First synthesis of methyl 3-amino-4-(het)aryl-1H-pyrrole-2-carboxylates as useful scaffolds in medicinal chemistry

Article abstract of DOI:10.1016/j.tet.2004.01.019

The preparation of new methyl 4-(het)aryl-3-amino-1H-pyrrole-2- carboxylates was achieved starting from commercial arylacetonitriles. This four steps synthesis afforded with good yields interesting building-blocks useful in the access to many nitrogen het

Full text of DOI:10.1016/j.tet.2004.01.019

Tetrahedron 60 (2004) 2267–2270
First synthesis of methyl 3-amino-4-(het)aryl-1H-pyrrole-2-
carboxylates as useful scaffolds in medicinal chemistry
*
Christophe Rochais, Vincent Lisowski, Patrick Dallemagne and Sylvain Rault
´ ´
CERMN, UFR des Sciences Pharmaceutiques, Universite de Caen Basse-Normandie, 5, rue Vaubenard, Caen 14032, France
Received 3 October 2003; revised 9 December 2003; accepted 12 January 2004
Abstract—The preparation of new methyl 4-(het)aryl-3-amino-1H-pyrrole-2-carboxylates was achieved starting from commercial
arylacetonitriles. This four steps synthesis afforded with good yields interesting building-blocks useful in the access to many nitrogen
heterocycles with potential therapeutic interest.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
synthesis of the pyrrole analogs of 8, we first replaced
thiophene thioglycolate in the previous sequence by
diethylaminomalonate (DEAM), according to the Chen’s
procedure used for the access to 5-substituted 3-amino-1H-
pyrrole-2-carboxylates.6
The anthranilic acids are widely used as interesting
building-blocks in the field of medicinal chemistry and
allow, for example, the synthesis of several antiinflamma-
tory drugs like mefenamic acid, and more recently some
protein tyrosine phosphatase inhibitors.1 With the aim of
investigating new heterocyclic bioisosters of the latter, our
group has recently developed furane2 and thiophene3
analogs of anthranilic acids and we wish to extend herein
this study to the pyrrole derivatives. In fact the latter are
often reported as crucial intermediates in the synthesis of
various potent heterocycles.4 Although some groups have
published work about 3-aminopyrrole-2-carboxylates, none
of these papers were concerned with the title 4-(het)aryl
compounds 1, since only 4,5-unsubstituted 2, 5-aryl 3 or
4-arylmethyl 4 derivatives were reported (Fig. 1).5–7 We
therefore decided to investigate a convenient route towards
these potential useful scaffolds.
This method, involved in p-methoxyphenyl series led to the
first methyl 3-amino-4-aryl-1H-pyrrole-2-carboxylate 9a,
but in very poor yield (Scheme 2).
In order to improve this sequence, we focused on the
isolation of the enamine 10a as a key intermediate in the
synthesis of 9a, since Elliot alleged it was possible to isolate
it with a benzyl substituent in the place of the aryl one.7 We
Figure 1.
2. Results and discussion
During our previous work in thiophene series, we focused
on the preparation, by formylation of commercial arylaceto-
nitriles 5, of stable enolates 6 which were involved, after
activation by a sulfonylbenzene leaving group, in a Kirsch’s
cyclisation.8 The latter was performed by treatment with
methyl thioglycolate and sodium methoxide and led to the
attempted methyl amino-4-arylthiophene-3-carboxylates 8
(Scheme 1). With the aim to apply this pathway to the
Keywords: Aminoarylypyrrolecarboxylates; Enamine; Diethyl-
aminomalonate; Cyclisation.
*
Corresponding author. Tel.: þ33-2-31-56-59-10; fax: þ33-2-31-93-11-
Scheme 1. (i) HCO2Et, NaH, THF; (ii) ClSO2C6H5, DMF; (iii)
HSCH2CO2Me, MeONa, MeOH.
88; e-mail address: dallemagne@pharmacie.unicane.fr
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.01.019

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C. Rochais et al. / Tetrahedron 60 (2004) 2267–2270
Table 1.
(Het)Ar
Product
Overall yield (%)
4-Methoxyphenyl
Phenyl
9a
9b
9c
9d
9e
9f
9g
9h
9i
41
66
58
49
74
68
66
65
46
80
4-Methylphenyl
4-Fluorophenyl
4-Chlorophenyl
4-Bromophenyl
3,4-Dichlorophenyl
3,4-Dimethoxyphenyl
Scheme 2. (i) DEAM, MeONa, MeOH.
first tried to reach this goal by treatment of the tosyl
derivative 7a with DEAM, but all the attempts in various
experimental conditions failed. The reaction involving the
enol displaced from its sodium salt 6a and DEAM in diluted
methanol was also unsuccessful, whereas utilization in this
sequence of the hydrochloric salt of DEAM in anhydrous
methanol and in the presence of triethylamine afforded the
attempted enamine 10a in 95% yield (Scheme 3). The latter
was subsequently cyclised and transesterified into 9a using
sodium methoxide in methanol with 43% yield.
2-Thienyl
3-Thienyl
9j
In summary, we have developed an efficient preparation of
new methyl 3-amino-4-(het)aryl-1H-pyrrole-2-carboxy-
lates, in four steps from commercially available inexpensive
starting materials. These products constitute building-
blocks useful in the access to many nitrogen heterocycles
with potential therapeutic interest.
Scheme 3. (i) (1) AcOH, H2O, (2) DEAM–HCl, Et3N, MeOH; (ii) MeONa,
MeOH.
3. Experimental
3.1. General
This relative poor yield could have been explained by the
1
two isomeric forms E and Z observed in H NMR for 10a
in 1/5 respective proportions as already demonstrated by
Lim.9 In fact we first though that only the Z isomer could
be cyclised as it was recently demonstrated by Redman10
in furane series. According to this hypothesis, the
unreacted E isomer should be recovered in the reaction
mixture, but none trace of the latter was observed. So we
alleged that an E/Z isomerisation occurred during
intramolecular cyclisation through an imine form 11,
the equilibrium being displaced by the formation of 9
from (Z) 10 (Scheme 4).
Commercial reagents were used as received without
additional purification. Melting points were determined on
¨
a Kofler melting point apparatus and are uncorrected. IR
spectra were taken with a Perkin–Elmer spectrum BX
FT-IR spectrometer. 1H NMR (400 MHz) and 13C
(100 MHz) spectra were recorded on a JEOL Lambda 400
Spectrometer. Chemical shifts are expressed in parts per
million downfield from TMS as an internal standard. Mass
Spectra were recorded on a JEOL JMS GCMate with
ionising potential of 70 eV and with pfk as internal standard
for high-resolution procedure.
Eight other methyl 3-amino-4-(het)aryl-1H-pyrrole-2-car-
boxylates 9b–j have been synthesized according to this
pathway with 41–80% overall yields from 6 (Table 1).
3.2. General procedure for the preparation of the
enamine 10a–j
3.2.1. {[2-Cyano-2-(p-methoxyphenyl)vinyl)]amino}-
diethyl malonate (10a). Diethylaminomalonate hydrochlo-
ride (1.81 g, 8.56 mmol) and TEA (873 mL, 6.28 mmol)
were added to a solution of 6a (1 g, 5.7 mmol) in methanol
(20 mL). The reaction mixture was then heated for 4 h.
Methanol was then removed and the residue was diluted in
dichloromethane (100 mL). The organic layer was washed
with water, and then dried over calcium chloride. Filtration
and evaporation afforded the title compound 10a (1.88 g,
99%), as an unstable yellow oil which was used without
further purification, IR (KBr): 3382; 2199; 1743;
1
1630 cm21. H NMR Z/E mixture 5/1 (CDCl3): d¼7.36
(d, 2Hphenyl, J¼8.8 Hz, E), 7.23 (d, 2Hphenyl, J¼8.8 Hz, Z),
7.01 (d, 1H, J¼13.0 Hz, CHN, Z), 6.95 (d, 2Hphenyl
,
J¼8.8 Hz, E), 6.86 (d, 2Hphenyl, J¼8.8 Hz, Z), 6.75 (d,
Scheme 4.

C. Rochais et al. / Tetrahedron 60 (2004) 2267–2270
2269
1H, J¼13.3 Hz, CHN, E), 5.70 (m, 1H, NH, E), 5.65 (dd,
1H, J¼13.0, 8.3 Hz, NH, Z), 4.65 (d, 1H, J¼8.3 Hz,
CH(CO2Et)2, Z), 4.55 (d, 1H, J¼8.4 Hz, CH(CO2Et)2, E),
4.31 (m, 4H, CH2, ZþE), 3.82 (s, 3H, OCH3, E), 3.80 (s, 3H,
OCH3, Z), 1.32 (t, 6H, J¼7.1 Hz, CH3, ZþE); MS m/z:
332.0.
J¼8.3 Hz, CH(CO2Et)2), 4.31 (m, 4H, CH2), 3.88 (s, 3H,
OCH3), 3.86 (s, 3H, OCH3), 1.32 (t, 6H, J¼7.1 Hz, CH3);
MS m/z: 362.1.
3.2.9. {[2-Cyano-2-(2-thienyl)vinyl)]amino}diethylmalo-
nate (10i). From 2-(2-thienyl)-3-hydroxyacrylonitrile (3 g);
1
black oil 10i (4.97 g, 81%); H NMR Z isomer (CDCl3):
3.2.2. {[2-Cyano-2-(phenylvinyl)]amino}diethylmalonate
(10b). From 2-phenyl-3-hydroxyacrylonitrile (3 g); yellow
d¼7.30–6.78 (m, 4H), 5.90 (dd, 1H, J¼12, 6.8 Hz, NH),
4.66 (d, 1H, J¼6.8 Hz, CH(CO2Et)2), 4.30 (m, 4H, CH2),
1.32 (m, 6H, CH3); MS m/z: 308.1.
1
oil 10b (5.9 g, 95%); H NMR Z isomer (CDCl3): d¼7.32
(m, 4Hphenyl), 7.11 (d, 1H, J¼12.9 Hz, CHN), 5.82 (dd, 1H,
J¼12.9, 8.3 Hz, NH), 4.70 (d, 1H, J¼8.3 Hz, CH(CO2Et)2),
4.30 (m, 4H, CH2), 1.32 (t, 6H, J¼7.1 Hz, CH3); MS m/z:
302.1.
3.2.10. {[2-Cyano-2-(3-thienyl)vinyl)]amino}diethylma-
lonate (10j). From 2-(3-thienyl)-3-hydroxyacrylonitrile
1
(3.8 g); yellow syrup 10j (7.7 g, 98%); H NMR Z isomer
(CDCl3): d¼7.40–6.77 (m, 4H), 5.88 (dd, 1H, J¼12.4,
8.0 Hz, NH), 4.67 (d, 1H, J¼8.0 Hz, CH(CO2Et)2), 4.31 (m,
4H, CH2), 1.32 (t, 6H, J¼7.2 Hz, CH3); MS m/z: 308.1.
3.2.3. {[2-Cyano-2-(p-methylphenyl)vinyl)]amino}-
diethyl malonate (10c). From 2-(p-methylphenyl)-3-hydro-
xyacrylonitrile (2 g); yellow oil 10c (3.9 g, 97%); 1H NMR
Z isomer (CDCl3): d¼7.20 (d, 2Hphenyl, J¼8.2 Hz), 7.12 (d,
1H, J¼12.9 Hz, CHN), 7.10 (d, 2Hphenyl, J¼8.2 Hz), 5.73
(dd, 1H, J¼12.9, 8.2 Hz, NH), 4.69 (d, 1H, J¼8.2 Hz,
CH(CO2Et)2), 4.31 (m, 4H, CH2), 2.31 (s, 3H, CH3), 1.32 (t,
6H, J¼7.1 Hz, CH3); MS m/z: 316.1.
3.3. General procedure for the intramolecular ring
closure
3.3.1. Methyl 3-amino-4-(p-methoxyphenyl)-1H-pyrrole-
2-carboxylate (9a). To a solution of 10a (1.80 g, 5.7 mmol)
in methanol (10 mL) was added sodium methoxide
(330 mg, 6.2 mmol). The reaction mixture was then stirred
for 30 min at room temperature, then heated for 3 h.
Methanol was then partially removed and water added.
The resulted precipitate was then filtered off, washed with
petroleum ether and dry to afford the title product 9a
(580 mg, 41%), white powder. Mp 140 8C. IR (KBr): 3431;
3.2.4. {[2-Cyano-2-(p-fluorophenyl)vinyl)]amino}diethyl
malonate (10d). From 2-(p-fluorophenyl)-3-hydroxyacryl-
1
onitrile (1.75 g); yellow oil 10d (3.4 g, 98%); H NMR Z
isomer (CDCl3): d¼7.24–6.79 (m, 5H), 6.13 (dd, 1H,
J¼12.6, 8.4 Hz, NH), 4.66 (d, 1H, J¼8.4 Hz, CH(CO2Et)2),
4.30 (m, 4H, CH2), 1.32 (t, 6H, J¼7.1 Hz, CH3); MS m/z:
308.1.
1
3123; 2913; 2833; 1684; 1604 cm21. H NMR (CDCl3):
8.12 (br s, 1H, NH); 7.37 (d, 2Hphenyl, J¼8.7 Hz); 6.95 (d,
2Hphenyl, J¼8.7 Hz); 6.80 (s, 1H, CHNH); 4.51 (br s, 2H,
NH2); 3.83 (s, 6H, OCH3). 13C NMR (CDCl3): 158.22;
158.05; 144.24; 128.42; 126.04; 124.98; 118.10; 114.43;
114.38; 55.33; 50.77. HRMS m/z (EI) 246.1004 (Mþ, 43.4,
C13H14N2O3 required 246.1000).
3.2.5. {[2-Cyano-2-(p-chlorophenyl)vinyl)]amino}diethyl
malonate (10e). From 2-(p-chlorophenyl)-3-hydroxyacryl-
onitrile (4 g); yellow oil 10e (7.5 g, 99%); 1H NMR Z
isomer (CDCl3): d¼7.39 (d, 1H, J¼13 Hz, CHN), 7.28–
7.16 (m, 4Hphenyl), 5.84 (dd, 1H, J¼13, 8.0 Hz, NH), 4.70
(d, 1H, J¼8.0 Hz, CH(CO2Et)2), 4.34 (m, 4H, CH2), 1.31 (t,
6H, J¼7.1 Hz, CH3); MS m/z: 336.1.
3.3.2. Methyl 3-amino-4-phenyl-1H-pyrrole-2-carboxy-
lates (9b). From 10b (5.60 g), yellow solid (2.76 g, 69%).
Mp 152 8C. IR (KBr): 3379; 3304; 3035; 2879; 1691;
1605 cm21. 1H NMR (CDCl3): 8.40 (br s, 1H, NH), 7.43 (m,
5Hphenyl), 6.80 (s, 1H, CHNH), 4.67 (br s, 2H, NH2), 3.86 (s,
3H, OCH3). 13C NMR (CDCl3): 160.72; 142.08; 134.06;
128.96; 127.11; 127.31; 126.23; 120.97; 114.84; 50.80. MS
m/z: 216.1.
3.2.6. {[2-Cyano-2-(p-bromophenyl)vinyl)]amino}-
diethyl malonate (10f). From 2-(p-bromophenyl)-3-hydro-
xyacrylonitrile (4.3 g); yellow oil 10f (7.3 g, 99%); IR
1
(KBr): 3378; 2198; 1754; 1633 cm21. H NMR Z isomer
(CDCl3): d¼7.41 (d, 2Hphenyl, J¼8.3 Hz), 7.20 (d, 1H,
J¼13 Hz, CHN), 7.17 (d, 2Hphenyl, J¼8.3 Hz), 5.92 (dd, 1H,
J¼13, 8.1 Hz, NH), 4.71 (d, 1H, J¼8.1 Hz, CH(CO2Et)2),
4.26 (m, 4H, CH2), 1.31 (m, 6H, CH3); MS m/z: 381.9.
3.3.3. Methyl 3-amino-4-(p-methylphenyl)-1H-pyrrole-
2-carboxylate (9c). From 10c (3.69 g), yellow solid (1.60 g,
60%). Mp 142 8C. IR (KBr): 3398; 3318; 3203; 3022; 1688;
1595 cm21. 1H NMR (CDCl3): 8.40 (br s, 1H, NH), 7.34 (d,
2Hphenyl, J¼7.8 Hz), 7.21 (d, 2Hphenyl, J¼7.8 Hz), 6.83 (s,
1H, CHNH), 4.50 (br s, 2H, NH2), 3.86 (s, 3H, OCH3), 2.37
(s, 3H, CH3). 13C NMR (CDCl3): 160.71; 143.13; 135.90;
130.97; 129.63; 127.05; 126.45; 120.84; 114.78; 50.77;
21.08. MS m/z: 230.1.
3.2.7. {[2-Cyano-2-(3,4-dichlorophenyl)vinyl)]amino}-
diethyl malonate (10g). From 2-(3,4-dichlorophenyl)-3-
hydroxyacrylonitrile (2.5 g); yellow solid 10g (4.3 g, 99%);
1H NMR Z isomer (CDCl3): d¼7.54–7.13 (m, 4H), 5.97
(dd, 1H, J¼12.9, 8.1 Hz, NH), 4.72 (d, 1H, J¼8.1 Hz,
CH(CO2Et)2), 4.36 (m, 4H, CH2), 1.33 (t, 6H, J¼7.2 Hz,
CH3); MS m/z: 371.1.
3.2.8. {[2-Cyano-2-(3,4-dimethoxyphenyl)vinyl)]amino}-
diethyl malonate (10h). From 2-(3,4-dimethoxyphenyl)-3-
hydroxyacrylonitrile (8 g); yellow oil 10h (4.46 g, 78%); IR
3.3.4. Methyl 3-amino-4-(p-fluorophenyl)-1H-pyrrole-2-
carboxylate (9d). From 10d (3.4 g), yellow solid (1.25 g,
50%). Mp 156 8C. IR (KBr): 3392; 3310; 3217; 3120; 1665;
1600 cm21. 1H NMR (CDCl3): 8.42 (br s, 1H, NH), 7.41 (d,
2Hphenyl, J¼8.4 Hz), 7.09 (d, 2Hphenyl, J¼8.4 Hz), 6.82 (s,
1
(KBr): 3301; 2195; 1760; 1637 cm21. H NMR Z isomer
(CDCl3): d¼7.06 (d, 1H, J¼12.9 Hz, CHN), 6.82 (m,
3Hphenyl), 5.72 (dd, 1H, J¼12.9, 8.3 Hz, NH), 4.70 (d, 1H,
1H, CHNH), 4.40 (br s, 2H, NH2), 3.87 (s, 3H, OCH3). 13
C

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C. Rochais et al. / Tetrahedron 60 (2004) 2267–2270
NMR (CDCl3): 162.75; 160.72; 160.30; 146.38; 129.95;
129.92; 128.83; 128.79; 128.70; 117.06; 115.94; 115.72;
113.63; 50.83. MS m/z: 234.0.
3.3.10. Methyl 3-amino-4-(3-thienyl)-1H-pyrrole-2-car-
boxylate (9j). From 10j (7.74 g), off-white solid (4.58 g,
82%). Mp 180 8C. IR (KBr): 3379; 3304; 3106; 1686;
1595 cm21. 1H NMR (CDCl3): 8.30 (br s, 1H, NH), 7.39 (m,
3.3.5. Methyl 3-amino-4-(p-chlorophenyl)-1H-pyrrole-2-
carboxylate (9e). From 10e (7 g), yellow solid (3.90 g,
75%). Mp 180 8C. IR (KBr): 3396; 3314; 3195; 2954; 1684;
1584 cm21. 1H NMR (CDCl3): 8.40 (br s, 1H, NH), 7.39 (d,
2Hphenyl, J¼8.8 Hz), 7.36 (d, 2Hphenyl, J¼8.8 Hz), 6.84 (s,
1Hthiophene), 7.21 (s, 1Hthiophene), 7.20 (d, 1Hthiophene,
J¼4.75 Hz), 6.88 (s, 1H, CHNH), 4.61 (br s, 2H, NH2),
3.86 (s, 3H, OCH3). 13C NMR (CDCl3): 160.50; 143.04;
134.08; 126.81; 125.99; 124.94; 121.62; 118.94; 109.16;
50.82. MS m/z: 222.1.
1H, CHNH), 4.35 (br s, 2H, NH2), 3.87 (s, 3H, OCH3). 13
C
NMR (CDCl3): 160.72; 143.52; 132.48; 131.95; 129.09;
128.29; 120.91; 113.77; 100.56; 50.87. MS m/z: 250.1.
Acknowledgements
3.3.6. Methyl 3-amino-4-(p-bromophenyl)-1H-pyrrole-2-
carboxylate (9f). From 10f (7.31 g), yellow solid (3.90 g,
69%). Mp 198 8C. IR (KBr): 3395; 3315; 3196; 1686;
1600 cm21. 1H NMR (CDCl3): 8.42 (br s, 1H, NH), 7.51 (d,
2Hphenyl, J¼8.2 Hz), 7.33 (d, 2Hphenyl, J¼8.2 Hz), 6.85 (s,
´ ´
´
We thank the French ‘Societe de Chimie Therapeutique’ for
a doctorant grant to Ch. R., the ‘Groupe de Recherche
Servier’ and Y. Dat for the recording of mass spectra.
1H, CHNH), 4.58 (br s, 2H, NH2), 3.87 (s, 3H, OCH3). 13
C
NMR (CDCl3): 160.72; 143.52; 132.96; 132.05; 131.80;
128.63; 120.79; 119.95; 113.79; 50.87. MS m/z: 295.9.
References and notes
3.3.7. Methyl 3-amino-4-(3,4-dichlorophenyl)-1H-pyr-
role-2-carboxylate (9g). From 10g (4 g), yellow solid
(2.05 g, 67%). Mp 170 8C. IR (KBr): 3392; 3310; 3206;
2951; 1668; 1565 cm21. 1H NMR (CDCl3): 8.38 (br s, 1H,
1. Xin, Z.; Oost, T. K.; Abad-Zapatero, C.; Hajduk, P. J.; Pei, Z.;
Szczepankiewicz, B. G.; Hutchins, C. W.; Ballaron, S. J.;
Stashko, M. A.; Lubben, T.; Trevillyan, J. M.; Jirousek, M. R.;
Liu, G. Bioorg. Med. Chem. 2003, 13, 1887–1890.
2. Lisowski, V.; Vu, D. N.; Feng, X.; Rault, S. Synthesis 2002, 6,
753–756.
NH), 7.45 (d, 2Hphenyl, J¼8.2 Hz), 7.29 (d, 2Hphenyl
,
J¼8.2 Hz), 6.86 (s, 1H, CHNH), 4.40 (br s, 2H, NH2),
3.86 (s, 3H, OCH3). 13C NMR (CDCl3): 160.72; 140.54;
134.19; 132.95; 131.06; 130.81; 129.90; 128.59; 127.20;
126.15; 112.68; 50.93. MS m/z: 285.1.
3. Lisowski, V.; Enguehard, C.; Lancelot, J. C.; Caignard, D. H.;
Lambel, S.; Leonce, S.; Pierre, A.; Atassi, G.; Renard, P.;
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4. (a) Altmann, E.; Missbach, M.; Widler, L.; Maibaum, J. K. WO
Patent 97/49706, 1997. (b) Normann, M. H.; Chen, N.; Chen,
Z.; Fotsch, C.; Hale, C.; Han, N.; Hurt, R.; Jenkins, T.;
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3.3.8. Methyl 3-amino-4-(3,4-dimethoxyphenyl)-1H-pyr-
role-2-carboxylate (9h). From 10h (3.85 g), off-white solid
(2.58 g, 85%). Mp 169 8C. IR (KBr): 3463; 3358; 3275;
1
1661; 1597 cm21. H NMR (CDCl3): 8.31 (br s, 1H, NH),
6.94 (m, 2Hphenyl), 6.86 (d, 1Hphenyl, J¼8.2 Hz), 6.77 (s, 1H,
CHNH), 4.53 (br s, 2H, NH2), 3.84 (s, 9H, OCH3). 13C
NMR (CDCl3): 162.32; 149.91; 147.48; 128.61; 128.52;
127.79; 126.73; 119.47; 114.65; 111.72; 110.73; 55.91;
55.84; 50.91. MS m/z: 276.1.
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3.3.9. Methyl 3-amino-4-(2-thienyl)-1H-pyrrole-2-car-
boxylate (9i). From 10i (1.64 g), brown solid (0.68 g,
57%). Mp 170 8C. IR (KBr): 3395; 3316; 3195; 2960; 1670;
1569 cm21. 1H NMR (CDCl3): 8.31 (br s, 1H, NH), 7.22 (d,
1Hthiophene, J¼5.0 Hz), 7.08 (m, 2Hthiophene), 6.91 (s, 1H,
CHNH), 3.87 (s, 3H, OCH3), 3.51 (br s, 2H, NH2). 13C
NMR (CDCl3): 160.50; 144.57; 137.25; 125.70; 125.27;
123.41; 123.19; 122.71; 112.61; 50.87. MS m/z: 222.1.
7. Elliot, A. J.; Morris, P. E.; Petty, S. L.; Williams, C. H. J. Org.
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