A Convenient Synthesis of 5-Trifluoromethyl-5-cyclopropyl-Substituted Pyrazolines

A new method for the preparation of 5-trifluoromethyl-5-cyclopropylpyrazoline derivatives via cesium hydroxide mediated condensation reaction of trifluoromethyl--cyclopropyl-substituted unsaturated ketones with hydrazines was reported.The approach featuring mild reaction conditions, broad substrates scope and good functional group tolerance, provided a strategy to synthesize new functionalized pyrazolines bearing both trifluoromethyl and cyclopropyl groups.Pyrazolines are a very important class of nitrogen-containing heterocyclic compounds and have a wide application in the field of pharmaceuticals, agrochemicals and material sciences. 1Due to the advantage of trifluoromethyl (CF3) group in improving the lipophilicity, bioavailability and metabolic stability of organic molecules, 2 trifluoromethyl-substituted pyrazolines have gained particular attentions. 3The condensation of 1,1,1-trifluoro--enones with substituted hydrazines constitutes the most common synthetic method for trifluoromethyl-substituted pyrazolines. 4Recently, the dipolar cycloaddition of CF3CHN2 with electrondeficient alkenes or allenes and formal [4 + 1]-annulation of trifluoroethylidene sulfur ylide with azoalkenes as new strategies to construct 5-(trifluoromethyl)pyrazolines have been developed. 5Despite of these advances, there is an urge demand to synthesize new trifluoromethyl-substituted pyrazolines with multiple functional groups. 6clopropyl group as a structural moiety in many natural products and bioactive molecules, has unique stereospecific, electronic and conformational properties, making it a wide range of applications in organic 716