Page 209 - 80_01
P. 209
Novel
compounds
containing
1,3,4--oxadiazole…
out.
These
crystals
were
filtered,
washed
with
water
and
dried.
c.
Synthesis
of
3--methyl--4--(substituted
phenyl
hydrazono)--pyrazoline--5--one
(III)
3--methyl--4--(4|--substituted
phenyl
hydrazono)--pyrozoline--5--one
(III)
was
synthesized
by
thecondensation
of
4--substituted
phenyl
hydrazono
acetoacetic
ester
(II)
and
hydrazine
in
the
presence
of
required
amounts
of
dimethylformamide.
The
mixture
was
subjected
to
microwave
irradiation
at
150W
intermittently
at
30
sec
intervals
for
2
minutes.
After
complete
conversion
as
indicated
by
TLC,
the
reaction
mixture
was
cooled
and
washed
with
cold
water.
The
precipitated
III
was
filtered
recrystallized
from
ethanol.
d.Synthesis
of
{4--[3--Methyl--5--oxo--4--(substituted
phenyl
hydrazono)--4,5--
dihydro--pyrazol--1--yl]--phenoxy--
acetic
acid
ethyl
ester
(IV)
A
mixture
of
III,
anhydrous
K2CO3
and
DMF
was
stirred
at
room
temperature
for
8
hours.
The
reaction
mixture
was
diluted
with
ice
cold
water.
The
separated
solid
was
filtered
and
recrystallized
from
ethanol.
e.
Synthesis
of
{4--[3--Methyl--5--oxo--4--(4|--aryl--hydrazono)--4,5--dihydro--pyrazol--1--
yl]--phenoxy}--acetic
acid
hydrazides
(V)
A
mixture
of
IV
and
hydrazine
hydrate
in
ethanol
was
refluxed
for
five
hours.
The
reaction
mixture
was
cooled
to
room
temperature
and
poured
in
ice
cold
water
with
continuous
stirring.
The
separated
solid
was
filtered,
washed
with
water
and
recrystallized
from
ethanol.
Other
members
of
the
series
Vwere
prepared
on
the
same
lines.
The
reaction
scheme
is
depicted
in
Scheme
1.
2.1.2.
Synthesis
of
2--(4--acetyl--
--5,5--disubstituted
4,5--dihydro--[1,3,4]oxadiazole--
2--yl(methyloxyphenyl)--5--methyl--4(aryl
hydrazono)--
--pyrazol--3--ones
(VII)
a.
Synthesis
of
{4--[3--
methyl--
5--
oxo--
4--(4|--phenyl
hydrazono)--
4,5--dihydro--
pyrazol--1--yl]--phenoxy}--acetic
acid
(1--phenyl--ethylidene)--hydrazide
(VI)
A
mixture
of
V
(0.01
mol)
in
hot
methanol
(25
mL),
acetophenone
(0.01
mol)
and
a
drop
of
glacial
acetic
acid
were
refluxed
for
3
hours.
The
solid
separated
was
filtered,
washed
with
cold
methanol
and
recrystallized
from
methanol
to
give
VIa.
Compounds
VI
b--h
were
synthesized
on
similar
lines.
b.
Synthesis
of
2--(4--acetyl--5,5--disubstituted
4,5--dihydro--[1,3,4]oxadiazole--2--
yl(methyloxyphenyl)--5--methyl--4(4|--substituted
phenyl
hydrazono)--pyrazol--3--
ones
(VII)
A
mixture
of
VIa
(0.01
mol)
and
an
excess
of
acetic
anhydride
(10
mL)
were
refluxed
for
2
hours.
The
excess
acetic
anhydride
was
distilled
off
and
the
residue
was
poured
on
to
crushed
ice.
The
solid
obtained
was
filtered,
washed
with
water
and
recrystallized
from
aqueous
methanol
to
get
VIIa.
The
cyclization
reaction
was
extended
to
other
hydrazones
VI
b–j
and
in
each
case
the
respective
compound
was
isolated.
The
reaction
scheme
is
given
in
Scheme
2.
203
