ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 4, pp. 781–782. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © S.D. Fazylov, O.A. Nurkenov, Zh.S. Akhmetkarimova, D.R. Zhienbaeva, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82,
No. 4, pp. 699–700.
LETTERS
TO THE EDITOR
Synthesis of N-Substituted Thioamides of Benzoic Acids
under Microwave Activation
S. D. Fazylov, O. A. Nurkenov, Zh. S. Akhmetkarimova, and D. R. Zhienbaeva
Institute of Organic Synthesis and Coal Chemistry of the Republic of Kazakhstan,
ul. Alikhanova 1, Karaganda, 100008 Kazakhstan
e-mail: faziosu@rambler.ru
Received November 22, 2011
DOI: 10.1134/S1070363212040317
Thioamide derivatives are of particular interest since
they are reactive compounds successfully used in organic
synthesis of biologically active compounds. There are
various synthetic approaches to thioamides. One of the
most common is the Willgerodt–Kindler reac-tion [1,
2], which includes a prolonged reflux (2–4 h) of
reaction mixture in DMF. In order to reduce the
reaction time, we studied the reaction of substituted benz-
aldehydes with heterocyclic secondary amines, morpho-
line I and 1-benzylpiperazine II, in the presence of
sulfur [3] under microwave irradiation. The reactions were
carried out in DMF medium to get the comparative data.
R1
S
O
NH + S + R2
C
R2
X
N
X
C
H
R1
VI−XI
I, II
III−V
X = O (I, VI–VIII), NCH2C6H5 (II, IX–XI); R1 = R2 = H (III, VI, IX); R1 = R2 = CH3O (IV, VII, X); R1 = H,
R2 = F (V, VIII, XI).
It was established that methane thiones VI–XI can
be synthesized in 2 min at 750 W with breaks every 10 s.
The structure and identity of compounds VI–XI was
confirmed by the authentic synthesis under convective
heating in DMF medium. Thus, the behavior of the
reaction components under microwave activation does
not differ from that occurring at the convective
heating, and some synthetic features can be attributed
to the behavior of the reaction substrates in a micro-
wave field [4].
amine, and 1.09 g of sulfur powder was added 10 ml of
DMF, and it was heated for 2 h at 100°C to complete
release of hydrogen sulfide. The reaction progress was
monitored by TLC. The cooled reaction mixture was
diluted with water (50 ml), the precipitate formed was
filtered off and recrystallized from isopropyl alcohol.
General method for synthesis of thioamides VI–
XI under microwave irradiation conditions. Into a
100 ml flat-bottomed flask of heat-resistant glass was
placed a mixture of 3.61 g of aromatic aldehyde, 3 g of
1-benzylpiperazine, and 1.09 g of sulfur powder in
10 ml of DMF. The reaction mixture was subjected to
microwave irradiation for 2 min at 750 W with breaks
every 10 s. The reaction progress was monitored by
TLC. The product was isolated and purified as
described above.
1
The H NMR spectra of compounds VI–XI were
recorded on a Bruker AM-400 spectrometer in DMSO-
d6 relative to the residual proton signals (2.50 δH and
δC 39.50). TLC analysis was performed on Silufol UV-
254 plates eluting with CHC13–EtOH. The melting
points were determined on a Boёtius instrument.
General procedure for the synthesis of thio-
amides VI–XI under convection heating conditions.
To a mixture of 3.61 g of aromatic aldehyde, 3 g of
(4-Benzylpiperazin-1-yl)(phenyl)methane thione
(VI). Yield 3.11 g (66%) under convection heating
conditions and 3.53 g (75%) under microwave irradia-
781
Fazylov
