Synthesis of novel N-aryl-2,5-dihydro-2-iminofuran-3-carboxamides and their chemical transformations

Article abstract of DOI:10.1007/s00706-011-0615-2

Novel N-aryl-2,5-dihydro-2-iminofuran-3-carboxamides have been synthesized by condensation of tertiary α-hydroxyketones with N-aryl-2- cyanoacetamides· The obtained products were transformed to corresponding iminium chlorides, hydrogen sulfates, 2-oxo and

Full text of DOI:10.1007/s00706-011-0615-2

Monatsh Chem (2012) 143:687–694
DOI 10.1007/s00706-011-0615-2
ORIGINAL PAPER
Synthesis of novel N-aryl-2,5-dihydro-2-iminofuran-3-
carboxamides and their chemical transformations
Lusine Karapetyan
Received: 11 August 2010 / Accepted: 5 August 2011 / Published online: 1 September 2011
Ó Springer-Verlag 2011
Abstract Novel N-aryl-2,5-dihydro-2-iminofuran-3-car-
boxamides have been synthesized by condensation of
tertiary a-hydroxyketones with N-aryl-2-cyanoacetamides.
The obtained products were transformed to corresponding
iminium chlorides, hydrogen sulfates, 2-oxo and 2-(dicy-
anomethylene) derivatives. All new compounds were
characterized by NMR and IR spectral data and elemental
analysis.
In this paper, I report the condensation of tertiary a-
hydroxyketones with other compounds containing active
methylene groups, viz., N-aryl-2-cyanoacetamides, in the
presence of sodium methoxide affording N-aryl-2,5-dihy-
dro-2-iminofuran-3-carboxamides. The reactions reported
herein proceed under mild conditions, and the starting
materials are readily available.
Keywords Tertiary a-hydroxyketones Á
2,5-Dihydrofuran Á Cyanoacetamides Á
Sodium methoxide Á Malononitrile
Results and discussion
The condensation of tertiary a-hydroxyketones 1a, 1b
(1 eq) with N-aryl-2-cyanoacetamides 2a–2d (1 eq) in the
presence of sodium methoxide (0.1 eq) in dry methanol at
35–40 °C for 5 h afforded N-aryl-2,5-dihydro-2-imino-
furan-3-carboxamides 3a–3d and N-aryl-4-methyl-2-oxo-
1-oxaspiro[4.5]dec-3-ene-3-carboxamides 4a–4d in high
yields (Scheme 1).
Introduction
2,5-Dihydro-2-oxofuran derivatives are a large family of
heterocycles that include synthetically useful compounds,
several natural products [1–15], and a number of drugs
with diverse biological activities such as antifungal, anti-
bacterial, and anti-inflammatory properties [16–20]. Thus,
there has been a continuous interest in the development of
efficient and convenient methods for the preparation of
these heterocycles and in their applications [11–15, 21–23].
One of the most convenient and common methods of
synthesis of functionalized 2,5-dihydro-2-oxofurans is the
condensation of a-hydroxyketones with compounds con-
taining active methylene groups (dimethyl malonate, ethyl
cyanoacetate, ethyl acetoacetate) in basic conditions [20,
24, 25].
The structures of synthesized compounds 3a–3d and
4a–4d were apparent from IR and NMR spectra and
their chemical transformations. The IR, H, and 13C NMR
1
spectroscopic data are in agreement with the proposed
structures. The IR spectra of compounds 3a–3d and 4a–4d
ꢀ
showed bands at m = 1,630–1,650 (C=N) and
3,240–3,254 cm-1 (=N–H). The 1H NMR spectra of
compounds 3a–3d and 4a–4d exhibited a singlet identified
as C=NH proton (d = 7.21–7.23 ppm). The 13C NMR
spectra of 3a–3d and 4a–4d exhibited 11–13 and 13–15
signals, respectively, in agreement with the proposed
structures.
The suggested mechanism for the formation of imino-
lactones 3a–3d and 4a–4d begins by the addition of the
hydroxyl group on the nitrile group followed by a Knoe-
venagel condensation leading to ring formation according
to Scheme 1. It was noticed that the ease of ring formation
L. Karapetyan (&)
Chemistry Department, Yerevan State University,
1, A. Manoukyan Str, 0025 Yerevan, Armenia
e-mail: lousine_karapetyan@yahoo.com
123

688
L. Karapetyan
H3C
CONHR1
CN
Scheme 1
O
CONHR1
H3C
O
H2C CONHR1
NH
H3C
H2C
C
R2
R3
CH3ONa, CH3OH
35-40 °C, 5h
+
R2
R3
R2
R3
OH
NH
O
O
1a, 1b
2a-2d
3a-3d
4a-4d
1a: R2=R3=CH3
: R1 = C6H5
: R1 = 4-MeC6H4
2a
1b: R2,R3=(CH2)5
2b
2c: R1 = 2,6-(Me)2C6H3
2d: R1 = 2,4-(Me)2C6H3
CONHR1
CONHR1
O
COOH
Scheme 2
H3C
R2
R3
H3C
H3C
H2O, pH 4-5
with aq.HCl
20% aq. H2SO4
75-80 °C, 3h
R2
R3
H3C
H3C
85-90 °C, 3 h
NH
O
O
O
O
3a 3d
5a 5d
7a
-
-
4a 4d
6a 6d
-
-
was due to the presence of a gem-dialkyl producing a Thorpe-
Ingold conformational effect [26–28], which states that alkyl
substitution on a central methylene causes compression of the
internal angle, leading to an easier ring formation. Le Bigot
etal. havereported[29, 30] a reactionclose tothe formation of
iminolactones: the formation of iminocoumarin by the con-
densation of nitrile with salicylaldehyde.
NaOH) and easily transform to 2-iminoderivatives 3a–3d
and 4a–4d upon treatment with potassium carbonate.
Iminium salts 8a–8d, 9a–9d, and 10a–10d are readily
hydrolyzed in aqueous solution for 2 h resulting in lactones
5a–5d and 6a–6d.
Further study of chemical transformations of 2-imino-
lactones 3a–3d and 4a–4d showed that, as expected, they
were very reactive compounds and readily perform reactions
of NH-group substitution. Thus, the reaction with malono-
nitrile readily and in high yields affords condensation
products N-aryl-2-(dicyanomethylene)-2,5-dihydrofuran-3-
carboxamides 11a–11d and 12a–12d at the expense of the
methylene group of malononitrile (Scheme 5).
2-Iminolactones 3a–3d and 4a–4d are readily hydro-
lyzed with aqueous hydrochloric acid (at pH 4–5) for 3 h
with formation of N-aryl-2,5-dihydro-2-oxofuran-3-car-
boxamides 5a–5d and 6a–6d (Scheme 2). Further
hydrolysis of the amide group under more rigid conditions
(upon heating the reaction mixture in the presence of sul-
furic acid) was also carried out in 5a as one example. That
resulted in 2,5-dihydro-4,5,5-trimethyl-2-oxofuran-3-car-
boxylic acid (7a) [31]. The rearrangement of furan
derivatives 3a–3d and 4a–4d to pyrrole derivatives in
concentrated sulfuric acid was not observed (Scheme 3).
The novel 2-iminoderivatives 3a–3d and 4a–4d readily
form iminium salts (hydrochlorides 8a–8d and 9a–9d and
hydrogen sulfates 10a–10d) with mineral acids (both with
HCl and H2SO4, pH 1–2) (Scheme 4). Iminium hydro-
chlorides 8a–8d and 9a–9d have also been obtained by
passing gaseous hydrogen chloride through a benzene
solution of 2-iminolactones 3a–3d and 4a–4d. Iminium
salts 8a–8d, 9a–9d, and 10a–10d are water-soluble com-
pounds and are readily titrated by alkali solution (0.1 N
Conclusion
Herein I report synthesis of novel N-aryl-2,5-dihydro-2-
iminofuran-3-carboxamides 3a–3d and 4a–4d via a simple
and convenient method by condensation of tertiary a-
hydroxyketones with N-aryl-2-cyanoacetamides under mild
basic conditions. The obtained products were transformed to
corresponding iminium chlorides, hydrogen sulfates, 2-oxo
and 2-(dicyanomethylene) derivatives. The structures of
synthesized compounds 3a–3d and 4a–4d were character-
ized by IR, 1H, and 13C NMR spectral data. The performed
chemical reactions of the compounds 3a–3d and 4a–4d
confirmed that compounds 3a–3d and 4a–4d are imi-
nodihydrofurans and not pyrrolinones, which are isomeric to
them.
CONHR1
O
CONHR1
NH
H3C
H3C
H2SO4
R2
R3
R2
R3
N
H
O
Experimental
3a 3d
4a 4d
-
-
All solvents were dried by standard methods. Melting
points were measured with an Electrothermal 9100
Scheme 3
123

Synthesis of novel N-aryl-2,5-dihydro-2-iminofuran-3-carboxamides
689
CONHR1
NH. HCl
Scheme 4
H3C
R2
R3
CONHR1
H3C
O
CONHR1
O
H3C
R2
R3
8a-8d
4
0
9a 9d
R2
R3
-
%
NH
a
q
O
.
CONHR1
H
H3C
S
O
O
3a
3d
-
R2
R3
5a-5d
6a-6d
NH. H2SO4
O
10a 10d
-
K2CO3
8a-8d
9a 9d
3a-3d
4a 4d
-
-
10a-10d
0.1 n NaOH
CONHR1
CONHR1
H3C
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-phenylfuran-3-car-
boxamide (3a, C14H16N2O2)
Prepared from 1.02 g 1a and 1.6 g 2-cyano-N-phenylacet-
CN
CN
H3C
EtOH,room temp.
reflux
R2
R3
+
R2
R3
CN
CN
NH
-NH3
O
O
amide (2a). White crystals; yield 95%; m.p.: 144–145 °C;
3a 3d
4a 4d
11a 11d
-
12a 12d
-
-
-
ꢀ
Rf = 0.52 (acetone/benzene1:2); IR: m = 3,300 (NH), 3,240
(NH), 1,680 (C=O), 1,640 (C=N), 1,620 (C=C), 1,600–1,500
(Ar) cm-1; 1H NMR (DMSO-d6/CCl4 1:3): d = 1.42 (s, 6H,
2CH3), 2.35 (s, 3H, CH3), 7.21 (s, 1H, =NH), 7.34–7.45 (m,
5H, Ar–H), 11.35 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/
CCl4 1:3): d = 11.81, 24.16, 87.64, 118.26, 126.28, 126.89,
127.78, 138.43, 160.41, 166.21, 170.77 ppm.
Scheme 5
apparatus. Elemental analyses (C, H, and N) were per-
formed using a Heraeus CHN-O-Rapid analyzer, and
results agreed with calculated values. IR spectra were
recorded on a Specord 751 R spectrometer in Vaseline oil.
1H NMR and 13C NMR spectra were recorded on a Varian
Mercury-300 VX spectrometer at 300 and 75.46 MHz,
respectively. NMR spectra were obtained in DMSO-d6/
CCl4 1:3 solutions and are reported as parts per million
(ppm) downfield from tetramethylsilane as internal stan-
dard. The abbreviations used are singlet (s), bs (broad
singlet), doublet (d), triplet (t), and multiplet (m). The
purity of synthesized compounds was controlled by means
of thin-layer chromatography (TLC) on Silufol UV-25
plates, eluent acetone/benzene 1:2, developed by iodine
vapors.
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-(4-methyl-
phenyl)furan-3-carboxamide (3b, C15H18N2O2)
Prepared from 1.02 g 1a and 1.74 g 2-cyano-N-(4-methyl-
phenyl)acetamide (2b). White crystals; yield 93%; m.p.:
139–140 °C; Rf = 0.54 (acetone/benzene 1:2); IR:
ꢀ
m = 3,300 (NH), 3,240 (NH), 1,680 (C=O), 1,640 (C=N),
1
1,620 (C=C), 1,600–1,500 (Ar) cm-1; H NMR (DMSO-
d6/CCl4 1:3): d = 1.48 (s, 6H, 2CH3), 2.28 (s, 3H,
Ar–CH3), 2.40 (s, 3H, CH3), 7.21 (s, 1H, =NH), 7.34 (d,
2H, J = 8.0 Hz, Ar–H), 7.45 (2H, d, J = 8.0 Hz, Ar–H),
9.88 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3):
d = 11.81, 22.96, 24.16, 87.64, 118.26, 126.28, 126.89,
127.78, 138.43, 160.41, 166.21, 170.77 ppm.
The syntheses of compounds 1a, 1b were conducted
according to known procedures [32] and compounds 2a–2d
were prepared by the reaction of ethyl cyanoacetate with
arylamines [33].
N-(2,6-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-tri-
methylfuran-3-carboxamide (3c, C16H20N2O2)
Prepared from 1.02 g 1a and 1.88 g 2-cyano-N-(2,6-
dimethylphenyl)acetamide (2c). White crystals; yield
93%; m.p.: 106–107 °C; Rf = 0.56 (acetone/benzene
General procedure for the preparation of N-aryl-2,5-
dihydro-2-iminofuran-3-carboxamides 3a–3d and
4a–4d
ꢀ
1:2); IR: m = 3,300 (NH), 3,254 (NH), 1,680 (C=O),
1
1,640 (C=N), 1,620 (C=C), 1,600–1,500 (Ar) cm-1; H
A mixture of 1a, 1b (10 mmol), 2a–2d (10 mmol), and
sodium methoxide (1 mmol) in 20 cm3 dry methanol was
heated at 35–40 °C for 5 h. The solvent was removed
under reduced pressure. Water was poured into the residue.
The solid precipitate obtained was filtered, washed with
water, and recrystallized from ethanol.
NMR (DMSO-d6/CCl4 1:3): d = 1.44 (s, 6H, 2CH3), 2.23
[s, 6H, Ar–(CH3)2], 2.42 (s, 3H, CH3), 7.21 (s, 1H, =NH),
7.34 (s, 3H, Ar–H3,4,5), 10.99 (s, 1H, NH) ppm; 13C NMR
(DMSO-d6/CCl4 1:3): d = 11.81, 18.16, 24.16, 87.64,
118.26, 126.27, 126.89, 127.76, 138.43, 160.41, 166.21,
170.77 ppm.
123

690
L. Karapetyan
N-(2,4-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-tri-
methylfuran-3-carboxamide (3d, C16H20N2O2)
N-(2,4-Dimethylphenyl)-2-imino-4-methyl-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide (4d, C19H24N2O2)
Prepared from 1.02 g 1a and 1.88 g 2-cyano-N-(2,4-
dimethylphenyl)acetamide (2d). White crystals; yield
94%; m.p.: 142–143 °C; Rf = 0.56 (acetone/benzene
Prepared from 1.42 g 1b and 1.88 g 2d. White crystals;
yield 94%; m.p.: 160–161 °C; Rf = 0.59 (acetone/benzene
ꢀ
1:2); IR: m = 3,400 (NH), 3,240 (NH), 1,670 (C=O), 1,635
1
(C=N), 1,620 (C=C), 1,600–1,500 (Ar) cm-1; H NMR
ꢀ
1:2); IR: m = 3,300 (NH), 3,250 (NH), 1,680 (C=O),
1
1,640 (C=N), 1,620 (C=C), 1,600–1,500 (Ar) cm-1; H
(DMSO-d6/CCl4 1:3): d = 1.30 (m, 1H), 1.52 (m, 2H),
1.62–1.84 (m, 7H, C5H10), 2.28 [s, 6H, Ar–(CH3)2], 2.43
(s, 3H, CH3), 6.91 (d, 1H, J = 8.0 Hz, Ar–H5), 6.93 (s, 1H,
Ar–H3), 7.22 (s, 1H, =NH), 8.01 (d, 1H, J = 8.0 Hz, Ar–
H6), 11.38 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/CCl4
1:3): d = 12.08, 18.16, 21.22, 22.96, 23.96, 32.39, 87.64,
118.26, 126.28, 126.89, 127.78, 138.43, 160.41, 166.21,
170.77 ppm.
NMR (DMSO-d6/CCl4 1:3): d = 1.47 (s, 6H, 2CH3), 2.28
[s, 6H, Ar–(CH3)2], 2.44 (s, 3H, CH3), 6.91 (d, 1H,
J = 8.0 Hz, Ar–H5), 6.93 (s, 1H, Ar–H3), 7.23 (s, 1H,
=NH), 8.01 (d, 1H, J = 8.0 Hz, Ar–H6), 11.38 (s, 1H, NH)
ppm; 13C NMR (DMSO-d6/CCl4 1:3): d = 11.81, 18.16,
22.96, 24.16, 87.64, 118.26, 126.27, 126.89, 127.76,
138.43, 160.41, 166.21, 170.77 ppm.
2-Imino-4-methyl-N-phenyl-1-oxaspiro[4.5]dec-3-ene-3-
carboxamide (4a, C17H20N2O2)
General procedure for the preparation of N-aryl-2,5-
dihydro-2-oxofuran-3-carboxamides 5a–5d and 6a–6d
Prepared from 1.42 g 1b and 1.6 g 2a. White crystals; yield
95%; m.p.: 122–123 °C; Rf = 0.54 (acetone/benzene 1:2);
A mixture of 2-iminoderivative 3a–3d or 4a–4d (3 mmol)
and 8 cm3 water in the presence of hydrochloric acid (pH
4–5) was heated at 85–90 °C for 3 h, cooled, extracted
with diethyl ether (3 9 10 cm3), and the extract was dried
with magnesium sulfate. After removal of the solvent, the
residue was recrystallized from petroleum ether.
ꢀ
IR: m = 3,400 (NH), 3,240 (NH), 1,670 (C=O), 1,635
1
(C=N), 1,620 (C=C), 1,600–1,500 (Ar) cm-1; H NMR
(DMSO-d6/CCl4 1:3): d = 1.27 (m, 1H), 1.47 (m, 2H),
1.58–1.82 (m, 7H, C5H10), 2.33 (s, 3H, CH3), 7.21 (s, 1H,
=NH), 7.34–7.45 (m, 5H, Ar–H), 11.35 (s, 1H, NH) ppm;
13C NMR (DMSO-d6/CCl4 1:3): d = 12.08, 21.22, 23.96,
32.39, 87.64, 118.26, 126.28, 126.89, 127.78, 138.43,
160.41, 166.21, 170.77 ppm.
2,5-Dihydro-4,5,5-trimethyl-2-oxo-N-phenylfuran-3-
carboxamide (5a, C14H15NO3)
White crystals; yield 78%; m.p.: 97–98 °C (ref. [31] 96.5–
98 °C).
2-Imino-4-methyl-N-(4-methylphenyl)-1-oxaspiro[4.5]dec-
3-ene-3-carboxamide (4b, C18H22N2O2)
Prepared from 1.42 g 1b and 1.74 g 2b. White crystals;
yield 92%; m.p.: 123–124 °C; Rf = 0.56 (acetone/benzene
2,5-Dihydro-4,5,5-trimethyl-N-(4-methylphenyl)-2-oxo-
furan-3-carboxamide (5b, C15H17NO3)
ꢀ
1:2); IR: m = 3,400 (NH), 3,240 (NH), 1,670 (C=O), 1,635
White crystals; yield 78%, m.p.: 91–92 °C; Rf = 0.53
1
(C=N), 1,620 (C=C), 1,600–1,500 (Ar) cm-1; H NMR
ꢀ
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
(DMSO-d6/CCl4 1:3): d = 1.27 (m, 1H), 1.47 (m, 2H),
1.58–1.82 (m, 7H, C5H10), 2.28 (s, 3H, Ar–CH3), 2.35 (s,
3H, CH3), 7.22 (s, 1H, =NH), 7.34 (d, 2H, J = 8.0 Hz, Ar–
H), 7.45 (d, 2H, J = 8.0 Hz, Ar–H), 9.78 (s, 1H, NH) ppm;
13C NMR (DMSO-d6/CCl4 1:3): d = 12.08, 21.22, 22.96,
23.96, 32.39, 87.64, 118.26, 126.28, 126.89, 127.78,
138.43, 160.41, 166.21, 170.77 ppm.
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.48 (s, 6H,
2CH3), 2.28 (s, 3H, s, Ar–CH3), 2.40 (s, 3H, CH3), 7.34 (d,
2H, J = 8.0 Hz, Ar–H), 7.45 (d, 2H, J = 8.0 Hz, Ar–H),
9.88 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3):
d = 11.81, 22.96, 24.16, 87.62, 118.26, 126.28, 126.89,
127.78, 138.43, 158.40, 161.21, 176.77 ppm.
N-(2,6-Dimethylphenyl)-2-imino-4-methyl-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide (4c, C19H24N2O2)
N-(2,6-Dimethylphenyl)-2,5-dihydro-4,5,5-trimethyl-2-
oxofuran-3-carboxamide (5c, C16H19NO3)
Prepared from 1.42 g 1b and 1.88 g 2c. White crystals; yield
93%; m.p.: 143–144 °C; Rf = 0.59 (acetone/benzene 1:2);
White crystals; yield 65%; m.p.: 101–102 °C; Rf = 0.54
ꢀ
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
ꢀ
IR: m = 3,400 (NH), 3,240 (NH), 1,670 (C=O), 1,635 (C=N),
1,620 (C=C), 1,600–1,500 (Ar) cm-1; 1H NMR (DMSO-d6/
CCl4 1:3): d = 1.31 (m, 1H), 1.57 (m, 2H), 1.63–1.85 (m,
7H, C5H10), 2.22 [s, 6H, Ar–(CH3)2], 2.40 (3H, s, CH3), 7.02
(s, 3H, Ar–H3,4,5), 7.23 (s, 1H, =NH), 11.02 (s, 1H, NH) ppm;
13C NMR (DMSO-d6/CCl4 1:3): d = 12.08, 18.16, 21.22,
23.96, 32.39, 87.66, 118.27, 126.29, 126.89, 127.77, 138.44,
160.41, 166.21, 170.77 ppm.
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.44 (s, 6H,
2CH3), 2.23 [s, 6H, Ar–(CH3)2], 2.42 (s, 3H, CH3), 7.34
(s, 3H, Ar–H3,4,5), 10.99 (s, 1H, NH) ppm; 13C NMR
(DMSO-d6/CCl4 1:3): d = 11.81, 18.18, 24.16, 87.64,
118.26, 126.27, 126.89, 127.76, 138.44, 158.42, 162.22,
176.77 ppm.
123

Synthesis of novel N-aryl-2,5-dihydro-2-iminofuran-3-carboxamides
691
1
N-(2,4-Dimethylphenyl)-2,5-dihydro-4,5,5-trimethyl-2-
oxofuran-3-carboxamide (5d, C16H19NO3)
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.30 (m, 1H),
1.52 (m, 2H), 1.62–1.84 (m, 7H, C5H10), 2.28 [s, 6H,
Ar–(CH3)2], 2.43 (s, 3H, CH3), 6.91 (d, 1H, J = 8.0 Hz,
Ar–H5), 6.93 (s, 1H, Ar–H3), 8.04 (d, 1H, J = 8.0 Hz,
Ar–H6), 11.38 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/CCl4
1:3): d = 12.08, 18.16, 21.22, 22.96, 23.96, 32.39, 87.64,
118.26, 126.28, 126.89, 127.78, 138.43, 158.44, 162.24,
176.74 ppm.
White crystals; yield 73%; m.p.: 109–110 °C; Rf = 0.54
(acetone/benzene 1:2); IR: ꢀm = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.47 (s, 6H,
2CH3), 2.28 [s, 6H, Ar–(CH3)2], 2.44 (s, 3H, CH3), 6.91 (d,
1H, J = 8.0 Hz, Ar–H5), 6.93 (s, 1H, Ar–H3), 8.04 (d, 1H,
J = 8.0 Hz, Ar–H6), 11.36 (s, 1H, NH) ppm; 13C NMR
(DMSO-d6/CCl4 1:3): d = 11.81, 18.16, 22.96, 24.16,
87.64, 118.26, 126.27, 126.89, 127.76, 138.43, 159.42,
162.20, 176.74 ppm.
2,5-Dihydro-4,5,5-trimethyl-2-oxofuran-3-carboxylic
acid (7a)
A mixture of 0.98 g 5a (4 mmol) and 14 cm3 sulfuric acid
(20%) was heated at 75–80 °C until the oily layer
completely disappeared. The mixture was cooled, extracted
with diethyl ether (3 9 15 cm3) and dried with magnesium
sulfate. Ether was distilled off. Recrystallization from xylol
afforded 0.55 g (80%) 7a. M.p.: 112–113 °C (ref. [31]
112–113 °C).
4-Methyl-2-oxo-N-phenyl-1-oxaspiro[4.5]dec-3-ene-3-car-
boxamide (6a, C17H19NO3)
White crystals; yield 79%; m.p.: 135–136 °C; Rf = 0.57
ꢀ
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.27 (m, 1H),
1.47 (m, 2H), 1.58–1.82 (m, 7H, C5H10), 2.35 (s, 3H, CH3),
7.34–7.45 (m, 5H, Ar–H), 11.35 (s, 1H, NH) ppm; 13C
NMR (DMSO-d6/CCl4 1:3): d = 12.08, 21.22, 23.96,
32.39, 87.64, 118.26, 126.28, 126.89, 127.78, 138.43,
159.42, 162.20, 176.74 ppm.
General procedure for the preparation of N-aryl-2,5-
dihydro-2-iminofuran-3-carboxamide hydrochlorides
8a–8d and 9a–9d
Method A: To a solution of 2-iminoderivative 3a–3d or
4a–4d (10 mmol) in 15 cm3 ethanol was added 1 cm3
hydrochloric acid (35%). The mixture was refluxed at room
temperature for 10 min. After ethanol had been partially
distilled off, the resulting precipitate was filtered off,
washed with diethyl ether, and dried.
4-Methyl-N-(4-methylphenyl)-2-oxo-1-oxaspiro[4.5]dec-3-
ene-3-carboxamide (6b, C18H21NO3)
White crystals; yield 79%; m.p.: 145–147 °C; Rf = 0.57
ꢀ
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
Method B: Through a benzene solution of 2-iminode-
rivative 3a–3d or 4a–4d (10 mmol), gaseous hydrogen
chloride was passed. The resulting precipitate was filtered
off, washed with diethyl ether, and dried.
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.26 (m, 1H),
1.45 (m, 2H), 1.60–1.82 (m, 7H, C5H10), 2.30 (s, 3H, Ar–
CH3), 2.40 (s, 3H, CH3), 7.34 (d, 2H, J = 8.0 Hz, Ar–H),
7.45 (d, 2H, J = 8.0 Hz, Ar–H), 11.35 (s, 1H, NH) ppm;
13C NMR (DMSO-d6/CCl4 1:3): d = 12.08, 21.22, 22.96,
23.96, 32.39, 87.64, 118.26, 126.28, 126.89, 127.78,
138.43, 159.42, 162.20, 176.74 ppm.
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-phenylfuran-3-car-
boxamide hydrochloride (8a, C14H16N2OÁHCl)
White crystals; yield 93% (A), 98% (B); m.p.: 236–239 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 11.42 (s, 6H, 2CH3),
2.35 (s, 3H, CH3), 7.34–7.45 (m, 5H, Ar–H), 9.22 (s, 1H,
NH-Ar), 10.34 (bs, 2H, =NHÁHCl) ppm.
N-(2,6-Dimethylphenyl)-4-methyl-2-oxo-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide (6c, C19H23NO3)
White crystals; yield 80%; m.p.: 133–134 °C; Rf = 0.59
ꢀ
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-(4-methyl-
phenyl)furan-3-carboxamide hydrochloride
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
1
cm-1; H NMR (DMSO-d6/CCl4 1:3): d = 1.31 (m, 1H),
(8b, C15H18N2O2ÁHCl)
1.57 (m, 2H), 1.63–1.85 (m, 7H, C5H10), 2.22 (s, 6H, Ar–
CH3), 2.40 (s, 3H, CH3), 7.02 (s, 3H, Ar–H3,4,5), 11.02 (s,
1H, NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3): d = 12.08,
18.16, 21.22, 23.96, 32.39, 87.66, 118.27, 126.29, 126.89,
127.77, 138.44, 158.48, 162.21, 176.76 ppm.
White crystals; yield 93% (A), 97% (B); m.p.: 208–212 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.42 (s, 6H, 2CH3),
2.28 (s, 3H, Ar–CH3), 2.40 (s, 3H, CH3), 7.34 (d, 2H,
J = 8.0 Hz, Ar–H), 7.45 (d, 2H, J = 8.0 Hz, Ar–H), 9.24
(s, 1H, NH), 10.44 (bs, 2H, =NHÁHCl) ppm.
N-(2,4-Dimethylphenyl)-4-methyl-2-oxo-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide (6d, C19H23NO3)
White crystals; yield 80%; m.p.: 168–169 °C; Rf = 0.59
(acetone/benzene 1:2); IR: m = 3,280 (NH), 1,760 (C=O),
1,680 (C=O), 1,660 (C=N), 1,620 (C=C), 1,600–1,500 (Ar)
N-(2,6-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-tri-
methylfuran-3-carboxamide (8c, C16H20N2O2ÁHCl)
White crystals; yield 92% (A), 97% (B); m.p.: 229–232 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.45 (s, 6H, 2CH3),
2.23 [s, 6H, Ar–(CH3)2], 2.42 (s, 3H, CH3), 7.34 (s, 3H,
ꢀ
123

692
L. Karapetyan
Ar–H3,4,5), 9.38 (s, 1H, NH), 10.48 (bs, 2H, =NHÁHCl)
mixture was refluxed at room temperature for 10 min. The
formed precipitate was filtered off, washed with ether, and
dried.
ppm.
N-(2,4-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-tri-
methylfuran-3-carboxamide (8d, C16H20N2O2ÁHCl)
White crystals; yield 92% (A), 97% (B); m.p.: 222–225 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.45 (s, 6H, 2CH3),
2.28 [s, 6H, Ar–(CH3)2], 2.44 (s, 3H, CH3), 6.92 (d, 1H,
J = 8.0 Hz, Ar–H5), 6.94 (s, 1H, Ar–H3), 8.01 (d, 1H,
J = 8.0 Hz, Ar–H6), 9.44 (s, 1H, NH), 10.52 (bs, 2H,
=NHÁHCl) ppm.
2-Imino-4-methyl-N-phenyl-1-oxaspiro[4.5]dec-3-ene-3-
carboxamide hydrochloride (9a, C17H20N2O2ÁHCl)
White crystals; yield 93% (A), 99% (B); m.p.: 181–185 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.27 (m, 1H), 1.47 (m,
2H), 1.58–1.82 (m, 7H, C5H10), 2.35 (s, 3H, CH3),
7.34–7.45 (m, 5H, Ar–H), 9.22 (s, 1H, NH–Ar), 10.34
(bs, 2H, =NHÁHCl) ppm.
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-phenylfuran-3-
carboxamide hydrogensulfate (10a, C14H16N2O2ÁH2SO4)
1
White crystals; yield 87%; m.p.: 250–254 °C; H NMR
(DMSO-d6/CCl4 1:3): d = 1.42 (s, 6H, 2CH3), 2.35 (s, 3H,
CH3), 7.34–7.45 (m, 5H, Ar–H), 9.22 (s, 1H, NH–Ar),
10.34 (bs, 2H, =NHÁH2SO4) ppm.
2,5-Dihydro-2-imino-4,5,5-trimethyl-N-(4-methylphenyl)-
furan-3-carboxamide hydrogensulfate
(10b, C15H18N2O2ÁH2SO4)
1
White crystals, yield 85%; m.p.: 243–147 °C; H NMR
(DMSO-d6/CCl4 1:3): d = 1.42 (s, 6H, 2CH3), 2.28 (s, 3H,
Ar–CH3), 2.40 (s, 3H, CH3), 7.34 (d, 2H, J = 8.0 Hz, Ar–
H), 7.45 (d, 2H, J = 8.0 Hz, Ar–H), 9.24 (s, 1H, NH),
10.44 (bs, 2H, =NHÁH2SO4) ppm.
2-Imino-4-methyl-N-(4-methylphenyl)-1-oxaspiro[4.5]-
dec-3-ene-3-carboxamide hydrochloride
N-(2,6-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-
trimethylfuran-3-carboxamide hydrogensulfate
(10c, C16H20N2O2ÁH2SO4)
(9b, C18H22N2O2ÁHCl)
White crystals; yield 84% yield; m.p.: 260–262 °C; 1H
NMR (DMSO-d6/CCl4 1:3): d = 1.45 (s, 6H, 2CH3), 2.23
[s, 6H, Ar–(CH3)2], 2.42 (s, 3H, CH3), 7.34 (s, 3H, Ar–
White crystals; yield 91% (A), 98% (B); m.p.: 170–174 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.26 (m, 1H), 1.45 (m,
2H), 1.60–1.82 (m, 7H, C5H10), 2.30 (s, 3H, Ar–CH3), 2.40
(s, 3H, CH3), 7.34 (d, 2H, J = 8.0 Hz, Ar–H), 7.45 (d, 2H,
J = 8.0 Hz, Ar–H), 9.22 (s, 1H, NH), 10.34 (bs, 2H,
=NHÁHCl) ppm.
H
3,4,5), 9.38 (s, 1H, NH), 10.48 (bs, 2H, =NHÁH2SO4) ppm.
N-(2,4-Dimethylphenyl)-2,5-dihydro-2-imino-4,5,5-
trimethylfuran-3-carboxamide hydrogensulfate
(10d, C16H20N2O2ÁH2SO4)
N-(2,6-Dimethylphenyl)-2-imino-4-methyl-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide hydrochloride
(9c, C19H24N2O2ÁHCl)
1
White crystals; yield 85%; m.p.: 252–256 °C; H NMR
(DMSO-d6/CCl4 1:3): d = 1.45 (s, 6H, 2CH3), 2.28 [s, 6H,
Ar–(CH3)2], 2.44 (s, 3H, CH3), 6.91 (d, 1H, J = 8.0 Hz,
Ar–H5), 6.94 (s, 1H, Ar–H3), 8.01 (d, 1H, J = 8.0 Hz,
Ar–H6), 9.42 (s, 1H, NH), 10.52 (bs, 2H, =NHÁH2SO4) ppm.
White crystals; yield 91% (A), 98% (B); m.p.: 195–200 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.31 (m, 1H), 1.57 (m,
2H), 1.63–1.85 (m, 7H, C5H10), 2.22 [s, 6H, Ar–(CH3)2],
2.42 (s, 3H, CH3), 7.02 (s, 3H, Ar–H3,4,5), 9.36 (s, 1H, NH),
10.78 (bs, 2H, =NHÁHCl) ppm.
General procedure for the hydrolysis of compounds
8a–8d, 9a–9d, and 10a–10d
N-(2,4-Dimethylphenyl)-2-imino-4-methyl-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide hydrochloride
A solution of compound 8a–8d, 9a–9d, or 10a–10d
(3 mmol) in 5 cm3 water was heated at 85–90 °C for 2 h.
The mixture was cooled and extracted with diethyl ether
(3 9 7 cm3), and the extract was dried with magnesium
sulfate. The solvent was distilled off, and the residue was
recrystallized from petroleum ether. The products were
identical to compounds 3a–3d and 4a–4d in melting points.
(9d, C19H24N2O2ÁHCl)
White crystals; yield 91% (A), 98% (B); m.p.: 175–180 °C;
1H NMR (DMSO-d6/CCl4 1:3): d = 1.30 (m, 1H), 1.52 (m,
2H), 1.62–1.84 (m, 7H, C5H10), 2.28 [s, 6H, Ar–(CH3)2],
2.44 (s, 3H, CH3), 6.92 (d, 1H, J = 8.0 Hz, Ar–H5), 6.94
(s, 1H, Ar–H3), 8.01 (d, 1H, J = 8.0 Hz, Ar–H6), 9.38
(s, 1H, NH), 10.86 (bs, 2H, =NHÁHCl) ppm.
Reaction of compounds 8a–8d, 9a–9d, and 10a–10d
with potassium carbonate
General procedure for the preparation of N-aryl-2,5-
dihydro-2-iminofuran-3-carboxamide hydrogensulfates
10a–10d
To an aqueous solution of hydrochloride 8a–8d, 9a–9d, or
hydrogen sulfate 10a–10d, a concentrated aqueous solution
of potassium carbonate was added (until pH 7–8). The
precipitate was filtered off and washed with water to afford
To a solution of 2-iminoderivative 3a–3d (2 mmol) in
5 cm3 ethanol was added 0.6 cm3 sulfuric acid (40%). The
123

Synthesis of novel N-aryl-2,5-dihydro-2-iminofuran-3-carboxamides
693
2-(Dicyanomethylene)-N-(2,4-dimethylphenyl)-2,5-dihy-
dro-4,5,5-trimethylfuran-3-carboxamide
(11d, C19H19N3O2)
imino derivatives 3a–3d and 4a–4d. The combined sam-
ples with corresponding iminolactones 3a–3d and 4a–4d
did not depress the melting points.
White crystals; yield 94%; m.p.: 210–212 °C; Rf = 0.61
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
General procedure for the preparation of N-aryl-2-
(dicyanomethylene)-2,5-dihydrofuran-3-carboxamides
11a–11d and 12a–12d
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
1
d = 1.47 (s, 6H, 2CH3), 2.28 [s, 6H, Ar–(CH3)2], 2.44 (s,
3H, CH3), 6.91 (d, 1H, J = 8.0 Hz, Ar–H5), 6.94 (s, 1H,
Ar–H3), 8.01 (d, 1H, J = 8.0 Hz, Ar–H6), 11.38 (s, 1H,
NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3): d = 11.81,
18.16, 22.96, 24.16, 46.00, 87.62, 115.15, 118.24, 126.26,
126.87, 127.76, 138.43, 160.41, 166.21, 170.77 ppm.
A mixture of 3a–3d or 4a–4d (5 mmol) and 0.33 g mal-
ononitrile (5 mmol) in 10 cm3 absolute ethanol was
refluxed at room temperature until ammonia evolution had
ceased. After removal of the solvent, water was poured to
the crystalline residue, and the formed precipitate was fil-
tered off, washed with water, and recrystallized from
ethanol/water 2:1.
2-(Dicyanomethylene)-4-methyl-N-phenyl-1-oxaspiro-
[4.5]dec-3-ene-3-carboxamide (12a, C20H19N3O2)
White crystals, yield 94%; m.p.: 159–160 °C; Rf = 0.59
2-(Dicyanomethylene)-2,5-dihydro-4,5,5-trimethyl-N-
phenylfuran-3-carboxamide (11a, C17H15N3O2)
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
White crystals; yield 94%; m.p.: 175–176 °C; Rf = 0.57
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
d = 1.27 (m, 1H), 1.47 (m, 2H), 1.58–1.82 (m, 7H, C5H10),
2.35 (s, 3H, CH3), 7.34–7.45 (m, 5H, Ar–H), 11.35 (s, 1H,
NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3): d = 12.08,
21.22, 23.96, 32.39, 46.20, 87.64, 115.15, 118.26, 126.28,
126.89, 127.78, 138.43, 160.41, 166.10, 170.77 ppm.
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
d = 1.42 (6H, s, 2CH3), 2.35 (s, 3H, CH3), 7.34–7.45 (m,
5H, Ar–H), 11.35 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/
CCl4 1:3): d = 11.81, 24.16, 46.00, 87.64, 115.14, 118.24,
126.26, 126.88, 127.76, 138.44, 160.44, 167.22,
171.77 ppm.
2-(Dicyanomethylene)-4-methyl-N-(4-methylphenyl)-1-
oxaspiro[4.5]dec-3-ene-3-carboxamide
(12b, C21H21N3O2)
2-(Dicyanomethylene)-2,5-dihydro-4,5,5-trimethyl-N-(4-
methylphenyl)furan-3-carboxamide (11b, C18H17N3O2)
White crystals; yield 94%; m.p.: 165–166 °C; Rf = 0.59
White crystals; yield 92%; m.p.: 163–164 °C; Rf = 0.61
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
1
d = 1.26 (m, 1H), 1.45 (m, 2H), 1.60–1.82 (m, 7H, C5H10),
2.30 (s, 3H, Ar–CH3), 2.40 (s, 3H, CH3), 7.34 (d, 2H,
J = 8.0 Hz, Ar–H), 7.45 (d, 2H, J = 8.0 Hz, Ar–H), 11.35
(s, 1H, NH) ppm; 13C NMR (DMSO-d6/CCl4 1:3):
d = 12.08, 21.22, 22.96, 23.98, 32.38, 46.20, 87.64,
115.15, 118.26, 126.28, 126.89, 127.78, 138.43, 160.44,
167.24, 170.78 ppm.
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
d = 1.44 (s, 6H, 2CH3), 2.28 (s, 3H, Ar–CH3), 2.40 (s, 3H,
CH3), 7.34 (d, 2H, J = 8.0 Hz, Ar–H), 7.45 (d, 2H,
J = 8.0 Hz, Ar–H), 11.35 (s, 1H, NH) ppm; 13C NMR
(DMSO-d6/CCl4 1:3): d = 11.81, 22.96, 24.14, 46.10,
88.22, 115.15, 118.26, 126.28, 126.89, 127.78, 138.43,
160.41, 166.21, 170.77 ppm.
2-(Dicyanomethylene)-N-(2,6-dimethylphenyl)-4-methyl-1-
oxaspiro[4.5]dec-3-ene-3-carboxamide
(12c, C22H23N3O2)
2-(Dicyanomethylene)-N-(2,6-dimethylphenyl)-2,5-dihy-
dro-4,5,5-trimethylfuran-3-carboxamide
(11c, C19H19N3O)
White crystals, yield 93%; m.p.: 164–165 °C; Rf = 0.65
White crystals, yield 93%; m.p.: 189–190 °C; Rf = 0.61
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
d = 1.31 (m, 1H), 1.57 (m, 2H), 1.63–1.85 (m, 7H, C5H10),
2.22 [s, 6H, Ar–(CH3)2], 2.40 (s, 3H, CH3), 7.02 (s, 3H,
Ar–H3,4,5), 11.02 (s, 1H, NH) ppm; 13C NMR (DMSO-d6/
CCl4 1:3): d = 12.08, 18.16, 21.22, 23.96, 32.39, 46.20,
87.66, 115.15, 118.27, 126.29, 126.89, 127.77, 138.44,
160.41, 166.21, 170.77 ppm.
d = 1.50 (s, 6H, 2CH3), 2.23 [s, 6H, Ar–(CH3)2], 2.42 (s,
3H, CH3), 7.34 (s, 3H, Ar–H3,4,5), 10.99 (s, 1H, NH) ppm;
13C NMR (DMSO-d6/CCl4 1:3): d = 11.81, 18.16, 24.16,
46.00, 87.66, 115.15, 118.30, 126.25, 126.88, 127.76,
138.43, 160.42, 166.20, 170.76 ppm.
123

694
L. Karapetyan
9. Avetisyan AA, Tokmadzhyan GG (1987) Khim Geterotsikl So-
edin 6:723
2-(Dicyanomethylene)-N-(2,4-dimethylphenyl)-4-methyl-1-
oxaspiro[4.5]dec-3-ene-3-carboxamide
(12d, C22H23N3O2)
10. Avetisyan AA, Tokmadjyan GG (1993) Chem J Arm 46:219
11. Marshallin PG (1970) In: Rodd EH (ed) Chemistry of carbon
compounds, vol IID, chapter 17. Elsevier, New York
12. Siddall JB (1972) US Patent 3700694; (1973) Chem Abstr
78:43254
White crystals; yield 91%; m.p.: 240–242 °C; Rf = 0.65
ꢀ
(acetone/benzene 1:2); IR: m = 3,240 (NH), 2,219 (CN),
1,680 (C=O), 1,670 (C=N), 1,635 (C=C), 1,620 (C=C),
13. Payne GB (1965) US Patent 3177227; (1965) Chem Abstr
63:6866e
1
1,600–1,500 (Ar) cm-1; H NMR (DMSO-d6/CCl4 1:3):
d = 1.30 (m, 1H), 1.52 (m, 2H), 1.62–1.84 (m, 7H, C5H10),
2.28 [s, 6H, Ar–(CH3)2], 2.43 (s, 3H, CH3), 6.91 (d, 1H,
J = 8.0 Hz, Ar–H5), 6.94 (s, 1H, Ar–H3), 8.01 (d, 1H,
J = 8.0 Hz, Ar–H6), 11.38 (s, 1H, NH) ppm; 13C NMR
(DMSO-d6/CCl4 1:3): d = 12.08, 18.16, 21.22, 22.96,
23.96, 32.36, 46.20, 87.64, 115.15, 118.26, 126.28,
126.89, 127.78, 138.43, 160.41, 166.21, 170.77 ppm.
14. Laduwahetty T (1995) Contemp Org Synth 2:133
15. Collins I (1996) Contemp Org Synth 3:295
16. Larock RC, Reifling B (1978) J Org Chem 43:131 (and references
therein)
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