Radical-Polar Crossover Enabled Triple Cleavage of CF 2 Br 2 : A Multicomponent Tandem Cyclization to 3-Fluoropyrazoles.

The elaboration of step-economy and catalytic approaches for accessing diverse fluorinated heterocyclics is highly desirable. Described herein is a radical-polar crossover enabled three-component cyclization to polysubstituted fluoropyrazoles by using CF 2 Br 2 as a novel C1F1 synthon. Mechanistic experiments revealed that the in situ generation of the reactive intermediate gem -difluorovinylimine ion is the key to this transformation. This protocol unlocks the novel reactivity of CF 2 Br 2 and adds significant synthetic values to fluorine chemistry.