 3H), 3.65 (t, J¼3.6 Hz,
d
6.98e6.91 (m, 4H), 5.66 (t, J¼2.8 Hz, 1H), 4.13 (d, J¼2.8 Hz, 2H),
2H). 2.96 (t, J¼3.6 Hz, 2H). 13C NMR (100M, CDCl3):
d 155.25, 151.00,
3.02 (s, 3H). 13C NMR (100M, CDCl3):
d
160.16, 157.77, 150.80, 150.39,
149.11, 139.45, 138.58, 128.84, 128.74, 126.69, 124.21, 113.96, 55.50,
142.46, 124.67, 124.59, 115.46, 115.24, 53.62, 49.41, 31.85. HRMS (EI)
51.85, 48.91, 46.18, 33.48. HRMS (EI) (m/z): [MþH]þ Calcd for
(m/z): [MþH]þ Calcd for C11H11N2OFI 332.9900, found 332.9915.
C19H20N2O2I 435.0569, found 435.0567.
4.2.6. 3-Fluoro-N-((E)-5-(iodomethylene)-3-methyloxazolidin-2-
4.2.14. N-((E)-3-(tert-Butyl)-5-(iodomethylene)oxazolidin-2-y-li-
ylidene)aniline (3ag). Light yellow oil. 1H NMR (400M, CDCl3):
dene)aniline (3da). Dark brown oil. 1H NMR (400M, CDCl3):
d
7.21e7.16 (m,1H), 6.82e6.70 (m, 3H), 5.70 (t, J¼2.8 Hz,1H), 4.14 (d,
d
7.24e7.22 (m, 2H), 6.99e6.97 (m, 3H), 5.49 (t, J¼2.8 Hz, 1H), 4.16
Please cite this article in press as: Huang, S.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.04.080

6
S. Huang et al. / Tetrahedron xxx (2015) 1e8
(d, J¼2.8 Hz, 2H), 1.51 (s, 9H). 13C NMR (100M, CDCl3):
d
151.03,
(3 mL). The reaction tube was stirred for 12 h in a 50 ꢀC oil bath with
the gradual formation of white precipitation. Subsequently, the
reaction was quenched with K2CO3 aqueous solution to make the
PH beyond 9. The mixture was extracted with EA (3ꢁ10 mL) and the
combined organic layers were dried over Na2SO4, filtered and
concentrated. Pure products 5 were obtained by column chroma-
tography (silica gel, with a mixture of hexane/ethyl acetate (10:1) as
eluent).
147.41, 146.82, 128.63, 122.39, 54.43, 50.19, 47.72, 27.31. HRMS (EI)
(m/z): [MþH]þ Calcd for C14H18N2OI 357.0464, found 357.0462.
4.2.15. N-((E)-3-(tert-Butyl)-5-(iodomethylene)oxazolidin-2-y-li-
dene)-4-methoxyaniline (3dc). Dark brown oil. 1H NMR (400M,
CDCl3):
d
6.96e6.94 (m, 2H), 6.82e6.80 (m, 2H), 5.51 (t, J¼2.8 Hz,
1H), 4.17 (d, J¼2.8 Hz, 2H), 3.78 (s, 3H), 1.52 (s, 9H). 13C NMR (100M,
CDCl3):
d 155.06, 151.12, 147.26, 124.12, 114,17, 113.94, 55.58, 54.34,
50.12, 47.53, 27.29. HRMS (EI) (m/z): [MþH]þ Calcd for C15H22N2O2I
4.3.1. N-((E)-5-(Iodomethylene)-3-methylthiazolidin-2-yliden-e)ani-
387.0569, found 387.0573.
line (5aa). Dark brown oil. 1H NMR (400M, CDCl3):
d 7.29e7.26 (m,
2H), 7.08e7.04 (m, 1H), 6.92e6.90 (m, 2H), 5.93 (t, J¼2.8 Hz, 1H),
4.2.16. N-((E)-5-(Iodo(phenyl)methylene)-3-methyloxazolidin-2-
4.16 (d, J¼2.8 Hz, 2H), 3.10 (s, 3H). 13C NMR (100M, CDCl3):
d 156.15,
ylidene)aniline (3fa). Yellow solid. 1H NMR (400M, CDCl3):
d
7.57 (d,
151.24, 137.32, 129.09, 123.62, 122.15, 62.88, 61.88, 33.21. HRMS (EI)
J¼7.4 Hz, 2H), 7.29e7.19 (m, 5H), 7.08 (d, J¼7.6 Hz, 2H), 6.98 (t,
(m/z): [MþH]þ Calcd for C11H12N2SI 330.9766, found 330.9763.
J¼7.4 Hz, 1H), 4.33 (s, 2H), 3.07 (s, 2H). 13C NMR (100M, CDCl3):
d
150.30, 146.04, 145.26, 136.55, 129.76, 128.55, 128.16, 128.12,
4.3.2. 3-Chloro-N-((E)-5-(iodomethylene)-3-methylthiazolidin-2-
123.65, 122.60, 73.25, 56.80, 31.65. HRMS (EI) (m/z): [MþH]þ Calcd
ylidene)aniline (5ab). Dark brown oil. 1H NMR (400M, CDCl3):
d 7.18
for C17H16N2O2I 391.0307, found 391.0300.
(t, J¼8.0 Hz,1H), 7.03e7.00 (m,1H), 6.92 (t, J¼2.0 Hz,1H), 6.80e6.78
(m, 1H), 5.97 (t, J¼2.8 Hz, 1H), 4.16 (d, J¼2.8 Hz, 2H), 3.10 (s, 3H). 13
C
4.2.17. 4-Chloro-N-((E)-5-(iodo(phenyl)methylene)-3-methylo-xazo-
NMR (100M, CDCl3): d 156.52,152.33,136.65,134.35,130.02,123.49,
lidin-2-ylidene)aniline (3ff). Yellow solid. 1H NMR (400M, CDCl3):
122.42, 120.41, 63.40, 61.83, 33.13. HRMS (EI) (m/z): [MþH]þ Calcd
d
7.53e7.51 (m, 2H), 7.29e7.20 (m, 3H), 7.14e7.12 (m, 2H), 6.99e6.97
for C11H11N2SICl 364.9376, found 364.9387.
(m, 2H), 4.31 (s, 2H), 3.04 (s, 3H). 13C NMR (100M, CDCl3):
d
150.53,
144.98, 144.67, 136.52, 129.66, 128.51, 128.36, 128.20, 127.54, 124.93,
4.3.3. 4-Chloro-N-((E)-5-(iodomethylene)-3-methylthiazolidin-2-
73.38, 55.62, 31.58. HRMS (EI) (m/z): [MþH]þ Calcd for
ylidene)aniline (5ac). Dark brown oil. 1H NMR (400M, CDCl3):
C
17H15N2O2ICl 424.9918, found 424.9917.
d
7.24e7.20 (m, 2H), 6.85e6.82 (m, 2H), 5.96 (t, J¼2.8 Hz, 1H), 4.16
(d, J¼2.8 Hz, 2H), 3.11 (s, 3H). 13C NMR (100M, CDCl3):
d 156.53,
4.2.18. N-((E)-5-(1-Iodopentylidene)-3-methyloxazolidin-2-y-li-
149.69, 136.72, 129.10, 128.72, 123.49, 63.38, 61.88, 33.17. HRMS (EI)
dene)-4-methoxyaniline (3gc). Yellow solid. 1H NMR (400M, CDCl3):
(m/z): [MþH]þ Calcd for C11H11N2SICl 364.9376, found 364.9367.
d
7.01 (d, J¼8.0 Hz, 2H), 6.79 (d, J¼8.0 Hz, 2H), 4.09 (s, 2H), 3.77 (s,
3H), 3.00 (s, 3H), 2.45 (t, J¼6.8 Hz, 2H), 1.47e1.40 (m, 2H), 1.33e1.24
4.3.4. N-((E)-5-(Iodomethylene)-3-methylthiazolidin-2-yliden-e)-4-
(m, 2H), 0.90 (t, J¼7.6 Hz, 3H). 13C NMR (100M, CDCl3):
d
155.11,
methylaniline (5ad). Dark brown oil. 1H NMR (400M, CDCl3):
d 7.07
150.32, 144.41, 139.53, 124.29, 113.88, 76.84, 55.51, 54.91, 34.95,
(d, J¼8.0 Hz, 2H), 6.80 (d, J¼8.0 Hz, 2H), 5.92 (t, J¼2.8 Hz, 1H), 4.15
31.71, 31.07, 21.39, 13.86. HRMS (EI) (m/z): [MþH]þ Calcd for
(d, J¼2.8 Hz, 2H), 3.11 (s, 3H), 2.31 (s, 3H). 13C NMR (100M, CDCl3):
C
16H22N2O2I 385.0777, found 385.0802.
d 156.16, 148.63, 137.34, 132.99, 129.66, 121.87, 62.83, 61.82, 33.18,
21.00. HRMS (EI) (m/z): [MþH]þ Calcd for C12H14N2SI 344.9922,
4.2.19. N-((E)-5-(1-Iodo-2,2-dimethylpropylidene)-3-methylo-xazo-
found 344.9912.
lidin-2-ylidene)aniline (3ha). Yellow solid. 1H NMR (400M, CDCl3):
d
7.24 (t, J¼8.0 Hz, 2H), 7.02 (d, J¼8.0 Hz, 2H), 6.98 (t, J¼8.0 Hz, 1H),
4.4. General procedure for the synthesis of imidazolidine
derivatives 7
4.16 (s, 2H), 3.01 (s, 3H), 1.22 (s, 9H). 13C NMR (100M, CDCl3):
d
150.89, 146.66, 142.29, 128.50, 123.55, 122.34, 93.29, 58.28, 38.26,
31.45, 29.80. HRMS (EI) (m/z): [MþH]þ Calcd for C15H20N2OI
A mixture of propargylamine (0.36 mmol), carbodiimide
371.0620, found 371.0637.
(0.3 mmol), and K2CO3 (0.45 mmol, 61.4 mg) in ethyl acetate (3 mL)
was treated with iodine (0.3 mmol). After stirring for 12 h at 25 ꢀC,
the reaction mixture was quenched with Na2S2O3 aqueous solution
(0.1 mol/L) and extracted with EA (3ꢁ10 mL). The combined organic
layers were dried over Na2SO4, filtered and concentrated. Pure
products 7 were obtained by column chromatography (silica gel,
with a mixture of hexane/ethyl acetate (20:1) as eluent).
4.2.20. N-((E)-5-(1-Iodo-2,2-dimethylpropylidene)-3-methylo-xazo-
lidin-2-ylidene)-4-methoxyaniline (3hc). Yellow solid. 1H NMR
(400M, CDCl3):
d
6.96 (d, J¼8.0 Hz, 2H), 6.77 (d, J¼8.0 Hz, 2H), 4.15
(s, 2H), 3.77 (s, 3H), 2.99 (s, 3H), 1.23 (s, 9H). 13C NMR (100M,
CDCl3): d 150.78, 142.48, 139.86, 124.33, 113.89, 99.22, 58.38, 55.59,
38.34, 31.58, 29.89. HRMS (EI) (m/z): [MþH]þ Calcd for C16H22N2O2I
401.0726, found 401.0737.
4.4.1. N-((E)-4-(Iodomethylene)-1-methyl-3-(p-tolyl)imidazo-ledin-
2-ylidene)-4-methylaniline (7aa). Light yellow solid. 1H NMR
4.2.21. 4-Chloro-N-((E)-5-(1-iodo-2,2-dimethylpropylidene)-3-
(400M, CDCl3):
(d, J¼9.0 Hz, 2H), 4.57 (t, J¼2.5 Hz, 1H), 4.11 (d, J¼2.5 Hz, 2H), 2.75
(s, 3H), 2.28 (s, 3H), 2.18 (s, 3H). 13C NMR (100M, CDCl3):
150.05,
d
7.05 (q, J¼8.0 Hz, 4H), 6.79 (d, J¼8.0 Hz, 2H), 6.57
methyloxazolidin-2-ylidene)aniline (3hf). Light yellow solid. 1H
NMR (400M, CDCl3):
d
7.17 (d, J¼8.0 Hz, 2H), 6.98 (d, J¼8.0 Hz, 2H),
d
4.17 (s, 2H), 3.00 (s, 3H), 1.23 (s, 9H). 13C NMR (100M, CDCl3):
145.39, 145.31, 137.59, 133.74, 130.12, 129.96, 128.78, 128.37, 122.42,
d
151.13, 145.38, 124.04, 128.51, 127.31, 124.83, 93.63, 58.25, 38.31,
58.02, 40.22, 34.65, 21.19, 20.75. HRMS (EI) (m/z): [MþH]þ Calcd for
31.47, 31.34, 29.81. HRMS (EI) (m/z): [MþH]þ Calcd for C15H19N2OICl
C19H21N3I 418.0780, found 418.0770.
405.0231, found 405.0239.
4.4.2. N-((E)-1-Benzyl-4-(iodomethylene)-3-(p-tolyl)imidazo-lidin-
4.3. General procedure for the synthesis of thiazolidine de-
rivatives 5
2-ylidene)-4-methylaniline (7ba). Light yellow solid. 1H NMR
(400M, CDCl3):
d 7.41e7.36 (m, 2H), 7.34e7.31 (m, 3H), 6.77 (d,
J¼8.0 Hz, 2H), 6.59 (d, J¼8.0 Hz, 2H), 4.60 (t, J¼2.4 Hz, 1H),4.46 (s,
A mixture of isothiocyanate (0.3 mmol) and propargylamines
(0.3 mmol) was treated with iodine (0.3 mmol) in ethyl acetate
2H), 4.01 (d, J¼2.4 Hz, 2H), 2.29 (s, 3H), 2.17 (s, 3H). 13C NMR (100M,
CDCl3):
d 148.89, 145.66, 145.10, 137.50, 136.95, 133.79, 130.03,
Please cite this article in press as: Huang, S.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.04.080

S. Huang et al. / Tetrahedron xxx (2015) 1e8
7
129.83, 128.77, 128.44, 128.12, 127.83, 127.61, 122.18, 54.53, 49.86,
40.88, 21.16, 20.72. HRMS (EI) (m/z): [MþH]þ Calcd for C25H25N3I
494.1093, found 494.1124.
6.74e6.70 (m, 2H), 6.56e6.52 (m, 2H), 4.13 (s, 2H), 2.73 (s, 3H), 1.78
(t, J¼7.7 Hz, 2H), 1.14e1.06 (m, 2H), 0.92e0.84 (m, 2H), 0.67 (t,
J¼7.3 Hz, 3H). 13C NMR (100M, CDCl3):
d 163.27, 160.80, 159.31,
156.94, 152.44, 144.55, 137.08, 136.13, 135.14, 131.75, 131.66, 123.58,
123.50, 121.41, 116.17, 115.94, 115.08, 114.86, 62.11, 37.62, 34.19,
4.4.3. N-((E)-4-(Iodo(phenyl)methylene)-1-methyl-3-(p-tolyl) imi-
dazoledin-2-ylidene)-4-methylaniline (7fa). Yellow solid. 1H NMR
32.04, 21.78, 13.95. 19F NMR (376M, CDCl3):
d
ꢂ113.27, ꢂ123.98.
(400M, CDCl3):
2.72 (s, 3H), 2.23 (s, 3H), 2.10 (s, 3H). 13C NMR (100M, CDCl3):
151.60, 145.85, 141.08, 138.35, 136.27, 134.92, 129.99, 129.86,
d
6.88e6,81 (m, 7H), 6.67e6.57 (m, 6H), 4.34 (s, 2H),
HRMS (EI) (m/z): [MþH]þ Calcd for C21H23N3IF2 482.0905, found
482.0931.
d
128.89, 128.77, 128.52, 127.52, 126.32, 122.28, 83.78, 62.81, 35.02,
21.05, 20.88. HRMS (EI) (m/z): [MþH]þ Calcd for C25H25N3I
494.1093, found 494.1128.
4.4.10. 4-Chloro-N-((E)-3-(4-chlorophenyl)-4-(1-iodopentyli-dene)-
1-methylimidazolidin-2-ylidene)aniline (7ge). Light yellow solid. 1H
NMR (400M, CDCl3):
d 7.24e7.22 (m, 2H), 7.12e7.09 (m, 2H),
7.00e6.98 (m, 2H), 6.56e6.54 (m, 2H), 4.13 (s, 2H), 2.69 (s, 3H), 1.80
(t, J¼7.7 Hz, 2H), 1.16e1.08 (m, 2H), 0.93e0.86 (m, 2H), 0.68 (t,
4.4.4. N-((E)-4-(1-Iodopentylidene)-1-methyl-3-(p-tolyl)imida-zoli-
din-2-ylidene)-4-methylaniline (7ga). Light yellow solid. 1H NMR
J¼7.3 Hz, 3H). 13C NMR (100M, CDCl3):
d 152.05, 147.24, 138.53,
(400M, CDCl3):
d
7.08e7.03 (m, 4H), 6.83 (d, J¼8.0 Hz, 2H), 6.54 (d,
136.62, 134.02, 131.14, 129.33, 128.40, 126.11, 123.84, 76.94, 62.20,
J¼8.0 Hz, 2H), 4.11 (s, 2H), 2.67 (s, 3H), 2.30 (s, 3H), 2.21 (s, 3H), 1.78
(t, J¼7.9 Hz, 2H), 1.17e1.09 (m, 2H), 0.90e0.83 (m, 2H), 0.66 (t,
37.61, 34.43, 31.97, 21.73, 13.93. HRMS (EI) (m/z): [MþH]þ Calcd for
C21H23Cl2N3I 514.0314, found 514.0347.
J¼7.4 Hz, 3H). 13C NMR (100M, CDCl3):
d 152.20, 146.14, 137.74,
137.70, 137.14, 129.85, 129.61, 129.50, 128.81, 122.34, 76.06, 62.52,
37.48, 34.63, 32.05, 21.65, 21.24, 20.81, 13.85. HRMS (EI) (m/z):
[MþH]þ Calcd for C23H28N3I 474.1406, found 474.1436.
4.5. General procedure for the synthesis of oxazolidine de-
rivatives 8
A
mixture of isocyanate (0.3 mmol) and propargylamine
4.4.5. N-((E)-4-(1-Iodo-2,2-dimethylpropylidene)-1-methyl-3-(p-
(0.3 mmol) was treated with NBS (0.3 mmol) in ethyl acetate
(3 mL). After stirring for 12 h at 50 ꢀC, the reaction mixture was
quenched with Na2S2O3 aqueous solution (0.1 mol/L) and extracted
with EA (3ꢁ10 mL). The combined organic layers were dried over
Na2SO4, filtered and concentrated. Pure products 8 were obtained
by column chromatography (silica gel, with a mixture of hexane/
ethyl acetate (4:1) as eluent).
tolyl)imidazolidin-2-ylidene)-4-methylaniline (7ha). Light yellow
solid. 1H NMR (400M, CDCl3):
d
6.93 (t, J¼8.0 Hz, 4H), 6.82 (d,
J¼8.0 Hz, 2H), 6.62 (d, J¼8.0 Hz, 2H), 4.22 (s, 2H), 2.81 (s, 3H), 2.27
(s, 3H), 2.25 (s, 3H), 0.99 (s, 9H). 13C NMR (100M, CDCl3):
146.99,
d
145.41, 136.99, 134.72, 132.57, 129.38, 128.66, 128.39, 128.23, 122.14,
57.12, 54.82, 52.13, 40.36, 27.61, 21.06, 20.61. HRMS (EI) (m/z):
[MþH]þ Calcd for C23H28N3I 474.1406, found 474.1416.
4.5.1. N-((E)-5-(Bromomethylene)-3-methyloxazolidin-2-ylide-ne)-
4-chloroaniline (8ah). Brown oil. 1H NMR (400M, CDCl3):
d 7.20 (d,
4.4.6. N-((E)-1-(tert-Butyl)-4-(iodo(phenyl)methylene)-3-(p-to-lyl)
imidazolidin-2-ylidene)-4-methylaniline (7ia). Light yellow solid. 1H
J¼8.6 Hz, 2H), 6.97 (d, J¼8.6 Hz, 2H), 5.85 (t, J¼2.7 Hz, 1H), 4.16 (d,
J¼2.7 Hz, 2H), 3.03 (s, 3H). 13C NMR (100M, CDCl3):
d
152.12, 148.49,
NMR (400M, CDCl3):
d
6.80e6.73 (m, 3H), 6.67 (d, J¼8.0 Hz, 2H),
6.46 (d, J¼8.0 Hz, 2H), 6.22 (s, 4H), 6.10 (d, J¼8.0 Hz, 2H), 4.37 (s,
144.71, 128.67, 127.79, 124.80, 82.63, 51.19, 31.75. HRMS (EI) (m/z):
2H), 2.02 (s, 3H), 1.96 (s, 3H), 1.57 (s, 9H), 13C NMR (100M, CDCl3):
[MþH]þ Calcd for C11H11N2OBr 300.9743, found 300.9736.
d
149.33, 145.88, 141.80, 140.97, 136.74, 135.81, 129.85, 129.72,
128.54, 128.10, 127.86, 127.33, 126.29, 121.76, 64.92, 56.50, 54.55,
27.61, 20.86, 20.60. HRMS (EI) (m/z): [MþH]þ Calcd for C28H31N3I
536.1563, found 536.1558.
4.5.2. N-((E)-5-(Bromomethylene)-3-methyloxazolidin-2-ylide-ne)-
4-methoxyaniline (8ac). Brown oil. 1H NMR (400M, CDCl3):
d 6.98
(d, J¼9.0,Hz, 2H), 6.81 (d, J¼9.0 Hz, 2H), 5.84 (t, J¼2.7 Hz, 1H), 4.15
(d, J¼2.7 Hz, 2H), 3.78 (s, 3H), 3.03 (s, 3H). 13C NMR (100M, CDCl3):
4.4.7. N-((E)-4-(1-Iodopentylidene)-1-methyl-3-(o-tolyl)imida-zoli-
d
155.32, 149.55, 148.87, 193.43, 124.18, 113.99, 82.07, 55.50, 51.19,
din-2-ylidene)-2-methylaniline (7gb). Light yellow solid. 1H NMR
31.83. HRMS (EI) (m/z): [MþH]þ Calcd for C12H13N2O2Br 296.0160,
(400M, CDCl3):
d 7.20e7.17 (m, 3H), 7.13e7.10 (m, 1H), 6.97e6.90
found 296.0169.
(m, 2H), 6.74 (t, J¼7.3 Hz, 1H), 6.54 (d, J¼7.6 Hz, 1H), 4.15 (s, 2H),
2.60 (s, 3H), 2.33 (s, 3H), 2.08 (s, 3H), 1.76e1.69 (m, 2H), 1.17e1.10
(m, 2H), 0.89e0.83 (m, 2H), 0.67 (t, J¼7.1 Hz, 3H). 13C NMR (100M,
Acknowledgements
CDCl3):
d 150.05, 147.33, 138.26, 137.59, 135.81, 130.77, 130.29,
We thank the National Natural Science Foundation of China, 973
program (2015CB856600) and the Research Fund for the Doctoral
Program of Higher Education of China (20130071130009) for fi-
nancial support.
129.69, 129.63, 128.78, 126.82, 125.90, 122.19, 121.27, 74.86, 62.66,
37.02, 34.07, 32.53, 21.80, 18.62, 18.03, 14.00. HRMS (EI) (m/z):
[MþH]þ Calcd for C23H29N3I 474.1406, found 474.1440.
4.4.8. N-((E)-4-(1-Iodopentylidene)-1-methyl-3-phenylimidaz-oli-
References and notes
din-2-ylidene)aniline (7gc). Light yellow solid. 1H NMR (400M,
CDCl3):
d 7.24e7.15 (m, 5H), 7.01e6.97 (m, 2H), 6.75e6.72 (m, 1H),
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