Radical-Polar Crossover Enabled Triple Cleavage of CFBr: 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 CFBr as a novel C1F1 synthon. Mechanistic experiments revealed that the generation of the reactive intermediate -difluorovinylimine ion is the key to this transformation. This protocol unlocks the novel reactivity of CFBr and adds significant synthetic values to fluorine chemistry.