Acid‐Mediated Three Component Assembly of 4‐Fluoropyrazoles from α‐Fluoronitroalkenes, Hydrazines, and Aldehydes.

A new approach for the synthesis of highly pharmaceutically relevant 4‐fluoropyrazoles via oxidative annulation of α‐fluoronitroalkenes with in situ prepared hydrazones was developed. The reaction is efficiently promoted by trifluoroacetic acid while atmospheric oxygen was used as an oxidant. Broad substrate scope was demonstrated, using both electron‐rich and electron‐deficient nitroalkenes as well as different hydrazones derived from aromatic aldehydes. The mechanistic details were also outlined. [ABSTRACT FROM AUTHOR]