J.-T. Li et al. / Ultrasonics Sonochemistry 17 (2010) 11–13
13
As shown in Table 1, with the increasing of the molar ratio of
2,3-epoxy-1,3-diphenyl -1-propanone and hydrochloric acid from
1:0.1 to 1:0.2, higher yield (89%) was achieved in the similar reac-
tion time (Entry 2). When increasing the molar ratio to 1:0.3, the
conversion was completed in 14 min, but the yield was reduced
to 82% (Entry 3). We deduce that some of the phenylhydrazine
may combine with hydrochloric acid to produce the inert phen-
ylhydrazine hydrochloride with the increasing of the concentra-
tion of hydrochloric acid, thus, the yield of 2a could hardly be
increased. The results showed that changing the molar ratio of
1a with hydrochloric acid had a significant effect on the yield
of 2a, and the optimum molar ratio of 1a and hydrochloric acid
was 1:0.2.
tions and environment friendly, which make it a useful and
attractive process for the synthesis of these compounds.
In conclusion, we have found an efficient and practical proce-
dure for the synthesis of some 5-aryl-1,3-diphenylpyrazole via
the condensation of 3-aryl-2,3-epoxy-1-phenyl-1-propanone and
phenylhydrazine under ultrasound irradiation at room
temperature.
Acknowledgement
The project was supported by Natural Science Foundation of
Hebei Province (B2006000969), China.
In order to verify the effect of ultrasound irradiation, we have
performed the reaction of 3-aryl-2,3-epoxy-1-phenyl-1-propanone
and phenylhydrazine catalyzed by hydrochloric acid by stirring in
the absence of sonication, the yields of 5-ary-1,3-diphenyllpyraz-
ole, for example, 2b was obtained in 73%, while under ultrasound
2b was obtained in 95% yield (Table 2, Entry b). It showed that
ultrasound irradiation improved the result.
We also repeated the experiment reported in Ref. [18], put 3-(2-
nitrophenyl)-2,3-epoxy-1-phenyl-1-propanone and phenylhydr-
azine into the mixture of methanol, chloroform and acetic acid,
and then lying at 8 °C for 240 min. This reaction gave 2b in 42%
yield which was not only lower than that reported in reference
(86%), but also lower than the result of our method (95%) (Table
2, Entry b). The method has many other disadvantages, such as
hardly controlled temperature, longer reaction time, and the use
of toxic organic solvent and so on.
From the results above, a typical experimental procedure was
chosen: 3-aryl-2,3-epoxy-1-phenyl-1-propanone (1, 1.0 mmol),
phenylhydrazine (0.130 g, 1.2 mmol), ethanol (2 mL) and hydro-
chloric acid (0.2 equiv). Using this system, we did a series of exper-
iments to prepare 5-aryl-1,3-diphenylpyrazole under ultrasound
irradiation. The results were summarized in Table 2.
As shown in Table 2, the condensation of 3-aryl-2,3-epoxy-1-
phenyl-1-propanone with phenylhydrazine affords product 2 in
good yields, which are, in general, similar or higher than those de-
scribed in literatures [7–12]. It is also worth noting that the elec-
tronic effects of substituents on the benzene ring seem to have
no effect on the yields of products.
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Compared with other reported methods, we can deduce that the
present method represented a better procedure with main advan-
tages of operational simplicity, higher yields, mild reaction condi-