Novel compounds containing1,3,4-‐oxadiazole…
203
out. Thesecrystalswere filtered,washedwithwateranddried.
c. Synthesis of 3-‐methyl-‐4-‐(substituted p enyl 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. Themixturewas subjected tomicrowave irradiationat 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.
Theprecipitated
III
was filteredrecrystallized fromethanol.
d.Synthesis of {4-‐[3-‐Methyl-‐5-‐oxo-‐4-‐(substituted phenyl hydrazono)-‐4,5-‐
dihydro-‐pyrazol-‐1-‐yl]-‐phenoxy-‐aceticacidethyl ester (IV)
A mixture of
III
, anhydrous K
2
CO
3
and DMF was stirred at room
temperature for 8 hours. The reaction mixture was diluted with ice cold water.
Theseparatedsolidwas filteredandrecrystallized fromethanol.
e. Synthesisof {4-‐[3-‐Methyl-‐5-‐oxo-‐4-‐(4
|
-‐aryl-‐hydrazono)-‐4,5-‐dihydro-‐pyrazol-‐1-‐
yl]-‐phenoxy}-‐aceticacidhydrazides (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
coldwaterwith continuous stirring. The separated solidwas filtered, washedwith
water and recrystallized from ethanol. Other members of the series
V
were
preparedonthesame lines. Thereactionscheme isdepicted inScheme
1.
2.1.2. Synthesisof 2-‐(4-‐acetyl-‐ -‐5,5-‐disubstituted4,5-‐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}-‐aceticacid(1-‐phenyl-‐ethylidene)-‐hydrazide(VI)
A mixture of
V
(0.01 mol) in hot methanol (25 mL), acetophenone (0.01
mol) andadropof glacial aceticacidwererefluxed for3hours. Thesolidseparated
was filtered, washedwith coldmethanol and recrystallized frommethanol to give
VI
a. Compounds
VI
b-‐hweresynthesizedonsimilar 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)
Amixtureof
VI
a (0.01mol) andanexcess of acetic anhydride (10mL)were
refluxed for 2hours. The excess acetic anhydridewas distilledoff and the residue
was pouredon to crushed ice. The solidobtainedwas filtered, washedwithwater
andrecrystallized fromaqueousmethanol toget
VII
a. The cyclizationreactionwas
extended to other hydrazones
VI
b–j and in each case the respective compound
was isolated. Thereactionscheme isgiven inScheme
2
.
