Reaction of benzoyl chlorides with Huisgen's zwitterion: synthesis of functionalized 2,5-dihydro-1H-pyrroles and tetrasubstituted furans

Article abstract of DOI:10.1016/j.tet.2008.03.044

The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dimethyl acetylenedicarboxylate is trapped by benzoyl chloride to yield functionalized 2,5-dihydro-1H-pyrroles. The presence of electron-withdrawing groups at the para position o

Full text of DOI:10.1016/j.tet.2008.03.044

Tetrahedron 64 (2008) 5221–5225
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Tetrahedron
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Reaction of benzoyl chlorides with Huisgen’s zwitterion: synthesis of
functionalized 2,5-dihydro-1H-pyrroles and tetrasubstituted furans
*
Issa Yavari , Ako Mokhtarporyani-Sanandaj, Loghman Moradi, Anvar Mirzaei
Chemistry Department, Tarbiat Modares University, PO Box 14115-175, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dimethyl acetylenedi-
carboxylate is trapped by benzoyl chloride to yield functionalized 2,5-dihydro-1H-pyrroles. The presence
of electron-withdrawing groups at the para position of benzoyl chloride leads to tetrasubstituted furans.
The structures of these products were confirmed by single-crystal X-ray diffraction studies.
Ó 2008 Published by Elsevier Ltd.
Received 14 October 2007
Received in revised form 27 February 2008
Accepted 13 March 2008
Available online 15 March 2008
Keywords:
Electron-deficient acetylenes
Aminofurans
2,5-Dihydro-1H-pyrrole
Benzoyl chloride
Isocyanides
1. Introduction
alkyl(aryl)amino-5-aryl-3,4-furandicarboxylates 5 (Scheme 2).
When these reactions were carried out with benzoyl chlorides
having electron-donating groups (such as Me or OMe) at the para
position, complex reaction mixtures were obtained, which was not
investigated.
The rich chemistry that stems from the addition of nucleophiles
to activated acetylenic compounds has evoked considerable in-
terest. Isocyanides are known to form zwitterions with activated
acetylene compounds such as dimethyl acetylenedicarboxylate
(DMAD).1–4 In recent years, work in our laboratory has shown that
these types of zwitterions can be trapped by a variety of electro-
philes and proton donors, for the synthesis of heterocyclic com-
pounds.5–9 Hence, it was of interest to investigate the reactivity of
the isocyanide–DMAD zwitterion toward benzoyl chlorides.
The structures of compounds 4a–4d and 5a–5e were deduced
from their elemental analyses and their IR, 1H NMR, and 13C NMR
spectroscopies and single-crystal X-ray analyses. For example, the
1H NMR spectrum of 4a exhibited five singlets identified as methyl
(d 1.12 and 2.43), methoxy (d 3.86 and 4.03), and OH (d 4.00) pro-
tons, along with multiplets for the aromatic protons. The 1H-
decoupled 13C NMR spectrum of 4a showed 20 distinct resonances
that confirm the proposed structure. The presence of two Ar–Me
signals in the 1H and 13C NMR spectra of 4a can be explained in
terms of restricted rotation in the dimethylphenyl group. The IR
spectrum of 4a displayed characteristic carbonyl (1740, 1700,
1686 cmꢀ1) and O–H (3365 cmꢀ1) stretching vibrations. The 1H
NMR spectrum of 5c exhibited four singlets identified as tert-butyl
(d 1.55), methoxy (d 3.82 and 4.00), and NH (d 7.00) protons, along
with two doublets (d 7.64 and 8.25, 3J¼8.9 Hz) for the aromatic
region. The 13C NMR spectrum of 5c showed 14 distinct resonances
in agreement with the proposed structure.
2. Results and discussion
In this paper, we report the results of our studies involving the
reactions of zwitterions derived from isocyanides 1 and dialkyl
acetylenedicarboxylates 2 in the presence of benzoyl chlorides 3,
which constitute a synthesis of functionalized 2,5-dihydro-1H-
pyrroles 4 and tetrasubstituted furans 5.10–14 Thus, the 1:1 in-
termediate generated by the addition of alkyl(aryl) isocyanides to
DMAD was trapped by benzoyl chloride to yield dimethyl 1-alkyl-
(aryl)-2-hydroxy-5-oxo-2-phenyl-2,5-dihydro-1H-pyrrole-3,4-
dicarboxylates 4 (Scheme 1). The presence of electron-withdrawing
groups at the para position of benzoyl chloride leads to dimethyl 2-
Unambiguous evidences for the structures of 4a and 5d were
obtained from single-crystal X-ray analyses. The ORTEP15 diagrams
of 4a and 5d are shown in Figures 1 and 2. The structures were
deduced from the crystallographic data and the same were as-
sumed for the other derivatives on account of their NMR spectro-
scopic similarities.
* Corresponding author. Tel.: þ98 21 88006631; fax: þ98 21 88006544.
E-mail address: yavarisa@modares.ac.ir (I. Yavari).
0040-4020/$ – see front matter Ó 2008 Published by Elsevier Ltd.
doi:10.1016/j.tet.2008.03.044

5222
I. Yavari et al. / Tetrahedron 64 (2008) 5221–5225
R'O2C
CO2R'
O
CO2R'
CO2R'
_
C
+
CH2Cl2 , rt
OH
Ph
Cl
+
R N
+
O
N
R
Yield/%
82
75
65
70
R
4
R'
2
3a
R
1
R'
2,6-Dimethylphenyl
Cyclohexyl
a 2,6-Dimethylphenyl
b Cyclohexyl
a
a
b
c
d
Me
Me
Me
Et
b
t
t
Cyclohexyl
Bu
c
Bu
Cyclohexyl
Et
Scheme 1. Synthesis of compounds 4.
O
CO2Me
CO2Me
MeO2C
_
+
CH2Cl2 , rt
Cl
+
+
R N C
H
N
R
O
X
CO2Me
X
5
R
X
Yield/%
2a
3
b
c
X
R
1
Cl
a
Cyclohexyl
75
78
80
70
72
Cl
t
a
Bu
NO2
2,6-Dimethylphenyl
b
c
Cl
Cyclohexyl
b
c
t
NO2
Bu
1,1,3,3-Tetramethylbutyl
2,6-Dimethyl phenyl
Cyclohexyl
d
e
NO2
d
1,1,3,3-Tetramethylbutyl
NO2
Scheme 2. Synthesis of compounds 5.
Figure 1. X-ray crystal structure (ORTEP) of 4a.
Although the mechanistic details of the reaction are not known,
a plausible rationalization may be advanced to explain the product
formation. Presumably, the zwitterionic intermediate16,17 6 formed
from isocyanides and dialkyl acetylenedicarboxylates is attacked by
benzoyl chloride to furnish intermediate 7, which is converted to 8.
This intermediate can lose chloride ion to generate the stabilized
cation 9, which is converted to 10 by absorbing H2O (presumably
from moisture). Intermediate 10 is converted to 4 via the open-
chain structure 11 (Scheme 3). However, when X¼NO2 or Cl,
intermediate 8 eliminates Clþ ion to produce 12. Nucleophilic at-
tack of H2O on this intermediate leads to 5 (Scheme 3). Thus, the
presence of electron-withdrawing groups at the para position of
benzoyl chloride changes the reaction pathway and leads to the
formation of a different product.
Figure 2. X-ray crystal structure (ORTEP) of 5d.
for the synthesis of functionalized 2,5-dihydro-1H-pyrroles and
tetrasubstituted furans. The present procedure has the advantage
that not only the reaction is performed under neutral conditions
but also the reactants can be mixed without any prior activation or
modification. The simplicity of the present procedure makes it an
interesting alternative to other approaches.
3. Experimental
3.1. General
In conclusion, we report novel transformations involving ben-
zoyl chlorides and dialkyl acetylenedicarboxylates in the presence
of isocyanides, which afford a new application of benzoyl chlorides
The reagents and solvents used in this work were obtained from
Fluka and were used without further purification. Mp: Electrother-
mal-9100 apparatus. IR spectra: Shimadzu IR-460 spectrometer, in

I. Yavari et al. / Tetrahedron 64 (2008) 5221–5225
5223
1
2
+
CO2R'
CO2R'
C
N
C
R
N
6
+ 3
CO2R'
CO2R'
Cl
R'O2C
CO2R'
Ph
R
O
N
R
O
X
7
MeO2C
CO2Me
R'O2C
CO2R'
R'O2C
CO2R'
Cl
_
_
Cl
X = NO2,Cl
Cl
X = H
Cl
N
R
N
R
Ph
N
R
O
O
9
O
X
X
12
X
H O
2
+
8
H O
2
+
R'O2C
CO2R'
OH
MeO2C
CO2Me
H
N
R
O
10
Ph
N
R
O
13
CO2R'
O
R'O2C
5
O
C
4
NH Ph
R
11
Scheme 3. Proposed mechanism for the formation of compounds 4 and 5.
cmꢀ1
.
1H and 13C NMR spectra: Bruker DRX-500 AVANCE in-
(OMe), 93.1 (C–N), 126.3 (2CH), 128.5 (CH), 129.0 (2CH), 129.1
(CH), 129.2 (CH), 130.0 (CH), 131.1 (C), 136.2 (C), 137.7 (C),
139.6 (C), 140.3 (C), 146.5 (C), 162.5 (C]O), 162.6 (C]O), 163.2
(C]O).
strument, in CDCl3 at 500.1 and 125.7 MHz, respectively; d in parts
per million and in hertz. EIMS: Finnigan-MAT-8430 mass
spectrometer, at 70 eV, in m/z. Elemental analyses: Heraeus CHN-O-
J
Rapid analyzer.
3.2.1.1. X-ray crystal structural determination of 4a. Structural
determination and refinement data: formula, C22H21NO6, Mr 395.40;
crystal size, 0.10ꢂ0.10ꢂ0.10 mm3; crystal system, monoclinic,
a¼8.2989(4), b¼18.1793(8), c¼13.7544(6) Å, b¼94.6380(10); space
3.2. General procedure for the synthesis of functionalized
2,5-dihydro-1H-pyrroles (4) and tetrasubstituted furans (5)
To a stirred solution of dialkyl acetylenedicarboxylate (2 mmol)
and benzoyl chloride (0.28 g, 2 mmol) in dry CH2Cl2 (10 mL) was
added a solution of the isocyanide (2 mmol) in dry CH2Cl2 (5 mL) at
room temperature. The reaction mixture was stirred for 24 h. The
solvent was removed under reduced pressure and the residue was
separated by silica gel (Merck 230–240 mesh) column chroma-
tography using hexane–EtOAc mixtures as eluent.
group, P21/c; Z¼4, V¼2068.17(16) Å3, Dcalcd¼1.270 g cmꢀ3
;
R¼0.0412 (for 5179 reflections), Rw¼0.1102; ꢀ11ꢃhꢃ11, ꢀ25ꢃkꢃ25,
ꢀ19ꢃlꢃ19; Mo Ka radiation (l¼0.71073 Å); T¼100(2) K. The crys-
tallographic data of 1a have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication number
CCDC-647813. Copies of the data can be obtained, free of charge, via
the internet (http://www.ccdc.cam.ac.uk/data_request/cif), e-mail
(data_request@ccdc.cam.ac.uk) or fax (þ44 1223 336033).
3.2.1. Dimethyl 1-(2,6-dimethylphenyl)-2-hydroxy-5-oxo-2-
phenyl-2,5-dihydro-1H-pyrrole-3,4-dicarboxylate (4a)
3.2.2. Dimethyl 1-cyclohexyl-2-hydroxy-5-oxo-2-phenyl-2,5-
dihydro-1H-pyrrole-3,4-dicarboxylate (4b)
Colorless crystals, mp 193–195 ꢁC, 0.65 g, yield 82%. IR (KBr)
(nmax/cmꢀ1): 3365 (OH), 1740, 1700 and 1686 (C]O), 1272, 1212.
MS, m/z (%): 395 (Mþ, 18), 120 (8), 105 (42), 77 (10), 59 (28), 58
(100), 44 (70). Anal. Calcd for C22H21NO6 (395.39): C, 66.83; H,
5.35; N, 3.54%. Found: C, 65.95; H, 5.41; N, 3.45%. 1H NMR: d 1.12
(3H, s, Me), 2.43 (3H, s, Me), 3.86 (3H, s, OMe), 4.00 (1H, s, OH),
4.03 (3H, s, OMe), 6.83 (m, CH), 7.16 (2H, d, 3J¼7.0 Hz, CH), 7.20
(2H, d, 3J¼7.5 Hz, CH), 7.29 (2H, t, 3J¼8.0 Hz, CH), 7.37 (1H, t,
3J¼7.0 Hz, CH). 13C NMR: d 18.0 (Me), 20.0 (Me), 53.6 (OMe), 53.7
Colorless crystals, mp 167–170 ꢁC, 0.56 g, yield 75%. IR (KBr)
(nmax/cmꢀ1): 3450 (OH), 1722, 1701 and 1681 (C]O), 1262, 1206.
Anal. Calcd for C20H23NO6 (373.38): C, 64.33; H, 6.21; N, 3.75%.
Found: C, 64.48; H, 6.27; N, 3.83%. 1H NMR: d 0.88–0.96 (1H, m,
CH), 1.06–1.24 (3H, m, CH), 1.50–1.52 (1H, m, CH), 1.58–1.61 (1H,
m, CH), 1.71–1.75 (2H, m, CH), 1.99–2.10 (2H, m, CH), 3.09–3.14
(1H, m, CH), 3.64 (3H, s, OMe), 3.92 (3H, s, OMe), 4.98 (1H, s, OH),
7.35–7.39 (3H, m, CH), 7.50 (2H, d, 3J¼7.0 Hz, CH). 13C NMR: d 25.5

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I. Yavari et al. / Tetrahedron 64 (2008) 5221–5225
(CH2), 26.4 (CH2), 26.5 (CH2), 29.4 (CH2), 30.5 (CH2), 53.1 (CH), 53.4
(OMe), 53.8 (OMe), 91.8 (C–N), 126.5 (2CH), 128.8 (2CH), 129.4
(CH), 134.8 (C), 135.8 (C), 148.3 (C), 161.8 (C]O), 162.7 (C]O),
163.8 (C]O).
3.3.2. Dimethyl 2-(1,1-dimethylethyl)amino-5-(4-nitrophenyl)-3,4-
furandicarboxylate (5c)
Light brown crystals, mp 135–137 ꢁC, 0.60 g, yield 80%. IR (KBr)
(nmax/cmꢀ1): 3165 (NH), 1728 (C]O), 1667 (C]O), 1327, 1245, 1091,
843. Anal. Calcd for C18H20N2O7 (376.34): C, 57.44; H, 5.36; N, 7.44%.
Found: C, 57.51; H, 5.40; N, 7.48%. 1H NMR: d 1.55 (9H, s, CMe3), 3.82
(3H, s, OMe), 4.00 (3H, s, OMe), 7.00 (br, NH), 7.64 (2H, d, 3J¼8.9 Hz,
2CH), 8.25 (2H,d, 3J¼8.9 Hz, 2CH). 13C NMR: d 30.1 (CMe3), 51.8
(CMe3), 53.5 (OMe), 53.6 (OMe), 90.0 (N–C]C), 117.9 (C), 124.3
(2CH), 124.8 (2CH), 135.4 (C), 138.7 (C), 146.4 (O–C]C), 162.3 (NCO),
165.0 (C]O), 165.9 (C]O).
3.2.3. Di(tert-butyl) 1-cyclohexyl-2-hydroxy-5-oxo-2-phenyl-2,5-
dihydro-1H-pyrrole-3,4-dicarboxylate (4c)
White powder, mp 191–193 ꢁC, 0.59 g, yield 65%. IR (KBr) (nmax
/
cmꢀ1): 3390 (OH), 1705, 1700 and 1680 (C]O), 1290, 1163. Anal.
Calcd for C26H35NO6 (457.54): C, 68.25; H, 7.71; N, 3.06%. Found: C,
68.41; H, 7.79; N, 3.11%. 1H NMR: d 0.89–0.93 (1H, m, CH), 1.06–1.12
(2H, m, CH), 1.26 (9H, s, CMe3), 1.34–1.51 (3H, m, CH), 1.57 (9H, s,
CMe3), 1.70–1.80 (2H, m, 2CH), 2.08–2.15 (2H, m, 2CH), 3.01–3.08
(m, 1H, CH), 6.07 (s, 1H, OH), 7.39 (1H, t, 3J¼7.0 Hz, CH), 7.43 (2H, t,
3J¼7.0 Hz, 2CH), 7.52 (2H, d, 3J¼7.5 Hz, 2CH). 13C NMR: d 24.5 (CH2),
25.0 (CH2), 25.5 (CH2), 28.2 (CMe3), 28.6 (CMe3), 29.6 (CH2), 31.4
(CH2), 51.3 (CH), 84.3 (CMe3), 84.5 (CMe3), 91.6 (C–N), 126.4 (2CH),
128.8 (2CH), 129.2 (CH), 135.3 (C), 136.8 (C), 146.4 (C), 161.0 (C]O),
161.4 (C]O), 164.5 (C]O).
3.3.3. Dimethyl 2-(cyclohexylamino)-5-(4-nitrophenyl)-3,4-
furandicarboxylate (5d)
Light brown crystals; mp 176–178 ꢁC, 0.56 g, yield 70%. IR (KBr)
(nmax/cmꢀ1): 3140 (NH), 1722 (C]O), 1671 (C]O), 1327, 1224, 1103,
841. Anal. Calcd for C20H22N2O7 (402.38): C, 59.69; H, 5.51; N, 6.96%.
Found: C, 59.78; H, 5.60; N, 6.98%. 1H NMR: d 1.25–1.32 (1H, m, CH),
1.38–1.47 (4H, m, 4 CH), 1.65–1.68 (1H, m, CH), 1.79–1.82 (2H, m,
2CH), 2.05–2.07 (2H, m, 2CH), 3.75–3.77 (1H, m, CH), 3.79 (3H, s,
OMe), 3.95 (3H, s, OMe), 6.73 (1H, d, 3J¼7.8 Hz, NH), 7.60 (2H, d,
3J¼8.8 Hz, 2CH), 8.20 (2H, d, 3J¼8.8 Hz, 2CH). 13C NMR: d 24.2
(2CH2), 25.3 (CH2), 33.4 (2CH2), 51.3 (OMe), 51.7 (OMe), 52.9 (CH),
88.8 (N–C]C), 117.9 (C), 124.0 (2CH), 124.2 (2CH), 135.0 (C), 137.9
(C), 146.0 (O–C]C), 161.6 (NCO), 164.4 (C]O), 165.3 (C]O).
3.2.4. Diethyl 1-cyclohexyl-2-hydroxy-5-oxo-2-phenyl-2,5-
dihydro-1H-pyrrole-3,4-dicarboxylate (4d)
Colorless crystals, mp 140–142 ꢁC, 0.56 g, yield 70%. IR (KBr)
(nmax/cmꢀ1): 3440 (OH), 1720, 1703 and 1681 (C]O), 1260, 1201.
Anal. Calcd for C22H27NO6 (401.44): C, 65.82; H, 6.78; N, 3.49%.
Found: C, 65.93; H, 6.82; N, 3.54%. 1H NMR: d 0.87–0.90 (1H, m, CH),
1.13–1.15 (1H, m, CH), 1.14 (3H, t, 3J¼7.2 Hz, 3CH), 1.37 (3H, t,
3J¼7.2 Hz, 3CH), 1.18–1.21 (2H, m, CH), 1.66–1.69 (2H, m, CH), 1.70–
1.72 (2H, m, CH), 2.01–2.05 (2H, m, CH), 3.08–3.11 (1H, m, CH), 3.76
(1H, s, OH), 4.08–4.19 (2H, m, CH), 4.40 (2H, q, 3J¼7.2 Hz, CH), 7.35–
7.40 (3H, m, CH), 7.48 (2H, d, 3J¼7.1 Hz, CH). 13C NMR: d 13.7 (CH3),
14.1 (CH3), 25.1 (CH2), 26.0 (CH2), 26.1 (CH2), 29.1 (CH2), 30.3 (CH2),
53.6 (CH), 62.1 (OCH2), 62.2 (OCH2), 91.3 (C–N), 125.9 (2CH), 128.6
(2CH), 129.0 (CH), 135.4 (C), 135.8 (C), 145.6 (C), 161.1 (C]O), 161.7
(C]O), 163.5 (C]O).
3.3.3.1. X-ray crystal structural determination of 5d. Structural
determination and refinement data: formula, C20H22N2O7, Mr
402.40; crystal size, 0.55ꢂ0.40ꢂ0.25 mm3; crystal system, triclinic,
a¼6.8628(5), b¼11.5872(9), c¼12.6526(9) Å, b¼80.4570(10); space
group, Pꢀ1; Z¼2, V¼945.10(12) Å3, Dcalcd¼1.414 g cmꢀ3; R¼0.0412
(for 3857 reflections), Rw¼0.0843; ꢀ9ꢃhꢃ9, ꢀ16ꢃkꢃ16, ꢀ17ꢃlꢃ17;
Mo Ka radiation (l¼0.71073 Å); T¼100(2) K. The crystallographic
data of 1a have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication number CCDC-628362.
Copies of the data can be obtained, free of charge, via the inter-
net (http://www.ccdc.cam.ac.uk/data_request/cif), e-mail (data_
request@ccdc.cam.ac.uk) or fax (þ44 1223 336033).
3.3. Dimethyl 2-(4-chlorophenyl)-5-(cyclohexylamino)-3,4-
furandicarboxylate (5a)
Light yellow crystals; mp 157–160 ꢁC (lit. 18, reported as an oil),
0.59 g, yield 75%. IR (KBr) (nmax/cmꢀ1): 3275 (NH), 1738 (C]O),
1685 (C]O), 1365, 1268, 1171, 742. Anal. Calcd for C20H22ClNO5
(391.84): C, 61.30; H, 5.66; N, 3.57%. Found: C, 60.88; H, 5.60; N,
3.62%. 1H NMR: d 0.94–0.97 (1H, m, CH), 1.07–1.10 (1H, m, 1CH),
1.19–1.25 (2H, m, 2CH), 1.24–1.40 (1H, m, 1CH), 1.52–1.54 (1H, m,
1CH), 1.59–1.64 (1H, m, 1CH), 1.71–1.79 (2H, m, 2CH), 2.10–2.14 (1H,
m,1CH), 3.04–3.09 (1H, m, CH), 3.63 (3H, s, OMe), 3.87 (3H, s, OMe),
6.33 (1H, br, NH), 7.46 (2H, d, 3J¼8.5 Hz, 2CH), 7.55 (2H, d, 3J¼8.5 Hz,
2CH). 13C NMR: d 25.5 (2CH2), 26.2 (2CH2), 26.3 (CH2), 52.3 (OMe),
52.5 (OMe), 53.2 (CH), 91.21 (N–C]C), 128.6 (2CH), 128.7 (2CH),
134.4 (C), 136.0 (CH), 137.3 (C), 146.2 (O–C]C), 160.7 (NCO), 162.6
(C]O), 163.1 (C]O).
3.3.4. Dimethyl 2-(4-chlorophenyl)-5-[(1,1,3,3-tetramethyl-
butyl)amino]-3,4-furandicarboxylate (5e)
Light brown crystals, mp 98–100 ꢁC, 0.62 g, yield 72%. IR (KBr)
(nmax/cmꢀ1): 3240 (NH), 1725 (C]O), 1669 (C]O), 1325, 1211, 1100,
839. Anal. Calcd for C22H28N2O7 (432.44): C, 59.69; H, 5.51; N,
6.96%. Found: C, 59.41; H, 5.56; N, 7.01%. 1H NMR: d 1.03 (9H, s,
CMe3), 1.25 (2H, s, CH2), 1.56 (6H, s, CMe2), 3.78 (3H, s, OMe), 3.95
(3H, s, OMe), 7.08 (1H, br, NH), 7.59 (2H, d, 3J¼8.8 Hz, 2CH), 8.21
(2H, d, 3J¼8.8 Hz, 2CH). 13C NMR: d 29.6 (CMe2), 31.4 (CMe3), 31.7
(CMe3), 51.3 (OMe), 52.9 (OMe), 53.4 (CMe2), 56.7 (CH2), 89.4
(N–C]C), 117.5 (C), 123.7 (2CH), 124.3 (2CH), 134.9 (C), 138.1 (C),
145.8 (O–C]C), 161.7 (NCO), 164.5 (C]O), 165.4 (C]O).
3.3.1. Dimethyl 2-(4-chlorophenyl)-5-[(2,6-dimethylphenyl)-
amino]-3,4-furandicarboxylate (5b)
References and notes
Light brown crystals; mp 149–151 ꢁC, 0.64 g, yield 78%. IR (KBr)
(nmax/cmꢀ1): 3149 (NH), 1725 (C]O), 1684 (C]O), 1339, 1250, 1090,
848. Anal. Calcd for C22H20ClNO5 (413.85): C, 63.85; H, 4.87; N,
3.38%. Found: C, 63.92; H, 4.74; N, 3.42%. 1H NMR: d 1.20 (3H, s,
CH3), 2.40 (3H, s, CH3), 3.75 (3H, s, OMe), 3.94 (3H, s, OMe), 6.48
(1H, br, NH), 6.86–6.87 (1H, m, CH), 7.11–7.17 (2H, m, 2CH), 7.25 (2H,
d, 3J¼8.7 Hz, 2CH), 7.33 (2H, d, 3J¼8.7 Hz, 2CH). 13C NMR: d 18.3
(CH3), 20.1 (CH3), 53.1 (OMe), 53.2 (OMe), 93.4 (N–C]C), 128.8
(2CH), 128.9 (1CH), 129.0 (2CH), 129.4 (CH), 129.5 (CH), 132.4 (C),
135.2 (C), 137.4 (C), 138.2 (C), 139.8 (C), 140.6 (C), 146.8 (O–C]C),
161.6 (NCO), 163.0 (C]O), 163.1 (C]O).
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