Synthesis of new (Pyrimido[4,5-e][1,3,4] thiadiazin-7-yl)hydrazine derivatives

Article abstract of DOI:10.1080/10426500903299893

New (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazines were synthesized via the cyclocondensation of alkyl-2-phenylhydrazinecarbodithioates as bidentate nucleophiles with 5-bromo-2,4-dichloro-6-methylpyrimidine as an electrophile and further replacement of

Full text of DOI:10.1080/10426500903299893

Phosphorus, Sulfur, and Silicon, 185:1782–1787, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500903299893
SYNTHESIS OF NEW (PYRIMIDO[4,5-e][1,3,4]
THIADIAZIN-7-YL)HYDRAZINE DERIVATIVES
Javad Azizian,1 Ramin Miri,2 Mohammad Kazem
Mohammadi,1 Fatemeh Sheikholeslami Farahani,1
Javad Hosseini,1 and Mohsen Nikpour3
1Department of Chemistry, Science and Research Branch, Islamic Azad University,
Tehran, Iran
2Medicinal & Natural Products Chemistry Research Center, Shiraz University of
Medical Sciences, Shiraz, Iran
3Faculty of Science, Islamic Azad University, Ahvaz Branch, Ahvaz, Iran
New (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazines were synthesized via the cycloconden-
sation of alkyl-2-phenylhydrazinecarbodithioates as bidentate nucleophiles with 5-bromo-
2,4-dichloro-6-methylpyrimidine as an electrophile and further replacement of chlorine
atom on the seven number position of pyrimido[4,5-e][1,3,4]thiadiazin by hydrazine in boil-
ing ethanol.
Keywords Bidentate nucleophile; 5-bromo-2,4-dichloro-6-methylpyrimidine; electrophile;
heterocyclization; pyrimido[4,5-e][1,3,4]thiadiazine
INTRODUCTION
The biological activities of pyrimido[4,5-e][1,3,4]thiadiazines persuaded us to search
for efficient synthetic methods for this class of heterocyclic compounds, which are described
as nucleoside analogues,1,2 and anti-inflammatory, hypotensive, diuretic,3,4 and phosphodi-
esterase inhibitor agents.2 Previous routes to such a system involved the heterocyclization of
6-hydrazino-substituted uracils with isothiocyanates and N-bromosuccinimide,1–5 conden-
sation of 2,4-dichloro-5-nitro-6-methylpyrimidine with dithizone6 via the Smiles rearrange-
ment, reaction of thiosemicarbazide with 4,5-dihalopyrimidines,7 cyclocondensation of
thiosemicarbazide with 5-bromobarbituric acid,8 and condensation of 5-bromo-2-chloro-6-
methyl-4-(1-methylhydrazino) pyrimidine with carbon disulfide and alkyl halides9 or isoth-
10
iocyanates. Previously, we described the formation of fused [1,3,4]thiadiazines by the
condensation of alkyl-2-phenylhydrazinecarbodithioates with heterocyclic polyhalides.11,12
A more efficient method for achieving such a transformation would be the reaction of a
substituted or unsubstituted hydrazine with 4,6-dichloropyrimidine-5-carbaldehyde, which
Received 26 June 2009; accepted 31 August 2009.
The authors thank the Medicinal & Natural Products Chemistry Research Center, Shiraz University of
Medical Sciences, Shiraz, Iran, and Dr. M. M. Ghanbari for valuable assistance.
Address correspondence to Javad Azizian, Faculty of Science, Islamic Azad University, Science and Research
Branch, Tehran, Iran. E-mail: azizian@cc.sbu.ac.ir
1782

(PYRIMIDO[4,5-e][1,3,4]THIADIAZIN-7-YL)HYDRAZINE DERIVATIVES
1783
would allow formation of the desired ring system in a single step. Such a similar transfor-
mation has been reported for chloroformylpyridines13; condensations of hydrazine itself
with such pyrimidinylaldehydes and pyrimidinylketones were reported14,15 and related
transformations were carried out on solid support to yield pyrimidone products.16 Such
a transformation of 4,6-dichloro-2-phenylpyrimidine-5-carbaldehyde and phenylhydrazine
proceeding with concomitant displacement of a second hydrazine molecule to form N-
[(1,6-diphenyl-7-H-pyrazolo[4,5-e]pyrimidin-4-ylidene)amino]aniline was reported.17,18
RESULTS AND DISCUSSION
Our strategy for the synthesis of (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazines
4a–h, which are potential precursors for further heterocyclic systems, is a hydrazine
substitution of the chlorine atom of 3-alkylsulfanyl-7-chloro-5-methyl-1-phenyl-1H-
pyrimido[4,5-e][1,3,4]thiadiazines 3a–h. Compounds 3a–e were recently prepared,11 and
new compounds 3f–h were prepared by the same procedure. The structures assigned to
compounds 3f–h were substantiated by spectral data. The 1H NMR spectra were devoid of
the signals at ca. 6.0 and 9.0 ppm (δ) for NH groups of the precursor’s 2f–h and showed
further downfield shifts for aromatic protons and a signal at 2.35 ppm for the methyl
group of precursor 1 indicating the construction of a thiadiazine ring around the 4- and
5-positions of the pyrimidine ring. Further proof came from their IR spectra, which lacked
the N–H stretching frequencies of their precursor’s 2f–h and confirmed the presence of the
methyl group and the chlorine atom in compounds 3f–h by two stretching frequencies at
about 2900 and 850 cm−1, respectively. Mass spectra showed the expected molecular ion
peak, and the fragmentation pattern indicated the loss of alkylthio groups from compounds
3f–h and 4a–h, which is in line with the proposed structure as shown in Schemes 1 and 2.
a-g
R
Ph
N
R
a
b
c
d
e
f
Cl
N
Cl
Br
-CH3
-CH2-CH3
-CH2-CH2-CH3
-CH2-CH2-CH2-CH3
C6H5CH2
Cl
N
S
S
NEt3
N
+
HN
NH
MeCN
N
N
reflux(3 h)
-
Ph
S
S
R
-
-P-Cl- C6H4CH2-
Me
-P-Br- C6H4CH2
Me
g
h
-
2 a-h
3 a-h
-P-NO2- C6H4CH2
1
Scheme 1 Preparation of pyrimido[4,5-e][1,3,4]thiadiazines.
Hence, the condensation of 5-bromo-2,4-dichloro-6-methylpyrimidine 1 with alkyl-
2-phenylhydrazinecarbodithioates (2f–h) in alkaline acetonitrile afforded a group of
pyrimido[4,5-e][1,3,4]thiadiazine derivatives. The orientation of this reaction was recently
determined.11,19
Microanalytical data for compounds 3a–h had no significant difference with the
expected data. We also found that the chlorine atom in the 7-position of the products
3a–h could be easily replaced by hydrazine in boiling ethanol, and C–Cl stretching bands
were absent in IR spectra of compounds 4a–h (Scheme 2). The structures of 1-(3-(aryl-
alkyl thio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazine (4a–h)
are shown in Scheme 2.

1784
J. AZIZIAN ET AL.
a-g
R
NH2
HN
Ph
a
b
c
d
e
f
-CH3
-CH2-CH3
-CH2-CH2-CH3
-CH2-CH2-CH2-CH3
C6H5CH2
N
N
H2N
NH2
N
3 a-h
EtOH
Reflux (3-4 hr)
-
N
-
S
S
R
-P-Cl- C6H4CH2-
-P-Br- C6H4CH2
g
h
-
4 a-h
-P-NO2- C6H4CH2
Me
Scheme 2 General procedure for the reaction of pyrimido[4,5-e][1,3,4]thiadiazines with hydrazine.
CONCLUSION
In conclusion, the condensation of 5-bromo-2,4-dichloro-6-methylpyrimidine with
alkyl-2-phenylhydrazinecarbodithioates and further replacement of the 7-chlorine atom
with hydrazine is a convenient and general procedure for preparation of new pyrimido[4,5-
e][1,3,4]thiadiazine derivatives. In the majority of cases, this methodology was allowed ac-
cess in simple steps to a diverse range of (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazine.
This work represents a new, general method for preparation of the (pyrimido[4,5-
e][1,3,4]thiadiazin-7-yl)hydrazines, which are useful precursors for the synthesis of novel
heterocyclic systems.
EXPERIMENTAL
Melting points were recorded on an Electrothermal type 9100 melting point apparatus.
Infrared spectra were recorded as KBr disks on a Shimadzu model 420 spectrophotometer.
The 1H NMR and 13C NMR spectra were recorded on a Bruker AC 300 spectrometer. All
the chemical shifts were quoted in ppm using the high-frequency positive convention; the
1H and 13CNMR spectra were referenced to external SiMe4. The mass spectra were scanned
on a Varian Mat CH-7 instrument at 70 eV. Elemental analysis was obtained on a Thermo
Finnigan Flash EA microanalyzer. The purity of all of the new compounds was tested by
TLC using chloroform as a mobile phase. 5-Bromo-2,4-dichloro-6-methylpyrimidine was
prepared according to the published procedure.20
General Procedure for the Preparation
of Pyrimido[4,5-e][1,3,4]thiadiazines 3f–h
A mixture of compound 1 (2.5 mmol, 0.61 g), alkyl-2-phenylhydrazinecarbodithioate
2 (2.5 mmol), and triethylamine (1 mL) in acetonitrile (10 mL) was refluxed under an
atmosphere of nitrogen for 3 h. After the reaction was completed, the mixture was cooled
to room temperature and then evaporated under reduced pressure. The residue was washed
with water and crystallized from ethanol prior to washing with light petroleum 40–60 to
give products 3f–h (Scheme 1).
3-(4-Chlorobenzylthio)-7-chloro-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,
3,4]thiadiazine (3f). Yellow powder, 60% yield, mp 135–136◦C, IR (KBr cm−1):
1
865, 1670, 2930, 2960. H NMR (CDCl3) δ 2.27 (s, 3H, Ph-Me), 4.31 (s, 2H,S-CH2),
7.25–7.77 (m, 9H).13CNMR (CDCl3) δ 22.1(Ph- Me), 45.5 (-S-CH2-), 131.1, 132.9, 133.5,
135.2, 137.3, 146.6, 154.6(2 Ph), 157.3(Ph-Cl), 164.3, 173.56. m/z, 436(5%), 434(32%),

(PYRIMIDO[4,5-e][1,3,4]THIADIAZIN-7-YL)HYDRAZINE DERIVATIVES
1785
432(44%), 277(10%), 275(32%). Found (%): C, 52.61; H, 3.29; N, 13.02; S, 14.75. Calc.
for C19H14Cl2N4S2 (%): C, 52.66; H, 3.26; N, 12.93; S, 14.80.
3-(4-Bromobenzylthio)-7-chloro-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,
3,4]thiadiazine (3g). Yellow powder, 54% yield, mp 128–130◦C, IR (KBr cm−1): 850,
1620, 2900, 2950. 1H NMR (CDCl3) δ 2.34 (s, 3H, Ph-Me), 4.25 (s, 2H,S-CH2), 7.28–7.70
(m, 9H) 13CNMR (CDCl3) δ 22.7(Ph- Me), 43.5 ( S CH2 ), 122.2, 130.8,134.5,
137.9, 140.0, 143.7,149.6 (2 Ph), 156.0(Ph-Cl), 167.4, 170.4 m/z, 480(19%), 478(75%),
476(58%), 277(5%), 275(15%). Found (%): C, 47.71; H, 5.92; N, 11.77; S, 13.39. Calc.
for C19H14BrClN4S2 (%): C, 47.76; H, 2.95; N, 11.73; S, 13.42.
3-(4-Nitrobenzylthio)-7-chloro-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,
3,4]thiadiazine (3h). Yellow powder, 63% yield, mp 147–149◦C, IR (KBr cm −1):
1
860, 1580, 2900, 2970. H NMR (CDCl3) δ, 2.31 (s, 3H, Ph-Me), 4.35 (s, 2H,S CH2),
7.35–7.88 (m, 9H).13C NMR (CDCl)3 δ 23.1(Ph- Me), 44.0( S CH2 ), 124.3, 131.8,
133.0, 136.7, 153.4, 151.6, 155.9, 158.3, 166.3, 174.8 m/z, 445(12%), 443(38%),
277(15%), 275(48%). Found (%): C, 51.43; H, 3.10; N, 15.73; S, 14.49. Calc. for
C19H14ClN5O2S2 (%): C, 51.41; H, 3.18; N, 15.78; S, 14.45.
General Procedure for the Reaction of 3a–h with Hydrazine
A mixture of each of compounds 3a–h (5 mmol) in ethanol (20 mL) was heated
under reflux with hydrazine (excess) for 4 h. The solvent was removed, and the residue was
washed with water and then crystallized from ethanol to give products 4a–h (Scheme 2).
1-(5-Methyl-3-(methylthio)-1-phenyl-1H-pyrimidio[4,5-e][1,3,4]thiadiazin-
7-yl)hydrazine (4a). Yellow powder, yield 60%, mp 195–197◦C. IR (KBr, cm−1): 1200,
1
1400–1600, 2900, 3050, 3210, 3250, 3300. H NMR (CDCl3) 2.35 (s, 3H, 8-Me), 2.52
(s, 3H, S Me), 3.72 (m, 2H, NH2), 6.14 (m, 1H, NH), 7.10–7.63 (m, 5H). 13C NMR
(CDCl3) δ 15.5(S-Me), 21.7(Ph-Me), 107.5, 123.6, 126.4, 128.6, 141.3(Ph), 143.4, 158.4,
158.5, 164.1. MS, m/z: 318. Found (%): C, 49.10; H, 4.4; N, 26.44; S, 20.19. Calc. for
C13H14N6S2 (%): C, 49.04; H, 4.43; N, 26.39; S, 20.14.
1-(3-(Ethylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazin-
7-yl)hydrazine (4b). Yellow powder, yield 67%, mp 160–162◦C. IR (KBr, cm−1): 1250,
1
1420–1600, 2930, 3050, 3200, 3270, 3285. H NMR (CDCl3) δ 1.35 (t, 3H, Me, J 7.5
Hz), 2.38 (s, 3H, 8-Me), 3.16 (q, 2H, S CH2, J 7.5 Hz), 3.72 (m, 2H, NH2), 6.53 (m, 1H,
NH), 7.21–7.65 (m, 5H). 13C NMR (CDCl3) δ 14.65,21.34 (S-Et), 25.83 (Ph-Me), 115.8,
118.5,129.3, 131.2, 145.1(Ph), 152.9, 154.4, 161.7, 163.8. MS, m/z: 332. Found (%): C,
50.64; 4.91; N, 25.26; S, 19.33. Calc. for C14H16N6S2 (%): C, 50.58; H, 4.85; N, 25.28; S,
19.29.
1-(5-Methyl-1-phenyl-3-(propylthio)-1H-pyrimido[4,5-e][1,3,4]thiadiazin-
7-yl)hydrazine (4c). Yellow powder, yield 70%, mp 152–154◦C. IR (KBr, cm−1): 1235,
1440–1610, 2950, 3000, 3230, 3265, 3310. 1H NMR (CDCl3) δ .92 (t, 3H, Me), 1.85 (m,
2H, CH2 ), 2.84 (t, 2H, S CH2, J 7.5 Hz), 3.72 (m, 2H, NH2), 6.67 (m, 1H, NH),
7.18–7.63 (m, 5H).13C NMR (CDCl3) δ 13.1 (S-Pr), 21.3(Ph-Me),24(S-Pr), 31.6 (S-Pr),
113.2, 117.0,128.5, 132.8, 147.3(Ph), 153.3, 156.7, 160.1, 165.9. MS, m/z: 346. Found
(%): C, 52.05; H, 4.90; N, 24.29; S, 18.45. Calc. for C15H16N6S2 (%): C, 52.00; H, 4.85;
N, 24.26; S, 18.51.
1-(3-(Butylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazin-
7-yl)hydrazine (4d). Yellow powder, yield 65%, mp 149–150◦C. IR (KBr, cm−1): 1180,
1
1420–1650, 2920, 3070, 3215, 3275, 3350. H NMR (CDCl3) δ 1.30 (t, 3H, Me, J 7.5

1786
J. AZIZIAN ET AL.
Hz), 2.33 (s, 3H, 8-Me), 3.1 (q, 2H, S CH2, J 7.5 Hz), 3.75 (m, 2H, NH2), 6.42 (m,
1H, NH) 7.17–7.63 (m, 5H). 13C NMR(CDCl3) δ 14.25 (S-Bu), 21.34 (Ph-Me), 22.65
(S-Bu), 27.50(S-Bu), 31.81 (S-Bu), 112.3, 118.1,128.1, 133.5(Ph), 143.6, 152.0, 155.7,
163.9, 165.1. MS, m/z: 360. Found (%): C, 53.38; H, 5.46; N, 23.38; S, 17.82. Calc. for
C16H20N6S2 (%): C, 53.31; H, 5.59; N, 23.31; S, 17.79.
1-(3-(Benzylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]thiadiazin-
7-yl)hydrazine (4e). Yellow powder, yield 75%, mp 148–150◦C. IR (KBr, cm−1): 1230,
1450–1635, 2925, 3000, 3255, 3285, 3290. 1H NMR (CDCl3) δ 2.35 (s, 3H, 8-Me), 3.72
(m, 2H, NH2), 4.28 (s, CH2 ), 6.18 (m, 1H, NH), 7.08–7.72 (m, 10H).13C NMR δ
21.3(Ph-Me), 42.2(S CH2 ), 119.5, 130.2, 131.5, 132.7,133.6,133.8,142.1,150.3, 156.8,
165.5. MS, m/z: 394. Found (%): 57.87; H, 4.65; N, 21.36; S, 16.30. Calc. for C19H18N6S2
(%): C, 57.84; H, 4.61; N, 21.3; S, 16.26.
1-(3-(4-Chlorobenzylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]
thiadiazin-7-yl)hydrazine (4f). Yellow powder, yield 80%, mp 180–182◦C. IR (KBr,
cm−1): 1215, 1420–1675, 2940, 3100, 3200, 3220, 3310. 1H NMR (CDCl3) δ 2.35 (s, 3H,
8-Me), 3.70 (m, 2H, NH2), 4.85 (s, CH2 ), 6.56 (m, 1H, NH), 7.15–7.71 (m, 9H).13C
NMR (CDCl3) δ 21.7(Ph-Me), 43.3(S-CH2), 130.7, 133.2, 133.9, 135.8, 137.3, 143.4,
151.5, 156.2, 166.8. MS, m/z: 430(19%), 428(60%). Found (%): C, 53.27; H, 3.92; N,
19.54; S, 18.05. Calc. for C19H17ClN6S2 (%): C, 53.21; H, 3.99; N, 19.59; S, 17.95.
1-(3-(4-Bromobenzylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]
thiadiazin-7-yl)hydrazine (4g). Yellow powder, yield 76%, mp 189–191◦C. IR (KBr,
cm−1): 1210, 1440–1680, 2880, 3080, 3185, 3260, 3355. 1H NMR (CDCl3) δ 2.32 (s, 3H,
8-Me), 3.75 (m, 2H, NH2), 4.80 (s, CH2 ), 6.72 (m, 1H, NH), 7.34–7.78 (m, 9H). 13
C
NMR (CDCl)3 δ 21.9(Ph-Me), 44.2(S CH2 ), 125.1, 130.2, 133.8, 134.2, 150.3, 152.5,
154.4, 156.8, 165.5. MS, m/z: 474(54%), 472(54%). Found (%): C, 48.12; H, 3.66; N,
17.81; S, 13.49. Calc. for C19H17BrN6S2 (%): C, 48.20; H, 3.62; N, 17.75; S, 13.55.
1-(3-(4-Nitrobenzylthio)-5-methyl-1-phenyl-1H-pyrimido[4,5-e][1,3,4]thia
diazin-7-yl)hydrazine (4h). Yellow powder, yield 66%, mp 172–174◦C. IR (KBr,
cm−1): 1225, 1410–1620, 2900, 3050, 3210, 3280, 3300. 1H NMR (CDCl3) δ 2.37 (s, 3H,
8-Me), 3.73 (m, 2H, NH2), 5.15 (s, CH2 ), 6.83 (m, 1H, NH), 7.59–7.74 (m, 9H). 13
C
NMR (CDCl)3 δ 22.4 (Ph-Me), 44.2(S CH2 ), 126.7, 131.9, 133.1, 137.3, 153.1, 155.8,
157.2, 160.8, 169.2. MS, m/z: 439. Found (%): C, 51.88; H, 3.93; N, 22.34; S, 14.63. Calc.
for C19H17N7O2S2 (%): C, 51.92; H, 3.90; N, 22.31; S, 14.59.
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