| 2-Pyrazoline core is a very interesting five-membered heterocycle, which has been explored in recent years due to its vast
applications as the core structure of bioactive and industrial
agents. Based on literature studies, versatile synthetic approaches have been employed for the preparation of 2-
pyrazolines, among them the reaction between hydrazines and
α,β-unsaturated enones as the most used method. In this
review article, different methods for the synthesis of 2-pyrazolines using hydrazine derivatives were classified and presented.
Initially, numerous catalytic methods for the preparation of 2-
pyrazolines from hydrazines and α,β-unsaturated enones are
reviewed and various aspects of these methods discussed
including catalyst efficiency, catalyst recovery, green chemistry,
cost-effectiveness, scope of the method, enantioselectivity, and
yield. In addition, reactions between hydrazines and other
reagents in multicomponent and two-component reactions,
developed recently, are discussed. Finally, some of the
important applications of 2-pyrazolines are summarized. |