136
K. R. Reddy, R. Mamatha, M. S. S. Babu, K. Shiva Kumar, and G. Narayanaswamy
Vol 51
Erlenmeyer flask and was subjected to microwave irradiation at
(200 W) at 70ꢀC, intermittently at 30-s interval for specified
time (Table 1). After the completion of reaction (monitored by
TLC), added reaction mixture is cold to RT, treated with
crushed ice, and acidified with dilute acetic acid. The product
separated was filtration and re-crystallized from ethanol to
obtain desired compound 4a–e.
Method C by grinding method. Hydrazinecarbothioamides
3a–e (0.005 mol) and NaOH pellets (0.01 mol) were grinded in
a mortar with a pestle made of porcelain for 5–10 min at RT.
The mixture turns pasty after few minutes of grinding. The
reaction was monitored by TLC. After the completion of
reaction, resulting slurry was poured into ice cold water and
acidified with acetic acid. The crude solid thus separated was
collected and re-crystallized from ethanol.
7-((5-Mercapto-4-phenyl-4H-1,2,4-triazol-3-yl)methoxy)-4-
methyl-2H-chromen-2-one (4a). Yield: 79%, mp: 124–126ꢀC;
elemental analysis: Anal. Calcd for C19H15O3N3S: C-62.45, H-
4.14, and N-11.50; found: C-62.40, H-4.10, and N-11.44; IR
(KBr, cmÀ1): 3045, 2923(Ar—H), 1715 (C═O), 1248, 1035,
and 845; 1H-NMR (300 MHz, DMSO-d6): d 2.2 (s, 3H, CH3),
d 4.8 (s, 2H, OCH2), d 5.6 (s,1H, C═C—H), d 6.7–7.7 (m,
8H ArH), d 14.4 (s, 1H, SH); ES-MS: m/z (m + 1): 347.11.
7-((5-Mercapto-4-p-tolyl-4H-1,2,4-triazol-3-yl)methoxy)-4-
methyl-2H-chromen-2-one (4b). Yield: 75%, mp: 134–136ꢀC;
elemental analysis: Anal. Calcd for C20H17O3N3S: C-63.31, H-
4.52, and N-11.07; found: C-63.30, H-4.50, and N-11.04; IR
(KBr, cmÀ1): 3045 (Ar—H), 2923, 2896 (Aliphatic C—H), 1735
(C═O), and 1035 (—C—O); 1H-NMR (300, MHz, DMSO-d6): d
2.0 (s, 3H, Ar—CH3), d 2.2 (s, 3H, CH3), d 4.8 (s, 2H, OCH2), d
5.65 (s,1H, C═C—H), d 6.5–7.7 (m, 7H, ArH), d 14.2 (s,1H,
SH); ES-MS: m/z (m+ 1): 361.13.
hydrazinecarbothioamides 3a–e (0.005mol) was added gradually
to concentrated H2SO4 (3mL) in about 10 min; the reaction
mixture then heated at 80–90ꢀC for 2 h in an oil bath. After the
completion of reaction, monitored by TLC, the slurry was poured
into ice cold water. The crude solid thus separated was collected
and re-crystallized from ethanol to give compounds 5a–e.
Method
B
by MW method.
A
mixture of
hydrazinecarbothioamides 3a–e (0.005mol) and catalytic amount
of silica sulphuric acid [18] was taken in 50 mL Erlenmeyer flask
and was subjected to microwave irradiation at 200 W at 70ꢀC,
intermittently at 15-s interval for specified time (Table 1). After
the completion of reaction (monitor by TLC), added reaction
mixture is cold to RT and treated with crushed ice. The product
was extracted with ether (3 Â 25mL); combined ether layer is
washed with brine and cold water and dried over anhydrous Na2SO4.
The solid obtained after evaporation of ether is re-crystallized from
ethanol to give desired product 5a–e.
Method C by grinding method. Hydrazinecarbothioamides
3a–e (0.005mol) and silica sulphuric acid (0.005mol) was
grinded in a mortar with a pestle made of porcelain for 5–10 min
at RT. The mixture turns pasty after few minutes of grinding. The
reaction was monitored by TLC. After the completion of reaction,
resulting slurry was poured into ice cold water. The crude solid
thus separated was collected and re-crystallized from ethanol to
give compounds 5a–e.
4-Methyl-7-((5-(phenylamino)-1,3,4-thiadiazol-2-yl)methoxy)-
2H-chromen-2-one (5a).
Yield: 92%, mp: 184–186ꢀC;
elemental analysis: Anal. Calcd for C19H15O3N3S: C-62.45, H-
4.14, and N-11.50; found: C-62.10, H-4.10, and N-11.40; IR
(KBr, cmÀ1): 3428, 3409 (NH), 3022 (Ar—H), and 1714 (C═O);
1H-NMR (300 MHz, DMSO-d6): d 6.6–7.5 (m, ArH), d 4.8 (s,
2H, OCH2), d 2.0 (s, 3H, CH3); ES-MS: m/z (m+ 1): 365.08.
4-Methyl-7-((5-(p-tolylamino)-1,3,4-thiadiazol-2-yl)methoxy)-
7-((5-Mercapto-4-(4-methoxyphenyl)-4H-1,2,4-triazol-3-yl)
2H-chromen-2-one (5b).
Yield: 82%, mp: 146–148ꢀC;
methoxy)-4-methyl-2H-chromen-2-one (4c).
Yield: 78%,
elemental analysis: Anal. Calcd for C20H17O3N3S: C-63.31, H-
4.52, and N-11.07; found: C-63.30, H-4.50, and N-11.10; IR
(KBr, cmÀ1): 3409 (NH), 3020 (Aromatic CH), 2984, and 1714
(C═O); 1H-NMR (300 MHz, DMSO-d6): d 6.6–7.5 (m, 7H,
ArH), d 4.8 (s, 2H, OCH2), d 2.0 (s, 3H, CH3), d 1.8 (s, 3H,
CH3); ES-MS: m/z (m + 1): 379.23.
mp: 94–96ꢀC; elemental analysis: Anal. Calcd for C20H17O4N3S:
C-60.75, H-4.33, and N-10.63; found: C-60.45, H-4.30, and
N-10.44; IR (KBr, cmÀ1): 3049, 2944 (Ar—H), 2885
(Aliphatic C—H), 1725 (C═O), 1248, 1035, and 845; 1H-
NMR (300 MHz, DMSO-d6): d 2.2 (s, 3H, CH3), d 3.8
(s, 3H, Ar—OCH3), d 4.8 (s, 2H, OCH2), d 5.65 (s, 1H,
C═C—H), d 6.5–7.7 (m, 7H, ArH), d 14.2 (s, 1H, SH); ES-MS:
m/z (m+ 1): 377.12.
7-((5-(4-Methoxyphenylamino)-1,3,4-thiadiazol-2-yl)methoxy)-
4-methyl-2H-chromen-2-one (5c). Yield: 68%, mp: 122–124ꢀC;
elemental analysis: Anal. Calcd for C20H17O4N3S: C-60.75, H-4.33,
and N-10.63; found: C-60.70, H-4.30, and N-10.60; IR (KBr,
cmÀ1): 3385 (NH), 3045, 2922 (Aromatic CH), 1714 (C═O),
1248, 1172, 1036, 827, 731, and 565; 1H-NMR (300 MHz,
DMSO-d6): d 6.5–7.6 (m, 7H, ArH), d 4.8 (s, 2H, OCH2), d 3.28
(s, 3H, OCH3), d 1.8 (s, 3H, CH3); ES-MS: m/z (m + 1): 395.09.
7-((5-(4-Chlorophenylamino)-1,3,4-thiadiazol-2-yl)methoxy)-
4-methyl-2H-chromen-2-one (5d). Yield: 87%, mp: 218–220ꢀC;
elemental analysis: Anal. Calcd for C19H14O3N3SCl: C-57.07,
H-3.53, and N-10.51; found: C-57.05, H-3.50, and N-10.25; IR
(KBr, cmÀ1): 3385 (NH), 3045, 2922 (Aromatic CH), 1714
(C═O); 1H-NMR (300 MHz, DMSO-d6): d 6.5–7.6 (m, 7H,
ArH), d 4.8 (s, 2H, OCH2), d 1.8 (s, 3H, CH3); ES-MS: m/z
(m + 1): 399.04.
7-((4-(4-Chlorophenyl)-5-mercapto-4H-1,2,4-triazol-3-yl)
methoxy)-4-methyl-2H-chromen-2-one (4d). Yield: 84%, mp:
90–92ꢀC; elemental analysis: Anal. Calcd for C19H14O3N3SCl:
C-57.07, H-3.53, and N-10.51; found: C-57.00, H-3.50, and
N-10.50; IR (KBr, cmÀ1): 3049, 2944 (Ar—H), 2885
(Aliphatic C—H), 1696 (C═O), 1248, 1035, and 845 (C—Cl);
1H-NMR (300 MHz, DMSO-d6): d 2.2 (s, 3H, CH3), d 4.8 (s,
2H, OCH2), d 5.65 (s, 1H, C═C—H), d 6.5–7.7 (m, 8H, ArH),
d 14.2 (s, 1H, SH); ES-MS: m/z (m + 1): 381.08.
7-((4-(4-Bromophenyl)-5-mercapto-4H-1,2,4-triazol-3-yl)
methoxy)-4-methyl-2H-chromen-2-one (4e).
Yield: 89%, mp:
120–122ꢀC; elemental analysis: Anal. Calcd for C19H14O3N3SBr: C-
51.36, H-3.18, and N-9.46; found: C-51.30, H-3.10, and N-9.42; IR
(KBr, cmÀ1): 3049, 2944 (Ar—H), 2885 (Aliphatic C—H), 1696
(C═O),1248, 1035, and 845 (C—Cl); 1H-NMR (300 MHz, DMSO-
d6): d 2.2 (s, 3H, CH3), d 4.8 (s, 2H, OCH2), d 5.65 (s, 1H, C═C—
H), d 6.5–7.7 (m, 8H, ArH), d 14.2; ES-MS: m/z (m + 1): 425.02.
7-((5-(4-Bromophenylamino)-1,3,4-thiadiazol-2-yl)methoxy)-
4-methyl-2H-chromen-2-one (5e). Yield: 80%, mp: 184–186ꢀC;
elemental analysis: Anal. Calcd for C19H14O3N3SBr: C-51.36,
H-3.18, and N-9.46; found: C-51.10, H-3.10, and N-9.50; IR
(KBr, cmÀ1): 3385 (NH), 3045, 3048 (Aromatic CH), 1714
(C═O), 1248, 1172, 1036, 827,731, and 565; 1H-NMR
General procedure for synthesis of thiadiazoles compounds 5.
Method A by conventional method.
A mixture of
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet