Background: Pyrazole derivatives have remained a much studied class of heterocyclic compounds
with application in several scientific areas such as agrochemicals, pharmaceuticals and building blocks for
more elaborated structures. The cyclocondensation of enones with hydrazine derivatives is one of the most
valuable ways of synthesizing pyrazole derivatives. This method produces a racemic mixture of 4,5-dihydro-
1H-pyrazoles also known as pyrazolines which can be converted into aromatic pyrazoles by oxidative
Objective: The aim of this review article is to cover the state of the art oxidative aromatization of pyrazolines
Method: It was performed a comprehensive compilation from the literature concerning the reported methods
for oxidative aromatization of pyrazolines from the last thirty years. The review of each method was presented
along with a critical point of view.
Results: Several oxidant systems were applied for converting pyrazolines into pyrazoles. Most of the reviewed
protocols proved to be efficient for oxidize 1,3,5-trisubstituted pyrazolines when the group attached to the N1
was H, methyl and (substituted)-phenyl. On the other hand few methods were found to dehydrogenate pyrazolines
containing other than the above groups on N1 such as (thio)carbamoyl and amidinyl.
Conclusion: Conversion of pyrazolines into aromatic pyrazoles by oxidative aromatization attracted attention
in the last decades. A range of reagents has been reported for this purpose, but there is still the need for developing
general methods that fill the requirements of green chemistry and that are applicable for more elaborated