Preparation of derivatives of 2-cyano-3-(5-n-arylamino-or 5-N-alkyl-N-phenylamino-2-furyl)propenoic acids

Article abstract of DOI:10.1135/cccc19971105

(5-Bromo-2-furyl)methylidenemalonodinitrile (1) reacted with substituted aromatic amines under formation of (5-N-arylamino-2-furyl)methylidenemalonodinitriles 2a-2h whereas no reaction was observed with N-alkyl-N-phenylamines. Derivatives of 2-cyano-3-(5-

Full text of DOI:10.1135/cccc19971105

3-(5-Amino-2-furyl)propenoic Acid
1105
PREPARATION OF DERIVATIVES OF 2-CYANO-3-(5-N-ARYLAMINO-
OR 5-N-ALKYL-N-PHENYLAMINO-2-FURYL)PROPENOIC ACIDS
a1
a2
b
c
Peter SAFAR , Frantisek POVAZANEC , Pavel CEPEC and Nada PRONAYOVA
a Department of Organic Chemistry, Slovak Technical University, 812 37 Bratislava, Slovak
Republic; e-mail: 1 safar@chelin.chtf.stuba.sk, 2fpovazan@chelin.chtf.stuba.sk
b Wood Research Institute, 841 05 Bratislava, Slovak Republic; e-mail: cepec_p@computel.sk
c Central Laboratory, Slovak Technical University, 812 37 Bratislava, Slovak Republic;
e-mail: pronayov@cvt.stu.stuba.sk
Received July 25, 1996
Accepted December 11, 1996
(5-Bromo-2-furyl)methylidenemalonodinitrile (1) reacted with substituted aromatic amines under for-
mation of (5-N-arylamino-2-furyl)methylidenemalonodinitriles 2a–2h whereas no reaction was ob-
served with N-alkyl-N-phenylamines. Derivatives of 2-cyano-3-(5-N-alkyl-N-phenylamino-2-furyl)-
propenoic acid 5a–5o were prepared by reaction of the corresponding N-alkylanilines with 5-bromo-
2-furancarbaldehyde, followed by hydrolysis of the obtained Eiji salts and reaction with malonic acid
derivatives.
Key words: 3-(5-Amino-2-furyl)propenoic acid.
3-(5-N-Substituted amino-2-furyl)propenoic acids are usually prepared by reaction of
the corresponding 5-amino-2-furancarbaldehydes with active methylene compounds or
by nucleophilic substitution of activated 3-(5-N-substituted-2-furyl)propenoic acids
with aliphatic secondary amines1–5. So far, only little attention has been paid to the
preparation of 3-(5-N-arylamino- or 5-N-alkylphenylamino-2-furyl)propenoic acids be-
cause the starting 5-N-arylamino- or 5-N-alkyl-N-phenylamino-2-furancarbaldehydes
are not very stable and they are therefore unsuitable as precursors for obtaining propene
derivatives. 5-N-Phenylamino-2-furancarbaldehyde, is stable only as its acetyl deriva-
tive6, 5-N-methylphenylamino- or 5-N-ethylphenylamino-2-furancarbaldehyde were
isolated in low yields using a complicated procedure7,8. Nucleophilic substitution reac-
tion of 3-(5-bromo-2-furyl)propenoic acids with N-alkylamines does not take place.
RESULTS AND DISCUSSION
Reaction of compound 1 with two moles of aniline (Scheme 1) afforded two products
1
which were identified by H NMR analysis as (5-N-phenylamino-2-furyl)methylidene-
malonodinitrile (2a) and ketimine 3 (Eiji product). The latter had identical physical and
spectral properties as the compound prepared according to the literature6. The ratio of
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

1106
Safar, Povazanec, Cepec, Pronayova:
these products depended on the molar quantity of the aniline used. We assumed that
originally the reaction gives the product 2a which on addition of aniline and elimina-
tion of malonic acid affords the Eiji product 3.
We have found that addition of a small amount of malonodinitrile suppressed the
formation of the Eiji product 3 and the reaction afforded exclusively the product 2a.
Compound 1 reacted with substituted anilines in the presence of malonodinitrile to give
various substituted N-arylamino derivatives 2a–2g. The reaction course was influenced
by the solvent. The ketimine 3 was not formed in nonpolar solvents such as 1,4-dioxane
or 1,2-dimethoxyethane, however, the reaction time was extremely long (several days
to several weeks). In protic, as well as polar aprotic, solvents (acetonitrile, dimethylfor-
mamide, ethyl acetate) the reaction gave both compounds 2a and 3. No reaction with
aliphatic amines was observed, except with benzylamine which gave (5-N-benzyl-
amino-2-furyl)methylidenemalonodinitrile (2h) in high yield (Scheme 1). In contrast,
compound 1 did not react with N-alkyl-N-phenylamines.
Compound 3 was alkali hydrolyzed and, without isolation, subjected to reaction with
compounds containing active methylene group (malonodinitrile, methyl cyanoacetate
or cyanoacetamide) which resulted in aromatization of the 2,5-dihydrofuran nucleus
and gave compounds 2a, 4a, 4b (Scheme 1).
Derivatives 5a–5o were prepared by reaction of 5-bromo-2-furancarbaldehyde with
two moles of an N-alkyl-N-phenylamine (Scheme 2). However, we were not able to
NC
NC
Ar NH
2
Br
CN
Ar NH
CN
O
O
H
H
1
2a-2h
+
9
4
3
2
NC
1
7
6
R
CH CN
2
1
5
R
8
C H NH
Ar
N
H
CH NH Ar Br
2
O
1
O
6
5
H
3
2a, 4a, 4b
1
R
R
R
= CN
= COOCH
= CONH
2
In f ormulae
Ar
C H
2a,
4a,
4b,
2
a
1
1
3
6
5
4-Br-C H
b
c
d
e
6
4
4
4
4
2-Cl-C H
6
3-Cl-C H
6
4-Cl-C H
6
3,4-diCl-C H
f
6
3
g
4-F-C H
6
4
C H -CH
2
h
6
5
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

3-(5-Amino-2-furyl)propenoic Acid
1107
isolate the arising ketimine 3 even in the form of its perchlorate, as described in the
case of secondary aliphatic amines9. Therefore, we hydrolyzed the ketimine directly in
the reaction mixture and the liberated 5-N-alkyl-N-phenylamino-2-furancarbaldehyde
was treated in situ with malonic acid derivatives under formation of the corresponding
derivatives 5a–5o.
1) C H NHR
6
5
NC
2) CH ONa
3
1
1
Br
CHO
C H
6
N
R
R
R
3) NC CH
O
O
5
2
H
5a-5o
1
R
R
5
CH
CN
CN
CN
CN
CN
a
3
CH CH
b
c
3
2
CH (CH )
3
2 2
CH (CH )
d
e
3
2 3
(CH ) CH
3 2
CH
3
COOCH
COOCH
COOCH
COOCH
COOCH
f
g
3
3
3
3
3
CH CH
3
2
CH (CH )
h
3
2 2
CH (CH )
i
j
3
2 3
(CH ) CH
3 2
k
l
CH
CONH
CONH
CONH
CONH
CONH
3
2
2
2
2
2
CH CH
3
2
m
CH (CH )
3
2 2
CH (CH )
n
o
3
2 3
(CH ) CH
3 2
SCHEME 2
The reaction mixture was hydrolyzed using various bases. Hydrolysis with 10%
NaOH, followed by reaction with malonic acid derivatives, afforded products 5a–5o in
yields of 10–18%, with triethylamine the yields amounted to 20–32%. Although hydro-
lysis with morpholine gave good yields (66–84%), the desired products were accompa-
nied by the corresponding (5-morpholin-4-yl-2-furyl)methylidenemalonodinitrile which
could be removed only by chromatography. The reagent of choice appeared to be sodium
methoxide that gave yields 58–94% (Table I). The low yields found for N-isopropyl-
aniline are apparently due to the bulkiness of the nucleophile.
The 1H NMR spectra of compounds 2a, 4a and 4b exhibit signals of protons H-3 and
H-4. Compared with the spectrum of (5-amino-2-furyl)methylidenemalonodinitrile10
(7.38, H-3; 5.66, H-4 and 7.06, H-6), the signals of the corresponding protons in com-
pounds 2a, 4a and 4b are considerably shifted. Similar spectral characteristics were
observed also for substituted (5-N-arylamino-2-furyl)methylidenemalonodinitrile deri-
vatives (Table II). The H-6 proton signal was observed at 7.51–7.29, H-3 proton signals
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

1108
Safar, Povazanec, Cepec, Pronayova:
Calculated/Found
TABLE I
Characteristic data of compounds 2a–2g, 4a, 4b, 5a–5o
M.p., °C
Yield, %
Formula
M.w.
Compound
% C
% H
% N
2a
2ba
2cb
2dc
2ed
2fe
2g
4a
4b
5a
5b
5c
188–190
88
C14H9N3O
71.48
71.38
3.86
3.79
17.86
18.01
235.2
201–204
73
C14H8BrN3O
314.1
53.53
53.48
2.57
2.55
13.38
13.51
200–202
72
C14H8ClN3O
269.7
62.35
62.26
2.99
2.93
15.58
15.69
182–183
70
C14H8ClN3O
269.7
62.35
62.22
2.99
2.91
15.58
15.68
168–170
70
C14H8ClN3O
269.7
62.35
62.29
2.99
3.02
15.58
15.70
200–202
71
C14H7Cl2N3O
304.1
55.29
55.18
2.32
2.29
13.82
13.90
201–204
74
C14H8FN3O
253.2
66.40
66.28
3.18
2.99
16.59
16.71
172–174
90
C15H12N2O3
268.3
67.16
67.08
4.51
4.52
10.44
10.50
209–211
91
C14H11N3O2
253.3
66.40
66.31
4.38
4.33
16.59
16.71
134–135
86
C15H11N3O
249.3
72.28
72.10
4.45
4.56
16.86
16.73
96–98
80
C16H13N3O
263.3
72.99
72.83
4.98
4.83
15.96
15.87
103–105
90
C17H15N3O
277.3
73.63
73.48
5.45
5.50
15.15
15.02
5d
5e
228–230
84
C18H17N3O
291.4
74.20
73.98
5.88
5.71
14.42
14.29
123–125
57
C17H15N3O
277.3
73.63
73.81
5.45
5.51
15.15
15.37
5f
109–110
90
C16H14N2O3
282.3
68.07
67.91
5.00
4.92
9.92
9.78
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

3-(5-Amino-2-furyl)propenoic Acid
1109
TABLE I
(Continued)
Calculated/Found
% H
M.p., °C
Compound
Formula
M.w.
Yield, %
% C
% N
5g
5h
5i
139–141
82
C17H16N2O3
296.3
68.91
69.03
5.44
5.49
9.45
9.58
142–144
81
C18H18N2O3
310.4
69.66
69.51
5.85
5.91
9.03
8.96
104–106
93
C19H20N2O3
324.4
70.35
70.41
6.21
6.10
8.64
8.77
5j
106–108
64
C18H18N2O3
310.4
69.66
69.53
5.85
5.94
9.03
8.95
5k
5l
201–203
94
C15H13N3O2
267.3
67.40
67.32
4.90
4.98
15.72
15.80
197–199
87
C16H15N3O2
281.3
68.31
68.19
5.37
5.46
14.94
14.81
5m
5n
5o
202–204
92
C17H17N3O2
295.3
69.14
69.91
5.80
5.72
14.23
14.10
174–175
89
C18H19N3O2
309.4
69.88
69.71
6.19
6.26
13.58
13.66
217–219
71
C17H17N3O2
295.3
69.14
69.27
5.80
5.71
14.23
14.37
a Calculated: 25.44% Br, found: 25.39% Br. b Calculated: 13.14% Cl, found: 13.19% Cl. c Calculated:
13.14% Cl, found: 13.29% Cl. d Calculated: 13.14% Cl, found: 13.21% Cl. e Calculated: 23.31% Cl,
found: 23.25% Cl.
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

1110
Safar, Povazanec, Cepec, Pronayova:
TABLE II
1H NMR spectra of compounds 2a–2g, 4a, 4b, 5a–5o
Compound
H-3, d
H-4, d
H-6, s
3J(3,4)
Aromatic protons
2a
7.54
7.46
7.57
7.48
7.46
7.59
7.47
7.64
7.60
7.44
7.13
7.40
7.40
6.95
7.40
7.28
7.41
7.40
6.91
7.38
7.31
7.28
7.25
6.88
6.08
6.03
6.06
6.06
6.03
6.09
6.00
6.01
5.86
5.73
5.58
5.55
5.68
5.18
5.70
5.53
5.49
5.48
5.21
5.69
5.48
5.44
5.41
5.01
7.48
7.40
7.48
7.51
7.49
7.44
7.44
7.65
7.60
7.31
7.95
7.26
7.53
7.55
7.65
7.61
7.59
7.58
8.03
7.70
7.66
7.64
7.61
7.88
4.0
4.0
4.1
4.0
4.0
4.1
4.2
4.0
4.0
4.2
4.2
4.2
4.2
4.0
4.2
4.2
4.2
4.2
4.0
4.2
4.2
4.2
4.2
4.0
7.05–7.46 m, 5 H
7.30–7.43 m, 4 H
7.40–7.55 m, 4 H
7.01–7.45 m, 4 H
7.01–7.83 m, 4 H
7.38–7.58 m, 3 H
7.08–7.56 m, 4 H
6.25–7.62 m, 5 H
6.75–7.38 m, 7 H
7.50–7.60 m, 5 H
7.40–7.71 m, 5 H
7.53 s, 5 H
2b
2ca
2d
2eb
2fc
2gd
4ae
4bf
5ag
5bh
5ci
5dj
5ek
5fl
7.71 s, 5 H
7.32–7.62 m, 5 H
7.51–7.63 m, 5 H
7.50 s, 5 H
5gm
5hn
5io
5jp
5kr
5ls
5mt
5nu
5ov
7.51 s, 5 H
7.52 s, 5 H
7.41–7.61 m, 5 H
7.53–7.70 m, 5 H
7.51 s, 5 H
7.52 s, 5 H
7.41 s, 5 H
7.10–7.62 m, 5 H
Other signals: a 11.19 brs, 1 H (NH); b 10.50 brs, 1 H (NH); ; c 11.21 brs, 1 H (NH); d 11.10 brs, 1 H (NH);
e 3.71 s, 3 H (OCH3); 10.80 brs, 1 H (NH); f 10.31 brs, 1 H (NH); g 3.69 s, 1 H (CH3N); h 1.30 t,
3
3
3 H, J = 7.0 (CH3CH2N); 4.08 q, 2 H, J = 7.0 (CH3CH2N); i 1.70 m, 2 H (CH2); 0.96 t, 3 H (CH3);
1.23–1.88 m, 2 H (CH2); j 1.70 m, 2 H (CH2); 0.96 t, 3 H (CH3); 1.23–1.80 m, 2 H (CH2); 4.15 t, 2 H
(CH2); k 1.26–1.34 d, 6 H (2 × CH33); 4.60–4.92 m, 1 H (CH); l 3.68 s, 3 H (CH3N); 4.79 s, 3 H (CH3O);
m 3.80 s, 3 H (CH3O); 1.30 t, 3 H, J = 7.0 (CH3CH2N); 4.08 q, 2 H, J = 7.0 (CH3CH2N); n 3.77 s, 3 H
3
(CH3O); 4.03 t, 2 H (CH2); 1.73 m, 2 H (CH2); 0.96 t, 3 H (CH3); o 3.75 s, 3 H (CH3O); 4.05 t, 2 H
(CH2); 1.30–1.91 m, 4 H (2 × CH2); 0.89 t, 3 H (CH3); p 3.77 s, 3 H (CH3O); 4.60–4.91 m, 1 H (CH);
1.28–1.35 d, 6 H (2 × CH3); 3.65 s, 3 H (CH3N); 6.72 m, 2 H (NH2); 1.30 t, 3 H, 3J = 7.0
(CH3CH2N); 4.08 q, 2 H, 3J = 7.0 (CH3CH2N); 7.08 m, 2 H (NH2); t 0.96 t, 3 H (CH3); 1.65 m, 2 H (CH2);
4.00 t, 2 H (CH2); 7.08 m, 2 H (NH2); u 0.89 t, 3 H (CH3); 6.60 m, 2 H (NH2); v 1.13–1.21 d, 6 H
(2 × CH3); 4.31–4.73 m, 1 H (CH).
r
s
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

3-(5-Amino-2-furyl)propenoic Acid
1111
at 7.59–7.40 and H-4 proton signals at 6.09–5.86. For compounds 2a, 2h and 5k we
measured also 13C NMR spectra. The signals of protons C-2 to C-9 were assigned on
the basis of ref.10 and a standard NOE spectrum.
The trans-relation of the H-6 atom and the CN group in compounds 5f–5o can be
derived from the vicinal coupling constants 3J(C≡N,H-6) = 12.4 and 3J(C=O,H-6) = 5.6
TABLE III
Spectral properties of compounds 2a–2g, 4a, 4b, 5a–5o
IR spectra
Compound
UV spectra
ν(NH)
ν(CN)
ν(C=C)
2a
2b
2c
2d
2e
2f
236 (3.25)
465 (3.87)
468 (3.65)
458 (3.72)
469 (3.70)
472 (3.56)
466 (3.62)
469 (3.71)
464 (3.95)
458 (3.27)
462 (3.02)
464 (2.95)
464 (3.13)
465 (3.02)
461 (3.10)
462 (3.14)
461 (3.10)
462 (3.07)
462 (3.11)
461 (3.02)
457 (3.03)
458 (3.02)
458 (3.04)
459 (3.11)
458 (3.01)
3 280
3 250
3 303
3 290
3 230
3 235
3 255
3 280
3 310
2 220a
2 198a
2 196a
2 197a
2 196a
1 698b
1 690b
1 691b
1 701b
1 730b
1 684b
1 680b
1 676b
1 672b
1 672b
2 190
2 210
2 200
2 201
2 195
2 205
2 195
2 210
2 200
2 218
2 210
2 202
2 202
2 210
2 205
2 204
2 202
2 208
2 200
2 202
2 210
2 220
2 221
2 200
1 635
1 640
1 628
1 640
1 635
1 645
1 635
1 610
1 620
1 625
1 642
1 625
1 628
1 631
1 621
1 620
1 622
1 626
1 620
1 638
1 628
1 627
1 630
1 630
266 (3.32)
255 (3.28)
263 (3.36)
258 (3.18)
252 (3.22)
261 (3.31)
267 (3.59)
269 (3.57)
220 (2.46)
229 (2.44)
231 (2.47)
273 (2.63)
254 (2.53)
228 (2.43)
230 (2.47)
228 (2.43)
274 (2.49)
249 (2.53)
229 (2.41)
231 (2.43)
229 (2.46)
273 (2.51)
271 (2.46)
2g
4a
4b
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
a Related to the absorption of CN group, ν(CN). b Related to the absorption of CO group, ν(CO).
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

1112
Safar, Povazanec, Cepec, Pronayova:
in the spectrum of compound 5k. The marked downfield shift of the H-4 proton signal
in compounds 5e, 5j and 5o as compared with compounds 5d, 5i and 5n is probably
connected with the bulkiness of the isopropyl group.
Electron spectra of compounds 5a–5o (Table III) exhibit an absorption band at 220–274 nm
due to the π→π* electron transition of the aromatic and furan nuclei. Another intense
band, in the visible region, at 457–464 nm, corresponds to the n→π* transition of the
whole system. The IR spectra display characteristic vibrational bands of CN groups at
2 196–2 218 cm–1. In some cases this band is split, showing a nonequivalence of the
CN groups in the molecule, probably due to their orientation in the solid state (KBr
technique).
EXPERIMENTAL
The melting points were determined on a Boetius block and are uncorrected. Infrared spectra were
recorded on a PU 9800 FTIR Philips spectrometer using KBr technique (0.3 mg of compound/300 mg
KBr), calibration with polystyrene foil. Ultraviolet spectra (λmax, log ε) were measured on an M-40
1
(Zeiss, Jena) spectrophotometer in methanol, concentration 2 . 10–5 mol/dm3. H and 13C NMR spec-
tra (δ, ppm; J, Hz) were taken on a Varian VXR-300 spectrometer at 25 °C in hexadeuteriodimethyl
sulfoxide with tetramethylsilane as internal standard. The purity of the products and the reaction
course were monitored by TLC on Silufol (Merck), detection with iodine vapours and UV light.
(5-N-Benzylamino-2-furyl)methylidenemalonodinitrile (2h)
A mixture of (5-bromo-2-furyl)methylidenemalonodinitrile (1; 1.95 g, 0.01 mol), benzylamine (2.15 g,
0.02 mol) and methanol (20 ml) was refluxed for 1 h. After addition of water (10 ml) the mixture
was set aside for 12 h at room temperature. The deposited compound was collected, washed with
aqueous methanol and dried. Crystallization from methanol afforded 2.14 g (86%) of compound 2h,
m.p. 200–202 °C. UV spectrum: 455 (3.87). IR spectrum: 1 635 (CO), 2 190 (CN), 3 280. For
C15H11N3O (249.3) calculated: 72.28% C, 4.45% H, 16.86% N; found: 72.03% C, 4.37% H, 16.98% N.
3
1H NMR spectrum: 4.50 brs, 2 H (CH2N); 5.79 d, 1 H, J(3,4) = 4.2 (H-4); 7.13 s, 1 H (H-6); 7.36 d,
3
1 H, J(4,3) = 4.2 (H-3); 7.18–7.40 m, 5 H (phenyl). 13C NMR spectrum: 46.0 (Ar-CH2), 53.5 (C-7),
96.4 (C-4), 117.3 (C-9), 118.5 (C-8), 133.9 (C-3), 136.5 (C-6), 139.5 (C-2), 165.6 (C-5), 127.6,
127.8, 128.6 and 137.7 (phenyl).
(5-N-Arylamino-2-furyl)methylidenemalonodinitriles 2a–2g
Nitrile 1 (1.95 g, 0.01 mol) and malonodinitrile (0.2 g, 0.003 mol) were dissolved in boiling methanol
(20 ml) and a solution of the corresponding aromatic amine (0.02 mol) in methanol (5 ml) was added
in one portion. The mixture was refluxed until the starting compounds reacted completely (2–5 h,
monitoring by TLC). Water (10 ml) was added and the mixture was allowed to stand at room tem-
perature for 12 h. The product was collected by filtration, washed with aqueous methanol, dried and
purified by crystallization from methanol. The physicochemical characteristics of the obtained deriva-
tives are given in Tables I–III. 13C NMR spectrum of compound 2a: 57.1 (C-7), 96.4 (C-4), 116.6
(C-9), 117.8 (C-8), 135.1 (C-3), 135.6 (C-6), 140.6 (C-2), 161.0 (C-5), 118.8, 123.6, 129.4 and 137.5
(phenyl).
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

3-(5-Amino-2-furyl)propenoic Acid
1113
Nitrile, Methyl Ester and Amide of 2-Cyano-3-(5-N-phenylamino-2-furyl)propenoic Acid
(2a, 4a and 4b)
The corresponding derivative of malonic acid (0.0021 mol; 138 mg of malonodinitrile, 208 mg of
methyl cyanoacetate or 177 mg of cyanoacetamide) was added in one portion to a vigorously stirred
solution of compound 3 (hydrate; 0.75 g, 0.002 mol; prepared according to ref.6) in 80% methanol
(10 ml). After stirring at room temperature for 5 h, the precipitate was filtered, washed with dilute
methanol, dried and purified by crystallization from dimethyl sulfoxide. The physicochemical charac-
teristics of the products 2a, 4a and 4b are given in Tables I–III.
Nitriles, Methyl Esters and Amides of 2-Cyano-3-(5-N-Alkyl-N-phenylamino-2-furyl)propenoic
Acids 5a–5o
The appropriate secondary amine (0.022 mol; 2.36 g of N-methyl-N-phenylamine; 2.67 g of N-ethyl-
N-phenylamine; 2.97 g of N-phenyl-N-propylamine; 2.97 g of N-phenyl-N-isopropylamine or 3.28 g
of N-butyl-N-phenylamine) was added to a solution of 5-bromo-2-furancarbaldehyde (1.75 g, 0.01 mol)
in methanol (10 ml) and the mixture was refluxed until the 5-bromo-2-furancarbaldehyde reacted
completely (1–5 h, monitored by TLC). The reaction mixture was cooled to 5 °C and sodium meth-
oxide (0.56 g, 0.011 mol) in methanol (5 ml) and water (2 ml) was added. After stirring at room
temperature for 1 h, the corresponding malonic acid derivative (0.012 mol; 0.79 g of malonodinitrile;
1.19 g of methyl cyanoacetate; 1.0 g of cyanoacetamide) was added and stirring was continued for 2 h.
The reaction mixture was then set aside at 0 °C for 5 h, the precipitate was collected, washed with
ice-cold methanol, dried and purified by crystallization from methanol. The physicochemical charac-
teristics of the products 5a–5o are given in Tables I–III. 13C NMR spectrum of compound 5k: 34.8
1
1
(CH3N); 89.3 (C-7); 91.7, J(C-H) = 181.9 (C-4); 118.4, 3J(C-H,CN) = 12.4 (C-9); 130.6, J(C-H) =
1
3
179.9 (C-3); 130.0, J(C-H) = 161.3 (C-6); 142.9 (C-2); 160.8 (C-5); 164.2, J(C=O,H-6) = 5.6 (C-8);
123.2; 125.5; 129.5 and 139.9 (phenyl).
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Collect. Czech. Chem. Commun. (Vol. 62) (1997)