Basicity of secondary penta-2,4-diynylamines and their reactions with phenyl isothiocyanate

Article abstract of DOI:10.1023/B:RUGC.0000025149.63076.f5

Secondary penta-2,4-diynylamines were synthesized, and their pK _a(MeOH) values were obtained by means of nonaqueous potentiometric titration. The reactions of the amines with phenyl isothiocyanate, leading to 2-(phenylimino)-5-p(prop-2-ynilidene)thiazolidines, were studied. The N-butyl- and N-benzylthiazolidines with alkyl substituents at the triple bond, formed by the reactions, undergo autooxidation into thiazolidin-4-ones.

Full text of DOI:10.1023/B:RUGC.0000025149.63076.f5

Russian Journal of General Chemistry, Vol. 73, No. 12, 2003, pp. 1893 1899. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 12, 2003,
pp. 2002 2008.
Original Russian Text Copyright
2003 by Sipkina, Balova.
Basicity of Secondary Penta-2,4-diynylamines
and Their Reactions with Phenyl Isothiocyanate
N. Yu. Sipkina and I. A. Balova
Research Institute of Chemistry, St. Petersburg State University, St. Petersburg, Russia
Received December 5, 2001
Abstract Secondary penta-2,4-diynylamines were synthesized, and their pKa(MeOH) values were ob-
tained by means of nonaqueous potentiometric titration. The reactions of the amines with phenyl isothio-
cyanate, leading to 2-(phenylimino)-5-(prop-2-ynilidene)thiazolidines, were studied. The N-butyl- and
N-benzylthiazolidines with alkyl substituents at the triple bond, formed by the reactions, undergo autooxida-
tion into thiazolidin-4-ones.
The effect of alkynyl substituents on the basicity
of amines have been studied previously. The pKa
values of alk-2-ynylamines determined by non-
aqueous potentiometric titration proved to be lower
by about 1 pKa unit compared with those of the
corresponding alkylamines [1]. In the present work
we synthesized a series of secondary 5-alkyl(phenyl)-
substituted penta-2,4-diynylamines with the aim to
assess the effect of conjugated triple bonds on the
basicity of the amino group. Reactions of the syn-
thesized amines with phenyl isothiocyanate were also
studied.
Diacetylenic amines are known to be available in
good yields by alkylation of primary amines with
1-bromoalka-2,4-diynes [2]. We made use of this re-
action to prepare penta-2,4-diynylamines Ia Ih
(Scheme 1).
Scheme 1.
KBrO
HC CCH2OH, Cu+
RC CH
RC Br
60 80%
RC CC CCH2OH
50 56%
RC CC CCH2NHR
Ia Ih
R NH2
PBr3, py
RC CC CCH2Br
70 80%
40 90%
R = Bu, R = Bu (a), R = C6H13, R = Bu (b), R = Ph, R = Bu (c), R = Bu, R = PhCH2 (d), R = Ph, R = PhCH2 (e), R =
Bu, R = Ph (f), R = Ph, R = Ph (g), R = Bu, R = 2,5-Cl2C6H3 (h).
Andreev et al. [3] showed that the mono-to-di-
akynylation ratio in the Hoffmann synthesis of prop-
2-ynylamines can be controlled by varying reagent
ratio and solvent polarity: The higher the basicity of
the amine, the less polar solvent is required to prevent
diakynylation.
other cases secondary acetylenic amines were single
reaction products. Under the same conditions, N-
propargyl derivatives of benzylamine and aniline (com-
pounds IVa and IVb) were obtained. Apart from Ig,
the resulting amines are oily substances quickly
darkening on handling. Their spectral characteristics
are given in Table 1.
Diacetylenic amines I derived from the strongly
basic butyl- and benzylamines {pKa(H2O) 12.06 and
10.61, respectively [4]} were prepared in low-polarity
solvents (pentane, hexane, benzene). The reactions
with the weakly basic aniline {pKa(H2O) 4.63 [4]}
were performed in a polar solvent (acetonitrile). Di-
alkynylation was observed only in the synthesis of
N-butyl(undeca-2,4-diynyl)amine (Ib), and in all the
The pKa values of amines Ia Ie and IVa were
determined by nonaqueous potentiometric titration in
methanol using a glass working electrode and a silver
chloride reference electrode. The resulting data are
given below.
Comp. no.
Ia
Ib
Ic
Id
Ie
IVa
pKa(MeOH)
8.82 8.95 8.78 8.13
7.86 8.27
1070-3632/03/7312-1893$25.00 2003 MAIK Nauka/Interperiodica

1894
SIPKINA, BALOVA
Table 1. IR and 1H and 13C NMR spectra of N-(penta-2,4-diynyl)amines I and N-benzyl(prop-2-ynyl)amine (IVa)a
Comp.
no.
1
IR spectrum, , cm
1H NMR spectrum, , ppm
13C NMR spectrum, C, ppm
Ia
Ib
Ic
Id
1270, 2855, 2870, 2970, 0.84 0.99 (6H), 1.29 1.57 (8H), 2.33 t 13.3, 13.5, 18.7, 20.0, 21.8, 30.5, 30.8,
2980, 3030, 3070, 3450 (2H, J 7 Hz), 2.37 br.s (1H), 2.63 t 38.1, 47.7, 65.2, 67.7, 74.8, 78.2
J 6 Hz), 3.44 s (2H)
2265, 2850, 2870, 2975, 0.84 0.99 (6H), 1.25 1.63 (12H),
2985, 3030, 3075, 3450 1.63 br.s (1H), 2.29 t (2H, J 7 Hz), 28.1, 30.9, 31.5, 38.2, 47.7, 65.2,
2.63 t (2H, J 6 Hz), 3.40 s (2H) 67.9, 74.8, 78.1
13.6, 13.7, 18.7, 20.0, 22.1, 27.9,
2275, 2850, 2975, 2985, 0.92 t (3H, J 7 Hz,), 1.30 1.54 (4H), 13.8, 20.6, 32.2, 38.9, 48.4, 67.3,
3030, 3045, 3075, 3455 2.44 br.s (1H), 2.68 t (2H, J 7 Hz), 74.2, 76.2, 83.7, 122.8, 129.7, 129.8,
3.57 s (2H), 7.35 7.61 (5H)
132.7
2260, 2850, 2970, 2990, 0.95 t (3H, J 7 Hz), 1.36 1.60 (4H), 13.3, 18.7, 21.8, 30.5, 37.9, 52.3,
3030, 3045, 3075, 3455 2.07 br.s (1H), 2.33 t (2H, J 7 Hz), 65.0, 66.1, 75.8, 80.1, 127.3, 128.6,
3.45 s (2H), 3.82 s (2H), 7.23 7.40 128.7, 140.5
(5H)
Ie
If
2260, 2850, 2970, 3030, 2.11 br.s (1H), 3.55 s (2H), 3.87 s 37.3, 51.5, 66.7, 73.1, 75.8, 82.6,
3045, 3065, 3075, 3450 (2H), 7.20 7.64 (10H)
120.9, 126.6, 128.3, 128.4, 129.2,
129.3, 132.1, 139.6
2270, 2850, 2980, 3070, 0.90 t (3H, J 7 Hz), 1.32 1.56 (4H), 13.3, 18.6, 22.0, 30.5, 33.4, 65.2,
3450
2.28 t (2H, J 7 Hz), 4.05 d (2H,
67.3, 74.8, 79.6, 113.5, 117.8, 129.3,
J 6 Hz), 5.31 t (1H, J 6 Hz), 6.62 148.1
6.79 (3H), 7.16 m (2H)
Ig
Ih
260, 2855, 2975, 3035,
3040, 3065, 3070, 3450 6.85 (3H), 7.16 7.29 (2H), 7.32
7.59 (5H)
4.13 s (2H), 4.75 br.s (1H), 6.68
33.3, 66.5, 73.5, 76.7, 82.5 113.8,
118.4, 121.5, 129.1, 129.6, 130.0,
132.9, 147.8
2275, 2875, 2890, 3030, 0.92 t (3H, J 7 Hz), 1.26 1.60 (4H), 13.2, 18.6, 22.0, 30.3, 33.1, 64.4,
3075, 3450
2.33 t (2H, J 7 Hz), 4.10 d (2H, J 67.6, 73.4, 80.9, 112.1, 118.0, 118.1,
6 Hz), 5.23 t (1H, J 6 Hz), 6.72 d.d 132.7, 133.6, 144.5
(1H, J 8, 2 Hz), 6.83 d (1H, J
2 Hz), 7.28 d (1H, J 8 Hz)
IVa
2330, 2980, 3035, 3070, 2.49 t (1H, J 2 Hz), 3.36 d (2H, J 41.7, 52.4, 79.9, 81.2, 126.8, 128.3,
3320, 3450 2 Hz), 3.67 s (2H), 7.30 7.50 (5H) 128.9, 141.5
a
The NMR spectra of compounds Ia Id were measured in acetone-d , and the other spectra, in D CCN.
6
3
The pKa(MeOH) values of the amines show that
the introduction into the and positions with
for N-phenyl-substituted diacetylenic amines If and Ig
and thus concluded that their pKa(MeOH) values are
lower than 4.
respect to the nitrogen atom of two conjugated triple
bonds makes the resulting amines less basic compared
with the parent amines. Therewith, N-butyl- and N-
benzyl-substituted amines Ia Ie get appreciably closer
together in basicity. The presence of the second triple
bond results in that amines I have appreciably lower
pKa(MeOH) values compared with alk-2-ynylamines,
as, for instance, is the case with benzylamines Ie and
IVa. The pKa(MeOH) of N-butyl(nona-2,4-diynyl)-
amine (Ia) is lower by almost unit compared with that
of N-butyl(hept-2-ynyl)amine (8.82 vs. 9.79 [1]}.
Andreev et al. [1] also estimated pKa(MeOH) for N-
(hept-2-ynyl)-substituted aniline (4.53) and showed
that amines with pKa < 4 cannot be titrated in
methanol. We failed to determine equivalence points
Acetylenic compounds are widely used in the
synthesis of various heterocycles, including thiazo-
lines and thiazolidines [5]. Easton et al. [6] were first
to show that N-(prop-2-ynyl)-substituted thioureas
prepared by the reaction of secondary -acetylenic
amines with phenyl isothiocyanate cyclize on distilla-
tion to 5-methylene-1,3-thiazolidin-2-imines.
Later Azerbaev et al. [7] found that primary alk-2-
ynylamines and secondary alk-2-ynylamines react
with phenyl isothiocyanates to form 2-amino-5-
methylene-1,3-thiazolines and 5-methylene-1,3-thiazo-
lin-2-imines, respectively. Thioureas obtained from
N-phenyl- and N-benzyl-substituted
-acetylenic
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

BASICITY OF SECONDARY PENTA-2,4-DIYNYLAMINES
1895
amines underwent cyclization, which was explained
by steric effects of the phenyl and benzyl substituents.
Reactions of diacetylenic amines with phenyl isothio-
cyanate have not been explored.
the presence of alkali. The least basic amine Ih does
not react with phenyl isothiocyanate in the presence of
alkali, and the reaction mixture undergo tarring when
heated. In the complex mixture of reaction products
we identified 2,5-dichloroaniline. Its formation can be
explained by the isomerization of amine Ih under the
action of base into N-(nona-1,3-diynyl)aniline which
is readily hydrated in the presence of traces of
moisture and then hydrolyzes with elimination of a
secondary amine. Similar transformations were pre-
viously observed in isomerization of N-phenyl(alk-2-
ynyl)amines under the action of lithium (2-amino-
ethyl)amide [8].
It is known the conjugated triple bonds make di-
acetylenic amines more sensitive to nucleophilic
attack. We failed to isolate or detect thioureas in all
the reactions of amines Ia Ig with phenyl isothio-
cyanate, since the products fast cyclized into N-phenyl-
5-(prop-2-ynylidene)-1,3-thiazolidin-2-imines IIa IIg
(Scheme 2). The cyclization of the intermediate
thioureas occurred regioselectively, involving nucleo-
philic attack of the mercapto group by a triple-bond
carbon closest to nitrogen.
N-(Prop-2-ynyl)-substituted benzylamine IVa and
aniline IVb were reacted with phenyl isothiocyanate
in acetonitrile. The reactions gave cyclic products, N-
phenyl-5-methylene-1,3-thiazolidin-2-imines Va and
Vb (Scheme 3).
Moreover, with the more basic N-butyl- and N-
benzylamines Ia, Ib, and Id, which bear alkyl sub-
stituents at the triple bond, the reaction mixtures
contained, along with thiazolidinimines IIa, IIb, and
IId, their autooxidation products thiazolidin-4-ones
IIIa, IIIb, and IIId.
Scheme 3.
NPh
Scheme 2.
PhNCS
HC CCH2NHR
RN
S
NPh
S
NPh
S
IVa, IVb
Va, Vb
PhNCS
R N
R N
O
Ia Ig
+
R = PhCH2 (a), Ph (b).
C CR
C CR
H
H
Thus, the presence of conjugated triple bonds in
amines I decreases the basicity of the amino group
and thus affects its reactivity toward phenyl isothio-
cyanate. On the other hand, the activation of one triple
bond in the presence of the other facilitates nucleo-
philic attack in the course of heterocyclization of di-
acetylenic thioureas, which occurs regioselectively in
mild conditions and gives thiazolidinimines contain-
ing a triple bond in the substituent.
IIa IIg
IIIa, IIIb, IIId
R = Bu, R = Bu (a), C6H13 (b), Ph (c); R = PhCH2, R =
Bu (d), Ph (e); R = Ph, R = Bu (f), Ph (g).
The reaction products were isolated by chromato-
graphy and characterized by spectral data (Table 2)
and elemental analyses (Table 3). The H NMR spec-
1
tra of thiazolidinimines IIa IIg contain a characteristic
signal of the methylene group of the thiazolidine ring,
EXPERIMENTAL
and the carbon atom of this group gives a signal at
C
56 ppm. The spectra of thiazolidinones IIIa, IIIb, and
The IR spectra were measured on a Specord IR-75
1
IIId lack similar signals. At the same time, the 13C
spectrometer for 1% CCl4 solutions. The H and 13C
NMR spectra contain a signal near
assignable to the C=O group.
165 ppm,
NMR spectra were obtained on a Bruker DPX-300
spectrometer (300 and 75.5 MHz, respectively) for
CD3CN and (D3C)2CO solutions. Elemental analysis
was performed on a Hewlett Packard-185B instru-
ment.
C
The reaction progress was found to be dependent
of the basicity of the amines and the polarity of the
solvent. Stronger bases, specifically N-butyl- and N-
benzylamine derivatives, fast react with phenyl iso-
thiocyanate both in nonpolar (hexane, benzene) and in
polar solvents at room temperature. Weakly basic
N-phenylsubstituted diacetylenic amines If and Ig
react with phenyl isothiocyanate only in a polar sol-
vent (acetonitrile) and in the presence of potassium
hydroxide. In diethyl ether, no reaction occurs even in
The basicity constants were determined by non-
aqueous potentiometric titration of a 0.008 M solution
of amine in methanol with a 0.1 N solution of per-
chloric acid in methanol using a 150 pH meter with a
glass working electrode and a silver chloride re-
ference electrode filled with a saturated solution of
KCl in methanol. Reference diphenylguanidine, pKa
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

1896
SIPKINA, BALOVA
1
Table 2. IR and H and 13C NMR spectra of N-phenyl-5-(prop-2-ynylidene)-1,3-thiazolidin-2-imines IIa IIg, 2-(phenyl-
imino)-5-(prop-2-ynylidene)-1,3-thiazolidin-4-ones IIa, IIb, and IId, and N-phenyl-5-methylene-1,3-thiazolidin-2-imines
Va and Vba
Comp.
no.
1
IR spectrum, , cm
1H NMR spectrum, , ppm
13C NMR spectrum, C, ppm
IIa 1575, 1630, 2200, 2870, 0.83 1.05 (6H), 1.28 1.75 (8H), 2.32 m 13.3, 13.7, 19.1, 20.2, 22.0, 29.4, 31.1,
2930, 2960, 3020, 3070 (2H), 3.58 t (2H, J 7 Hz), 4.50 d (2H, J 45.8, 55.1, 77.6, 97.8, 100.4, 122.3,
2 Hz) 5.71 t (1H, J 2 Hz), 6.89 d (2H, J 123.2, 129.2, 142.9, 152.4, 154.8
7 Hz), 7.04 t (1H, J 7 Hz), 7.28 m (2H)
IIb 1575, 1625, 2200, 2885, 0.77 1.10 (6H), 1.20 1.89 (12H),
13.4, 13.6, 19.1, 19.7, 22.1, 28.0, 28.2,
2935, 2975, 3025, 3060 2.30 m (2H), 3.55 t (2H, J 6 Hz), 4.40 m 28.7, 30.9, 43.5, 54.6, 77.0, 97.8, 99.6,
(2H), 5.54 m (1H), 6.82 d (2H, J 7 Hz), 121.5, 122.4, 128.3, 141.9, 151.3, 153.8
6.94 t (1H, J 7 Hz), 7.21 t (2H)
IIc 1580,
1630,
2200,
0.99 t (3H, J 7 Hz), 1.40 m (2H), 1.65 m 13.6, 20.2, 29.1, 46.0, 55.5, 86.2, 96.5,
2865, 2875, 2935, 2965, (2H), 3.55 t (2H, J 7 Hz), 4.50 m (2H), 99.5, 122.3, 123.1, 123.5, 129.0, 129.4,
3025,
3035,
3070
5.88 m (1H), 6.91 d (2H, J 7 Hz), 7.08 t 129.5, 131.5, 152.3, 145.5, 154.5
(1H, J 7 Hz), 7.25 7.47 (7H)
IId 1580, 1635, 2200, 2875, 0.87 t (3H, J 7 Hz), 1.41 1.51 (4H), 13.3, 19.1, 22.0, 30.9, 49.5, 54.7, 77.5,
2935, 2965, 3025, 3070 2.31 m (2H), 4.28 m (2H), 4.74 s (2H), 98.6, 100.8, 122.3, 123.6, 127.9, 128.4,
5.58 m (1H), 6.95 d (2H, J 7 Hz), 7.09 t 128.5, 129.1, 129.4, 142.3, 152.1, 155.5
(1H, J 7 Hz), 7.27 7.45 (7H)
IIe 1570, 1630, 2200, 2875, 4.39 d (2H, J 2 Hz), 4.76 s (2H), 5.83 t 48.8, 54.3, 85.3, 95.9, 99.2, 121.6, 122.3,
2965, 3025, 3040, 3075 (1H, J 2 Hz), 6.97 d (2H, J 7 Hz), 7.09 t 123.0, 127.2, 127.6, 128.2, 128.3, 128.5,
(1H, J 7 Hz), 7.26 7.52 (12H)
128.7, 130.7, 136.5, 144.1, 151.2, 154.2
IIf 1575, 1630, 2210, 2860, 0.89 (3H), 1.29 1.58 (4H), 1.98 m (2H), 13.2, 19.1, 22.0, 30.9, 56.8, 77.3, 98.8,
2875, 2940, 2960, 3035, 4.86 m (2H), 5.71 m (1H), 6.95 d (2H, J 100.8, 121.9, 123.4, 124.0, 125.3, 129.2,
3070
7 Hz), 7.12 t (1H, J 7 Hz), 7.21 t (1H, 129.5, 141.0, 141.4, 151.9, 154.1
J 7 Hz), 7.33 m (2H), 7.43 m (2H),
7.64 d (2H, J 7 Hz)
IIg 1575, 1635, 2200, 2850, 5.01 m (2H), 6.00 m (1H), 6.93 d (2H, 57.0, 86.1, 97.0, 100.1, 121.9, 122.6,
2875, 3035, 3070
J 8 Hz), 7.07 t (1H, J 7 Hz), 7.16 t (1H, 123.4, 123.9, 124.8, 128.8, 128.9, 129.0,
J 7 Hz), 7.24 7.49 (9H), 7.75 d (2H, J 129.4, 131.6, 141.1, 143.2, 151.6, 152.6
7 Hz)
IIIa 1580, 1630, 1710, 2200, 0.88 t (3H, J 7 Hz), 0.99 t (3H, J 7 Hz), 13.0, 13.5, 19.5, 20.2, 22.0, 29.8, 30.6,
2815, 2825, 2935, 2960, 1.28 1.60 (6H), 1.75 q (2H, J 7 Hz), 43.0, 77.5, 107.2, 111.2, 121.4, 125.2,
3025, 3065, 3085
2.45 t. d (2H, J 7, 2 Hz), 3.94 t (2H, J 129.2, 135.0, 148.9, 150.0, 164.3
7 Hz), 6.66 t (1H, J 2 Hz), 7.02 d (2H, J
8 Hz), 7.20 t (1H, J 8 Hz), 7.42 m (2H)
IIIb 1585, 1630, 1720, 2215, 0.87 1.10 (6H), 1.19 1.64 (10H), 1.74 q 13.5, 13.8, 19.8, 20.2, 22.7, 28.3, 28.5,
2865, 2875, 2925, 2960, (2H, J 7 Hz), 2.45 t. d (2H, J 7, 2 Hz), 29.6, 31.4, 43.1, 77.6, 107.4, 111.2,
3020, 3035, 3060, 3080 3.93 t (2H, J 6 Hz), 6.60 t (1H, J 2 Hz), 121.3, 125.2, 129.8, 135.3, 148.8, 150.4,
6.92 d (2H, J 7 Hz), 7.13 t (1H, J 7 Hz), 164.9
7.34 m (2H)
IIId 1585, 1625, 1710, 2210, 0.88 t (3H, J 7 Hz), 1.33 1.57 (4H), 13.2, 19.5, 22.0, 30.5, 46.4, 77.5, 107.9,
2875, 2935, 2965, 3040, 2.45 t. d (2H, J 6, 2 Hz), 5.09 s (2H), 112.0, 121.3, 125.4, 128.1, 128.4, 128.9,
3075
6.71 t (1H, J 2 Hz), 6.97 d (2H, J 7 Hz), 129.8, 134.8, 136.6, 148.5, 150.3, 164.9
7.20 t (1H, J 7 Hz), 7.30 7.50 (7H)
Va 1570, 1635, 2855, 2880, 4.25 m (2H), 4.75 s (2H), 5.18 m (1H), 49.4, 55.6, 106.1, 122.3, 123.5, 127.8,
3035, 3060, 3075, 3080 5.24 m (1H), 6.94 d (2H, J 7 Hz), 7.08 t 128.4, 128.8, 129.1, 129.4, 137.6, 152.3,
(1H, J 7 Hz), 7.26 7.48 (7H)
156.7
Vb 1585, 1640, 2850, 2885, 4.80 m (2H), 5.16 m (1H), 5.20 m (1H), 57.7, 106.2, 121.9, 123.4, 123.8, 125.1,
3040, 3065, 3080, 3085 6.93 d (2H, J 7 Hz), 7.11 t (1H, J 7 Hz), 129.1, 129.5, 136.7, 141.2, 152.0, 155.2
7.22 t (1H, J 7 Hz), 7.33 m (2H), 7.44 m
(2H), 7.67 d (2H, J 7 Hz)
a
The NMR spectra of compounds IIa, IIb, and IIg were recorded in acetone-d , and the other spectra, in D CCN.
6
3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

BASICITY OF SECONDARY PENTA-2,4-DIYNYLAMINES
1897
Table 3. Melting points and elemental analyses of amine Ig, thiazolidin-2-imines IIc, IIe IIg, and Vb, and thiazolidin-4-
nes IIIa and IIId
Found, %
H
Calculated, %
H
Comp.
no.
mp, C (solvent)
Formula
C
N
C
N
Ig 63 64 (diethyl ether hexane)
IIc 76 78
(dichloromethane petroleum ether 40/70) 76.35
IIe 83 85
88.12,
88.57
75.96,
5.54,
5.87
6.55,
6.61
5.20,
5.09
6.40,
6.53
5.15,
5.12
7.07,
7.00
5.96,
5.79
6.01,
6.02
7.79,
7.76
7.56,
7.40
8.12,
8.23
7.67,
7.69
8.22,
8.11
7.43,
7.43
C17H13N
C17H13N
88.28
88.28
76.26
76.26
78.91
78.91
76.26
76.26 6.40
78.66 4.95
78.66 4.95
70.55 7.10
70.55 7.10
5.66
5.66
6.40
6.40
5.30
5.30
6.40
6.06
6.06
8.09
8.09
7.36
7.36
8.08
8.08
7.64
7.64
8.23
8.23
7.48
7.48
10.52
10.52
C22H22N2S
C22H22N2S
C25H20N2S
C25H20N2S
C22H22N2S
C22H22N2S
C24H18N2S
C24H18N2S
C18H26N2OS
C18H26N2OS
C23H24N2S
C23H24N2S
C16H14N2S
C16H14N2S
78.81,
(dichloromethane petroleum ether 40/70) 78.88
IIf 97 98 (ethanol)
76.27,
76.49
78.62,
78.69
70.68,
70.52
73.73,
IIg 147 148 (benzene)
IIIa 36 38 (hexane)
IIId 75 76
73.76
73.76
72.15
72.15
5.92
5.92
5.30
5.30
(dichloromethane petroleum ether 40/70) 73.80
Vb 88 89 (ethanol)
72.44,
72.56
5.41, 10.69,
5.58 10.68
11.29 [9]. Before each series of three titrations amines
were purified by preparative TLC. The pKa values
were calculated by the Henderson formula [4].
N-Butyl(undeca-2,4-diynyl)amine (Ib) was ob-
tained from 5.9 ml of butylamine and 4.52 g of
1-bromoundeca-2,4-diyne. Solvent pentane; eluent
petroleum ether (40/70) dichloromethane, 5:1 and
1:1. Yield 1.4 g (32%), undistillable oil. In addition,
a dialkylation product, N,N-bis(undeca-2,4-diynyl)-
butylamine was isolated. Yield 2.19 g (30%), undis-
tillable oil.
E10/2 E1x/2
pKax = pKa0 +
.
59
Here E1/2 in the half-neutralization potential of the
base, the indices – and 0 relate to the studied and
reference bases, respectively. The error was 0.03 pKa
unit. The equivalence point on the plot of E (mV) vs.
V (ml) was determined by differentiation of the titra-
tion curve.
N-Butyl(5-phenylpenta-2,4-diynyl)amine (Ic)
was obtained from 5.13 ml of butylamine and 2.81 g
of 1-bromo-5-phenylpenta-2,4-diyne. Solvent benzene;
eluent petroleum ether (40/70) dichloromethane, 1:1.
Yield 1.3 g (47%), undistillable oil.
N-(Penta-2,4-diynyl)amines
Ia Ih
(general
procedure). A solution of diacetylenic bromide in
20 ml of solvent was added to a solution of primary
amine in 20 ml of solvent. Reaction progress was
followed by TLC. The reaction was continued until
the starting bromide disappeared completely. The
reaction mixture was poured into water and extracted
with diethyl ether or dichlromethane. The extracts
were washed with water and dried over CaCl2. The
solvent was removed, and the reaction products were
purified by flash chromatography on silica gel (40
60 m) and recrystallized.
N-Benzyl(nona-2,4-diynyl)amine (Id) was ob-
tained from 6.98 ml of benzylamine and 3.14 g of
1-bromonona-2,4-diyne. Solvent benzene; eluent
petroleum ether (40/70) dichloromethane, 5:2. Yield
1.45 g (40%), undistillable oil.
N-Benzyl(5-phenylpenta-2,4-diynyl)amine (Ie)
was obtained from 5.59 ml of benzylamine and 3.73 g
of 1-bromo-5-phenylpenta-2,4-diyne. Solvent benzene;
eluents petroleum ether (40/70) dichloromethane, 1:2,
and petroleum ether (40/70) dichloromethane
methanol, 1:2:0.25. Yield 3.19 g (77%), undistillable
oil.
N-Butyl(nona-2,4-diynyl)amine (Ia) was obtained
from 7.61 ml of butylamine and 3.85 g of 1-bromo-
nona-2,4-diyne. Solvent hexane; eluent petroleum
ether (40/70) dichloromethane, 5:1 and 1:1. Yield
2.14 g (60%), undistillable oil.
N-Phenyl(nona-2,4-diynyl)amine (If) was ob-
tained from 5.83 ml of aniline and 3.22 g of 1-bromo-
nona-2,4-diyne. Solvent benzene; eluent petroleum
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

1898
SIPKINA, BALOVA
ether (40/70) diethyl ether, 3:1. Yield 1.53 g (45%),
undistillable oil.
methane, 1:5 and 1:1. Thiazolidinimine IIc, 0.50 g
(38%), was obtained.
N-Phenyl(5-phenylpenta-2,4-diynyl)amine (Ig)
was obtained from 5.83 ml of aniline and 3.46 g of
1-bromo-5-phenylpenta-2,4-diyne. Solvent benzene.
The product was recrystallized from ether hexane.
Yield 2.29 g (62%).
N-Phenyl-3-benzyl-5-(hept-2-ynylidene)-1,3-
thiazolidin-2-imine (IId) and 3-benzyl-5-(hept-2-
ynylidene)-2-(phenylimino)-1,3-thiazolidin-4-one
(IIId). The reaction of 1.02 g of N-benzyl(nona-2,4-
diynyl)imine with 0.55 ml of phenyl isothiocyanate
was performed in pentane. The reaction products were
isolated by preparative TLC. Eluent petroleum ether
(40/70) dichloromethane, 1:1. Thiazolidinimine IId,
0.36 g (30%), undistillable oil quickly darkrning in air,
and 0.09 g (13%) of thiazolidinone IIId were obtained.
N-(2,5-Dichlorophenyl)(nona-2,4-diynyl)amine
(Ih) was obtained from 1.79 g of 2,5-dichloroaniline
and 2.92 g of 1-bromonona-2,4-diyne. Solvent aceto-
nitrile; eluent petroleum ether (40/70) dichlorome-
thane, 5:1. Yield 0.98 g (39%).
N-Phenyl-3-benzyl-5-(3-phenylprop-2-ynyl-
idene)-1,3-thiazolidin-2-imine (IIe). The reaction of
0.60 g of N-benzyl(5-phenylpenta-2,4-diynyl)amine
with 0.29 ml of phenyl isothiocyanate was performed
in acetonitrile. Eluent petroleum ether (40/70) di-
chloromethane, 3:2. Thiazolidinimine IIe, 0.42 g
(43.8%), was obtained.
N-Benzyl(prop-2-ynyl)amine (IVa) was obtained
from 32.7 ml of benzylamine and 7.2 ml of 1-chloro-
prop-2-yne. Solvent benzene. Yield 7.53 g (51%), bp
100 104 C (5 mm), n2D0 1.5400.
Reaction of penta-2,4-diynylamines Ia Ih and
prop-2-ynylamines IVa and IVb with phenyl iso-
thiocyanate (general procedure). A solution of
phenyl isothiocyanate in 20 ml of solvent was added
to a solution of amine in 20 ml of solvent. Reaction
progress was followed by TLC. The reaction was
continued until the starting amine disappeared. The
solvent was removed in a vacuum, and the reaction
products were isolated by flash chromatography on
silica gel (40 60 m) or by recrystallization.
N,3-Diphenyl-5-(hept-2-ynylidene)-1,3-thiazo-
lidin-2-imine (IIf). The reaction of 0.52 g of N-
phenyl(nona-2,4-diynyl)amine with 0.29 ml of phenyl
isothiocyanate was performed in acetonitrile in the
presence of 0.03 g of KOH. The reaction product was
recrystallized from ethanol. Thiazolidinimine IIf,
0.39 g (46%), was obtained.
N,3-Diphenyl-5-(3-phenylprop-2-ynylidene)-1,3-
thiazolidin-2-imine (IIg). The reaction of 1.38 g of
N-phenyl(5-phenylpenta-2,4-diynyl)amine with
0.72 ml of phenyl isothiocyanate was performed in
acetonitrile in the presence of 0.07 g of KOH. The
reaction product was recrystallized from benzene.
Thiazolidinimine IIg, 0.98 g (45%), was obtained.
N-Phenyl-3-butyl-5-(hept-2-ynylidene)-1,3-thia-
zolidin-2-imine (IIa) and 3-butyl-5-(hept-2-ynyl-
idene)-2-(phenylimino)-1,3-thiazolidin-4-one (IIIa).
The reaction of 1.18 g of N-butylnona-2,4-diynyl-
amine and 0.74 ml of phenyl isothiocyanate was
performed in diethyl ether. Eluent petroleum ether
(40/70) dichloromethane, 5:1 and 1:1. Thiazolidin-
imine IIa, 0.52 g (26%), undistillable oil quckly
darkening in air, and 0.58 g (29%) of thiazolidinone
IIIa were obtained.
N-Phenyl-3-benzyl-5-methylene-1,3-thiazolidin-
2-imine (Va). The reaction of 2.27 g of N-benzyl-
(prop-2-ynyl)amine with 1.91 ml of phenyl isothio-
cyanate was performed in acetonitrile. Eluent petro-
leum ether (40/70), petroleum ether (40/70) di-
chloromethane, 4:1. Thiazolidinimine Va, 1.71 g
(39%), undistillable oil, was obtained.
N-Phenyl-3-butyl-5-(non-2-ylidene)-1,3-thiazol-
idin-2-imine (IIb) and 3-butyl-5-(non-2-ynylidene)-
2-(phenylimino)-1,3-thiazolidin-4-one (IIIb). The
reaction of 0.48 g of N-butyl(undeca-2,4-diynyl)amine
with 0.26 ml of phenyl isothiocyanate was performed
in petroleum ether (40/70) under argon. Eluent pet-
roleum ether diethyl ether, 9:1. Thiazolidinimine IIb,
0.038 g (6%), and 0.63 g (89%) of thiazolidinone IIIb,
undistillable oils quickly darkening in air, were
obtained.
N,3-Diphenyl-5-methylene-1,3-thiazolidin-2-
imine (Vb). The reaction of 1.71 g of N-phenyl(prop-
2-ynyl)amine with 1.56 ml of phenyl isothiocyanate
was performed in acetonitrile. The reaction pro-
duct was recrystallized from ethanol. Thiazol-
idinimine Vb, 1.51 g (44%), was obtained.
N-Phenyl-3-butyl-5-(3-phenylprop-2-ynylidene)-
1,3-thiazolidin-2-imine (IIc). The reaction of 0.81 g
of N-butyl-(5-phenylpenta-2,4-diynyl)amine with
0.45 ml of phenyl isothiocyanate was performed in
acetonitrile. Eluent petroleum ether (40/70) dichloro-
ACKNOWLEDGMENTS
The work was finacially supported by the Russian
Foundation for Basic Research (project no. 98332749)
and INTAS (grant no. 9731999).
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BASICITY OF SECONDARY PENTA-2,4-DIYNYLAMINES
1899
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