A facile one-pot synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one derivatives via a multicomponent reaction

Article abstract of DOI:10.1080/17415993.2011.588951

A facile synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one derivatives is achieved via a three-component reaction involving 3-(2-bromoacetyl)-4-hydroxy-6- methyl-2H-pyran-2-one, thiocarbohydrazide with various carbonyl compounds in one-pot under stirring. The main advantage of this procedure is the short reaction time, high yields, simple workup, and purification of products by non-chromatographic methods, i.e. by simple recrystallization from ethanol. The structures of newly prepared compounds have been established by elemental analysis and spectral data.

Full text of DOI:10.1080/17415993.2011.588951

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A facile one-pot synthesis of 1,3,4-
thiadiazine-5-yl-pyran-2-one
derivatives via a multicomponent
reaction
Santhosh Penta a & Rajeswar Rao Vedula a
a Department of Chemistry, National Institute of Technology,
Warangal, 506 004, Andhra Pradesh, India
Version of record first published: 13 Jun 2011
To cite this article: Santhosh Penta & Rajeswar Rao Vedula (2011): A facile one-pot synthesis of
1,3,4-thiadiazine-5-yl-pyran-2-one derivatives via a multicomponent reaction, Journal of Sulfur
Chemistry, 32:4, 327-333
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Journal of Sulfur Chemistry
Vol. 32, No. 4, August 2011, 327–333
A facile one-pot synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one
derivatives via a multicomponent reaction
Santhosh Penta and Rajeswar Rao Vedula*
Department of Chemistry, National Institute of Technology, Warangal-506 004, Andhra Pradesh, India
(Received 7 February 2011; final version received 13 May 2011)
A facile synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one derivatives is achieved via a three-component reac-
tion involving 3-(2-bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one, thiocarbohydrazide with various
carbonyl compounds in one-pot under stirring. The main advantage of this procedure is the short reaction
time, high yields, simple workup, and purification of products by non-chromatographic methods, i.e. by
simple recrystallization from ethanol. The structures of newly prepared compounds have been established
by elemental analysis and spectral data.
R2
C
N
R1
N
NH
OH
O
N
O
S
H3C
Keywords: 1,3,4-thiadiazine; 3-(2-bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one; thiocarbohy-
drazide; one-pot; multicomponent reactions
1. Introduction
Over the past several years, chemists have been aware of the environmental implications of their
chemistry. Nowadays, they are trying to develop new synthetic methods, reaction conditions, and
use of chemicals that reduce risks to humans and the environment. A multicomponent reaction
(MCR), offering a straightforward route to generate complexity and diversity in a single operation,
is an extremely powerful tool in combinatorial chemistry and drug discovery. However, if the
one-pot MCRs could be carried out under solvent- and catalyst-free conditions, it would be most
efficient synthetic methods of organic synthesis. MCRs are processes ‘in which more than two
educts directly get converted into their products by one-pot reaction’. MCRs play an important role
in modern organic chemistry, because they generally exhibit higher atom economy and selectivity
*Corresponding author. Email: vrajesw@yahoo.com
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2011 Taylor & Francis
DOI: 10.1080/17415993.2011.588951
http://www.informaworld.com

328 S. Penta and R.R. Vedula
as well as produce fewer by-products compared with classical multistep synthesis. Further, in
many cases, MCRs are easy to perform, inexpensive, and quick, consume less energy, and involve
simple experimental procedures (1–3).
3-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one (dehydroacetic acid) is a versatile starting
material, and its derivatives find wider application in the synthesis of heterocyclic compounds (4–
6). Some 4-hydroxy-2-pyrans have also been tested as anticoagulant agents (7). The nitrogen and
sulfur heterocyclic systems are very interesting because of their physicochemical properties with
relevance to the design of new drugs. In those compounds containing 1,3,4-thiadiazines are bio-
logically active compounds, many of these derivatives are used for cardiotonic and hypertensive
activities (8, 9) and can be used for treatment of tumors and acquired immunodeficiency syndrome
(10). A survey of literature reveals that much work remains to be done with 1,3,4-thiadiazines.
Some heteroaryl-1,3,4-thiadiazines have been reported in the literature starting from phenacyl
bromide or chloroacetic acid and pyrazolyl-1-thiocarbonylhydrazide (11). Schiff bases form a
significant class of compounds in medicinal and pharmaceutical chemistry with several biologi-
cal applications that include antibacterial, antifungal, and antitumor activity (12–18). Moreover,
much interest has been focused on the biological activity of 1,3,4-thiadiazine derivatives. So we
describe an efficient, solvent-free, one-pot method for the title compounds (Scheme 1).
R2
C
N
R1
N
NH
OH
O
O
OH
O
N
O
O
Br
H
N
H
S
Solvent-free /
Stirring
N
R1
R2
+
H2N
NH2
+
H3C
O
S
H3C
2
3
1
4
4 R1
R2
p-Tolyl
p-Anisyl
o-Hydroxy phenyl
Phenyl
4 R1
R2
Ph
p-Tolyl
p-Anisyl
p-Chloro phenyl
Et
(a) H
(b) H
(c) H
(d) H
(e) Me
(f) Me
(g) Me
(h) Me
(i) Me
(j) Me
Me
(k) R1 = R2 = Cyclohexylidene
Scheme 1. One-pot and solvent-free synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one derivatives
via three-component reaction.
2. Results and discussion
In continuation of our earlier work on the development of useful new synthetic methodologies (19–
24), we observed that an equimolar mixture of 3-(2-bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-
2-one, thiocarbohydrazide, and various carbonyl compounds on stirring at room temperature for
a period of 30 min, followed by stirring at 50–60 ◦C for about 1 h resulted in the formation
of the title compounds. The reaction path for the formations of products can be explained by
the S-acylation of thiocarbohydrazide with 1, followed by intramolecular cyclization to give
pyran substituted 2-hydrazino-6H-1,3,4-thiadiazines. These underwent further condensation with
carbonyl compounds to give the Schiff bases 4a–k (Scheme 2).
All the structures of newly synthesized compounds have been confirmed by their spectral data.
1
The H NMR spectrum of compound 4a shows prominent peaks for –pyran CH3 at δ 2.13,
Ar CH3 at δ 2.33, CH2 of thiadiazine at δ 4.65 and C-4 proton of pyran at δ 5.87. The 13C NMR
−

Journal of Sulfur Chemistry 329
H
N
N
OH
O
O
OH
N
O
NH2
R1
EtOH/
O
Br
S
H
N
H
R2
EtOH
(3)
N
4
H2N
NH2
+
H3C
O
H3C
O
S
5
2
1
Scheme 2. Two-step synthesis of 1,3,4-thiadiazine-5-yl-pyran-2-one derivatives.
spectrum of 4a also shows the peaks at δ 19.9, 21.7, 107.1, and 163.4 for pyran methyl, CH2 of
=
thiadiazine, C-4 of pyran, and C O of pyran, respectively. The remaining protons and carbons
were observed in the expected region. All the above spectral data clearly indicates the formation
of the title products.
The structures of final products were also confirmed by synthesizing 4a unambiguously.
Reaction of equimolar mixture of 3-(2-bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one,
(1 mmol), thiocarbohydrazide (1 mmol) in ethanol gave 3-(2-hydrazino-6H-[1,3,4]thiadiazin-5-
yl)-4-hydroxy-6-methyl-pyran-2-one 5. This on reaction with 3 in ethanol gave the corresponding
Schiff base 4a.A plausible mechanism of formation of these compounds is presented in Scheme 3.
The products obtained by both methods were found to be identical by mixed melting point
measurements, Co-TLC and spectral data.
H2N
H
N
NH
NH2
N
R
O
S
R
+
NH2
N
R
R
S
N
HO
Br
N
-H2O
Δ, -HBr
NH2
H
NH2
N
H
S
N
O
H
1
2
N
R
N
R
N
N
H
N
N
O
NH2
N
S
N
R2
OH
R2
S
N
R1
R2
S
N
-H2O
H
H
H
R1
R1
5
3
4
OH
O
R=
H3C
O
Scheme 3. Plausible mechanism.
3. Conclusion
We have developed a facile multicomponent and one-pot synthesis for the title compounds using
readily available starting materials without application of any catalyst. When compared with
the classical reaction conditions, these new synthetic methods have various advantages, such as
good yields, shorter reaction time, inexpensive, and easy workup. These new derivatives may be
beneficially utilized in drug research.

330 S. Penta and R.R. Vedula
4. Experimental
4.1. General
All the reagents and solvents were pure, purchased from commercial sources and were used
without further purification unless otherwise stated. 3-(2-Bromoacetyl)-4-hydroxy-6-methyl-2H-
pyran-2-one (25) was prepared by a literature procedure. Melting points were determined in
open capillaries with a ‘Cintex’ melting point apparatus, Mumbai, India, and were uncorrected.
CHNS analysis was done by Carlo Erba EA 1108 automatic elemental analyzer. The purity of
the compounds was checked by TLC plates (E. Merck Mumbai, India). IR spectra (KBr) were
recorded on a Bruker WM-4(X) spectrometer (577 models). 1H NMR spectra were recorded on
a Bruker WM-400 spectrometer in δ ppm using TMS as standard. Mass spectra (EI-MS) were
determined on perkin Elmer (SCIEX API- 2000, ESI) at 12.5 ev.
4.2. General procedure for the synthesis of compounds 4a–k
3-(2-Bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one, (1 mmol), thiocarbohydrazide(1 mmol)
and 1 ml of 3 were taken in a round bottom flask and stirred at room temperature for about 30 min.
Then the reaction mixture was heated for about 1 h at 50–60 ◦C, cooled to room temperature, the
solid separated was filtered, washed with cooled methanol, and recrystallized from ethanol to give
yellow solids.
4.2.1. 4-Hydroxy-6-methyl-3-{2-[Nꢀ-(4-methyl-benzylidene)-hydrazino]-6H-[1,3,4]thiadiazin-
5-yl}-pyran-2-one (4a)
Color: yellow solid; yield 95%; mp. 247–248 ◦C; IR (KBr, υ max, cm−1): 1602 (C N), 1693
=
1
=
(C O), 3174 (NH), 3311 (OH); H NMR (400 MHz, DMSO-d6): δ 2.13 (s, 3H, pyran CH3),
−
2.33 (s, 3H, ArCH3), 4.65 (s, 2H, CH2 of thiadiazine), 5.87 (s, 1H, C-4 of pyran), 7.25 (d,
=
−
2H, J = 8.0 Hz, ArH), 7.55 (d, 2H, J = 8.0 Hz, ArH), 8.07 (s, 1H, CH Ar), 12.17 (s, 1H,
NH, D2O, exchangeable), 15.64 (s, 1H, OH); 13C NMR (DMSO-d6, δ ppm): 19.4, 21.7, 22.5,
−
92.1, 107.1, 127.3, 128.2, 130.1, 131.9, 140.4, 145.5, 151.6, 154.7, 163.2, 163.4. Anal. calcd. for
C17H16N4O3S: C, 57.29; H, 4.52; N, 15.72. Found: C, 57.21; H, 4.46; N, 15.66.
4.2.2. 4-Hydroxy-3-{2-[Nꢀ-(4-methoxy-benzylidene)-hydrazino]-6H-[1,3,4]thiadiazin-5-yl}-6-
methyl-pyran-2-one (4b)
Color: yellow solid; yield 84%; mp. 252–254 ◦C; IR (KBr, υmax, cm−1): 1608 (C N), 1685
=
1
=
(C O), 3176 (NH), 3311 (OH); H NMR (400 MHz, DMSO-d6): δ 2.13 (s, 3H, pyran CH3),
−
3.79 (s, 3H, OCH3), 4.65 (s, 2H, CH2 of thiadiazine), 5.85 (s, 1H, C-4 of pyran), 7.00 (d, 2H,
=
−
−
J = 8.0 Hz,ArH), 7.60(d, 2H, J = 8.0 Hz,ArH), 8.05(s, 1H, CH Ar), 12.10(s, 1H, NH, D2O,
exchangeable), 15.69 (s, 1H, OH); 13C NMR (DMSO-d6, δ ppm): 19.2, 21.8, 55.2, 91.2, 106.6,
114.3, 126.5, 128.2, 144.1, 154.0, 158.6, 160.6, 162.5, 162.6. Anal. calcd. for C17H16N4O4S: C,
54.83; H, 4.33; N, 15.04. Found: C, 54.80; H, 4.29; N, 14.96.
4.2.3. 4-Hydroxy-3-{2-[Nꢀ-(2-hydroxy-benzylidene)-hydrazino]-6H-[1,3,4]thiadiazin-5-yl}-6-
methyl-pyran-2-one (4c)
Color: yellow solid; yield 87%; mp. 296–298 ◦C; IR (KBr, υmax, cm−1): 1604 (C N), 1683
=
1
=
(C O), 3189 (NH), 3376 (OH); H NMR (400 MHz, DMSO-d6): δ 2.15 (s, 3H, pyran CH3),

Journal of Sulfur Chemistry 331
−
4.65 (s, 2H, CH2 of thiadiazine), 5.91 (s, 1H, C-4 of pyran), 7.32–7.62 (m, 4H, ArH), 7.87 (s,
1H, CH Ar), 11.57 (s, 1H, NH, D2O, exchangeable). 13C NMR (DMSO-d6, δ ppm): 19.5,
92.7, 99.8, 102.5, 116.2, 119.5, 128.8, 129.9, 131.4, 132.3, 154.7, 157.3, 162.3, 163.2, 163.8,
169.1. Anal. calcd. for C16H14N4O4S: C, 53.62; H, 3.94; N, 15.63. Found: C, 53.58; H, 3.90;
N, 15.59.
=
−
−
4.2.4. 3-[2-(Nꢀ-Benzylidene)-hydrazino)-6H-[1,3,4]thiadiazin-5-yl]-4-hydroxy-6-methyl-
pyran-2-one (4d)
Color: yellow solid; yield 85%; mp. >300 ◦C; IR (KBr, υmax, cm−1): 1610 (C N), 1689 (C O),
3169 (NH), 3407 (OH); 1H NMR (400 MHz, DMSO-d6): δ 2.13 (s, 3H, pyran CH3), 4.65 (s, 2H,
=
=
−
=
−
CH2 of thiadiazine), 5.87 (s, 1H, C-4 of pyran), 7.40–7.72 (m, 5H,ArH), 8.07 (s, 1H, CH Ar)
11.10 (s, 1H, NH, D2O, exchangeable), 15.64 (s, 1H, OH); 13C NMR (DMSO-d6, δ ppm): 19.2,
21.8, 106.5,126.6, 127.3, 128.7, 128.8, 129.8, 130.0, 133.9, 144.5, 154.1, 162.8, 174.8. Anal.
calcd. for C16H14N4O3S: C, 56.13; H, 4.12; N, 16.36. Found: C, 56.09; H, 4.10; N, 16.31.
−
4.2.5. 4-Hydroxy-3-[2-(Nꢀ-(isopropylidene)-hydrazino]-6H-[1,3,4]thiadiazin-5-yl]-6-methyl-
pyran-2-one (4e)
Color: yellow solid; yield 92%; mp. 202–206 ◦C; IR (KBr, υmax, cm−1): 1610 (C N), 1689
=
1
=
(C O), 3165 (NH), 3327 (OH); H NMR (400 MHz, DMSO-d6): δ 1.93 (s, 3H, pyran CH3), 2.13
−
−
(s, 6H, 2CH3), 4.54 (s, 2H, CH2 of thiadiazine), 5.87 (s, 1H, C-4 of pyran), 11.10 (s, 1H, NH,
D2O, exchangeable), 15.64 (s, 1H, OH); 13C NMR (DMSO-d6, δ ppm): 16.5, 19.9, 21.7, 22.5,
92.1, 107.1, 151.6, 154.7, 161.2, 163.4, 167.0, 182.7. ESI-MS 295 [M + H]+; Anal. calcd. for
C12H14N4O3S: C, 48.97; H, 4.79; N, 19.04. Found: C, 48.91; H, 4.71; N, 19.94.
4.2.6. 4-Hydroxy-6-methyl-3-[2-[Nꢀ-(1-phenyl-ethylidene)-hydrazino]-6H-[1,3,4]thiadiazin-
5-yl}-pyran-2-one (4f)
Color: yellow solid; yield 90%; mp. 286–288 ◦C; IR (KBr, υmax, cm−1): 1610 (C N), 1685
=
1
=
(C O), 3159 (NH), 3325 (OH); H NMR (400 MHz, DMSO-d6): δ 2.15 (s, 3H, pyran CH3), 2.32
= −
−
(s, 3H, C CH3, 4.64 (s, 2H, CH2 of thiadiazine), 5.90 (s, 1H, C-4 of pyran), 7.40–7.42 (m, 5H,
ArH) 11.50 (s, 1H, NH, D2O, exchangeable). 13C NMR (DMSO-d6, δ ppm): 16.9, 19.8, 22.5,
−
91.5, 107.1, 121.5, 127.4, 128.2, 130.1, 131.9, 150.8, 153.7, 161.5, 165.0, 170.6. Anal. calcd. for
C17H16N4O3S: C, 57.29; H, 4.52; N, 15.72. Found: C, 57.22; H, 4.49; N, 15.68.
4.2.7. 4-Hydroxy-6-methyl-3-{2-[Nꢀ-(1-p-tolyl-ethylidene)-hydrazino]-6H-[1,3,4]thiadiazin-
5-yl}-pyran-2-one (4g)
Color: yellow solid; yield 89%; mp. 272–274 ◦C; IR (KBr, υmax, cm−1): 1617 (C N), 1690
=
1
=
(C O), 3177 (NH), 3378 (OH); H NMR (400 MHz, DMSO-d6): δ 2.26 (s, 3H, pyran CH3), 2.33
−
(s, 3H, CH3), 2.34 (s, 3H, CH3), 4.57, (s, 2H, CH2 of thiadiazine), 6.20 (s, 1H, C-4 of pyran),
7.26 (d, 2H, J = 8.0 Hz, ArH), 7.74 (d, 2H, J = 8.0 Hz, ArH). 13C NMR (DMSO-d6, δ ppm):
14.1, 19.5, 20.8, 22.4, 100.0, 125.7, 125.8, 126.1, 128.2, 128.9, 129.0, 129.1, 162.5, 162.9, 163.8,
167.4. Anal. calcd. for C18H18N4O3S: C, 58.36; H, 4.90; N, 15.12. Found: C, 58.31; H, 4.87;
N, 15.10.

332 S. Penta and R.R. Vedula
4.2.8. 4-Hydroxy-3-[2-{Nꢀ-[1-(4-methoxy-phenyl)-ethylidene]-hydrazino}-6H-
[1,3,4]thiadiazin-5-yl}-6-methyl-pyran-2-one (4h)
Color: yellow solid; yield 92%; mp. 212–214 ◦C; IR (KBr, υmax, cm−1): 1602 (C N), 1689
=
1
=
(C O), 3150 (NH), 3347 (OH); H NMR (400 MHz, DMSO-d6): δ 2.28 (s, 3H, pyran CH3), 2.41
= −
−
−
(s, 3H, C CH3), 3.84 (s, 3H, OCH3), 4.55 (s, 2H, CH2 of thiadiazine), 6.17 (s, 1H, C-4 of
−
pyran), 6.97 (d, 2H, J = 8.8 Hz, ArH), 7.73 (d, 2H, J = 8.8 Hz, ArH), 11.50 (s, 1H, NH, D2O,
exchangeable);13C NMR (DMSO-d6, δ ppm): 14.0, 19.5, 26.3, 55.2, 100.1, 113.8, 127.4, 127.7,
130.4, 160.2, 160.5, 162.6, 163.0, 163.6, 167.0, 169.4. Anal. calcd. for C18H18N4O4S: C, 55.95;
H, 4.70; N, 14.50. Found: C, 55.91; H, 4.66; N, 14.47.
4.2.9. 3-(2-{Nꢀ-[1-(4-Chloro-phenyl)-ethylidene]-hydrazino}-6H-[1,3,4]thiadiazin-5-yl}-4-
hydroxy-6-methyl-pyran-2-one (4i)
Color: yellow solid; yield 87%; mp. 188–190 ◦C; IR (KBr, υmax, cm−1): 1600 (C N), 1687
=
1
=
(C O), 3157 (NH), 3324 (OH); H NMR (400 MHz, DMSO-d6): δ 2.15 (s, 3H, pyran CH3), 2.30
= −
−
(s, 3H, C CH3), 4.56 (s, 2H, CH2 of thiadiazine), 5.93 (s, 1H, C-4 of pyran), 7.50 (d, 2H,
J = 8.0 Hz, ArH), 7.79 (d, 2H, J = 8.0 Hz, ArH). 13C NMR (DMSO-d6, δ ppm): 19.0, 21.1, 22.2,
91.0, 108.0, 127.6, 127.7, 128.5, 133.7, 133.9, 136.6, 151.9, 153.2, 162.5, 168.9. Anal. calcd. for
C17H15ClN4O3S: C, 52.24; H, 3.87; N, 14.33. Found: C, 52.20; H, 3.84; N, 14.30.
4.2.10. 3-(2-{Nꢀ-(sec-Butylidene-hydrazino)-6H-[1,3,4]thiadiazin-5-yl]-4-hydroxy-6-methyl-
pyran-2-one (4j)
Color:yellowsolid;yield89%;mp. 217–219 ◦C;IR(KBr, υmax, cm−1):1617(C N), 1689(C O),
=
=
1
−
3189 (NH), 3364 (OH); H NMR (400 MHz, DMSO-d6): δ 1.06 (t, 3H, J = 8 Hz, CH3), 1.94 (s,
− = −
− = −
3H, of CH3 of pyran ring), 2.23 (s, 3H, N C CH3), 2.29 (q, 2H, J = 8 Hz, N C CH2), 4.65
−
−
(s, 2H, CH2 of thiadiazine), 6.18 (s, 1H, C-4 of pyran), 11.17 (s, 1H, NH, D2O, exchangeable).
13C NMR (DMSO-d6, δ ppm):14.5, 19.3, 24.9, 25.4, 26.7, 97.2, 102.7, 154.1, 159.7, 161.0, 162.9,
164.7, 168.6. Anal. calcd. for C13H16N4O3S: C, 50.64; H, 5.23; N, 18.17. Found: C, 50.60; H,
5.20; N, 18.13.
4.2.11. 3-[2-(Nꢀ-Cyclohexylidene-hydrazino)-6H-[1,3,4]thiadiazin-5-yl]-4-hydroxy-6-methyl-
pyran-2-one (4k)
Color: yellow solid; yield 86%; mp. 278–280 ◦C; IR (KBr, υmax, cm−1): 1619 (C N), 1685
=
1
=
−
(C O), 3163 (NH), 3375 (OH). H NMR (400 MHz, DMSO-d6): δ 1.60–1.63 (m, 6H, 3CH2 of
cyclohexyl), 2.23 (s, 3H, CH3 of pyran ring), 2.27–2.29 (m, 2H, CH2 of cyclohexyl), 2.43–2.46
−
(m, 2H, CH2 of cyclohexyl), 4.65 (s, 2H, CH2 of thiadiazine), 5.85 (s, 1H, C-4 of pyran), 12.10
(s, 1H, NH, D2O, exchangeable), 15.69 (s, 1H, OH); 13C NMR (DMSO-d6, δ ppm): 19.3,
24.9, 25.4, 26.7, 27.2, 34.6, 41.3, 101.2, 102.7, 142.5, 157.1, 161.4, 161.7, 168.4, 168.6. Anal.
calcd. for C15H18N4O3S: C, 53.88; H, 5.43; N, 16.75. Found: C,53.84; H, 5.40; N, 16.71.
−
−
4.3. General procedure for the synthesis of 3-(2-hydrazino-6H-[1,3,4]thiadiazin-5-yl)-4-
hydroxy-6-methyl-pyran-2-one (5)
3-(2-Bromoacetyl)-4-hydroxy-6-methyl-2H-pyran-2-one (1 mmol) and thiocarbohydrazide
(1 mmol) are taken in 5 ml of anhydrous ethanol and refluxed for about 1 h. The yellow solid

Journal of Sulfur Chemistry 333
obtained on cooling was filtered, washed with methanol, and recrystallized from ethanol to give
yellow solid.
Color: yellow solid; yield 89%; mp. 265–267 ◦C; IR (KBr, υmax, cm−1): 1604 (C N), 1690
=
1
=
(C O), 3175 (NH), 3328 (OH). H NMR (400 MHz, DMSO-d6): 2.13 (s, 3H, CH3 of pyran
−
−
ring), 4.65 (s, 2H, CH2 of thiadiazine), 5.87 (s, 1H, C-4 of pyran), 10.05 (s, 1H, N+H, D2O,
−
−
exchangeable), 12.34 (s, NH2, D2O exchangeable), 15.64 (s, 1H, OH); EI-MS 254[M ].Anal.
calcd. for C9H10N4O3S: C, 42.51; H, 3.96; N, 22.03. Found: C, 41.94; H, 3.84; N, 21.93.
4.4. General procedure for the synthesis of 4a from 3-(2-hydrazino-6 H-[1,3,4]
thiadiazin-5-yl)-4-hydroxy-6-methyl-pyran-2-one (5)
A mixture of compound 5 (1 mmol) and 3 (1 mmol) in 5 ml of anhydrous ethanol was refluxed
for about 1 h. The solid obtained was cooled, filtered, washed with methanol, and recrystallized
from ethanol.
Acknowledgements
The authors are thankful to the Director, NIT, Warangal, for providing facilities. One of the authors (Santhosh Penta) is
thankful to the Director for awarding Institute Fellowship.
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