N-(2,2-Dichloro-2-phenylethylidene)arenesulfonamides in reactions with secondary amines

Article abstract of DOI:10.1134/S1070363208070141

N-(2,2-Dichloro-2-phenylethylidene)arenesulfonamides were synthesized by a modified procedure, and their reactions with secondary amines were studied for the first time. Reactions of imines with dialkylamines proceed at room temperature to afford α,α-dichloromethylbenzene and N,N-dialkyl-N′-(arenesulfonyl)formamidines arising from the haloform cleavage of the initially formed unstable N-(1-dialkylamino-2,2-dichloro-2- phenylethyl)arenesulfonamides. When the reaction is carried out upon cooling to 0°C, the products of the nucleophilic addition of secondary amines to azomethines, N-(1-dialkylamino-2,2-dichloro-2-phenylethyl) are formed in yields of no higher than 5%. Nonempirical calculations of ¹³C-¹H spin-spin coupling constants and their experimental measurements for the series of the synthesized N-arenesulfonamides were performed to show that these compounds exist in solutions exclusively as E isomers. Preferable conformations of the investigated compounds and the relative energies of their E and Z isomers in the gas phase were determined by quantum-chemical calculations at the MP2/6-311G**level of theory. The NMR spectral data revealed restricted rotation of the N,N-dialkylamino group about the partially double C-NAlk₂ bond in the molecules of N-arenesulfonylformamidines.

Full text of DOI:10.1134/S1070363208070141

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 7, pp. 1371–1379. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © I.B. Rozentsveig, G.N. Rozentsveig, A.N. Mirskova, K.A. Chernyshev, L.B. Krivdin, G.G. Levkovskaya, 2008, published in Zhurnal
Obshchei Khimii, 2008, Vol. 78, No. 7, pp. 1135–1143.
N-(2,2-Dichloro-2-phenylethylidene)arenesulfonamides
in Reactions with Secondary Amines
I. B. Rozentsveig, G. N. Rozentsveig, A. N. Mirskova,
K. A. Chernyshev, L. B. Krivdin, and G. G. Levkovskaya
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: i_roz@irioch.irk.ru
Received July 9, 2007
Abstract—N-(2,2-Dichloro-2-phenylethylidene)arenesulfonamides were synthesized by a modified procedure,
and their reactions with secondary amines were studied for the first time. Reactions of imines with
dialkylamines proceed at room temperature to afford α,α-dichloromethylbenzene and N,N-dialkyl-N'-
(arenesulfonyl)formamidines arising from the haloform cleavage of the initially formed unstable N-(1-
dialkylamino-2,2-dichloro-2-phenylethyl)arenesulfonamides. When the reaction is carried out upon cooling to
0°C, the products of the nucleophilic addition of secondary amines to azomethines, N-(1-dialkylamino-2,2-
dichloro-2-phenylethyl) are formed in yields of no higher than 5%. Nonempirical calculations of 13C–1H spin–
spin coupling constants and their experimental measurements for the series of the synthesized N-
arenesulfonamides were performed to show that these compounds exist in solutions exclusively as E isomers.
Preferable conformations of the investigated compounds and the relative energies of their E and Z isomers in
the gas phase were determined by quantum-chemical calculations at the MP2/6-311G** level of theory. The
NMR spectral data revealed restricted rotation of the N,N-dialkylamino group about the partially double С–
NAlk2 bond in the molecules of N-arenesulfonylformamidines.
DOI: 10.1134/S1070363208070141
The combination of the electron-deficient azo-
methine group and the dichloromethylene fragment in
the molecules of N-(2,2-dichloro-2-phenylethylidene)-
arenesulfonamides allows these compounds to be
considered as promising reagents for various synthetic
applications, like preparation of various polyfunctional
cyclic or acyclic amides containing pharmacophore
fragments, which are of interest as NH acids, potential
ligands, and monomers. However, unlike chloral
arenesulfonylimines, arenesulfonylimines derived from
α,α-dichlorophenylacetaldehyde are less studied. Many
important synthetic routes using these representatives
of activated azomethines as key reagents could not be
realized mainly due to the absence of convenient
methods of their synthesis.
Earlier we showed [1–5] that the reaction of N,N-
dichloroarenesulfonamides with phenylacetylene
results in formation of mixtures of arenesulfonamide
derivatives I–IV, of which N-chloro-N-(2-chloro-2-
phenylvinyl)amides Ia–Ic, N-(2-phenyl-2-chlorovinyl)-
amides IIa–IIc, 1,1-bis(arenesulfonylamino)-2,2-di-
chloro-2-phenylethanes IIIa–IIIc, and N-(arene-
sulfonyl)dischlorophenylacetaldimines IVa–IVc were
isolated in 40–75% yields.
A plausible mechanism of the formation of imines
IVa–IVc in this reaction should involve the step of
addition of dichloroamides to phenylacetylene to form
adducts Ia–Ic and their subsequent isomerization, as
discussed in detail in [1–3].
In this connection, an actual problem was to im-
prov of the protocol for preparation of N-sulfonyl-
imines derived from dichlorophenyl-acetaldehyde,
based on the reaction of N,N-dichloroarenesulfon-
amides with phenylacetylene, and further develop of
the chemistry of these azomethines.
No alternative synthetic approaches to imines IVa–
IVc have so far been developed. The known schemes
for synthesis of halogenated imines, based on
condensation of amides, isocyanates, or sulfonyl
isocyanates with aldehydes [6], are not used for
1371

1372
ROZENTSVEIG et al.
ArSO2NHCH
IIа_IIc
CClPh
ArSO2NClCH
CClPh
(ArSO2NH)2CHCCl2Ph
ArSO2NCl2 + PhC
CH
Iа_Ic
IIIа_IIIc
ArSO2N
CHCCl2Ph
IVа_IVc
Ar = Ph (a), 4-ClC6H4 (b), 4-MeC6H4 (c).
azomethine derivatives of α,α-dichlorophenylacetal-
dehyde, apparently due to a highly laborous
experiment and poor availability of dichlorophenyl-
acetaldehyde.
enamides Ia–Ic, while heating at the final reaction
stage favors 1,3-chlorotropic rearrangement, thus
increasing the yields of target azomethines IVa–IVc.
Imines IVa–IVc precipitate upon cooling of the
reaction mixture and can be readily separated and used
for further synthetic transformations without additional
crystallization. When the reaction mixture is kept cool
for a long time after imines IVa–IVc have been
separated, by-product diaminoethanes IIIa–IIIc
precipitate. It is noteworthy that no N-chloro-N-(2-
chloro-2-phenylvinyl)amides Ia–Ic and N-(2-phenyl-2-
chlorovinyl)amides IIa–IIc are present in the reaction
mixture.
We could optimize conditions for the reaction of
N,N-dichlorosulfonamides with phenylacetylene to
improve the yield of imines IVa–IVc and to simplify
the procedure.
It was found that the yields of target imines IVa–
IVc reach a maximum, when the reaction of N,N-
dichloroarenesulfonamides with acetylene is per-
formed under argon in CCl4. Therewith, reagent
addition order is of principal importance. When N,N-
dichloroamide is added to a solution of phenyl-
acetylene, the yields of imines IVa–IVc are
substantially higher than when the reagents are mixed
in the reverse order (90–95 vs. 40–64%). The reaction
has an inductive period after which it proceeds with a
notable self-heating (up to 50°C). It is important that
the reaction mixture is heated for 3 h at 50–60°C after
the exothermic process has been complete.
Therefore, conditions were found that allowed us to
substantially improve the yields of target azomethines
IVa–IVc and exclude fomation of hardly separable by-
products.
The formation of diamides IIIa–IIIc and imines
IVa–IVc is proved by spectral data. Physicochemical
characteristics of these are consistent with published
data [4, 5] (Tables 1 and 2).
It can be suggested that the found conditions un-
favor side reactions, such as chlorination and
oligomerization of phenylacetylene and addition of
excess dichloroamide to initially formed N-chloro-
Reported reactions of dichlorophenylacetaldimines
with N-nucleophiles were limited to reactions with
carboxamides and arenesulfonamides [4, 5], acryl-
amide [7], thioacetamide, and thiourea [8]. The amides
Table 1. Yields, melting points, and elemental analyses of 1,1-bis(arenesulfonylamino)-2,2-dichloro-2-phenylethanes IIIa–
IIIc and N-(2,2-dichloro-2-phenylethylidene)arenesulfonamides IVa–IVc
Found, %
Calculated, %
Comp. Yield,
mp,
Formula
no.
%
°С
С
Cl
N
S
C
Cl
N
S
6
3
210–213
217–219
200–202
101–102
104–105
105–106
50.02
43.09
50.98
50.90
46.04
52.37
14.15
25.22
13.42
21.43
29.24
20.29
6.02
5.53
5.89
4.61
4.03
4.37
13.92
12.02
12.98
9.45
C20H18Cl2N2O4S2
C20H16Cl4N2O4S2
C22H22Cl2N2O4S2
C14H11Cl2NO2S
C14H10Cl3NO2S
C15H13Cl2NO2S
49.49
43.34
51.46
51.23
46.37
52.64
14.61
25.58
13.81
21.60
29.33
20.72
5.77
5.05
5.46
4.27
3.86
4.09
13.21
11.57
12.49
9.77
IIIa
IIIb
IIIc
IVa
IVb
IVc
7
90
95
91
8.29
8.84
9.04
9.37
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

N-(2,2-DICHLORO-2-PHENYLETHYLIDENE)ARENESULFONAMIDES
1373
1
Table 2. IR and H NMR spectra of 1,1-bis(arenesulfonylamino)-2,2-dichloro-2-phenylethanes IIIa–IIIc and N-(2,2-di-
chloro-2-phenylethylidene)arenesulfonamides IVa–IVc
IR spectrum, ν, cm–1
1Н NMR spectrum (DMSO-d6), δ, ppm
Comp.
no.
3JNH–CH
,
Hz
NH
SO2
другие
CH
NH
Ar
3220
3220
3220
–
1160, 1340
1160, 1320
1165 1340
1160, 1310
1170, 1310
1650, 1310
3040 (=С–Нarom
3040 (=С–Нarom
3045 (=С–Нarom
1620 (C=N)
)
)
)
5.90 t
5.79 t
5.38 t
8.51 s
8.58 s
8.55 s
8.86 d
7.40–7.52 m
7.27–7.98 m
7.29–7.67 m
7.33–7.83 m
7.35–7.90 m
7.30–7.82 m
11
11.5
9.3
–
IIIa
IIIb
IIIc
IVa
IVb
IVc
9.02 d
8.28 d
–
–
–
–
1630 (C=N)
–
–
1630 (C=N)
–
were shown to add to the imino group to afford the
corresponding diamides.
The presence of compounds VIII and IX in the
reaction mixtures was proved by physicochemical
1
methods (see Experimental). The H NMR spectra
We have continued our systematic reactivity
research and studied reactions of arenesulfonylimines
IVa–IVc with secondary amines.
contain signals of the NH–CH fragment and signals of
the aromatic rings and dialkylamino groups with
expected integral intensities.
It was found that compounds IVa–IVc react with
excess dialkylamines in carbon tetrachloride without
heating by way of haloform cleavage to form N-
(dialkylaminomethylidene)arenesulfonamides V–VII
in good yields.
The formation of amidines V–VII is confirmed by
spectral methods. Compounds Va–Vc, VIa, VIb, and
VIIa were described earlier [9, 19], and their
physicochemical characteristics are consistent with
published data (Tables 3 and 4). Amidines Vd, VIc,
and VIIb were synthesized for the first time.
The formation of α,α-dichloromethylbenzene was
1
proved by NMR spectroscopy. Thus, the H NMR
1
As follows from the H and 13C NMR spectra,
spectra of the reaction mixtures contained a signal at
6.6 ppm, which is consistent with the spectrum of an
authentic sample.
formamidines Va–Vd, VIa–Vc, VIIa, and VIIb exist
in solutions as individual isomers, and it was one of
the aims of the present work to assign their
configuration. The structure of these compounds was
established by means of two-dimensional homo- and
heteronuclear correlation techniques 2D-NOESY,
Furthermore, the reactions of imines IVa and IVb
with diethylamine under cooling involve addition of
the secondary amine to the imino group to form
compounds VIII and IX. We failed to isolate pure
adducts VIII and IX because of their low stability. The
yields of these products were no higher 5% as judged
from the NMR spectra.
1
HSQC, and HMBC. The measured H and 13С NMR
chemicals shifts and 13С–1Н coupling constants, that
confirm the structure of all the studied compounds, are
listed in Tables 4 and 5.
R1
To establish the configuration of the obtained
formamidines, we made use of a method based on
experimental measurement and theoretical calculation
of 13С–1H coupling constants which are quite sensitive
to the orientation of the lone electron pair (LEP) on the
nitrogen atom in azomethines, as was first shown with
oximes [10]. The drastic difference of the direct 13С–
1Н coupling constants with the imine carbon atom is,
first, due to through-space interaction of the nitrogen
LEP with an adjacent bond cis to the LEP. This opens
an additional channel for transmission of spin–spin
coupling interaction, leading to a positive contribution
into the total 1Jcis constant. Second, the electron density
HNR1R2
ArSO2N CHN
+ PhCHCl2
R2
Va_Vd, VIa_VIc, VIIa, VIIb
IVa_IVc
0oC
ArSO2NHCHCCl2Ph
NEt2
R1 = R2 = Et
5%
VIII, IX
Ar = Ph (Va–Vd, VIII), 4-ClC6H4 (VIa–VIc, IX), 4-MeC6H4
(VIIa, VIIb), R1 = R2 = Et (Va, VIa, VIIa), Pr (Vb, VIb), Bu
(Vc), R1 = Me, R2 = Pr (Vd, VIc, VIIb).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

1374
ROZENTSVEIG et al.
Table 3. Yields, melting points, and elemental analyses of N,N-dialkyl-N'-(arenesulfonyl)formamidines Va–Vd, VIa–VIc,
VIIa, and VIIb
Found, %
Calculated, %
Comp. Yield,
mp, °С
Formula
no.
%
(mp [9])
С
H
N
S
C
H
N
S
83
75
77
62
89
81
67
73
59
72–73 (73–75)
63–66 (60–65)
43–47 (36–45)
–
55.41
58.15
60.38
54.75
48.23
51.75
47.63
56.53
56.38
6.68
7.43
8.07
6.31
5.38
6.23
5.13
7.06
7.08
11.82
10.62
9.73
13.83
11.14
11.01
12.99
11.85
10.74
11.32
12.82
12.95
C11H16N2O2S
C13H20N2O2S
C15H24N2O2S
C11H16N2O2S
54.98
58.18
60.78
54.98
6.71
7.51
8.16
6.71
5.50
6.32
5.50
7.13
7.13
11.66
10.44
9.45
13.34
11.95
10.82
13.34
11.67
10.59
11.67
12.60
12.60
Vа
Vb
Vc
Vda
VIа
VIb
VIc
VIIа
VIIba
11.16
10.52
9.51
11.66
10.20
9.25
78–81 (75–80)
82–85 (80–83)
79–80
C11H15ClN2O2S 48.09
C13H19ClN2O2S 51.56
C11H15ClN2O2S 48.09
10.53
11.47
11.38
10.20
11.01
11.01
57–61 (55–60)
–
C12H18N2O2S
C12H18N2O2S
56.67
56.67
a Tarry compounds.
Table 4. IR and 1Н NMR spectra of N,N-dialkyl-N'-(arenesulfonyl)formamidines Va–Vd, VIa–VIc, VIIa, and VIIb
IR spectrum, ν, cm–1 1Н NMR spectrum (CDCl3), δ, ppm
Comp. no.
C=N
SO2
СНalkyl
HC=N
s-cis-Alkа
s-trans-Alkb
Ar
1620
1610
1160, 1290 2950–2980
1160, 1290 2960–2985
8.16
8.08
3.48 q; 1.14 t
3.38 q; 1.26 t
7.47–7.89
7.37–7.77
Vа
3.26 t; 1.47 m; 0.74 t
3.18 t; 1.52 m; 0.78 t
Vb
1610
1140, 1290 2945–2970
8.15
3.41 t; 1.52 m; 1.27 m; 0.87 t 3.30 t; 1.59 m; 1.30 m; 0.95 t 7.44–7.88
Vc
Vd (s-cis)
Vd (s-trans)
1620
1620
1150, 1290 2950–2980
1150, 1290 2950–2980
8.13
8.16
3.38 t; 1.56 m; 0.84 t
2.97 s
3.08 с
7.42–7.93
7.42–7.93
3.29 t; 1.62 m; 0.88 t
1620
1620
1160, 1310 2950–2980
1150, 1310 2940–2970
8.14
8.14
3.48 q; 1.15 t
3.39 q; 1.27 t
7.43–7.82
7.43–7.81
VIa
VIb
3.37 t; 1.58 m; 0.87 t
3.28 t; 1.65 m; 0.92 t
VIc (s-cis)
1620
1620
1160, 1290 2945–2980
1160, 1290 2945–2980
8.13
8.16
3.40 t; 1.59 m; 0.87 t
2.99 s
3.11 s
7.43–7.82
7.43–7.82
VIc (s-trans)
3.31 t; 1.65 m; 0.91 t
1620
1620
1140, 1330 2940–2990
1160, 1310 2950–2990
1160, 1310 2950–2990
8.01
8.14
8.17
3.34 q; 1.01 t
3.40 t; 1.61 m; 0.87 t
2.98 s
3.27 q; 1.13 t
3.09 s
7.13–7.61
7.26–7.76
7.26–7.76
VIIа
VIIb (s-cis)
VIIb (s-trans) 1620
а N–Alk group is s-cis to the C=N bond. b N–Alk group is s-trans to the C=N bond.
3.29 t; 1.65 m; 0.91 t
1Jcis
13C
is transferred from the nitrogen LEP orbital to the
1H
Alk2N
1H
1Jtrans
Alk2N
antibonding orbital of a bond trans to the LEP (nσ–σ*
interaction). As a result, the latter bond is elongated,
the spin-spin coupling gets weaker, and the coupling
constant decreases. All this leads to a negative
contribution into the total 1Jtrans constant. The nature of
this effect is well studied in a series of theoretical
works [11] and widely used for configurational
assessment of azomethines of various structures [12].
13C
N
N
SO2Ar
ArO2S
E
Z
[13], including all the four spin–spin coupling
contributions at the nonrelativistic level: Fermi contact
(JFC), spin–dipole (JSD), diamagnetic spin–orbital
(JDSO), and paramagnetic spin–orbital (JPSO), using
The coupling constants were calculated using by
the use of a well-established nonempirical Second
Order Polarization Propagator Approach (SOPPA)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

N-(2,2-DICHLORO-2-PHENYLETHYLIDENE)ARENESULFONAMIDES
1375
Table 5. 13С NMR chemical shifts and 13С–1Н coupling constants of N,N-dialkyl-N'-(arenesulfonyl)formamidines Va–Vd,
VIa–VIc, VIIa, and VIIb
13С NMR chemicals shifts (CDCl3), δ, ppm
J, Hz
Comp. no.
Vа
С=N
Ci
Co
Cm
Cp
s-cis-Alkа
46.80; 11.71
s-trans-Alkb
40.62; 14.12
1J(C1,Нα)
180.3
157.95 142.40 128.37 125.84 131.39
158.92 142.64 128.40 125.97 131.39
180.3
180.9
180.5
180.9
180.3
180.9
180.5
181.4
180.9
180.3
180.3
Vb
54.02; 19.62; 10.51
47.67; 21.56; 10.87
Vc
158.78 142.58 128.47 126.05 131.50 52.16; 28.48; 19.40; 13.40 45.80; 30.44; 19.71; 13.48
Vd (s-cis)
Vd (s-trans)
VIa
159.28 142.54 128.63 126.23 131.70
159.02 142.43 128.68 126.32 131.78
158.08 141.17 128.74 127.67 137.72
158.99 141.26 128.87 127.77 137.89
159.25 142.34 128.98 127.96 138.11
158.99 141.14 129.68 126.32 138.78
157.88 139.57 126.01 129.07 142.08
159.18 140.08 126.46 129.33 142.34
158.92 139.71 126.56 129.38 142.46
49.68; 19.28; 10.96
33.48
39.51
56.32; 21.14; 10.61
40.87; 14.28
47.05; 11.88
54.30; 19.90; 10.77
49.90; 19.34; 11.11
33.65
VIb
47.88; 21.78; 11.14
39.68
VIc (s-cis)
VIc (s-trans)
VIIa
56.53; 21.31; 10.75
40.76; 14.25
46.86; 11.82
49.79; 19.44; 11.12
33.57
VIIb (s-cis)
39.56
VIIb (s-trans)
56.42; 21.55; 10.77
a N–Alk group is s-cis to the C=N bond. b N–Alk group is s-trans to the C=N bond.
special Dunning’s correlation-consistent basis sets [14]
augmented with functions icluding intrinsic correlation
effects [15] and the Sauer’s basis set [16], as described
in [17].
Internal rotation about the С–NAlk2 bond in
formamidines V–VII is restricted due to its partially
double character caused by conjugation of the
dialkylamino nitrogen LEP with the azomethine π
system. This is also proved by the calculated barriers
to internal rotation and the dynamic temperature
effects observed in the NMR spectra. The nitrogen
LEP in both the E and the Z isomers of model
formamidine X in the optimized preferable conforma-
tions is orthogonal to the plane of the azomethine
fragment. In the gas phase, according to the MP2/6-
311G** results for compound X, the activation barrier
of free rotation is 23 kcal mol–1. Actually, the alkyl
substituents in the N,N-dialkylamino groups in all the
studied N-arenesulfonylformamidines are structurally
Comparison of the experimental 13С–1Н coupling
constants with the calculated values (Tables 5 and 6)
shows that N-arenesulfonylformamidines all exist in
solution as individual Е isomers. Indeed, the
13
experimental С–1Н coupling constants of the studied
formamidines are nicely reproduced by those
calculated for the Е isomer of the corresponding model
amidine X and substantially differ from the calculated
spin–spin coupling constants for a hypothetical Z
isomer, that allows unambiguous assessment of Е
configuration to formamidines V–VII.
1
nonequivalent and give two sets of signals in the Н
and 13С NMR spectra, which is caused by the partially
Spin–spin coupling constants were calculated for
preferable rotamers of the E and Z isomers optimized
at the MP2/6-311G** level. The geometries and
relative energies are shown in Fig 1. It should be noted
that for the Е isomer of model compound X is 7.8 kcal
mol–1 more stable than the corresponding Z isomer in
their preferable conforma-tions. This is in line with the
above-discussed results based on the experimental
measurement and theoretical calculation of 13С–1Н
coupling constants, which provide unambiguos
evidence in favor of the Е configuration of all the
studied amidines.
double character of the C–NAlk2 bond and,
1
Table 6. Calculated (SOPPA) and experimental J(С1,Н)
coupling constants (Hz) for model formamidine X
Isomer JDSO
JPSO
–0.6
–0.4
JSD
0.7
0.5
JFC
J
Experiment
180.3a
E
1.3
1.2
177.1 178.5
187.3 188.6
Z
a For compound Vа.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

1376
ROZENTSVEIG et al.
consequently, a high barrier to restricted internal
rotation in these compounds. Analogous effects were
observed earlier in similar sulfonylformamidines
H3SO2N=CHNR2 (R = Me, Et) [18] and N,N-dimethyl
derivatives of arenesulfonylformamidines [9].
haloform cleavage under the action of secondary
amines was demonstrated for the first time, and a
convenient synthesis of N-arenesulfonyl-N',N'-dialkyl-
formamidines, alternative to that patented earlier [19],
was developed. The structure of the synthesized
compounds was studied by physicochemical methods.
Assignment of alkyl group signals to different
1
rotamers in the H NMR spectra of compounds Va–
EXPERIMENTAL
Vd, VIa–Vc, VIIa, and VIIb was made by the use of
the 2D-NOESY method which allows one to observe a
characteristic cross-peak of the N–CH2 protons of the
s-cis alkyl group and the azomethine proton. As an
illustration, we present in Fig. 2 the 2D-NOESY
spectrum of N'-(benzenesulfonyl)-N,N-dibutylform-
amidine (Vc).
1
The H and 13С NMR spectra were registered on a
1
Bruker DPX-400 spectrometer at 400.13 MHz for Н
and 100.61 MHz for 13С for 5–10% solutions in CDCl3
and DMSO-d6, internal reference HMDS. The 13С–1Н
coupling constants were measured using 2D HSQC
and HMBC pulse sequences with the following
parameters: spectrum width 800 Hz (1Н) and 5 kHz
(13С), pulse length 6 μs (1Н) and 14 μs (13С), relaxation
delay 2.5 s, acquisition time 2 s, digital resolution
0.1 Hz/point (1Н) and 0.5 Hz/point (13С).
It is interesting to mention that in the case of N-
methyl-N-propylformamidines Vd, VIc, and VIIb we
can observe restricted rotation on an NMR time scale:
The equilibrium s-trans:s-cis ratio of 70:30 is reached
within 2–3 h (Fig. 3).
N-(2,2-Dichloro-2-phenylethylidene)benzenesul-
fonamide (IVа) and 1,1-bis(benzenesulfonylamino)-
2,2-dichloro-2-phenylethane (IIIа). To a solution of
4 ml of phenylacetylene in 20 ml of carbon
tetrachloride, 6.78 g of N,N-dichlorobenzenesulfon-
amide was added in portions (0.4–0.5 g) with stirring
and argon bubbling. Each further portion of the
Therefore, in the present work the method of
preparation of arenesulfonylimines derived from
dichlorophenylacetaldehyde, based on the reaction of
N,N-dichloroarenesulfonamides with phenylacetylene,
was substantially optimized. The ability of N-(2,2-
chloro-2-phenylethylidene)arenesulfonamides to suffer
C
C
N
N
C
C
C
C
O
N
N
O
S
S
O
O
X(E), 0.0 kcal mol–1
X(Z), 7.8 kcal mol–1
Fig. 1. Predominant conformations and relative energies of the E and Z isomers of model formamidine X, calculated by the MP2/6-
311G** method.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

N-(2,2-DICHLORO-2-PHENYLETHYLIDENE)ARENESULFONAMIDES
1377
Bu
N
Bu
s-cis
s-trans
CH3 (s-trans)
CH2 (s-cis)
CH2 (s-trans)
CH3 (s-cis)
Hα
C
N
Hα
CDCl3
N–CH2CH2 (s-cis)
N–CH2CH2 (s-trans)
Hp
N–CH2 (s-trans)
N–CH2 (s-cis)
Hm
o
H
SO2
δ, ppm
CH3 (s-cis)
CH3 (s-trans)
1
2
3
4
5
6
7
8
CH2 (s-cis)
CH2 (s-trans)
N–CH2CH2 (s-cis)
N–CH2CH2 (s-trans)
N–CH2 (s-trans)
N–CH2 (s-cis)
CDCl3
p
Hm
o
H
H
Hα
8
7
6
5
4
3
2
1
δ, ppm
Fig. 2. 2D-NOESY spectrum of N'-(benzenesulfonyl)-N,N-dibutylformamidine (XVI) in CDCl3 (400.13 MHz).
dichloroamide was added after the heat release pro-
duced by the previously added portion had been
complete. The mixture was not allowed to overheat
above 40°C. After all dichloroamide has been added,
the reaction mixture was stirred for 2–3 h at 55–60°C,
kept at –5°C until imine IVа precipitated. The
precipitate was separated by filtration, washed on the
filter with CCl4, and dried under a vacuum over Р2О5.
When the filtrate was stored in the cold 3 days,
diamide IIIa precipitated. The yields of compounds
IVа and IIIa were 8.86 g (90%) and 0.50 g (3%),
respectively.
then the solvent was removed in acvacuum. The
residue was washed with water, dried, and crystallized
from CCl4 or hexane. Yield 1.40 g (83%).
Formamidines Vb–Vd, VIa–VIc, VIIa, and VIIb
were synthesized similarly by the reactions of
azomethines IVa–IVc with diethylamine, dipropyl-
amine, dibutylamine, and methylpropylamine. The
yields, melting points, and spectral characteristics of
compounds Vа–Vc, VIа, Vb, and VII are given in
Tables 3, 4, and 5.
N-(2,2-Dichloro-1-diethylamino-2-phenylethyl)-
benzenesulfonamide (VIII) was detected by 1H NMR
in the reaction mixture of imine IVа and diethylamine.
Compounds IIIb, IIIc and IVb, IVc were obtained
similarly. The yields, melting points, and spectral
characteristics are given in Tables 1 and 2.
1
From the H NMR data, the yield of compound VIII
1
was 5%. Н NMR spectrum (CDCl3), δ, ppm: 1.07 t,
N'-(Benzenesulfonyl)-N,N-diethylformamidine
(Vа). Imine IVа, 2.3 g, and 2.0 ml of diethylamine
were stirred for 3 h in 20 ml of carbon tetrachloride,
3.20 q [10Н, N(C2H5)2], 5.05 s (1H, CH), 6.67 s (1H,
NH), 7.10–7.73 m (10H, Ar).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

1378
ROZENTSVEIG et al.
Me
N
Pr
N
H
H
C
N
C
N
Pr
Me
Cl
Cl
SO2
SO2
s-trans
s-cis
N–CH3 (s-trans)
CH3 (s-trans)
CH3 (s-cis)
N–CH3 (s-cis)
N–CH2 (s-trans)
N–CH2 (s-cis)
CH2 (s-trans)
CH2 (s-cis)
∞
128 min
32 min
8 min
2 min
δ, ppm
3.5
3.0
2.5
2.0
1.5
1.0
0.5
5. Drozdova, T.I. and Mirskova, A.N., Zh. Org. Khim.,
N-(2,2-Dichloro-1-diethylamino-2-phenylethyl)-
4-chlorobenzenesulfonamide (IX) was detected by
1H NMR in the reaction mixture of imine IVb and
2001, vol. 37, no. 2, p. 297.
6. Levkovskaya, G.G., Drozdova, T.I., Rozentsveig, I.B.,
and Mirskova, A.N., Usp. Khim., 1999, vol. 68, no. 7,
p. 638.
1
diethylamine. From the H NMR data, the yield of
compound IX was 7%. 1Н NMR (CDCl3), δ, ppm: 1.05
t, 3.12 q [10Н, N(C2H5)2], 4.98 s (1H, CH), 6.73 s (1H,
NH), 7.35–7.87 m (9H, Ar).
7. Rozentsveig, I.B., Ushakova, I.V., Kondrashov, E.V.,
Rozentsveig, G.N., Levkovskaya, G.G., and Mirskova, A.N.,
Zh. Org. Khim., 2005, vol. 41, no. 10, p. 1588.
ACKNOWLEDGMENTS
8. Rozentsveig, G.N., Aizina, Yu.A., Rozentsveig, I.B.,
Levkovskaya, G.G., Sarapulova, G.I., Mirskova, A.N.,
and Drozdova T.I., Zh. Org. Khim., 2003, vol. 39, no. 4,
p. 590.
The work was financially supported by the Russian
Foundation for Basic Research (project nos. 05-03-
32231 and 05-03-97202).
9. Mirskova, A.N., Levkovskaya, G.G., Bryuzgin, A.A.,
Drozdova, T.I., Kalikhman, I.D., and Voronkov, M.G.,
Zh. Org. Khim., 1990, vol. 26, no. 1, p. 140.
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