ortho ‐Allylation of 1‐Arylpyrazoles with Allyl Phenyl Ether via Iron‐Catalyzed CH Bond Activation under Mild Conditions

An iron salt and a bipyridine‐type ligand catalyze the ortho ‐allylation of 1‐arylpyrazoles and congeners with allyl phenyl ether under mild conditions (0 °C). The ligand, an organozinc base, and the nature of the allylating reagent are crucial for the success of this reaction. Under these conditions, a competitive phenylation reaction is largely retarded, and cross‐coupling of the organozinc with the allyl electrophile is minimized. The reaction may proceed via iron‐catalyzed ortho CH activation to form a metallic intermediate, which then reacts with the allyl ether in a γ selective fashion.