Oxidation of 2-cyanoprop-2-enethioamides with hydrogen peroxide

Article abstract of DOI:10.1007/s11172-012-0291-3

Oxidation of (E)-3-aryl-2-cyanoprop-2-enethioamides with 32% H ₂O₂ under mild conditions gave (E)-3-aryl-2-cyano-1- iminioprop-2-ene-1-sulfenates in 70-88% yields. Under the conditions of the Radziszewski reaction (H₂O₂, 10% aqueous KOH) or upon prolonged treatment with H₂O₂, (E)-3-aryl-2-cyanoprop-2- enethioamides underwent transformations leading to complex mixtures of oxidation products. In some cases, 3-aryloxirane-2,2-dicarboxamides were isolated from those mixtures in low yields (<20%). Treatment of 3-arylamino-2-cyanoprop-2- enethioamides with the system H₂O₂/KOH in ethanol afforded (arylaminomethylidene)malononitriles.

Full text of DOI:10.1007/s11172-012-0291-3

Russian Chemical Bulletin, International Edition, Vol. 61, No. 11, pp. 2082—2087, November, 2012
2082
Oxidation of 2ꢀcyanopropꢀ2ꢀenethioamides with hydrogen peroxide
V. V. Dotsenko,a,b S. G. Krivokolysko,a S. V. Shishkina,c and O. V. Shishkinc,d
aChemEx Laboratory, V. Dal´ EastꢀUkranian National University,
20a Molodyozhny kv., 91034 Lugansk, Ukraine.
Eꢀmail: Victor_Dotsenko@bigmir.net
bState Enterprise "Luganskstandartmetrologiya",
50 ul. Timiryazeva, 91021 Lugansk, Ukraine
cInstitute for Single Crystals, National Academy of Sciences of Ukraine,
60 prosp. Lenina, 61178 Kharkov, Ukraine.
dV. N. Karazin Kharkov National University,
4 pl. Svobody, 61022 Kharkov, Ukraine
Oxidation of (E)ꢀ3ꢀarylꢀ2ꢀcyanopropꢀ2ꢀenethioamides with 32% H2O2 under mild condiꢀ
tions gave (E)ꢀ3ꢀarylꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfenates in 70—88% yields. Under the
conditions of the Radziszewski reaction (H2O2, 10% aqueous KOH) or upon prolonged treatꢀ
ment with H2O2, (E)ꢀ3ꢀarylꢀ2ꢀcyanopropꢀ2ꢀenethioamides underwent transformations leadꢀ
ing to complex mixtures of oxidation products. In some cases, 3ꢀaryloxiraneꢀ2,2ꢀdicarboxꢀ
amides were isolated from those mixtures in low yields (<20%). Treatment of 3ꢀarylaminoꢀ2ꢀ
cyanopropꢀ2ꢀenethioamides with the system H2O2/KOH in ethanol afforded (arylaminoꢀ
methylidene)malononitriles.
Key words: cyanothioacetamide, thioamide Sꢀoxides, thioacrylamides, hydrogen peroxide,
the Radziszewski reaction, oxiraneꢀ2,2ꢀdicarboxamide, aminomethylidenemalononitrile, deꢀ
hydrosulfuration, Xꢀray diffraction analysis.
Scheme 1
Oxidation of thioamides is one of the least predictable
organic reactions (see reviews1). Its outcome largely deꢀ
pends on the substrate structure, the oxidant, and the reꢀ
action conditions. Most common oxidation products deꢀ
rived from thioamides include amides, thioamide Sꢀoxꢀ
ides, 1,2,4ꢀthiadiazoles, disulfides, benzothiazoles, ꢀoxo
thioamides, 1,2ꢀdithiolium salts, 1,2,4ꢀdithiazoles, and
1,2,3ꢀthiadiazolium salts. Hydrogen peroxide is one of the
most accessible and efficient agents for the transformation
of thioamides into amides, 1,2,4ꢀthiadiazoles, or thioꢀ
amide Sꢀoxides. If a thioamide molecule contains other
oxidizable functional groups, the reaction with H2O2 is
of interest as a method for simultaneous and/or selective
"one pot" modification of separate fragments of the moleꢀ
cule. From this point of view, the cyanothioacetꢀ
amide derivatives2 (3ꢀarylꢀ2ꢀcyanopropꢀ2ꢀenethioamides
1 (see Refs 3, 4) and 3ꢀarylaminoꢀ2ꢀcyanopropꢀ2ꢀenethioꢀ
amides 2 are very attractive substrates for peroxide oxidaꢀ
tion (Scheme 1).
i. H2O2, 10% KOH, EtOH.
the thioamide and cyano groups to form 3ꢀ(4ꢀchloroꢀ
phenyl)oxiraneꢀ2,2ꢀdicarboxamide (3a, Ar = 4ꢀClC6H4)
in low yield (see Scheme 1). In the present work, we tried
to study in more detail the oxidation of various 2ꢀcyanoꢀ
thioacrylamides with H2O2.
We found that brief heating of compounds 1 with excess
32% H2O2 in EtOH gives brightly colored (E)ꢀ3ꢀarylꢀ2ꢀ
cyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfenates (4) (Scheme 2).
For instance, the presence of the fragment C=C—CN
allows compound 1 to react in the Radziszewski reaction,5
with parallel epoxidation of the double bond.6 Earlier,7 we
have demonstrated that 3ꢀ(4ꢀchlorophenyl)ꢀ2ꢀcyanopropꢀ
2ꢀenethioamide (1a) treated with the system H2O2—KOH
undergoes simultaneous oxidation at the C=C bond and
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2065—2070, November, 2012.
1066ꢀ5285/12/6111ꢀ2082 © 2012 Springer Science+Business Media, Inc.

Oxidation of 2ꢀcyanopropꢀ2ꢀenethioamides
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 11, November, 2012 2083
Scheme 2
N(2)
C(10)
C(8)
S(1)
C(5)
C(4)
C(6)
C(9)
O(1)
C(3)
C(7)
C(1)
C(2)
N(1)
1, 4: Ar = 4ꢀClC6H4 (a); 2ꢀClC6H4 (b); 3ꢀMeOꢀ4ꢀHOC6H3 (c);
2ꢀfuryl (d)
Compounds 4 are bright red to cherryꢀcolored crystalꢀ
line solids that are insoluble in water and EtOH, moderꢀ
ately soluble in acetone, and well soluble in DMF. Iminꢀ
iopropenesulfenates 4 are stable when stored in air at
~20 C; however, they decompose readily when directly
exposed to sunlight. Likewise, in the presence of excess
H2O2, a heterogeneous reaction mixture containing comꢀ
pound 4 promptly undergoes further oxidation resulting in
a pale yellow homogeneous mixture with pH 1—2. Conꢀ
centrating this mixture gives colorless resinous products.
According to TLC and GLCꢀMS data, they are complex
mixtures of oxidation products, with oxiraneꢀ2,2ꢀdicarbꢀ
oxamides 3 as the major components. In some cases, comꢀ
pounds 3 can be obtained in the individual state. For inꢀ
stance, treatment of thioacrylamide 1a with H2O2 without
isolation of intermediate 4a affords oxiranedicarboxamide
3a (Ar = 4ꢀClC6H4) in 11% yield. In a similar way, diꢀ
amide 3b (Ar = 2ꢀClC6H4, 20% yield) is obtained from
isomeric thioamide 1b. The probable mechanism of forꢀ
mation of compounds 3 can involve oxidation of the
sulfenate fragment followed by hydrolysis as proposed earꢀ
lier8 and the subsequent Radziszewski tandem oxidation
of the cyano group that involves intramolecular epoxidaꢀ
tion through hydroperoxy imine intermediate 5 (Scheme 3).
The low yields of compounds 3 are probably due to
inevitable transformations of the oxirane ring and the
Fig. 1. Structure of (E)ꢀ3ꢀ(2ꢀchlorophenyl)ꢀ2ꢀcyanoꢀ1ꢀiminioꢀ
propꢀ2ꢀeneꢀ1ꢀsulfenate (4b).
carbamoyl groups in strongly acidic medium; clearly, the
oxidation of iminiopropenesulfenates 4 or 3ꢀarylꢀ2ꢀcyanoꢀ
propꢀ2ꢀenethioamides 1 cannot be recommended for the
preparative synthesis of compounds 3.
1
The H NMR spectra of iminiopropenesulfenates 4
show signals for the protons of the fragment Ar—CH=
and a very broadened peak at  8.73—8.98 for the signals
of the acidic H2N+ protons. The IR spectra contain abꢀ
sorption bands at 3330—3310 (N—H stretching of the
NH2 group) and 2220—2215 cm–1 (CN stretching of the
conjugated cyano group). Since the spectroscopic data
alone are insufficient for making a definitive conclusion
about the structure of compounds 4, we additionally exꢀ
amined (E)ꢀ3ꢀ(2ꢀchlorophenyl)ꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ
2ꢀeneꢀ1ꢀsulfenate (4b) by Xꢀray diffraction (Fig. 1).
Analysis of the bond lengths in structure 4b showed
that this compound exists in the crystal as a zwitterion.
The S(1)—O(1) bond (1.534(1) Å) is appreciably shorter
than the average S=O bond9 (1.577 Å); in addition, no
hydrogen atom at the O(1) atom was revealed. This sugꢀ
gests that the negative charge is localized on the O(1)
atom. The C(9)—N(1) bond length (1.315(2) Å) is comꢀ
Scheme 3

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Dotsenko et al.
parable with the average Csp2=NH+ bond length (1.316 Å);
the S(1)—C(9) bond (1.683(2) Å) is somewhat shorter
than the average value of a single S—C bond (1.712 Å).
Two H atoms were objectively located at the N(1) atom
in difference electronꢀdensity maps. These atoms form
the H(7) atom and the protonated imino group: the inꢀ
tramolecular contact H(7) H(1Na) (2.12 Å) is shorter
than the sum of the van der Waals radii (2.34 Å).
In the crystal, the molecules of 4b form tetramers by
means of the intermolecular hydrogen bond N(1)—
...
...
...
...
...
the intramolecular hydrogen bond N(1)—H(1Nb) O(1)
H(1Na) O(1)´ (–x, 0.5 + y, –0.5 – z) (H O, 1.87 Å;
...
...
...
(H O, 2.19 Å; N—H O, 121). Thus, structure 4b can
be represented as a superposition of two resonance strucꢀ
tures: thioamide Sꢀoxide (4bA) and iminium sulfenate
(4bB) (Scheme 4). A similar electron density distribution
has been found in compound 6.10
N—H O, 172) and the S...ꢀinteractions S(1) N(1)´
...
(x, 0.5 – y, 0.5 + z) (3.25 Å) and S(1) C(9)´ (x, 0.5 – y,
0.5 + z) (3.36 Å). The crystal structure is additionally
stabilized by the weak intermolecular hydrogen bond
...
...
N(1)—H(1Nb) Cl(1) (–x, –0.5 + y, –0.5 – z) (H Cl,
...
2.98 Å; N—H Cl, 140).
Reactions of H2O2 with 3ꢀarylaminoꢀ2ꢀcyanopropꢀ2ꢀ
enethioamides 2 follow an absolutely different pattern.
Compounds 2 were first synthesized at our laboratory as
early as the 1980s according to the Wolfbeis general proꢀ
cedure12 involving threeꢀcomponent condensation of an
amine, triethyl orthoformate, and cyanothioacetamide
(Scheme 5), although the only documented13 route to thioꢀ
acrylamides 2 that has been known hitherto involving reꢀ
actions of cyanothioacetamide with N,N´ꢀdiarylformꢀ
amidines. Compounds 2 exist as ~2 : 9 mixtures of cis and
trans isomers (1H NMR data).
Scheme 4
Oxidative cyclization of ꢀamino alkenethioamides in
the presence of halogens or H2O2 is known14,15 to be
a general approach to isothiazole derivatives. Unexpectedꢀ
ly, the oxidation of 3ꢀaminothioacrylamides 2 with H2O2
in the presence of KOH did not result in cyclization or
oxidative hydrolysis of the cyano group; instead, the startꢀ
ing compounds undergo dehydrosulfuration leading to
(arylaminomethylidene)malononitriles 7 in high yields
(see Scheme 5). The structures of compounds 7 were conꢀ
firmed by 1H and 13C NMR spectroscopy, IR spectroscoꢀ
py, and mass spectrometry as well as by independent synꢀ
thesis from aniline, triethyl orthoformate, and malonoꢀ
nitrile.12 According to the literature data, selective deꢀ
hydrosulfuration of primary thioamides to nitriles can be
effected under the action of diarylselenium and diarylꢀ
tellurium oxides,16 P(NEt2)3,17 phenylpropiolamidines
PhCCC(=NR1)NHR,18 the system EtO2CN=NCO2Et/
PPh3,19 S8/NaNO2 in liquid NH3,20 Ph3SnN=C=NSnPh3
and Ph3SnNHCN,21 TeCl4/Et3N and SeCl4/Et3N,22
Bu2SnO and (Bu3Sn)2O,23 the system benzotriazolꢀ1ꢀ
yloxytris(pyrrolidino)phosphonium hexafluorophosphate
A rather strong repulsion between the aromatic ring
and the substituent at the C(6) atom is evident from the
...
shortened intramolecular contacts H(5) C(8) (2.81 Å vs.
2.87 Å11 for the sum of the van der Waals radii of the
corresponding atoms), H(5)...C(10) (2.45 Å vs. 2.87 Å),
...
...
C(5) C(10) (3.06 Å vs. 3.42 Å), and H(7) Cl(1) (2.73 Å
vs. 3.06 Å). As a result, the ꢀsystems of the ring and
the substituent are not coplanar (the torsion angle
C(5)—C(6)—C(7)—C(8) is 32.3(3)), the double bond
C(7)=C(8) is twisted (the torsion angle C(6)—C(7)—
C(8)—C(10) is 7.4(3)), and the bond angle C(8)—C(7)—C(6)
is increased to 128.8(2). The substituent itself is also nonꢀ
planar, regardless of the presence of a conjugated ꢀsysꢀ
tem (the torsion angle C(7)—C(8)—C(9)—N(1) is
9.3(3)). This can be attributed to the repulsion between
Scheme 5
2, 7: Ar = Ph (a), 4ꢀEtC6H4 (b)

Oxidation of 2ꢀcyanopropꢀ2ꢀenethioamides
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 11, November, 2012 2085
: 7.17* (m, 5 H, Ph); 7.40 (m, 5 H, Ph); 8.36* and 9.20* (both
(PyBOP)—N,Nꢀdiisopropylethylamine (DIPEA),24 arenetꢀ
ellurinic anhydrides,25 1,1´ꢀthiocarbonyldiꢀ2(1H)ꢀpyꢀ
ridone,26 the systems pyridine—phenyl chloroformate27
and P2I4—Et3N,28 di(2ꢀpyridyl) sulfite (2ꢀPyO)2S=O,29
heavy metal acetates,30 and some other exotic systems and
reagents. However, this reaction has never been observed
before under the conditions of the Radziszewski oxidative
hydrolysis. The surprising passivity of the cyano groups in
compounds 2 and 7 toward the system H2O2/KOH is probꢀ
ably due to the specific pushꢀpull properties of the enamiꢀ
no nitrile fragment.
To sum up, noncatalytic mild oxidation of (E)ꢀ3ꢀarylꢀ
2ꢀcyanopropꢀ2ꢀenethioamides with hydrogen peroxide
gives primary oxidation products (the corresponding thioꢀ
amide Sꢀoxides (or iminium sulfenates)), the fragments
C=C and CN of the starting compounds remaining inꢀ
tact. The structures of the oxidation products were proved
by Xꢀray diffraction with (E)ꢀ3ꢀ(2ꢀchlorophenyl)ꢀ2ꢀcyꢀ
anoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfenate (4b) as an example.
When heated and treated with the system H2O2—KOH,
3ꢀanilinoꢀ2ꢀcyanopropꢀ2ꢀenethioamide and 2ꢀcyanoꢀ3ꢀ
[(4ꢀethylphenyl)amino]propꢀ2ꢀenethioamide undergo deꢀ
hydrosulfuration to yield the corresponding (arylaminoꢀ
methylidene)malononitriles.
3
br.s, 1 H each, C(S)NH2); 8.49* (d, 1 H, HC=, J = 13.2 Hz);
8.64 and 9.09 (both br.s, 1 H each, C(S)NH2); 8.73 (d, 1 H,
3
3
HC=, J = 14.2 Hz); 10.50 (d, 1 H, NH, J = 14.2 Hz); 13.77
(d, 1 H, NH, 3J = 13.2 Hz). 13C NMR (125 MHz, DMSOꢀd6),
: 81.449* (C(3)=C(2)); 86.995 (C(3)=C(2)); 116.805 (CN);
117.966* (CAr); 118.451 (CAr); 119.017* (CN); 125.111 (CAr);
125.748* (CAr); 129.986 (CAr); 130.281* (CAr); 138.682* (CAr);
140.497 (CAr); 151.149 (C(3)=C(2)); 151.771* (C(3)=C(2));
190.331* (C=S); 192.427 (C=S).
2ꢀCyanoꢀ3ꢀ[(4ꢀethylphenyl)amino]propꢀ2ꢀenethioamide (2b)
was obtained as described for compound 2a. Yield 85%, m.p.
180—185 C (decomp.). Found (%): C, 61.96; H, 5.69; N, 18.25.
C12H13N3S (M = 231.32). Calculated (%): C, 62.31; H, 5.66;
N, 18.17. IR, /cm–1: 3420, 3290, 3180 (NH), 2195 (CN).
3ꢀAryloxiraneꢀ2,2ꢀdicarboxamides (3). An excess of 32%
H2O2 (6.0 mL, ~62 mmol) was added to a stirred suspension of
3ꢀarylꢀ2ꢀcyanopropꢀ2ꢀenethioamide (1a,b) (2.0 g, 9 mmol) in
EtOH (15 mL). The reaction mixture was heated until thioꢀ
amide 1 began to dissolve, which was accompanied by appearꢀ
ance of red coloration and immediate formation of a crystalline
precipitate of the corresponding iminiopropenesulfenate 4a,b.
The reaction mixture was stirred at 40—50 C to complete homoꢀ
genization and decoloration (Caution! Evolution of oxygen) and
left at ~20 C for two weeks. The crystalline precipitate of comꢀ
pound 3 that gradually formed was filtered off and repeatedly
washed with EtOH and water.
3ꢀ(4ꢀChlorophenyl)oxiraneꢀ2,2ꢀdicarboxamide (3a). Yield
11%, colorless crystals, m.p. 223—224 C (cf. Ref. 7: 225—227 C).
The spectroscopic characteristics of compound 3a agree with
the literature data.7
Experimental
1
H NMR spectra were recorded on a Bruker DRXꢀ500 inꢀ
3ꢀ(2ꢀChlorophenyl)oxiraneꢀ2,2ꢀdicarboxamide (3b). The
yield of analytically pure product 3b was 0.44 g (20%), colorless
crystals, m.p. 197—199 C (EtOH). Found (%): C, 49.76; H, 3.80;
N, 11.65. C10H9ClN2O3 (M = 240.65). Calculated (%): C, 49.91;
H, 3.77; N, 11.64. IR, /cm–1: 3425, 3200, 3150 (NH), 1675,
1660 (C=O). H NMR (200 MHz, DMSOꢀd6), : 4.83 (s, 1 H,
C(3)H); 7.35—7.62 (m, 4 H, Ar); 7.88 and 8.11 (both br.s,
2 H each, 2 C(O)NH2).
Synthesis of (E)ꢀ3ꢀarylꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfꢀ
enates 4 (general procedure). Pulverized thioamide 1a—d
(4.5—5.0 mmol) was suspended in EtOH (12—15 mL) in a 100ꢀmL
beaker. Then an excess of 32% H2O2 (4.0 mL, ~42 mmol) was
added with stirring. The vigorously stirred mixture was gradually
heated until an exothermic reaction began. Thioamide 1 passed
into solution, the reaction mixture turned dark red, and the corꢀ
responding iminium sulfenate 4a—d formed as a voluminous
crystalline precipitate within a few seconds. The heating was
immediately terminated to avoid further oxidation. The reaction
mixture was rapidly cooled on an ice bath and stirred for 30 min.
The precipitate of iminium sulfenate 4a—d was filtered off and
repeatedly washed with EtOH, 50% aqueous EtOH, and light
petroleum. The compounds obtained are usually pure enough
for analytical purposes; when necessary, the products can be
recrystallized from EtOH—Me2CO or AcOH.
strument (500.13 MHz) in DMSOꢀd6 (for compounds 2 and 7b)
and a Varian Mercury VXꢀ200 instrument (199.97 MHz) in
DMSOꢀd6 (for compounds 3, 4, and 7a); Me4Si was used as the
internal standard. The 13C NMR spectra of compound 6b were
recorded on a Bruker DRXꢀ500 instrument (125.76 MHz) in
DMSOꢀd6 and CCl4—DMSOꢀd6 with Me4Si as the internal stanꢀ
dard. IR spectra were recorded on an IKSꢀ29 spectrophotoꢀ
meter (in Nujol). Elemental analysis was carried out on a Perꢀ
kin—Elmer C,H,Nꢀanalyzer. The mass spectrum of compound
7a was measured on a Varian 1200L spectrometer (direct inlet
probe, EI, 70 eV). The individuality of the compounds obꢀ
tained was checked by TLC on Silufol UVꢀ254 plates in acetꢀ
one—heptane (1 : 1); spots were visualized with the iodine vapor
or under UV light. Melting points were determined on a Kofler
hot stage and are given uncorrected. The starting compounds
3ꢀarylꢀ2ꢀcyanopropꢀ2ꢀenethioamides 1 were prepared by conꢀ
densation of cyanothioacetamide with aldehydes according to
known procedures.3,4
3ꢀAnilinoꢀ2ꢀcyanopropꢀ2ꢀenethioamide (2a) was obtained
according to a modified general procedure.12 A mixture of pulꢀ
verized cyanothioacetamide (3.0 g, 30 mmol), HC(OEt)3 (6.5 mL,
39 mmol), and aniline (2.75 mL, 30 mmol) was refluxed with
continuous stirring until the exothermic reaction subsided. Then
the mixture was diluted with EtOH (10 mL), brought to boiling,
and left to cool down. The dark yellow crystals that formed were
filtered off and washed with hot EtOH. The yield of thioacrylaꢀ
mide 2a was 5.50 g (90%), m.p. 210—211 C (from AcOH).
Found (%): C, 59.16; H, 4.46; N, 20.65. C10H9N3S (M = 203.27).
Calculated (%): C, 59.09; H, 4.46; N, 20.67. IR, /cm–1: 3420,
3270, 3180 (NH), 2195 (CN). 1H NMR (500 MHz, DMSOꢀd6),
1
(E)ꢀ3ꢀ(4ꢀChlorophenyl)ꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfꢀ
enate (4a). Yield 75%, bloodꢀred small crystals, m.p. 172—175 C
(decomp., EtOH—Me2CO, 1 : 3). Found (%): C, 50.48; H, 3.00;
* The signals for the minor (cis) isomer. The cis : trans ratio is
2 : 9 (1H NMR data).

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Dotsenko et al.
N, 11.87. C10H7ClN2OS (M = 238.70). Calculated (%): C, 50.32;
H, 2.96; N, 11.74. IR, /cm–1: 3310 (NH), 2215 (CN).
1H NMR (200 MHz, DMSOꢀd6), : 7.63 and 7.85 (both d,
2 H each, 4ꢀClC6H4, 3J = 8.2 Hz); 8.11 (s, 1 H, ArCH=); 8.83*
(br.s, 2 H, H2N+=).
(E)ꢀ3ꢀ(2ꢀChlorophenyl)ꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfꢀ
enate (4b). Yield 70%, bright red crystals, m.p. 165—168 C
(decomp., EtOH—Me2CO (1 : 2) or AcOH). Found (%): C, 50.44;
H, 2.99; N, 11.83. C10H7ClN2OS (M = 238.70). Calculated (%):
C, 50.32; H, 2.96; N, 11.74. IR, /cm–1: 3310 (NH), 2215 (CN).
1H NMR (200 MHz, DMSOꢀd6), : 7.49—7.66 (m, 3 H, Ar);
7.91 (m, 1 H, Ar); 8.28 (s, 1 H, ArCH=); 8.98* (br.s, 2 H,
H2N+=).
(E)ꢀ2ꢀCyanoꢀ3ꢀ(4ꢀhydroxyꢀ3ꢀmethoxyphenyl)ꢀ1ꢀiminiopropꢀ
2ꢀeneꢀ1ꢀsulfenate (4c). Yield 73%, bright red fine crystalline powꢀ
der, m.p. 188—190 C (decomp., Me2CO). Found (%): C, 52.62;
H, 4.07; N, 11.33. C11H10N2O3S (M = 250.28). Calculated (%):
C, 52.79; H, 4.03; N, 11.19. IR, /cm–1: 3330, 3185 (NH), 2220
(CN). 1H NMR (200 MHz, DMSOꢀd6), : 3.79 (s, 3 H, MeO);
6.93 (d, 1 H, Ar, 3J = 8.2 Hz); 7.36 (d, 1 H, Ar, 3J = 8.2 Hz), 7.56
(s, 1 H, Ar); 7.98 (s, 1 H, ArCH=); 8.74** (br.s, 2 H, H2N+=);
10.32 (s, 1 H, OH).
pound 7a is identical with a sample obtained from aniline, triꢀ
ethyl orthoformate, and malononitrile12 (TLC data).
[(4ꢀEthylphenyl)aminomethylidene]malononitrile (7b). Yield
56%, creamꢀcolored fine crystalline powder, m.p. 248—250 C
(EtOH—acetone). Found (%): C, 72.91; H, 5.66; N, 21.51.
C12H11N3 (M = 197.24). Calculated (%): C, 73.07; H, 5.62;
N, 21.30. IR, /cm–1: 3200—3160 (NH), 2207 and 2223 (2 CN),
1
1665 (C=C). H NMR (500 MHz, CCl4—DMSOꢀd6), : 1.21
(t, 3 H, CH2CH3, 3J = 7.6 Hz); 2.60 (q, 2 H, CH2CH3, 3J = 7.6 Hz);
7.11 and 7.26 (both d, 2 H each, Ar, 3J = 8.3 Hz); 8.25 (d, 1 H,
HC=, 3J = 13.5 Hz); 10.87 (d, 1 H, NH, 3J = 13.5 Hz). 13C NMR
(125 MHz, CCl4—DMSOꢀd6), : 15.226 (CH2CH3); 27.652
(CH2CH3); 52.178 (C=C(CN)2); 113.578 (CN); 115.730 (CN);
117.662 (CAr); 128.183 (CAr); 136.980 (CAr); 140.192 (CAr);
154.460 (C=C(CN)2).
For an Xꢀray diffraction experiment, the crystals of (E)ꢀ3ꢀ
(2ꢀchlorophenyl)ꢀ2ꢀcyanoꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfenate (4b)
were obtained by its recrystallization from EtOH—Me2CO (1 : 2).
The crystals are monoclinic, C10H7N2OSCl; at 20 C, a =
= 15.0992(8) Å, b = 9.0095(5) Å, c = 7.7519(5) Å,  = 101.878(6),
3
V = 1032.0(1) Å , Mr = 238.69, Z = 4, space group P21/c, dcalc
=
= 1.536 g cm–3, (MoꢀK) = 0.543 mm–1, F(000) = 488. The
intensities of 6253 reflections (2351 independent reflections,
Rint = 0.024) were measured on an Xcaliburꢀ3 diffractometer
(MoꢀK radiation, a CCD detector, graphite monochromator,
 scan mode, 2max= 55). The unit cell parameters were calcuꢀ
lated from the collected data. The structure was solved by the
direct methods with the SHELXTL program package.35 The
hydrogen atoms were located in the difference electronꢀdensity
maps and refined isotropically. The structure was refined on F2
by the fullꢀmatrix leastꢀsquares method in the anisotropic apꢀ
proximation for the nonꢀhydrogen atoms. Final residuals are
wR2 = 0.103 for 2308 reflections and R1 = 0.037 for 1699 reflecꢀ
tions with F > 4(F) (S = 0.980). Comprehensive data for strucꢀ
ture 4b have been deposited with the Cambridge Crystallographic
Data Centre (CCDC No. 842953).
(E)ꢀ2ꢀCyanoꢀ3ꢀ(2ꢀfuryl)ꢀ1ꢀiminiopropꢀ2ꢀeneꢀ1ꢀsulfenate
(4d). Yield 88%, cherryꢀred bright needles, decomp. >140 C.
Found (%): C, 49.20; H, 3.07; N, 14.53. C8H6N2O2S (M = 194.21).
Calculated (%): C, 49.48; H, 3.11; N, 14.42. IR, /cm–1: 3310
1
(NH), 2220 (CN). H NMR (200 MHz, DMSOꢀd6), : 6.81,
7.27, and 8.12 (all m, 1 H each, 2ꢀfuryl); 7.95 (s, 1 H, ArCH=);
8.73* (br.s, 2 H, H2N+=).
Synthesis of (arylaminomethylidene)malononitriles 7a,b (genꢀ
eral procedure). A 10% aqueous solution of KOH (3.0 mL,
5.4 mmol) was added to a suspension of an appropriate 3ꢀaminoꢀ
thioacrylamide 2a,b (5 mmol) in EtOH (10 mL). The reaction
mixture was heated with stirring to homogenization. The resultꢀ
ing red solution was filtered through a paper filter. The mother
liquor was cooled and an excess of 32% H2O2 (5.0 mL, ~51.7 mmol)
was added dropwise. This initiated a vigorous exothermic reacꢀ
tion accompanied by oxygen evolution and rapid formation of
a light yellow precipitate. The mixture was stirred at 20 C for 2 h
and the precipitate was filtered off. To remove inorganic impuriꢀ
ties, it was washed with water and dissolved in acetone—EtOH
(1 : 1). The resulting solution was filtered through a paper filter.
After 3—4 days, product 7a,b was isolated from the mother liquor.
(Anilinomethylidene)malononitrile (7a). Yield 80%, light yelꢀ
low crystals, m.p. 250—252 C (EtOH—acetone) (subl., transꢀ
formed into large colorless needles; cf. Refs: m.p. 240—242 C,12
253—255 C,31,32 254—256 C,33 and 245—247 C34). Found (%):
C, 70.80; H, 4.16; N, 24.80. C10H7N3 (M = 169.19). Calculatꢀ
ed (%): C, 70.99; H, 4.17; N, 24.84. IR, /cm–1: 3200—3180 (NH),
2210 and 2224 (2 CN), 1650 (C=C). 1H NMR (200 MHz,
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Received September 14, 2011;
in revised form October 18, 2012