Phosphine-Catalyzed [3 + 2] Cycloaddition Reaction of α-Diazoacetates and β-Trifluoromethyl Enones: A Facile Access to Multisubstituted 4-(Trifluoromethyl)pyrazolines.

A novel phosphine-catalyzed [3 + 2] cycloaddition of α-diazoacetates and β-trifluoromethyl enones has been developed that provides facile access to multisubstituted 4-(trifluoromethyl)pyrazolines in good to excellent yields at room temperature. In addition, a tandem [3 + 2] cycloaddition/Michael addition is also presented.