Alkali-Metal-Alkoxide Powered Zincation of Fluoroarenes Employing Zinc Bis-Amide Zn(TMP)2

Abstract

Reminiscent of Lochmann-Schlosser superbase recipes, the addition of two molar equivalents of KOtBu to Zn(TMP)2 (TMP=2,2,6,6-tetramethylpiperidide) transforms this mild zinc bis-amide base to a powerful metalating agent able to perform facile regioselective zincation of a wide range of sensitive fluoroarenes. Structural authentication of the intermediates post Zn−H exchange demonstrates activation of both TMP groups to form a range of higher order bis-aryl potassium zincates, isolable as solids and further functionalized in electrophilic interception reactions. Studies assessing the role of KOtBu reveal that the first equivalent undergoes co-complexation with Zn(TMP)2, enabling kinetic activation of the amide groups; whereas the second equivalent stabilizes the metalated intermediate preventing ligand redistribution. Showcasing its metalating power, this bimetallic KOtBu/Zn(TMP)2 partnership, can effect zincation of toluene and benzene at room temperature.